HomeMy WebLinkAbout1.23 Updated Aquifer Sustainability Study
1
TABLE OF CONTENTS
INTRODUCTION ......................................................................................................................................................... 2
BACKGROUND ........................................................................................................................................................... 2
AQUIFER CHARACTERISTICS ................................................................................................................................. 2
PRECIPITATION INFILTRATION ............................................................................................................................. 3
AQUIFER RECHARGE ............................................................................................................................................... 4
ANTICIPATED DIVERSIONS & DEPLETIONS ....................................................................................................... 5
TOTAL SPRING VALLEY AQUIFER DEMANDS ................................................................................................... 7
SUMMARY .................................................................................................................................................................. 8
FIGURE 1: SPRING VALLEY RANCH VICINITY MAP…………………………………………………………………………………………………….ATTACHED
FIGURE 2: SPRING VALLEY RANCH GEOLOGY MAP…………………………………………………………………..……………………………...ATTACHED
FIGURE 3: SPRING VALLEY RANCH 1991-2020 AVERAGE PRECIPITATION MAP…………………………….……………………………….ATTACHED
FIGURE 4: SPRING VALLEY RANCH NATIONAL LAND COVER MAP…………………………….………………………………………………….ATTACHED
TABLE 1: ESTIMATED PRECIPITATION AND INFILTRATION INTO THE SVA. *..................................................................................... 4
TABLE 2: ESTIMATED LOSSES TO FROM EVAPOTRANSPIRATION BY VEGETATION TYPE. ....................................................................... 5
TABLE 3: POTABLE WATER DEMANDS AND DEPLETIONS…………………………………………………………………………………………….ATTACHED
TABLE 4: NON-POTABLE WATER DEMANDS AND DEPLETIONS…………………………………………………………………………………….ATTACHED
TABLE 5: TOTAL POTABLE AND NON-POTABLE WATER DEMANDS AND DEPLETIONS…………….………………………………………….ATTACHED
TABLE 6: MONTHLY DEPLETION AND DELAYED RETURN FLOW FACTORS DECREED IN CASE NO. 87CW155 ........................................ 5
TABLE 7: TOTAL DIVERSIONS AND DEPLETIONS FOR SPRING VALLEY DEVELOPMENTS BASED ON DECREED PLANS FOR AUGMENTATION .... 8
2
INTRODUCTION
This report has been prepared to update previous engineering evaluations related to the
sustainability of the Spring Valley Aquifer (SVA) located approximately 6 miles southeast of
Glenwood Springs, CO (Figure 1). The SVA is identified as a major alluvial aquifer resource in the
Colorado Groundwater Atlas prepared by the Colorado Geological Survey. The purpose of this
updated study is to incorporate more modern datasets into the analysis and determine if recent
changes to precipitation, temperature, and resultant hydrology have altered the results of
previous analyses, all of which found the aquifer to have sufficient water in aquifer storage and
recharge to support Spring Valley Ranch (SVR) and other planned developments.
BACKGROUND
Colorado River Engineering (CRE) has reviewed previous studies related to the SVA.1 2 3 These
studies were undertaken in the early 2000’s to quantify the water availability and compare it to
the water demands associated with the SVR development as well as other planned developments
which were all contemplated to rely on the SVA. Gamba (2000) determined the probable amount
of annual recharge to the Spring Valley Aquifer (SVA) to be 10,059 acre-feet per year on average
based on average annual precipitation (1951-1980) of 19,908 acre-feet, evapotranspiration (ET)
losses of 9,249 acre-feet, and estimated surface flow losses down Landis Creek of 600 acre-feet.
The probable annual recharge was quantified to be well above the expected total development
groundwater diversions, which are not completely consumptive to the aquifer, of 1,100 acre-
feet which included 600 acre-feet from SVR and 500 acre-feet from other developments. HRS
provided review of the Gamba analysis with a resultant recharge estimate of 4,700 acre-feet,
which estimated crop ET from free surface water evaporation. The results of these studies have
been updated by CRE utilizing more modern datasets considering recent changes in precipitation,
satellite derived vegetation types, and more detailed consumptive use estimates.
The Gamba analysis quantified the total water in storage in the aquifer to be 68,000 to 105,000
acre-feet of which 38,000 to 46,000 acre-feet is stored in the SVA and 30,000 to 60,000 acre-feet
are available in the upland volcanic materials tributary to the SVA. The HRS analysis included a
similar estimate of 82,000 acre-feet of water available in storage in the SVA. The aquifer serves
as an underground reservoir to offset dry years with lower than normal recharge and to store
water in above normal recharge years.
AQUIFER CHARACTERISTICS
The cited Gamba report provides a detailed explanation of the geologic conditions that formed
the Spring Valley Hydrologic System, which is briefly summarized herein. The SVA tributary area
1 Gamba, J. 2000. The Spring Valley Hydrologic System. Prepared for Bill Peacher.
2 HRS Water Consultants, Inc, 2000. RE: Spring Valley Ranch – Review of Jerome Gamba & Associates, Inc.
Report, The Spring Valley Hydrologic System.
3 Wright Water Engineers, Inc. 2000. Water Requirements, Water Resources, and Spring Valley Area Water
Balance. Prepared for Spring Valley Development, Inc.
3
which contributes to recharge is approximately 15.4 square miles (Figure 1) and varies in
elevation from 6,870 to 9,400 feet. The aquifer was formed as soluble salts present in the
underlying Eagle Valley Evaporite formation were dissolved by groundwater resulting in collapse,
deformation, shear fracturing, and faulting of the overlying Maroon formation and volcanic rocks.
These processes resulted in the high infiltration rate and water bearing capacity of the volcanic
rocks. Millions of years of erosion have resulted in removal of softer, unconsolidated cinders and
ash from the surface and exposed the weather resistant basalt rocks. The ash and cinder lenses
that remain below the basalt provide pockets of highly porous materials that detain
groundwater, also called “hanging aquifers”. Water is channeled into these pockets via fractured
and rubblized basalt on the surface. These areas are interconnected by subsurface fractures that
slowly transmit water from higher elevations to lower elevations. The upland areas are the
primary area of recharge.
The SVA, which is a portion of the full contributing area of the aquifer, is a composite of a series
of confined aquifers within the sediments overlaying bedrock which produce artesian wells. The
confined aquifers in the lakebed sediments are comprised of sand and sandy gravel horizons
confined between layers of clay or sandy, gravely clays. The bedrock form of the lake basin is a
“half graben” with a fault on the south side of the basin. The blue gray clay layer acts as a seal
between the lake sediments and underlying volcanic rock materials.
PRECIPITATION INFILTRATION
There have been several updates to Colorado’s annual average precipitation analysis since the
1951-1980 dataset utilized by Gamba. Climate normals are updated every 10-years to reflect the
most recent 30-year period; the 1991-2020 climate normals were recently released. These data
are available at a station scale but are also available as a gridded dataset produced by the PRISM
Climate Group on an 800-meter resolution grid. This gridded data was overlain on the geologic
unit map within the SVA tributary area as defined on Figure C-1-E of the Gamba report. A geology
map is attached as Figure 2. The 1991-2020 average annual precipitation (Figure 3) was
calculated for each geologic unit which include: PPM – Pennsylvanian/Permian Maroon
Formation, Tb – Tertiary Volcanic Materials, and Ql – Quaternary Lake Sediments (aka SVA). The
average annual precipitation over the SVA tributary area was calculated to be 18,384 acre-feet
compared to the 19,908 acre-feet utilized by Gamba. This is a reduction of 1,524 acre-feet or
7.7%.
4
Table 1: Estimated Precipitation and Infiltration into the SVA. *
*Note minor discrepancy in total acreage based on digitization of boundaries from Gamba, 2000.
The infiltration rates by geologic unit utilized in the Gamba analysis were also utilized in the CRE
analysis, as they were deemed to be appropriate, and are included in Table 1. The local geology
exhibits relatively quick infiltration rates. Based on the assumed infiltration rates of the geologic
units, the estimated infiltration has been quantified to be 9,318 acre-feet compared to the 10,314
acre-feet calculated by Gamba. This is an infiltration reduction of 996 acre-feet or 9.7% and is
largely attributed to the reduced precipitation inputs.
The full annual amount of ET was assumed to deplete the available precipitation inputs,
regardless of whether water was available in soil moisture and available to plants or not, which
bases the analysis on a conservative aquifer recharge amount.
AQUIFER RECHARGE
The total amount of infiltration is not realized as recharge to the aquifer due to losses from ET
and surface runoff. Using the Gamba methodology, the probable recharge was determined using
the following formula:
Recharge = Precipitation – Evapotranspiration - Landis Creek surface flows Eq 1.1
Evapotranspiration was quantified by overlaying the National Land Cover Dataset (NLCD) (Figure
4), a satellite derived depiction of land cover, on the SVA Tributary area boundary and quantifying
the area of various vegetation types. The NLCD was cross-checked with aerial photos to ensure
accurate depiction of land cover types. If discrepancies were found, the area was included with
other vegetation types supported with aerial photography. Native vegetation ET rates were
obtained from the book values from the Handbook of Applied Hydrology, however, there are also
large, irrigated pastures located within the SVA aquifer. The potential evapotranspiration (PET)
from these irrigated pastures was updated using the Lease-Fallow Tool and ASCE standardized
methodology for pasture grass using the study period 2000-2019, which was conservatively
quantified to be 30-inches per year. Other vegetation types are shown in Table 2, below.
Shrub/Scrub utilized high range values for sagebrush in western regions of 10-inches. Deciduous
forest utilized the value for aspen of 23-inches. Evergreen forest utilized the average of the values
Geologic Unit Area (ac)Infiltration
Rate
Mean
Precip
(mm)
Mean
Precip
(in)
Average
Annual
Precipitation
Volume (AF)
Estimated
Infiltration
(AF)
PPM 2132 20%612 24 4281 856
Tb 6290 60%570 22 11763 7058
Ql 1453 60%491 19 2341 1404
Total 9875 18384 9318
5
for lodgepole and Engelmann spruce-fir of 17-inches. Mixed forest utilized the average value of
the deciduous and evergreen forests which is 20-inches. All of these values are greater than those
in the Gamba analysis and represent an increase in demands due to changes in climate as well as
more spatial detail to refine the vegetation types. The total annual potential ET was quantified
to be 13,842 acre-feet/year and represents a conservative value which assumes water is always
available to meet the demands of the various vegetation types.
Table 2: Estimated losses to from evapotranspiration by vegetation type.
Utilizing the Equation 1.1 results in the following estimated recharge:
Recharge = 18,384 – 13,842 - 600 = 3,942 acre-feet
These values represent average recharge conditions using conservative depletion assumptions.
This is water available for groundwater withdrawals without creating an aquifer deficit, i.e.,
“mining”, since it will be replenished on an average annual basis. The CRE estimated recharge is
6,117 acre-feet less than what was estimated by Gamba due to decreased precipitation inputs
and increased demands from evapotranspiration which are partly due to temperature and partly
due to increased spatial representativeness. The estimated annual recharge is similar to the HRS
results which quantified 4,700 acre-feet of recharge on average.
ANTICIPATED DIVERSIONS & DEPLETIONS
The development water demands for Storied Development’s amended SVR PUD plan (currently
being reviewed by Garfield County) will be less than the previously approved SVR PUD demands;
and less than the demands already decreed and covered by existing court approved
augmentation plans in Case Nos. 87CW155 and 98CW254, the latter being the operative plan for
augmentation. Basalt Water Conservancy District (BWCD) augments the structures, including
wells, surface and storage structures, which will supply water for the development. In sum, the
98CW254 augmentation plan allows for an annual water demand of 1457 acre-feet of diversions,
a total annual consumptive use of 974 acre-feet in a dry year, and an overall augmentation
requirement of 420 acre feet. The 98CW254 decree allows for modifications and reconfigurations
of the number of EQRs and amounts of irrigated acreage so long as the overall SVR PUD
consumptive use does not exceed 974 acre-feet annually. Tables 3-5 (attached) provide details
Vegetation Type Acreage (ac)ET
(in/yr)
ET Losses
(AF/yr)
Hay/Pasture/Herbaceous 756 30 1904
Shrub/Scrub 5031 10 4192
Deciduous Forest 3872 23 7421
Evergreen Forest 139 17 197
Mixed Forest 77 20 129
Total 9875 100 13842
6
of the potable, non-potable, and total diversions and depletions that are augmented pursuant to
the BWCD contracts, as incorporated and approved in Case No. 98CW254.
Potable diversions, which are attributed solely to groundwater sources, total 473.1 acre-feet with
associated depletions of 177.5 acre-feet and include domestic in-house and irrigation uses
associated with 695 EQR’s and 90 acres of domestic irrigation. The non-potable diversion, of
which a portion will be satisfied by senior surface water rights, total 983.9 acre-feet with
associated depletions of 796.96 acre-feet which includes uses of non-domestic irrigation for 420
acres and 24 acres of open surface water evaporation. Overall, the total project diversion
demands are 1,457 acre-feet with associated depletions of 974 acre-feet. Again, Case No.
98CW254, paragraph 10.c. allows for modification to the number of EQRs and irrigated acreage
if the depletions do not exceed 974 acre-feet.
In contrast, Storied Development’s amended SVR PUD proposal seeks to modify certain
components of the previously approved PUD including the type and number of development
units, irrigation requirements, and to add snowmaking as a use of its non-potable water system.
CRE has calculated the water requirements for the revised PUD plan and in sum, the total water
demand for the revised PUD plan is 1,221 acre-feet/year, with total consumptive use of 688 acre-
feet/year. This is less than the contemplated and approved water demand associated with the
currently approved PUD; however, for purposes of this report and aquifer sustainability analysis,
CRE utilizes the larger acre foot demands and depletions described above and approved in the
98CW254 case.
Because most of the lands to be irrigated are located within the SVA tributary area, irrigation
return flows will accrue to the aquifer and will not be totally consumptive to the aquifer. It is also
anticipated, based on land use approvals and engineering related to the expansion of the Spring
Valley Sanitation District, that treated wastewater effluent will also be returned within the SVA
tributary area. It was estimated that approximately 25% of the treated effluent would return to
the SVA by infiltration from the discharge point(s) along the Spring Valley Drainage basin
minimizing adverse impacts to the Spring Valley environment.4 In addition, Storied Development
will have rights to use the Spring Valley Sanitation District Pipeline decreed in Case No. 00CW21
in the amount of 3.48 c.f.s., conditional, for irrigation within the Spring Valley Sanitation District
service area which encompasses the SVA tributary area. The direct use of treated effluent for
irrigation will reduce the demand for groundwater and will supplement aquifer recharge.
Lagged well depletions will be calculated pursuant to the BWCD decree (Exhibit F, Case No.
87CW155) based on the locations of the constructed wells. The well location will determine the
lagged depletion zones which are used to quantify the timing of depletions to the stream from
well pumping. Case Nos. 87CW155 and 98CW254 classified the Spring Valley wells in Groups F1
(SVA) and F2 (Upland Aquifers). The monthly depletion percentages by Well Group are shown in
4 Wright Water Engineers, Inc. March 24, 1999. RE: Spring Valley Sanitation District Service Plan Amendment
(Exhibit 4.3 to Spring Valley Sanitation District Engineering Report for Application for site approval for
modification or expansion of an existing domestic wastewater treatment plant and application and certification
procedures for lift station and interceptors dated September 1999)
7
the following table which was attached as an exhibit in Case No. 87CW155. The timing of
depletions dictates the monthly augmentation replacement requirements during periods of
downstream call.
Table 6: Monthly Depletion and Delayed Return Flow Factors Decreed in Case No. 87CW155
TOTAL SPRING VALLEY AQUIFER DEMANDS
In addition to the demands associated with Spring Valley Ranch, several other subdivisions and
individual properties rely upon the Spring Valley Aquifer for all or a portion of their overall water
supplies. The following developments and associated plans for augmentation were reviewed and
are summarized in Table 7. The demands include Spring Valley Ranch, Los Amigos (Elk
Springs/Pinyon Mesa), Colorado Mountain College, Berkeley/Lake Springs Ranch, Lookout
Mountain Ranch, and individual lot owners. It is not known if Lookout Mountain Ranch relies on
the SVA for a portion of their water supplies because well construction logs and accounting are
unavailable; however, the total demand was included in the interest of being conservative. There
are approximately 30 individual properties with wells (or future wells) accessing the SVA area
with an estimated annual diversion of 30 acre-feet and an estimated depletion of 10 acre-feet,
which is based on engineering judgment. The total diversion from all developments relying on
the SVA totals approximately 1,920 acre-feet while the total depletions are approximately 1,263
acre-feet. The total diversions represent 49% of the anticipated recharge while the total
depletions represent only one third of the anticipated annual recharge to the SVA. The analysis
illustrates that the anticipated uses, based on conservative assumptions, do not result in long-
term mining of the groundwater aquifer as the average annual demands of the developments
8
are met by the average annual recharge to the aquifer. In addition, these demands do not
consider the fact that a portion of the SVR irrigation demands will be met with senior, surface
water rights, which results in irrigation return flows that deep percolate and recharge the SVA.
The sustainability analysis is conservative and supports the conclusion that there is adequate
groundwater supplies for all users of the SVA. This analysis, in conjunction with a groundwater
monitoring plan, allows all SVA water users to manage the water resource in a sustainable
manner.
Table 7: Total Diversions and Depletions for Spring Valley Developments Based on Decreed Plans for
Augmentation
SUMMARY
The estimated average annual recharge of 3,942 acre-feet is more than three times the estimated
depletion of 1,263 acre-feet for all users of the SVA. Under the proposed amended PUD plan,
groundwater withdrawals for irrigation will be less than calculated due to utilization of Landis
Creek surface water rights, which have historically been used to irrigate the property, and only
using groundwater for supplemental irrigation supplies. In addition to the annual recharge, it has
been estimated by Gamba that there is 68,000 to 105,000 acre-feet of water in storage in the
SVA and upland areas which essentially serve as an underground reservoir to balance extreme
dry year and extended drought-year recharge with water demands. As was found in previous
studies, there is sufficient water in storage in the SVA and available from annual recharge to serve
all the proposed uses without injuring the groundwater resource.
The groundwater levels in the SVA will experience seasonal and year to year fluctuations due to
variability in precipitation and snowpack inputs. Each of the subdivisions that pump water from
the SVA have a long term vested interest in a comprehensive groundwater monitoring plan to
understand baseline and future groundwater conditions. A groundwater monitoring plan is
currently being developed for implementation by these water users.
Development Case No.
Annual
Diversion
(AF)
Annual
Depletion
(AF)
Spring Valley Ranch 98CW256 1457.0 974.0
Los Amigos (Elk Springs and Pinyon Mesa)98CW312 159.8 117.0
Colorado Mountain College 99CW99 132.3 53.1
Lake Springs Ranch/Berkeley W-3571 105.2 97.6
Individual Lot Owners N/A 30.0 10.0
Lookout Mountain Ranch 84CW100 36.0 11.0
Grand Total 1920.3 1262.8
!(
!(!(
!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(!(
!(
!(
C
a
ttl
e
Creek
LandisCreek
LandisC reek
F i s h e r Creek
D
e
v
i
l
s
H
o
l
e
C
r
e
e
k
Ca t t le Creek
D
eadmansCreek
Me
s
a
C
r
e
e
k
Bear Creek
Grindsto
n
e
C
r
e
e
k
Old H
i
g
h
w
a
y
8
2
C
M
C
CM
C
Cottonwood
Pass
Old Dump
C
o
r
y
e
l
l
Fis
h
e
r
Ce
m
e
t
e
r
y
Kin
d
a
l
l
Cottonwood Pass
H
a
r
d
w
i
c
k
B
r
i
d
g
e
Fi
s
h
e
r
C
r
e
e
k
Loo
k
o
u
t
M
o
u
n
t
a
i
n
R
e
d
C
a
n
y
o
n
Source: Esri, Maxar, Earthstar Geographics, and the GIS UserCommunity4
Legend
Yield (gpm)
Yield
!(0 - 10
!(11 - 25
!(26 - 75
!(76 - 200
!(201 - 400
Spring Valley Aquifer
SVA_Tributary_Area
CountyRoads040711
Spring Valley Holdings LLCAll_Named_NHDFlowline
FType
Rivers
Ditches
Connector
Pipeline
Streams
Document Name: SpringValleyRanchAquifer.mxd
Drawn by: WR Approved by: WR Date: 4/5/2024
PO Box 1301Rifle, CO 81650Tel 970-625-4933
1,
4
0
0
2,
8
0
0
0
Graphic Scale in Feet
Client:
Figure:Spring Valley Aquifer and Wells
Vicinity Map 1
1273: Spring Valley Ranch
C
a
ttl
e
Creek
LandisCreek
LandisC reek
F i s h e r Creek
D
e
v
i
l
s
H
o
l
e
C
r
e
e
k
Ca t t le Creek
D
eadmansCreek
Me
s
a
C
r
e
e
k
Bear Creek
Grindsto
n
e
C
r
e
e
k
Old H
i
g
h
w
a
y
8
2
C
M
C
CM
C
Cottonwood
Pass
Old Dump
C
o
r
y
e
l
l
Fis
h
e
r
Ce
m
e
t
e
r
y
Kin
d
a
l
l
Cottonwood Pass
H
a
r
d
w
i
c
k
B
r
i
d
g
e
Fi
s
h
e
r
C
r
e
e
k
Loo
k
o
u
t
M
o
u
n
t
a
i
n
R
e
d
C
a
n
y
o
n
Source: Esri, Maxar, Earthstar Geographics, and the GIS UserCommunity4
Legend
Spring Valley Aquifer
SVA_Tributary_Area
CountyRoads040711All_Named_NHDFlowline
FType
Rivers
Ditches
Connector
Pipeline
Streams
Ql
Tb
PPM
Document Name: SpringValleyRanchAquifer.mxd
Drawn by: WR Approved by: WR Date: 4/4/2024
PO Box 1301Rifle, CO 81650Tel 970-625-4933
1,
4
0
0
2,
8
0
0
0
Graphic Scale in Feet
Client:
Figure:Spring Valley AquiferGeologic Units 2
1273: Spring Valley Ranch
20-25"
>25"
<20"
C
a
ttl
e
Creek
LandisCreek
LandisC reek
F i s h e r Creek
D
e
v
i
l
s
H
o
l
e
C
r
e
e
k
Ca t t le Creek
D
eadmansCreek
Me
s
a
C
r
e
e
k
Bear Creek
Grindsto
n
e
C
r
e
e
k
Old H
i
g
h
w
a
y
8
2
C
M
C
CM
C
Cottonwood
Pass
Old Dump
C
o
r
y
e
l
l
Fis
h
e
r
Ce
m
e
t
e
r
y
Kind
a
l
l
Cottonwood Pass
H
a
r
d
w
i
c
k
B
r
i
d
g
e
Fi
s
h
e
r
C
r
e
e
k
Loo
k
o
u
t
M
o
u
n
t
a
i
n
R
e
d
C
a
n
y
o
n
Source: Esri, Maxar, Earthstar Geographics, and the GIS UserCommunity4
Legend
Spring Valley Aquifer
SVA_Tributary_Area
CountyRoads040711
All_Named_NHDFlowline
FType
Rivers
Ditches
Connector
Pipeline
StreamsPrecipitation
inches
20
25
30
Document Name: SpringValleyRanchAquifer.mxd
Drawn by: WR Approved by: WR Date: 4/4/2024
PO Box 1301Rifle, CO 81650Tel 970-625-4933
1,
4
0
0
2,
8
0
0
0
Graphic Scale in Feet
Client:
Figure:Spring Valley Aquifer1990-2020 Normal Precipitation (in)3
1273: Spring Valley Ranch
C
a
ttl
e
Creek
LandisCreek
LandisC reek
F i s h e r Creek
D
e
v
i
l
s
H
o
l
e
C
r
e
e
k
Ca t t le Creek
D
eadmansCreek
Me
s
a
C
r
e
e
k
Bear Creek
Grindsto
n
e
C
r
e
e
k
Old H
i
g
h
w
a
y
8
2
C
M
C
CM
C
Cottonwood
Pass
Old Dump
C
o
r
y
e
l
l
Fis
h
e
r
Ce
m
e
t
e
r
y
Kin
d
a
l
l
Cottonwood Pass
H
a
r
d
w
i
c
k
B
r
i
d
g
e
Fi
s
h
e
r
C
r
e
e
k
Loo
k
o
u
t
M
o
u
n
t
a
i
n
R
e
d
C
a
n
y
o
n
Source: Esri, Maxar, Earthstar Geographics, and the GIS UserCommunity4
Legend
Spring Valley Aquifer
SVA_Tributary_Area
CountyRoads040711All_Named_NHDFlowline
FType
Rivers
Ditches
Connector
Pipeline
Streamsnlcd_co_utm13_Clip
NLCD_Land
Open Water
Developed, Open Space
Developed, Low Intensity
Developed, Medium Intensity
Developed, High Intensity
Deciduous Forest
Evergreen Forest
Mixed Forest
Shrub/Scrub
Herbaceous
Hay/Pasture
Cultivated Crops
Woody Wetlands
Emergent Herbaceous Wetlands
Document Name: SpringValleyRanchAquifer.mxd
Drawn by: WR Approved by: WR Date: 4/4/2024
PO Box 1301Rifle, CO 81650Tel 970-625-4933
1,
4
0
0
2,
8
0
0
0
Graphic Scale in Feet
Client:
Figure:Spring Valley AquiferNational Land Cover Data 4
1273: Spring Valley Ranch
In‐House Domestic
Irrigation
Total
Diversion In‐House Domestic
Irrigation
Total
Depletion
Jan 100% 23.1 0.0 23.1 1.5 0.0 1.5
Feb 100% 21.1 0.0 21.1 1.3 0.0 1.3
Mar 100% 23.1 0.0 23.1 1.5 0.0 1.5
Apr 100% 22.4 16.9 39.3 1.4 13.5 14.9
May 100% 23.1 27.0 50.1 1.5 21.6 23.1
Jun 100% 22.4 41.6 64.0 1.4 33.3 34.7
Jul 100% 23.1 47.3 70.4 1.5 37.8 39.3
Aug 100% 23.1 39.4 62.5 1.5 31.5 33.0
Sep 100% 22.4 24.8 47.2 1.4 19.8 21.3
Oct 100% 23.1 3.4 26.5 1.5 2.7 4.2
Nov 100% 22.4 0.0 22.4 1.4 0.0 1.4
Dec 100% 23.1 0.0 23.1 1.5 0.0 1.5
Total 272.7 200.4 473.1 17.2 160.3 177.5
EQR 695
Gal/EQR/day 350
Domestic Irrigation (ac)90
Lawn/Golf/Open Space Unit
Irrigation Diversion (AF/ac)2.24
Lawn/Golf/Open Space Unit
CU (AF/ac)1.79
Lawn/Golf/Open Space
Efficiency %80%
Domestic Depln (%)6.3%
Table 3: Potable Demands
Diversions (AF)Depletion (AF)
% Occupancy
Month
Diversions_Depletions
Jan 0.0 0 0.0 0 0 0
Feb 0.0 0 0.0 0 0 0
Mar 0.0 1.9 1.9 0 1.9 1.9
Apr 78.8 4.1 82.9 63.04 4.1 67.14
May 126.0 7 133.0 100.8 7 107.8
Jun 194.3 9.6 203.9 155.44 9.6 165.04
Jul 220.5 9.8 230.3 176.4 9.8 186.2
Aug 183.8 7.2 191.0 147.04 7.2 154.24
Sep 115.5 5.5 121.0 92.4 5.5 97.9
Oct 15.8 3.1 18.9 12.64 3.1 15.74
Nov 0.0 1 1.0 0 1 1
Dec 0.0 0 0.0 0 0 0
Total 934.7 49.2 983.9 747.76 49.2 796.96
Irrigated Area (ac)420
Evaporation Area (ac)24
Table 4: Non‐Potable Demands
Month Pond
Evaporation
Non‐Domestic
Irrigation Total
Diversions (AF)
Non‐
Domestic Pond Evaporation Total
Depletions (AF)
Diversions_Depletions
In‐House Irrigation Evap Total In‐House Irrigation Evap Total
Jan 23.1 0.0 0 23.1 1.5 0.0 0 1.5
Feb 21.1 0.0 0 21.1 1.3 0.0 0 1.3
Mar 23.1 0.0 1.9 25.0 1.5 0.0 1.9 3.4
Apr 22.4 95.7 4.1 122.2 1.4 76.6 4.1 82.1
May 23.1 153.0 7 183.1 1.5 122.4 7 130.9
Jun 22.4 235.9 9.6 267.9 1.4 188.7 9.6 199.7
Jul 23.1 267.8 9.8 300.7 1.5 214.2 9.8 225.5
Aug 23.1 223.2 7.2 253.5 1.5 178.6 7.2 187.2
Sep 22.4 140.3 5.5 168.2 1.4 112.2 5.5 119.2
Oct 23.1 19.2 3.1 45.4 1.5 15.4 3.1 19.9
Nov 22.4 0.0 1 23.4 1.4 0.0 1 2.4
Dec 23.1 0.0 0 23.1 1.5 0.0 0 1.5
Total 272.66 1135.10 49.20 1456.96 17.18 908.08 49.20 974.46
Table 5: Total Potable and Non‐Potable Demands
Month Total Diversion Total Depletion
Diversions_Depletions
Page 1 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
November 27, 2024 (updated January 9, 2025)
Storied Development LLC
c/o Jeff Butterworth
Via: JButterworth@storiedliving.com
RE: Spring Valley Ranch – Response to Matrix Design Group, Inc. Review Letter – Aquifer
Sustainability and Well Yield Physical Water Supply
Dear Jeff:
At the request of Storied Development, LLC, this letter presents the technical response to questions
and comments provided by Matrix Design Group, Inc. (“Matrix”) in its September 6, 2024 review letter
for Garfield County. Colorado River Engineering, Inc. (“CRE”) is addressing comments 1, 2, 3, and 5.
Comments 4, 6, and 7 are addressed by Roaring Fork Engineering (“RFE”) in a separate response. The
January 9, 2025 update to this letter is reflected in the responses to Comment No. 2 and provides
reference to the final LRE Water report dated March 8, 2025.
SUMMARY
The responses below provide information on 15 wells that have been drilled on the Spring Valley Ranch
project property. Pumping tests on 9 wells demonstrate that Spring Valley Ranch has an adequate
physical water supply for the project and 18 additional wells can be developed on the property. In
addition, the Spring Valley Aquifer is a known groundwater resource specifically recognized by the
Colorado Division of Water Resources. The Spring Valley Aquifer has been characterized by private
consultants, the Colorado Geological Survey, and the US Geological Survey. The sustainability of the
aquifer has been analyzed and peer reviewed by numerous consultants. CRE has provided a current
analysis with more refined data and analysis incorporating drier and hotter climate conditions that
demonstrates the groundwater resource can supply the anticipated future demands of the Spring Valley
Project and other existing/future projects.
Spring Valley Ranch owns all of the water rights on Landis Creek. There is no local call from senior
water rights on Landis Creek or Red Canyon Creek. Spring Valley Ranch is in BWCD Contract Service
Area A and is subject only to a downstream call on the Roaring Fork or Colorado Rivers. Releases
from Ruedi Reservoir pursuant to BWCD Contract Nos. 43 and 328 and the decrees in Case Nos.
84CW212, 98CW255, and 22CW3009 will augment downstream depletions on the Roaring Fork or
Colorado Rivers.
Spring Valley Ranch has demonstrated an adequate legal and physical water supply for the project.
Page 2 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
Comment 1 – Spring Valley Aquifer Physical Water Supply
The Matrix comment seeks additional information on the geology and characterization of the Spring
Valley Aquifer (“SVA”) groundwater resource. Matrix also makes an observation that the area is dry
arid climate with limited surface streamflows and Consolidated Reservoir in the adjacent drainage has
very little storage throughout the year. In response, it should be noted that the annual precipitation for
the tributary area for the SVA ranges from 16 inches to 30 inches. The surface soils and geology have
a high infiltration rate. Consolidated Reservoir is an irrigation reservoir that is full or could be full, usually
at the start of the irrigation season, but then continually drops in storage due to evaporation, seepage,
and irrigation releases. Thus, it is not an indicator of “limited streamflows” in the area.”
The SVA has been studied and characterized by Jerome Gamba and Associates in its March 10, 2000
report titled The Spring Valley Hydrologic System and by the Colorado Geological Survey/US
Geological Survey in the Geological Society of America Special Paper 366, 2002 titled Evaporite
Tectonism in the Lower Roaring Fork Valley, West Central Colorado. (Copies attached in Appendix A).
The Gamba study is summarized in the April 11, 2024 CRE report titled Spring Valley Aquifer
Sustainability Study. The CGS/USGS report utilizes data from the Spring Valley Ranch wells and
confirms the geological characterization presented by Gamba. The SVA is located in a closed basin
created by a collapse in the underlying Eagle Valley Evaporite which caused the Maroon formation
bedrock to shear at a fault line on the west side of the valley. The CGS/USGS report also provides an
alternative theory that a large block of the Maroon formation “rafted” toward the Roaring Fork River
Valley, leaving behind a closed basin. In both scenarios, the closed basin was a lake that filled with
alluvial, lacustrine (lake), and colluvial deposits creating a groundwater resource. The CGS/USGS
report states that “When early settlers first homesteaded this region, Spring Valley was a closed
depression and a lake occupied much of the valley floor (Calvin Cox, 1994, personal commun.). The
presence of lacustrine sediments beneath much of the valley supports this conclusion. The settlers
hand dug a drain ditch at the north end of the valley shortly before the end of the 19th century, drained
the lake, and turned the valley floor into agricultural land.” The characterization of the SVA is visually
presented in the attached Figures 1 and 2 from the two reports.
Due to the collapse or rafting of the bedrock, the land surrounding the basin became over-steepened
and experienced landslides. The resulting landslide deposits with large scarps or benches are
unconsolidated material containing large blocks of basalt and bouldery basalt rubble. The landslide
deposits and underlying fractured Maroon formation provide “upland aquifers” that are tributary to the
SVA. The surface and subsurface flow of water is towards the SVA. This conclusion, visually shown
on Figures 1 and 2, is supported by springs that emerge from the hillside to the east, wells drilled into
these “upland aquifers”, and a groundwater ridge to the west on Los Amigos Mesa and to the north on
Lookout Mountain. A continuous groundwater gradient to the southwest towards CMC, and to the
northwest towards Red Canyon, appear to be the discharge areas out of the SVA, into the Maroon
Page 3 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
formation, and ultimately to the Roaring Fork River. The aquifer deposits appear to seal the fault on the
west end of the SVA.
The SVA and the adjacent upland aquifers to the east have a significant amount of pore space storage
of groundwater. Gamba conservatively estimated that the SVA has between 38,000 and 46,000 acre
feet of storage and the upland aquifers have between 30,000 and 60,000 acre feet of storage. HRS
Water Consultants, Inc. peer reviewed the Gamba report in a March 10, 2000 letter (see Appendix A)
and estimated there is a total of 82,000 acre feet of storage in the Spring Valley area aquifers.
HRS also analyzed soils data and determined that the soils have high infiltration rates and low soil
moisture holding capacity, supporting the conclusion that a significant amount of the precipitation
infiltrates the soils and reaches the groundwater. Water is not tied up and trapped in the soil on a
cumulative basis year after year. HRS concluded that the average aquifer recharge rate is estimated
at 4,700 acre feet per year.
The CRE aquifer sustainability report estimated the annual recharge at approximately 3,950 acre feet
per year. This analysis includes several conservative assumptions. First, the full annual amount of ET
from vegetation was assumed to deplete the available precipitation inputs, regardless of whether water
was available in soil moisture and available to plants or not. Based on the low soil moisture holding
capacity and the distribution of precipitation throughout the year, adequate soil moisture would not be
available throughout the growing season. This assumption can account for water tied up in the soil that
is ultimately lost from the system. Second, the surface water runoff in Landis Creek that leaves the
basin down Red Canyon (600 acre feet apparently based on the WWE observations) is significantly
overstated and likely includes runoff from the Red Canyon Creek basin not tributary to Spring Valley.
In addition, any surface water flowing through Spring Valley to the northwest is diverted and used to
flood irrigate hay and pasture land. A portion of this surface flow will return to the groundwater after
application to the ground for irrigation. In addition, the ET depletions from the ground cover within the
tributary basin includes irrigation that occurs with the surface water flow.
The CRE aquifer sustainability study (and prior studies) do not include an estimate for discharge from
the aquifer in the comparison of water demands and annual recharge because the aquifer is a flow
through system with significant storage. The rate of discharge to the Roaring Fork River is likely a
function of the aquifer elevation, the higher the elevation the larger the ground water gradient controlling
the flow of groundwater.
Comment 2 – Existing Well Yield
The Matrix comment questions whether the pumping tests conducted by LRE Water demonstrate firm
yields as presented in the March 8, 2023 LRE Water report titled Spring Valley Ranch Physical Water
Supply Report. Matrix identified a concern with large drawdown of 340 feet in one of the wells. In
Page 4 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
response, the actual drawdown in SVH Well No. 10 was 245 feet, the 340-foot number was the depth
to groundwater. The large drawdown was due to the initial pumping rate of 40 gpm and the average
pumping rate of 11 gpm in a well that yields about 10 gpm. Regardless, SVR Well No. 10 will not be
used as a production well for the project.
The proposed water supply plan for the potable water system outlined by RFE is to develop at least 315
gpm from wells on the Middle Bench and on the mountain. The 315 gpm represents the maximum peak
day demand in June and July. During this time frame, the aquifer recharge from snowmelt is at higher
rates and well yields are anticipated to be higher than during the winter months when pumping tests
have been conducted on the wells.
As described below, there are five existing wells drilled on the Middle Bench with a long-term yield
estimated at 205 gpm. There is an existing well on the mountain below Hopkins Reservoir with a yield
of 75 gpm for a total of 280 gpm. Spring Valley Ranch can develop two additional decreed wells on the
Middle Bench, and has the right to develop up to 18 additional wells on the property. The additional
capacity can be added in the future when the project builds out and the water demand requires
additional supply.
In addition, there are three high capacity SVA wells. The three wells have been tested with a combined
long-term yield of approximately 600 gpm. Additional high-capacity wells can be developed in the SVA.
It is proposed to use the SVA wells to provide supplemental irrigation water for open space and golf
course areas, and to supply the snowmaking demand.
Fifteen wells have been drilled on the Spring Valley Ranch property to characterize the sub surface
geology and to evaluate the yield of wells in the SVA and the adjacent upland aquifers. The locations
of the wells are shown on the attached Figure 3. Pumping tests of these wells have occurred during
winter months when the seasonal groundwater elevations are lowest and the recharge is low. LRE
Water conducted pumping tests in the winter of 2022/2023 on eight of the wells, including one in the
SVA, five on the Middle Bench, and two in the upper mountain. RFE conducted pumping tests on one
Middle Bench well and one SVA well in 2021. WWE conducted pumping tests on three Middle Bench
wells in 1998, 1999 and 2000, and one SVA well in 2000. A summary of the well permits, well
construction data, and pumping tests is provided on the attached Table 1.
WWE conducted a 2 week pumping test on SVR Well No. 6 from February 29, 2000 – March 13, 2000.
The results are summarized in the attached March 21, 2000 letter and indicate a 250 gpm plus yield
from the SVA with pumping effects observed in a well 500 feet away, but not in a well 700 feet away.
WWE conducted several 24-hour tests in 1998 and 1999 on Middle Bench wells SVR Well No. 20
(Gamba No. 1), ASR Well No. 13 (Gamba No. 3), and ASR Well No. 14 (Gamba No. 4). WWE then
conducted testing in winter of 2000 for 11 days on SVR Well No. 20, for 36 days on ASR Well No. 13,
Page 5 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
and for 16 days on ASR Well No. 14. WWE opined that the wells had reliable yields of 30 gpm, 75 gpm,
and 30 gpm respectively for a total of 135 gpm.
RFE conducted 24-hour pumping tests on SVR Well No. 17 and SVR Well No. 20 in the fall of 2021.
SVR Well No. 17 is in the SVA, was pumped at 95 gpm, and can reliably yield at least 95 gpm. SVR
Well No. 20 is on the Middle Bench, was pumped at 65 gpm, and can reliably yield at least 30 gpm as
indicated in the WWE testing.
LRE Water conducted 24-hour pumping tests on 8 wells as described in the March 8, 2023 report
submitted with the current application to Garfield County. The SVA well tested by LRE Water was Spring
Valley Well No. 1. The LRE Water report data indicates that this SVA well can reliably yield at least
250 gpm and can pump at rates up to 550 gpm.
Well 36569-MH located on the mountain below Hopkins Reservoir was pumped at 100 gpm and could
reliably yield at least 75 gpm. The LRE analysis indicates that the well could be pumped at rates up to
195 gpm.
The Middle Bench wells have estimated long-term yields as follows. SVR Well No. 10 was pumped at
an average rate of 11 gpm and could reliably yield approximately 10 gpm. SVR Well No. 14 was
pumped at an average rate of 10 gpm and has a reliable yield of at least 30 gpm as indicated in prior
testing by WWE. SVR Well No. 15 was pumped at an average rate of 79 gpm and has a reliable yield
of at least 50 gpm. ASR Well No. 16 was pumped at an average rate of 54 gpm and appears to have
a reliable yield of approximately 20 gpm. SVR Well No. 20 was pumped at an average rate of 52 gpm
and confirms a reliable yield of at least 30 gpm. The LRE analysis indicates that the Middle Bench wells
could be pumped at rates up to more than 400 gpm.
The above pumping tests indicate that the SVA wells yield approximately 600 gpm. The current wells
on the Middle Bench have a reliable yield estimated at approximately 205 gpm. In addition, the
mountain well below Hopkins Reservoir adds another 75 gpm for a total of 280 gpm for the central
potable water system. The Spring Valley Ranch can develop one or two additional wells on the Middle
Bench at some point in the future when the potable water system demand requires additional supplies.
In the event the Middle Bench wells do not provide the full buildout potable water supply, one of the
SVA wells can be added to the potable water system. The pumping tests demonstrate that the
groundwater resources on the property are adequate to provide the physical water supply for the project.
Additional high capacity SVA wells can be developed and up to 18 additional wells can be drilled on the
property.
The LRE Water pumping tests and the RFE pumping tests included laboratory analysis of water
samples from the wells. The water quality results indicate that the groundwater resource is suitable for
Page 6 of 7
Colorado River Engineering
P.O. Box 1301
Rifle, CO 81650
(970) 625-4933
drinking water. The RFE Water Supply and Distribution report dated February 2, 2023 (updated
December 3, 2024) provides more detail.
Spring Valley Ranch has demonstrated an adequate physical water supply for the project.
Comment 3 – Irrigation Demand
The Matrix comment is that the annual consumptive use rate of 1.79 AF/acre stated in the Legal Water
Supply Report is low. There appears to be a consumptive use rate of 2.13 AF/acre in one report, there
is an apparent inconsistency in irrigation efficiency (67% vs 80%), an inconsistency in the peak daily
application rate (0.12 inch vs 0.22 inch), and an inconsistency in the golf course acreage (100 acres vs
124 acres).
The Legal Water Supply Report presents the decreed consumptive use rate of 1.79 AF/acre as decreed
in Case No. 98CW254 for the project and the value was based on the cooler and wetter climate data in
the 1990’s. The engineering tables are based on a consumptive use rate of 2.13 AF/acre (calculated
using climate data through 2020) and an irrigation efficiency of 80%. The Golf Course can have up to
124 acres of irrigation, which equates to a demand of 329 AF using 2.13 AF/acre and 80% irrigation
efficiency. The 100 acres in the RFE report was a typo and Matrix back calculated an efficiency of 67%
based on 100 acres of irrigation. The application of 0.12 inch in July in the RFE report appears to be a
typo. CRE agrees that the estimated water demand is 0.22 inch per day in July.
Comment 5 – Legal Water Supply
The Matrix comment raises questions about a local water rights administrative call on Landis Creek and
the flow of water in Landis Creek downstream from the project. Landis Creek terminates in Spring
Valley. The potential flow of water to the north is a ditch that could convey high flows from runoff into
Red Canyon Creek. Red Canyon Creek only flows during snowmelt and rainstorm runoff events.
Spring Valley Ranch owns all of the water rights on Landis Creek. There is no local call from senior
water rights on Landis Creek or Red Canyon Creek. Spring Valley Ranch will sweep the flow in Landis
Creek at its historic headgate consistent with historic irrigation practices. Spring Valley Ranch is in
BWCD Contract Service Area A and is subject only to a downstream call on the Roaring Fork or
Colorado Rivers. Releases from Ruedi Reservoir pursuant to BWCD Contract Nos. 43 and 328 and
the decrees in Case Nos. 84CW212, 98CW255, and 22CW3009 will augment downstream depletions
on the Roaring Fork or Colorado Rivers.
Spring Valley Ranch has demonstrated an adequate legal water supply for the project.
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 91
Figure 16. Schematic cross sections (E–E) showing two possible interpretations of the subsurface geology through Spring Valley. Upper cross
section depicts the Spring Valley structure as a half graben chiefly due to removal of evaporite from beneath the valley by dissolution. In the
lower cross section, the Spring Valley structure is shown as a pull-apart feature caused by evaporite flow toward the Roaring Fork River valley.
Location of cross section shown on Figure 2.
model, the sediment deposited in the Spring Valley structure
would directly overlie evaporite.
Strain along the southern margin of thehypothesizedrafted
block may be largely lateral shearing. The strain would occur
as sinistral-strike slip or oblique slip along a narrow, arcuate
fault zone that starts in the southeast corner of the structure,
bends to a nearly west trend, and disappears into the evaporitic
rocks that crop out beneath the volcanic rocks on the east wall
of the river valley (Fig. 2). Lateral strain on thenorthernmargin
of a rafted Spring Valley structure would in part be accom-
modated by thenarrow grabenthatextendsnorthwestwardfrom
Spring Valley and in part by the complex fault swarm between
the graben and the river valley.
Minor structures.Several small synclinal sags deform the
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdf
by Colorado School of Mines user
on 31 March 2022
FIGURE 1
C
a
ttl
e
Creek
LandisCreek
LandisC reek
F i s h e r Creek
D
e
v
i
l
s
H
o
l
e
C
r
e
e
k
Ca t t le Creek
D
eadmansCreek
Me
s
a
C
r
e
e
k
Bear Creek
Grindsto
n
e
C
r
e
e
k
Old
H
i
g
h
w
a
y
8
2
C
M
C
CM
C
Cottonwood
Pass
Old Dump
C
o
r
y
e
l
l
Fis
h
e
r
Ce
m
e
t
e
r
y
Ki
n
d
a
l
l
Cottonwood Pass
H
a
r
d
w
i
c
k
B
r
i
d
g
e
Fi
s
h
e
r
C
r
e
e
k
Lo
o
k
o
u
t
M
o
u
n
t
a
i
n
R
e
d
C
a
n
y
o
n
Source: Esri, Maxar, Earthstar Geographics, and the GIS User
Community4
Legend
Spring Valley Aquifer
SVA_Tributary_Area
CountyRoads040711All_Named_NHDFlowline
FType
Rivers
Ditches
Connector
Pipeline
Streams
Ql
Tb
PPM
Document Name: SpringValleyRanchAquifer.mxd
Drawn by: WR Approved by: WR Date: 4/4/2024
PO Box 1301Rifle, CO 81650Tel 970-625-4933
1,
4
0
0
2,
8
0
0
0
Graphic Scale in Feet
Client:
Figure:Spring Valley AquiferGeologic Units 2
1273: Spring Valley Ranch
Spring Valley RanchMap Key
Garfield County Parcels
Property Line
Spring Valley Holdings LLC
Well Location Source
!(Alta Survey 2022
!(LRE GPS 2022
!(WWE Well Map 2001
!(Not Drilled (Decreed)
Data Sources:
U.S. Bureau of Land Management
U.S. Census Bureau
U.S. Department of Agriculture
U.S. Geological Survey
CO Department of Water Resources
CO Department of Transportation
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
!(
36567-MH
(Gamba #5)
36569-MH
(Gamba #6)
36760-MH
ASR Well No. 15
(Gamba #1A)
51363-F
Spring Valley Ranch
Well No. 2 56722-F
SVH Well No. 10
86627-F
SVR Well No. 17
(WELL #03-2A)
86628-F
SVR Well No. 20
(Gamba #1)
86629-F
ASR Well No. 16
(Gamba #8)
86630-F
Spring Valley
Well No. 1
86631-F
Spring Valley Ranch
Well No. 3
76874-F
SVR Well No. 21
66298-F
ASR Well No. 13
(Gamba #3)
66299-F
ASR Well No. 14
(Gamba #4)
56717-F
SVH Well No. 5
56719-F
SVH Well No. 7
56720-F
SVH Well No. 8
56721-F
SVH Well No. 9
68886-F
SVR Well No. 19
68887-F
SVR Well No. 18
251164-
WELL #03-1251165-
WELL #03-2
251166-
WELL #03-3
35164-MH
Gamba #2
68889-F
SVH Well No. 6
Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community
Document Name: Figure 3 - SVR Well Inventory.mxdDrawn by: JT
Figure:
PO Box 1301Rifle, CO 81650Tel 970-625-4933 Client:Date: 11/21/2024Approved by: MG
3
1273
Well Inventory
:
1,
0
0
0
2,
0
0
0
0
Graphic Scale in Feet
Legal Name Shown on Maps by 1,2,3,4,5,6 Permit No. Associated Permit Associated Case Status UTMX UTMY Applicant
Well
Depth (ft)
Yield
(gpm)
Static Water
Level (ft)
Total Depth
(ft)Yield (gpm)Static Water
Level (ft)Yield (gpm)Static Water
Level (ft)
Field Well
Depth (ft)
Static Water
Level (ft)
Top of
Casing (in)
Spring Valley Well No. 1 LRE, WWE, CRE, Alta Survey 86630-F 23334-F, 28959-F, 324058-,
56716-F, 51362-F
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 307104.8 4375360.0
SPRING VALLEY HOLDINGS
LLC (ARDENNE, MARTIN V.)305 300 18 300 22 360 18.8 17
Spring Valley Ranch Well No. 2 LRE, WWE, CRE, Alta Survey 51363-F 12722-AD, 28960-F, 23679-
F
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 307215.3 4375575.2
SPRING VALLEY
DEVELOPMENT INC 0 0 0 20 6 207 4.6 4
Spring Valley Ranch Well No. 3 LRE, WWE, CRE, Alta Survey 86631-F 96896-, 23518-F, 28961-F,
52185-F
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 306850.4 4375444.8
SPRING VALLEY HOLDINGS
LLC (ARDENNE, MARTIN V.)111 20 25 10 44 69.4 39.7 17.5
SVR Well No. 17 LRE, Alta Survey 86627-F 66297-F, 251755-, 324057- 22CW3009
Well
Constructed 307746.9 4374255.8
SPRING VALLEY HOLDINGS
LLC (ARDENNE, MARTIN V.)320 100+ 9 75 - 300
0 and flowing
out 30
SVR Well No. 21 LRE 76874-F 67700-F, 276909- 22CW3009
Well
Constructed 307176.5 4375951.5
LAGIGLIA LOUIS &
DONNALYNE 80 10 43 - - - 52 -
SVR Well No. 20 (Gamba #1) LRE, WWE, Alta Survey 86628-F 68885-F, 34995-MH,
324055-, 66562-F 22CW3009 Well
Constructed 310198.7 4375286.2
SPRING VALLEY HOLDINGS
LLC (ARDENNE, MARTIN V.)223 95 105 220 30 107 51.69 113 250.3 110.8 13.5
ASR Well No. 13 (Gamba #3) LRE, WWE, CRE, Alta Survey 66298-F 35174-MH 82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 309141.1 4376515.5
SPRING VALLEY HOLDINGS
LLC 200 90 140 202 75+ 138 - - 212 143.1 32
ASR Well No. 14 (Gamba #4) LRE, WWE, CRE, Alta Survey 66299-F 35175-MH 82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 309490.1 4376213.5
SPRING VALLEY HOLDINGS
LLC 180 90 134 182 30-50 137 10 143.6 181.5 114 28
ASR Well No. 15 (Gamba #1A) LRE, WWE, CRE, Alta Survey 36760-MH -82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 310264.6 4375236.5 SPRING VALLEY DEV INC 220 100 105 100 112.8 209.6 111.5 18.5
ASR Well No. 16 (Gamba #8) LRE, CRE, Alta Survey 86629-F 245477-, 66563-F, 68888-F,
324056-
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 308943.8 4377148.5
SPRING VALLEY HOLDINGS
LLC (ARDENNE, MARTIN V.)260 50 23 60 20.25 152 18.9 21
35164-MH (Gamba #2) LRE, Alta Survey 35164-MH 251166-, Possibly 31598- -
Well
Constructed 311097.7 4374426.6 ASPEN SPRINGS RANCH 455 55 330 - - 364 320.6 18.5
36567-MH (Gamba #5) LRE, WWE, Alta Survey 36567-MH - -
Well
Constructed 310413.6 4378043.2 SPRING VALLEY DEV INC 250 6 70 7.7 89
36569-MH (Gamba #6) LRE, WWE, Alta Survey 36569-MH 35171-MH -
Well
Constructed 310020.7 4378457.2 SPRING VALLEY DVLP INC 163 70 10 100 20 175 8.9 -
SVH Well. No 6 WWE, CRE, Alta Survey 68889-F 51365-F, 28963-F, 56718-F,
12725-AD
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009 Permit Issued 306963.3 4375306.4
SPRING VALLEY HOLDINGS
LLC 400 250 125 470 0 4.4
SVH Well. No 10 LRE, CRE, Alta Survey 33819-MH 28967-F, 51369-F, 10102-
AD, 12729-AD, 56722-F
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009
Well
Constructed 309862.5 4375250.1 SPRING VALLEY RANCH 360 15 90 11.4 95.7 346 121.4 -
SVH Well. No 5 CRE, Alta Survey 56717-F 28962-F, 51364-F 82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009 Permit Issued 307250.7 4375474.5
SPRING VALLEY
DEVELOPMENT INC
SVH Well. No 7 CRE, Alta Survey 56719-F 28964-F, 51366-F 82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009 Permit Issued 307359.8 4375712.9
SPRING VALLEY
DEVELOPMENT INC
SVH Well. No 8 CRE, Alta Survey 56720-F 28965-F, 51367-F 82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009 Permit Issued 309498.0 4375620.9
SPRING VALLEY
DEVELOPMENT INC
SVH Well. No 9 CRE, Alta Survey 56721-F 28966-F, 51368-F, 10101-
AD
82CW0075, 84CW0212, 87CW0155, 98CW0255,
98CW0254, W3298, 22CW3009 Permit Issued 309600.8 4375527.3
SPRING VALLEY
DEVELOPMENT INC
SVR Well No. 18 Alta Survey 68887-F 66560-F 22CW3009 Permit Issued 307602.9 4374224.2
SPRING VALLEY HOLDINGS
LLC
SVR Well No. 19 Alta Survey 68886-F 66561-F 22CW3009 Permit Issued 307633.3 4374072.8
SPRING VALLEY HOLDINGS
LLC
SVR Ranch House DWR only 274091-- -
Well
Constructed 307133.0 4375953.7
SPRING VALLEY HOLDINGS
LLC 80 15 46
Well #03-1 Alta Survey 251164-- -
Well
Constructed 308523.6 4373784.9
SPRING VALLEY
DEVELOPMENT INC 280 50 92
Well #03-2 Alta Survey 251165-- -
Permit
Expired 307792.6 4373967.2
SPRING VALLEY
DEVELOPMENT INC
Well #03-3 Alta Survey 251166-- -
Permit
Expired 310496.7 4374895.5
SPRING VALLEY
DEVELOPMENT INC
Gamba #7 WWE
-- -
- - --
Data references:
1.)WWE - Report w/ Map "Spring Valley Upland Aquifer Pumping Tests - 2000" (2000-03-10) by Wright Water Engineers, Inc (Gamba Wells #1, 3, and 4 tested Jan/Feb 2000)
2.)WWE - Report w/ Map "Spring Valley Ranch Well No. 6" (2000-03-21) by Wright Water Engineers, Inc (SVR Well No. 6 tested Feb 29, 2000)
3.)LRE - Map "Spring Valley Ranch Well Locations and Pumping Test Rates", (2022-10-10) by LRE Water. Map shows Yield and Static Water Level of tested wells
4.)CRE - Map "Water Rights Summary Map", (2022-12-06) by Colorado River Engineering
5.)Alta Survey - Map obtained from Roaring Fork Engineering (data collected in 2022)
6.)DWR - Colorado Division of Water Resources data from well attribute tables and Well Construction Reports (data accessed October 2024)
7.)RFE - Table provided by Roaring Fork Engineering summarizing Static Water Level, Field Depth, and Top of Casing of tested wells (2024-10-22)
Table 1
Spring Valley Ranch Well Inventory
No Well Completion Report
RFE Measurement 2024 7
Not located - due to snow
Not Located - DNE
Possible duplicate of SVR Well No.
Well Description LRE Measurement 2022
3DWR Well Data 5 WWE Measurement 2000 1,2
Colorado River Engineering 11/21/2024
Geological Society of America
Special Paper 366
2002
73
Evaporite tectonism in the lower Roaring Fork River valley,
west-central Colorado
Robert M. Kirkham
Colorado Geological Survey, 5253 County Road 1 South, Alamosa, Colorado 81101, USA
Randall K. Streufert
Summit Geology and Consulting, Silverthorne, Colorado USA
Michael J. Kunk
James R. Budahn
Mark R. Hudson
William J. Perry Jr.
U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, Colorado 80225, USA
ABSTRACT
Evaporite tectonism in the lower Roaring Fork River valley in west-central Col-
orado has caused regional subsidence of a differentially downdropped area in the
southern part of the Carbondale collapse center during the late Cenozoic. A promi-
nent topographic depression coincides with this collapse area, and drainage patterns
within the collapse area contrast sharply with those outside of it. Miocene volcanic
rocks are downdropped asmuchas 1220 min the collapsearea.Muchofthestructural
lowering occurred along the margins of the collapse area. Major Laramide-age struc-
tures bound the east and west sides of the collapse area, but movement on these
structures during late Cenozoic collapse was in an opposite direction to their Lar-
amide movement. Within the interior part of the collapse area faults and folds have
as much as 300 m of structural relief. Large blocks of rock may be rafting into the
Roaring Fork River valley as underlying evaporite flows toward the valley. Sinkholes
arecommon in thecollapsearea,asareclosed,ornearlyclosed,structurallycontrolled
topographic depressions that are formed in both surficialdepositsandbedrock.Upper
Cenozoic deltaic and lacustrine deposits preserved on ridgelines and mesas document
the positions of former structural depressions that were initially filled with sediments
and later breached by erosion. At least 450 m of syn-collapse sediments accumulated
in a collapse depression on the north side of Mount Sopris. Complexly deformed and
brecciated deposits in the interior parts of the collapse center are interpreted as col-
lapse debris. Evaporite flow is an important element in the collapse process, and
during early stages of collapse it was perhaps the primary means of deformation.
Flow by itself, does not remove evaporite from the collapse area. Dissolution and
accompanying transport of dissolved constituents by groundwater and surface water
are the ultimate means by which evaporite exits the collapse area. Collapse continues
today, as evidenced by historic sinkholes and modern high-salinity loads in rivers and
thermal springs. Thick evaporite deposits still underlie much of the collapse area, so
collapse will likely continue in the future.
Kirkham, R.M., Streufert, R.K., Kunk, M.J., Budahn, J.R., Hudson, M.R., and Perry, W.J., Jr., 2002, Evaporite tectonism in the lower Roaring Fork River valley,
west-central Colorado,in Kirkham, R.M., Scott, R.B., and Judkins, T.W., eds., Late Cenozoic evaporite tectonism and volcanism in west-central Colorado:
Boulder, Colorado, Geological Society of America Special Paper 366, p. 73–99.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.74
Figure 1. Location map of the southern part of the Carbondalecollapse
center, lower Roaring Fork River valley (modified from Kirkham et
al., 2001b). Queries indicate locations where the collapse area bound-
ary is poorly constrained.
INTRODUCTION
Dissolution and flow of evaporitic rocks in the Pennsyl-
vanian Eagle Valley Evaporite during late Cenozoic time have
caused as much as 1220 m of differential subsidence in rocks
that overlie the evaporite. This structurally downdropped block
forms the southern part of the 1200 km
2 Carbondale collapse
center in the lower Roaring Fork River valley between the
towns of Glenwood Springs and Basalt (Fig. 1). Kirkham and
Scott (this volume) describe the conceptual model of evaporite
collapse and its relationships with surface water and ground-
water. Evaporite flow plays a major role in the collapse, and it
is responsible for lateral movement of large massesofevaporite
and causes subsidence in upland areas. However, dissolution is
the ultimate mechanism that removes evaporite from the col-
lapse area. Modern high salinity loads in rivers and springs
indicate that dissolution is active (Chafin and Butler, this vol-
ume; Kirkham and Scott, this volume).
Evaporitic rocks were first recognized in the region in the
late 1800s (A.R. Marvine in Peale, 1876). Subsequent geologic
investigations in the region reported on various aspectsofevap-
orite stratigraphy, depositional setting, and evidence of local-
ized evaporite tectonism and deformed upper Cenozoic rocks
and deposits. Kirkham and Scott (thisvolume)summarizethese
previous studies.
Evaporite tectonism, which includes the effects of both
flow and large-scale dissolution, has affected depositional pat-
terns and drainage systems in this area since shortly after the
evaporitic rocks were deposited (Freeman, 1971, 1972; Tweto,
1977). Kirkham and Streufert (1996) first reported regional late
Cenozoic collapse due to evaporitetectonisminthelowerRoar-
ing Fork River valley downstream of the town of Basalt (Fig.
1). The discovery of this regional collapse resulted from a
1:24000-scale geologic mapping program initiated by the Col-
orado Geological Survey (CGS) in 1993 and supported by geo-
chronologic, geochemical, and paleomagnetic studies by the
U.S. Geological Survey.
Geologic mapping provided the structuralandstratigraphic
background needed to recognize and understand the major ele-
ments of the collapse. Accurate correlation of upper Cenozoic
volcanic rocks in west-central Colorado was essential to char-
acterize many details of the collapse process and to constrain
the timing of the deformation.
40Ar/39Ar geochronologic dating
of 80 volcanic flows by Kunk and Snee (1998), Kunk et al.
(2001), and Kunk et al. (this volume) and geochemical and
isotopic studies of 220 samples by Unruh et al. (2001), fa-
cilitated the correlation of these rocks by Budahn et al. (this
volume). Average La/Yb and Hf/Ta ratios and preferred ages
for the compositional geochemical groups discussed in this pa-
per are listed in Table 1.
GEOLOGIC SETTING
The southern part of the Carbondale collapse center is de-
fined on at least three sides by major Laramide-age (Late Cre-
taceous to early Eocene) structures. The northern margin of the
collapse area is on the southern flank of the White River uplift,
the Basalt Mountain fault marks the eastern edgeofthecollapse
area, and theGrand Hogback monoclineformsthewesternside.
A long and narrow extension of the Carbondale collapse center
follows the monocline northwestward from near Glenwood
Springs (Scott et al., this volume). The southern margin of the
collapse center is poorly understood (Kirkham and Scott, this
volume), but is placed north of Mount Sopris.
The Middle and Upper Pennsylvanian Eagle Valley Evap-
orite crops out or underlies surficial deposits in the lower Roar-
ing Fork River valley downstream of Basalt, in the lower Crys-
tal River valley, in lower Cattle Creek, and on the south wall
of Glenwood Canyon upstream of Glenwood Springs (Fig. 1).
This formation, which consists of halite, gypsum, anhydrite,
clastic rocks, and carbonate rocks, was deposited in the Eagle
basin part of the Central Colorado trough. Thick sequences of
evaporite within the Roaring Fork diapir underlie the lower
Roaring Fork River valley. Mallory (1971) and De Voto et al.
(1986) reported the evaporite was as much as 2.7 km thick.
Perry et al. (this volume) estimate a maximum evaporite thick-
ness of 1.5 km based on interpretations of seismic reflection
data from lines that cross only the ends, but not the center part,
of the diapir. Most outcrops of the Eagle Valley Evaporite
within the southern Carbondale collapse center include thick
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 75
TABLE 1. AVERAGE CHONDRITE-NORMALIZED TRACE-ELEMENT RATIOS AND PREFERRED
40Ar/39Ar AND LASER-FUSION AGES OF SELECTED COMPOSITIONAL GEOCHEMICAL
GROUPS OF BASALTIC ROCKS IN THE LOWER ROARING FORK RIVER VALLEY
Geochemical
group
Average chondrite-
normalized La/Yb
Average chondrite-
normalized Hf/Ta
Preferred age or age range
(Ma)
1b 5.490 0.759 9.75 0.06 to 10.84 0.06
1c 8.005 0.754 10.60 0.07
2b 8.270 0.615 9.68 0.03 to 10.70 0.15
3a 7.926 0.474 No dates
4a 11.000 0.530 No dates
4b 11.659 0.541 9.68 0.03 to 10.49 0.07
5a 10.474 0.388 7.75 0.03
5b 10.312 0.440 7.75 0.04
6b 12.829 0.329 3.97 0.08
6b 12.118 0.285 2.90 0.01
6b 11.681 0.364 3.17 0.02
6c 12.389 0.377 3.05 0.04
10a 21.483 0.444 22.56 0.13
12a 11.959 0.765 13.29 0.28
12b 12.349 0.787 13.38 0.06
13a 13.593 0.928 13.57 0.05
Note:From Budahn et al. (this volume); Kunk and Snee (1998); Kunk et al. (2001, this volume).
beds of gypsum that are often highly deformed, but halite and
anhydrite are present only in the subsurface. A lithologic log
of the 933-m-deep Shannon Oil Rose #1 well, provides the best
subsurface information in the southern part of the Carbondale
collapse center (unpublished lithologic log by American Strati-
graphic Company, now held by the Denver Earth Resources
Library). This well, drilled near the mouth of Cattle Creek(Fig.
2), penetrated 18 m of alluvial gravel, then 915 m of gypsum,
anhydrite, halite, and clastic and carbonate rocks. The lower
285 m of the well was predominantly halite, and the well did
not reach the base of the evaporite sequence.
The Champlin Oil and Refining Blue #1 well was drilled
in thecenter ofthecollapseareaonthenorthsideoftheRoaring
Fork River between Carbondale and El Jebel (Fig. 2). The well
encountered evaporitic rocks to a depth of 707 m, but had to
be abandoned. The Mobil Oil Elk Camp Federal #F23X-22P,
located in theGrand Hogbackmonoclineonthesouthwestflank
of the White River uplift 22 km west of Glenwood Springs,
penetrated 4810 m of steeply dipping post-evaporite sedimen-
tary rocks before reaching the Eagle Valley Evaporite (unpub-
lished lithologic log by G.E.O., Inc.). Halite was encountered
at a depth of 5311 m and immediately began flowing into the
borehole (J.L. White, 1998, personal commun.). None of these
wells penetrated the entire evaporite sequence, because halite
caused drilling problems.
The unusually thick section of evaporitic rocks underlying
the lower Roaring Fork River valley may be related to tectonic
thickening or flow of evaporite beneath and adjacent to the
Grand Hogback monocline. When the monocline formed dur-
ing the Laramide orogeny, evaporite may have flowed toward
the point of greatest curvature of the monocline (Perry et al.,
this volume). Late Cenozoic flow from beneath adjacent up-
lands to the valley also thickened the evaporite beneath the
valley (Kirkham and Scott, this volume).
CHARACTERISTICS OF THE COLLAPSE AREA
Topography
The southern part of the Carbondale collapse center is a
roughly square-shaped topographic depression within an oth-
erwise mountainous region. The topographic depression is
readily apparent in an oblique shaded relief image of the region
(Fig. 3). The land surface within the collapse area is as much
as 1220 m lower than surrounding upland areas.
Conspicuous escarpments that descend rapidly intothecol-
lapse area mark the northern and easternmarginsofthecollapse
center (Fig. 3). Prominent, parallel, northwest-trending valleys
and ridges west (left) of the confluence of the Roaring Fork and
Crystal Rivers are related to differential erosion of Mesozoic
and Paleozoic sedimentary rocks within the Grand Hogback
monocline. Gently east-sloping, basalt-capped Sunlight Mesa
is north-northwest of these prominent valleys and ridges. A
broad, bowl-like depression superposedonthemesaisprobably
a result of differential collapse of the monocline. Northwest-
trending, parallel, relatively shallow valleys and low ridges
cross Sunlight Mesa. These landforms are associated with
bedding-plane faults caused by flexural slip of the collapsing
Grand Hogback monocline. Broad flat valleys, such as Spring
Valley and Cottonwood bowl, gently sloping basalt-cappedme-
sas like Los Amigos Mesa, which is the landform between
Spring Valley and the Roaring Fork River, and the rolling hills
of Missouri Heights typify the interior parts of the collapsearea
(Fig. 3). Los Amigos Mesa and the block of rock northeast of
the confluence of the Crystal and Roaring Fork Rivers jut far
out into the valley floor. These blocks may be rafting into the
valley as the underlying evaporite flows toward the river.
The land surface, particularly in the northeastern and cen-
tral parts of the collapse area, is hummocky. Drainagesof many
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Figure 2. Geologic features of the southern part of the Carbondale collapse center (modified from Kirkham et al., 2001b). BCT—Blue Creek
trough; BGT—Barbers Gulch trough; BP—Buck Point; CCB—CattleCreekbowl;CB—Cottonwoodbowl;CT—Crystalterracetrough;DRF—
doubly recumbent fold; LAS—Los Amigos sag; LBP—Little Buck Point; LM—Lookout Mountain; LT—Leon trough;PS—Polarissag;SBS—
Shippes Bowl sag; SDS—Shippes Draw sag; SPR—Spring Park Reservoir; TKK—Ti-Ke-Ki sag.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 77
WHITE RIVER PLATEAU
MH
R
o
a
r
i
n
g
Fork
Ri
v
e
rRiv
e
r
Cry
s
t
a
l
BM
LGM
LAM SV
SM
RTM
?
???
MS
Figure 3. Oblique shaded-relief digital elevation model of the lower Roaring Fork River valley, showing major geographic features (100 m
DEM provided by David Catts, 2001, U.S. Geological Survey). View is to north. Dashed line with hachures marks boundary of collapse area.
BM—Basalt Mountain; LAM—Los Amigos Mesa; LGM—Little Grand Mesa; MH—Missouri Heights; MS—Mount Sopris;RTM—RedTable
Mountain; SM—Sunlight Mesa; SV—Spring Valley. At the west edge of Little Grand Mesa, the collapse margin drops down into Glenwood
Canyon and is not visible in this perspective.
of the tributary streams within the collapse area are irregular,
poorly integrated, and sometimes interrupted by swallowholes.
The tributary streamsareincisedlittleandhaverelativelygentle
valley walls compared to the well-integrated and deeply and
sharply incised streams outside of the collapse area (Fig. 3).
Sinkholes are common in the area (Fig. 2) (Mock, thisvolume).
Several closed or nearly closed depressions lie within the col-
lapse area; they include broad, downwarped river terraces(sub-
sidence troughs) and shallow synclines formed in volcanic
rocks (synclinal sags) (Fig. 2).
Margins of the collapse area
We depict our preferred positions of the collapse area mar-
gins in Figures 1, 2, and 3. These boundaries are best defined
where upper Tertiary volcanic rocks are preserved. Upper Ter-
tiary basaltic flows immediately outside of the collapse center
are generally flat lying, whereas in the structural zones along
the margins of the collapse areas, these same flows dip as much
as 52 into the collapse center.
Western margin.The Grand Hogback monocline, a major
down-to-the-west fold created near the end of the Laramide
orogeny (Tweto, 1977), forms the western margin of the col-
lapse center in the lower Roaring Fork River valley (Fig. 2).
Lower Tertiary and older rocks within the monocline generally
dip 40 –60 westward (Murray, 1966; Kirkham et al., 1996,
1997). A subhorizontal erosion surface was cut across the
sharply folded lower Tertiary and older rocks during or prior to
the middle Miocene. A sequence of basaltic lava flows erupted
onto this erosion surface ca. 10.6–9.9 Ma (Kirkham et al.,
2001b; Kunk et al., this volume). Individual flows are as much
as 10 to 15 m thick. Many flows maintain fairly constant thick-
nesses across large areas and show no evidence of thickening
in the collapse area; some have pahoehoe flow structure. Such
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.78
Figure 4. Cross section A–A through Sunlight Mesa. Location of cross section shown on Figure 2.
characteristics indicate that the lava flows were originally
erupted onto the subhorizontal erosion surface (KenHon,1995,
written commun.).
Geologic relationships along the western margin ofthecol-
lapse center demonstrate that the Grand Hogback monocline
underwent down-to-the-east relaxation or unfolding during late
Cenozoic time. This movement of the monocline is opposite in
direction to its Laramide movement and is interpreted to result
from removal of evaporite from beneath the monocline, either
by flow and/or dissolution (Unruh et al., 1993; Kirkham et al.,
2001b). This relaxation or unfolding caused the overlying, sub-
horizontal basaltic caprock to tilt eastward into the Carbondale
collapse center, while simultaneously reducing the dips of the
lower Tertiary and older rocks within the monocline.Prominent
bends are apparent in the hogback ridge along the monocline
west of the confluence of the Crystal and Roaring Fork Rivers
where the ridge crosses the margin of the collapse area (Fig. 3).
The flattening of dip that was caused by late Cenozoic relaxa-
tion or unfolding of the monocline is responsible for the promi-
nent bends in the hogback ridge.
As the monocline relaxed, flexural slip occurredalongbed-
ding planes in the sedimentary rocks within the monocline,
much like the movement of a deck of cards as it topples over.
This slip formed a series of subparallel, down-to-the-west
flexural-slip faults (Murray, 1966, 1969; Stover, 1986) that rup-
tured the basalt flows and some overlying surficial deposits
(Figs. 2 and 4). The flexural-slip faults have normal displace-
ment and, because they follow bedding planeswithinthemono-
cline, probably become listric in the lower or synclinal limb of
the monocline.
A large remnant of ca. 10 Ma volcanic flows is preserved
on Sunlight Mesa southwest of Glenwood Springs. The flows
are broken by numerous northwest-striking, parallel, flexural-
slip faults and are tilted eastward into the collapse area (Figs.
2 and 4). Within the blocks bounded by the faults, the flows
typically dip 10 –20 east and locally have dips 40 . The
flexural-slip faults are recognizable only where lava flows and
certain surficial deposits unconformably overlie the folded
older sedimentary rocks. A prominent series of northwest-
striking, fault-controlled valleys and ridges that trend parallel
to the monocline are developed in the basalt cap (Figs. 5 and
6). These parallel ridges and valleys form a fault-controlled
trellis drainage pattern.
FaultsthatcutthevolcaniccaponSunlightMesaaredown-
thrown to the west, opposite in direction to the overall east tilt
of the basalt cap and to the east dip of flows within the fault
blocks (Kirkham et al., 1996, 1997). Flexural-slip faults are
widely spaced in areas where the basalt cap is underlain by the
Upper Cretaceous Mancos Shale and have greater displace-
ments than faults in areas underlain by the Upper Cretaceous
Mesaverde Group or lower Tertiary Wasatch Formation. A few
northeast-trending cross faults cut the basalt cap near the north
end of Sunlight Mesa (Figs. 2 and 5). A fault scarp in upper
Quaternary deposits along one of these faults (marked by “A”
in Figure 5) suggests latest Pleistocene or Holocene movement
(Kirkham et al., 1997).
A structurecontourmaponthetopoftheca.10Mabasaltic
rocks on Sunlight Mesa (Fig. 7) indicates this formerly flat-
lying basaltic cap now has an overall eastward slope of 6 –10
into the collapse center. This map confirms that the bowl-like
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Figure 5. Vertical aerial photograph of the Sunlight Mesa area (National Aerial Photography Program [NAPP] photo 6716–41),
where flexural-slip faults cut Miocene volcanic rocks that overlie an angular unconformity eroded acrosswest-dippingsedimentary
rocks in the Grand Hogback monocline. Note the prominent, parallel, northwest-striking, light-colored lineaments that are linear
grassy valleys (some are marked by arrows). Each valley is underlain by a west-dipping normal fault related to relaxation of the
monocline. The linear dark areas between the valleys are ridges formed by fault blocks capped by east-dipping volcanic rocks.
Arrows labeled “A” indicate ends of a cross fault that cuts upper Quaternary deposits. Bershenyi terrace has been folded by
Pleistocene diapirism. Town of Glenwood Springs in upper right. Scale and north arrow are approximate.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.80
Kd
Figure 6. Oblique aerial photograph of the northern end of Sunlight Mesa looking northwest. Prominent fault-controlled ridges and valleys
are formed in the ca. 10 Ma basalt flows that cap the mesa. Arrows denote some of the valleys. Note steep westward dip of Dakota Sandstone
(Kd) in Grand Hogback monocline.
depression on the mesa has a structural origin and is likely
related to differential collapse of the monocline. Late Miocene
volcanic flows drop 1040 m in elevation from the top of Sun-
light Peak to the lowest exposure of correlative flows on the
west side of the Roaring Fork River. This elevation difference
is the minimum amount of post–10 Ma collapse on the western
margin of the collapse center. Equivalent-age volcanic rocks
are 180 m lower in elevation on the east side of the river,
which suggests 1220 m of collapse since eruption of the ca.
10 Ma flows.
The average slope of the ground surface varies acrossSun-
light Mesa (Fig. 3). On the western side of the mesa, near and
east of Sunlight Peak, the surface slopes as much as 40% to the
east. The surface of the mesa flattens east of the zone of steep
slope and remains fairly flat until reaching the subcrop of the
Dakota Sandstone beneath the volcanic flows (Fig. 4). Rem-
nants of the basalt cap extend eastward beyond the Dakota sub-
crop in three areas (Kirkham et al., 1996, 1997), and in all three
locations the dip of the flows sharply increases east of the Da-
kota subcrop. Paleomagnetic measurements at three sites in the
basaltic flows in the wedge-shaped remnant east of the Dakota
subcrop along cross section A–A (Fig. 4) are consistent with
an interpretation of eastward tectonic tilting (Hudson et al., this
volume).
Flexural-slip faults associated with the Grand Hogback
monocline also offset upper Tertiary to lower Quaternary
basalt-rich gravel deposits west of Carbondale (Figs. 2 and 8).
Light-colored linear features in Figure 8 mark grassy swales
underlain by the faults, and the darker areas are the upthrown
blocks that are vegetated with sagebrush and/or gambel oak.
Prominent uphill-facing scarps mark the down-to-the-west
flexural-slip faults in the basalt-rich gravel deposits (Fig. 9).
Three of these faults offset upper Quaternary deposits that fill
one of the valleys between the mesas (Stover, 1986; Kirkham
et al., 1996).
Individual flexural-slip faults offset the Miocene basalt
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 81
Figure 7. Structure contour maps on the
top of the 7.75 Ma volcanic flows in
geochemical groups 5a and 5b and on
the top of the ca. 10 Ma rocks of groups
1b, 2b, 4a, and 4b (Table 1). Adapted
from Kirkham et al. (2001b). Geochem-
ical correlations are by Budahn et al.
(this volume). Dashed line indicates ap-
proximate location of generalized cross
section F–F (Fig. 22).
flows as much as 92 m. The upper Tertiary to lower Quaternary
gravel deposits are displaced a maximum of 30 m, whereas
the fault throw in the upper Quaternary deposits is only an
estimated 3 m. The increasing displacement in successively
older deposits indicates the flexural-slip faults associated with
the Grand Hogback monocline have experienced recurrent or
continuous movement during the late Cenozoic.
Northern margin.East of Glenwood Springs, near Look-
out Mountain (Fig. 2), the northern margin of the collapse cen-
ter is poorly constrained. The margin is arbitrarily placed at the
northern limit of evaporite on the south wall of Glenwood Can-
yon. Evaporitic rocks were probably once present north of their
modern outcrop, and late Cenozoic or older evaporite defor-
mation may have occurred there prior to removal of the evap-
orite by erosion.
Faulted remnants of ca. 10 Ma group 2b volcanic rocks
(Table 1) crop out on the south side of Lookout Mountain at
substantially lower elevations than other age-equivalent flows
that are widely distributed across the White River Plateau (Lar-
son et al., 1975; Kunk et al., this volume). The upper Miocene
flows on Lookout Mountain and those to the south and east
(Fig. 2) are within the collapse area. Deformation along the
collapse margin in the Lookout Mountain area appears to be
spread across a broad belt, with the collapse being accommo-
dated by several small faults and by tilting. Elevation differ-
ences between the group 2b rocks preserved on the WhiteRiver
Plateau and those on the northern margin of the collapse area
indicate a minimum vertical displacement of 680 m (Fig. 7).
The maximum amount of post–10 Ma collapse along the north-
ern margin is 1060 m, based on the elevation of ca. 10 Maflows
on the east valley wall of the Roaring Fork River.
East of Lookout Mountain is a 13-km-long basalt-capped
mesa called Little Grand Mesa or Dock Flats. A stacked se-
quence of thick flows caps the mesa, which is up to 5 km wide.
Group 5b flows (Table 1) crop out in the western part of Little
Grand Mesa, whereas group 5a rocks are found in the eastern
end. Both groups are ca. 7.75 Ma (Table 1). The volcanic flows
that cap Little Grand Mesa are not noticeably folded or faulted
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
A
B
B
N
0 .5 1 Km
Figure 8. Vertical aerial photograph of an area west of Carbondale (NAPP photograph 6717-8). Flexural-slip faults related to relaxation of the
Grand Hogback monocline underlie the light-colored, grassy meadows in upper Tertiary to lower Quaternary basalt-rich gravel deposits that
cap the mesas (some of the faults are marked with arrows). Three faintly visible faults (in box labeled “A”) cut upper Quaternary valley-fill
deposits. Faults shown in Figure 9 are labeled “B.” Scale and north arrow are approximate.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 83
LITTLE GRAND MESA
Figure 9. Photograph of flexural-slip fault with prominent uphill-facing scarp in upper Tertiary-lower Quaternary gravel deposits that cap a
mesa west of Carbondale. Arrows denote the scarp, which faces to the left. Other more subtle scarps are visible in front of and behind the
prominent scarp. View is to northeast, with Little Grand Mesa forming part of the skyline. See Figure 8 for location of photograph.
even though evaporite may occur in the subsurface beneath
much of the mesa. In several good exposures, stacked se-
quences of flows can be traced for hundreds of meters with no
apparent deformation. The flows on Little Grand Mesa occur
at the highest elevation of any 7.75 Ma flows in the region.
We conclude that differential collapse has not occurred be-
neath Little Grand Mesa during the past 7.75 m.y., but recog-
nize that the entire basalt-capped mesa may be an intact block
that uniformly lowered as underlying evaporite was removed
from beneath it. The northeastern margin of the collapse center
is placed at the top of a sharp monoclinal drape fold called the
Cottonwood monocline, which forms the southern edge of Lit-
tle Grand Mesa. If the intact block of Little Grand Mesa was
lowered by evaporite collapse, then the margin of the collapse
center probably follows the evaporite outcrop on the southern
wall of Glenwood Canyon, north of Little Grand Mesa (Fig. 1).
Evidence of evaporite tectonism, such as complex recumbent
folds (Fig. 10), unusual fault patterns in rocks overlying the
evaporite, and sinkholes, is present northeast of Little Grand
Mesa (Streufert et al., 1997). These features suggest evaporite
tectonism has affected this area, but this deformation may pre-
date the late Cenozoic.
Cottonwood monocline (Fig. 2) is a narrow and sinuous
fold with severalnearlyright-anglebends(Streufertetal.,1997;
Kirkham et al., 1995). The flat-lying, 7.75 Ma group 5a vol-
canic rocks (Table 1) capping Little Grand Mesa are abruptly
deformed by the monocline (Fig. 11). Within the monocline,
these volcanic rocks are moderately well exposed in a small
valley cut across the monocline (valley is left of symbol “CM”
in Figure 11). Cross section B–B (Fig. 12) is drawn perpen-
dicular to the monocline at the location of symbol “CM” on
Figure 11. Both the top and bottom limbs of the monocline are
sharp. Group 5a basalts dip as much as 44 into the collapse
center. They are lowered 180 m by Cottonwood monocline
(Figs. 6 and 12). A few very small displacement faults cut the
flows within the monocline, but folding accommodates most of
the monocline’s structural relief.
Cottonwood bowl lies at the bottom of the monocline. A
veneer of upper Tertiary to lower Quaternary sediments as
much as 35 m thick (unit QTs in Fig. 2; unit QTc in Fig. 12)
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.84
Figure 10. Photograph of a complex recumbent fold formed in the Eagle Valley Evaporite on the northeast side of Cottonwood Creek. View
is to northeast. Fold located northeast of Cottonwood monocline (“DRF” in Figure 2). Photograph by Beth L. Widmann.
blankets much of the floor of Cottonwood bowl. These locally
derived alluvial and colluvial sediments were mostly eroded
from the face of the monocline as it formed, accumulated in
the topographic depression of Cottonwood bowl at the toe of
the monocline, and have since been slightly dissected by ero-
sion. The low hills visible on the floor of Cottonwood bowl
(Fig. 11) are capped by these sediments, which overlie the
downdropped 7.75 Ma group 5a volcanic rocks. Although
poorly exposed, the volcanic rocks beneath the floor of Cotton-
wood bowl appear to be subhorizontal with an overall gentle
southward dip. This structural bench continues southward until
reaching a west-northwest-striking, broad monoclinal structure
on the north side of Cattle Creek.
Eastern Margin.The Basalt Mountain monocline forms
the eastern margin of the Carbondale collapse center (Fig. 2).
It merges with the Cottonwood monocline at the northeast
corner of the collapse center near Cottonwood Pass. The Basalt
Mountain monocline coincides with the Basalt Mountain fault,
a high-angle, Laramide-age fault with 3000 m of down-to-
the-east throw (Streufert et al., 1997; Kirkham et al., 1998).
Where the Eagle Valley Evaporite is at or near the ground sur-
face on the west side of the fault there is widespread evidence
of major collapse. On the east side of the fault, where the evap-
orite is overlain by as much as 2500 m of sedimentary and
volcanic rocks, there is no known evidence of collapse
(Fig. 13).
During the late Miocene, multiple group 4b flows (Table
1) erupted from the Basalt Mountain shield volcano on the east
side of the Basalt Mountain fault (Fig. 2 ) ca. 10.5–9.7 Ma.
Flows from the Basalt Mountain volcano extend nearly to Car-
bondale,14 km west of the crater (Fig. 7). As on the western
side of the collapse area, these flows were erupted onto a land-
scape with low topographic relief prior to any significant late
Cenozoic collapse (Kirkham et al., 1998). These late Miocene,
formerly flat-lying flowsarenowsharplytiltedwestwardwithin
the Basalt Mountain monocline, which is a broad hinge zone
with average width of 1.6 km. Although the group 4b flows
within the monocline are very broken and jumbled, they dip on
average 14 to the west. In the Missouri Heights area west of
the monocline, group 4b volcanic flows are broken by faults
and fractures, but generally are subhorizontal with only gentle
west and southwest dip. The minimum amount of post–10 Ma
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 85
CB
LGM
LGM
CM
CP
CB
LGM
Figure 11. Oblique aerial photograph looking east across Cottonwood bowl (CB) and Cottonwood monocline (CM). Syn-collapse sediments
underlie the rounded low hills in Cottonwood bowl. The dashed line with hachures marks top of Cottonwood monocline, which here forms
the margin of the Carbondale collapse center. The steep hillside that coincides with the monocline is a dip slope formed by tilted 7.75 Ma
basaltic flows. Little Grand Mesa (LGM), the flat surface in the upper left and in the foreground, is capped by nearly horizontal 7.75 Ma
basaltic flows. Cottonwood Pass (CP) is in the upper right. Cross section B–B (Figs. 2 and 12) crosses the monocline approximately at the
location indicated by CM.
collapse on the eastern margin ofthe collapsecenteris 580 m,
based on elevation differences between group 4b rocks at the
base of Basalt Mountain shield volcano and those exposed in
Missouri Heights. If Basalt Mountain was lowered by collapse
as a large intact block, a hypothesis discussed by Kirkham and
Scott (this volume), then the margin of the collapse center is
east of Basalt Mountain and the amount of structural relief re-
ported above represents only a portion of the total vertical sub-
sidence along the eastern margin.
A small cinder deposit and related flow near the southeast
end of Spring Park Reservoir (geochemical group 6b ) are pre-
served within the Basalt Mountain monocline and immediately
west of it (unit Tvp on Fig. 2). The cinders and flow have a
preferred age of 2.90 0.01 (Table 1). The lava from this
volcano originally flowed downhill awayfromtheeruptivecen-
ter. However, the northeastern and most distal end of the pre-
served flow is now as much as 73 m higher in elevation than
the cinder cone from which it was probably erupted. The flow
is tilted westward into the collapse center at an estimated 13 ,
which is similar to the tilt in the ca. 10 Ma Basalt Mountain
flows folded by the Basalt Mountain monocline (Kirkham et
al., 1998, 2001b). This suggests that much of the collapse ac-
commodated by the Basalt Mountain monocline occurred dur-
ing the past 3 m.y.
On the east side of the Basalt Mountain fault, where evap-
oritic rocks are deep in the subsurface, no evidence of evaporite
tectonism is recognized. Basalt Mountain shield volcano and
the flows from it appear to be intact and are not noticeably
deformed on the east sideof thefault.However,withthegreater
depth to the evaporite, overlying strata may have absorbed
strain, so that collapse could have occurred on the east side of
the fault without forming obvious structural features visible at
the ground surface. In such a scenario, theshieldvolcanowould
collapse as an intact block of rock. The ca. 10 Ma flows on
Basalt Mountain are at somewhat lower positions in the land-
scape than are other age-equivalent rocks at other locations in
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.86
Figure 12. Cross section B–B through the Cottonwood monocline on the northeast side of Cottonwood bowl, northern margin of collapse
center. Location of cross section shown in Figures 2 and 11.
Figure 13. Schematic cross section C–C through the Basalt Mountain monocline on the eastern margin of the collapse center. Approximate
location of cross section shown in Figure 2.
west-central Colorado (Kirkham et al., 2001a). Thus, the Basalt
Mountain volcano either was lowered by collapse as an intact
block, or the late Miocene landscape had several hundred me-
ters of relief. Flows from Basalt Mountain volcano are the only
ca. 10 Ma eruptions in the study area known to have flowed
into and blocked a late Miocene paleovalley, so perhaps there
was appreciable topographic relief during the late Miocene.
Southern margin.The southern margin of the collapse
center is more poorly defined than the other sides, largely be-
cause upper Cenozoic volcanic rocks are scarce (Fig. 2). Thick
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 87
deposits of middle(?) and late Tertiary fluvial gravel are pre-
served on the drainage divide between the Roaring Fork and
Crystal Rivers and on the west side of the Crystal River. We
conclude that these gravels accumulated in a gradually subsid-
ing basin related to evaporite tectonism. Therefore the margin
of the collapse center lies south of these deposits.
Fluvial gravels on Light Ridge south of Basalt abruptly
thicken where they cross the postulated margin of the late Ce-
nozoic collapse area (Fig. 2). A group 13a basalt flow dated at
13.57 0.05 Ma (Kunk et al., 2001) is interbedded with the
fluvial gravels at the north end of Light Ridge. This flow is
lowered by collapse at least 730 m, based on its elevation rela-
tive to age-equivalent flows outside the collapse area (Larson
et al., 1975). To accommodate the basalt flow and align with
the abrupt thickening of gravel on Light Ridge, the margin of
the collapse center, which trends north-northeast on the west
side of Basalt Mountain, must first bend 110 to aneaststrike,
then swing sharply southward (Fig. 2). The late Cenozoic col-
lapse margin probably turns to the west just south of Light
Ridge, and then runs generally west or northwest along the
north side of the Mount Sopris pluton until rejoining the Grand
Hogback monocline southwest of Carbondale.
A 35.21 0.03 Ma ash-flow tuff (Kunk et al., 2001) on
the northeast side of Mount Sopris (Fig. 2) also provides evi-
dence of the amount of subsidence on the southern margin of
the collapse center. The top of an age-equivalent intrusivestock
crops out at the summit of the nearby Mount Sopris (Streufert,
1999), therefore the land surface at the time of intrusion must
have been equal to or higher than the top of the stock. It is
unlikely that a deep paleovalley existed in close proximity to
the stock at the time of its emplacement. We conclude that the
ash-flow tuff was originally erupted onto a ground surface that
was probably equal to or perhaps even higher than the top of
the Mount Sopris stock and was subsequently lowered by col-
lapse. The tuff now crops out 1290–1460 m lower than the top
of the stock. Where last observed, the tuff disappears beneath
the Tertiary sediments that fill Sopris bowl and probably con-
tinues into the subsurface for some unknown depth beneath its
lowest outcrop. If the tuff was erupted onto a surface equal to
or higher than the top of the Mount Sopris stock, then the total
amount of post–35 Ma collapse probably exceeds 1460 m.
Structures within the interior of the collapse area
Structural deformation within the interior of the collapse
center involves both major and minor structures that affect
rocks and surficial deposits that overlie the evaporite. The style
and amount of deformation in the volcanic rocks, which were
erupted onto a low-relief surface prior to collapse, vary greatly.
Locally the volcanic rocks are nearly flat lying, even though
they were lowered athousand metersormoreinelevation.Else-
where, well-defined major structures, some with 300 m of
local structural relief, disrupt the volcanic rocks. The flows are
near vertical and perhaps overturned in at least one structure
(Hudson et al., this volume). We call elongate structural de-
pressions formed in volcanic rocks overlying the evaporitesyn-
clinal sags. Basin-like structural depressions in bedrock are re-
ferred to as bowls. Locally within the collapse center the
basaltic rocks are highly broken, fractured, and jostled; in these
areas individual structures are difficult to map at a scale of
1:24000. These intensely deformed deposits are mappedascol-
lapsedebris.MinorstructuraldepressionsformedinPleistocene
terraces are called troughs. Sinkholes are prevalent throughout
the collapse area (Mock, this volume) and common in some
troughs.
Heuschkel Park sag.Heuschkel Park sag is a generally
east-west-trending, major synclinal structure in volcanic rocks
north of Carbondale (Fig. 2). This structure, along with the
faulted and tilted basalt-capped mesa north of it, form promi-
nent landformsreadilyapparentonaerialphotographs(Fig.14).
The axis of the Heuschkel Park sag underlies the broad and flat
floor of Heuschkel Park. East of the park, the axis of the sag
gradually bends northward and eventually turns back to west,
creating a fishhook type of map pattern for the fold axis. To the
west, the sag axis appears to transition into a faulted structure.
Group 1b flows are widely distributedacrossthearea(Figs.
6 and 15). These 9.7–10.9 Ma flows (Kunk et al., this volume)
characterize the structural deformation of the Heuschkel Park
sag. Paleomagnetic studies at seven sites in and adjacent to the
Heuschkel Park sag indicate the flows on the north limb of the
sag may be strongly draped over the limb (Hudson et al., this
volume). These data demonstrate south tilts as steep as 53 ,
which exceeds the slope of the north valley wall. Beneath the
floor of Heuschkel Park, surficial deposits conceal the flows,
but they are essentially flat lying where they crop out on the
east end of the park, an interpretation supported by paleomag-
netic studies. The low ridge south of Heuschkel Park (Fig. 15)
is capped by group 1b flows in the southern limb of the sag.
These flows dip north, into the axis of the sag. The only other
volcanic rocks preserved on the south side of Heuschkel Park
are on Red Hill, where three samples of the 10.6 Ma group 1c
rocks (Table 1) were collected. Although these flows cannot be
used to precisely characterize the structure of the south limb of
the sag, their age and position in the landscape indicate the
structural relief on the south limb of the sag is much less than
that on the north limb.
North of the north valley wall is a gently to moderately
northward-sloping mesa that is capped by a stacked sequence
of basalt flows. The upper three flows in an outcrop on the rim
of the mesa north of the east end of the park are group 1b rocks.
A small-displacement, east-west-striking fault probably sepa-
rates the north-dipping flows beneath the mesa from the south-
dipping flows on the valley wall of the park. Total structural
relief in the group 1b volcanic rocks between the axis of the
sag and the north-sloping basalt-capped mesa is 300 m. The
north-sloping basalt-capped mesa is broken by 20 faults that
trendeitheraboutN35 –55 EorN10 –45 W.Manyofthefaults
abut or intersect at nearly right angles. Grassy meadows are
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.88
Carbondale
Fork
Crystal
Trough
R
o
a
r
i
n
g
River
Creek
Cattle
Heuschkel
Park
QTcd
Ri
v
e
r
C
r
y
s
t
a
l
Sag
QTcd
Diapir
Margin
N
0 .5 1 Km
Figure 14. Vertical aerial photograph of the Carbondale to Cattle Creek area (NAPP photograph 6717-236). Axis of Heuschkel Park sag trends
approximately east-west through the grassy meadow of Heuschkel Park, which is underlain by nearly horizontal ca. 10 Ma group 1b basaltic
flows (Table 1). Steeply south-dipping ca. 10 Ma flows are preserved on the tree-covered slope north of the park. Farther north is the north-
tilted mesa capped by ca. 10 Ma basalt, which is cut by several prominent faults (some marked by arrows) that intersect to form a rectilinear
pattern. This faulted basalt cap grades northeastward into collapse debris (QTcd) that underlies the hummocky topography in the right side of
the photograph. Scale and north arrow are approximate.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Figure 15. Geologic map of Heuschkel Park sag and cross section D–D (adapted from Kirkham and Widmann, 1997).
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.90
present along many of the faults, and they contrast sharplywith
the adjacent pine-covered hills between the faults, creating
quasi-rectilinear vegetation patterns on the mesa (Fig. 14).
The Heuschkel Park sag may simply be an asymmetrical
syncline due to removal of evaporite from beneath it. However,
the block of rock that includes the sag protrudes into and some-
what restricts the valley floor of the Roaring Fork River (Fig.
3). This block of rock may be rafting southward on underlying
evaporite, as the evaporite flows toward the river.
Spring Valley structure.Spring Valley is a nearly 6-km-
long, broad, flat, arcuate valley between Glenwood Springsand
Carbondale on the east side of the Roaring Fork River (Figs. 2
and 3). It is 300 m higher than the floor of the river valley,
and its orientation and position suggested Spring Valley was a
former paleovalley of the Roaring Fork River. However, fluvial
gravel deposits related to an ancestral Roaring Fork River have
not been found in or near Spring Valley. When early settlers
first homesteaded this region, Spring Valley was a closed de-
pression and a lake occupied much of the valley floor (Calvin
Cox, 1994, personal commun.). The presence of lacustrinesed-
imentsbeneath muchofthevalleysupportsthisconclusion.The
settlers hand dug a drain ditch at the north end of the valley
shortly before the end of the 19th century, drained the lake, and
turned the valley floor into agricultural land.
The oldest upper Tertiary volcanic rocks within the col-
lapse area crop out at the northern end of Spring Valley. These
group 10a rocks (Table 1), which are 22.56 0.13 Ma, are
only 300 m above the floor of the Roaring Fork River valley
and are 1200 m lower in elevation than age-equivalent flows
in the White River Plateau (Larson et al., 1975). Some of the
best outcrops of these early Miocene flows are within a narrow
graben at the northwest end of the Spring Valley structure (Fig.
2). Paleomagnetic studies of the early Miocene flows at three
sites within the graben indicate these rocks are strongly tilted
(Hudson et al., this volume). A model tilt of 100 15 south-
west was calculated for the flow on the east side of the graben,
suggesting it is overturned or nearly vertical.
The Spring Valley structure is concealed beneath the sur-
ficial deposits that fill the valley floor, and subsurface data are
limited, so the structure is poorly understood. Los Amigos
Mesa, which is capped by 7.75 Ma flows (group 5b) and ca. 10
Ma flows (groups 1b, 2b, and 3a), lies between Spring Valley
and the Roaring Fork River valley. Volcanic flows in the
northern end of this mesa are deformed by several small-
displacement faults, and at least one synclinal sag occurs on the
edges of the mesa (Fig. 2), but overall the mesa is little de-
formed. Along the western edgeofthemesa,theupperMiocene
volcanic rocks dip away from the river valley as much as 13 .
The underlying Maroon Formation dips more steeply away
from the river valley than do the overlying flows, indicating
pre–middle Miocene movement on the Cattle Creek anticline
and/or Roaring Fork diapir.
Much of the mountain side east of Spring Valley is under-
lain by broken, jumbled blocks and boulders of basalt in a large
landslide complex. This landslide complex developed in re-
sponse to the collapse of the Spring Valley structural depres-
sion, which removed the rock that supported the hillslope east
of the valley, effectively oversteepening the east valley wall.
This triggered movement of the hillslope toward the valley as
a large landslide complex. Large blocks of relatively intact ba-
salt are preserved within the landslide, but much of the basalt
was broken into bouldery rubble. Large scarps, which were
mapped as down-to-the-west faults by Kirkham et al. (1995)
and Kirkham and Widmann (1997), cut both the landslide de-
posits and adjacent bedrock. These structures may bemajorslip
planes related to massive failure of the entire rock mass and
overlying surficial deposits on the east side of Spring Valley.
A 174-m-deep groundwater exploration test hole (“SVR6”
in Figure 2) in the middle of the valley failed to reach bedrock
(Robin VerSchneider, 2001, personal commun.). Most material
penetrated by the well was fine-grained silt and clay, and no
basalt flowswereencountered.Theabundantclayandsiltfound
in thewellsuggestsalacustrineenvironmentpersistedinSpring
Valley for much of the time interval represented by the beds
penetrated in the drill hole. A thick sequence of reworked vol-
canic ash and clastic sediments eroded from adjacent hillslopes
was present at depths of 75–91 m in the drill hole. A.M.
Sarna-Wojcicki (2002, written commun.) geochemically cor-
related the ash with the Lava Creek B ash, which was recently
dated at 639 ka by Lanphere et al. (2002). The depth of burial
of the ash indicates the average sedimentation rate in the valley
since the middle Pleistocene was 140 mm/k.y. This rapidsed-
imentation rate suggests the Spring Valley structure had a high
rate of deformation during the past 639 ka.
Kirkham et al. (1995, 1997) and Kirkham and Widmann
(1997) considered the Spring Valley structure to be a half gra-
ben whose floor was tilted to the west (Fig. 16, upper diagram).
In this model, a large normal fault forms the western margin of
the structure, and Spring Valley is a structural low on the down-
dropped eastern side of the fault. Basaltic flows would underlie
the valley-fill deposits and overlie red beds of the Maroon For-
mation, if the structure is a half graben. As the valley tilted
westward, the hills east of the valley gradually became over-
steepened and eventually slid toward the valley.
An alternative model for the Spring Valley structure is pre-
sented in the lower diagram in Figure 16. In this model, the
large block of relatively intact basalt and underlying post-
evaporite Paleozoic sedimentary rocks between Spring Valley
and the Roaring Fork River valley is being rafted into the river
valley along an average travel path of S60 –70 W, as the un-
derlying evaporite flows toward areas with lower lithostatic
loads. The release zone for the structure coincides with the to-
pographic outline of the valley, which is a roughly north-south-
oriented valley with ends that flare back to the west. The west-
ern side of the rafted block would have slowly advanced into
the Roaring Fork River valley. As shown in Figure 3, this block
of rock does protrude into the river valley. In the rafted-block
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 91
Figure 16. Schematic cross sections (E–E) showing two possible interpretations of the subsurface geology through Spring Valley. Upper cross
section depicts the Spring Valley structure as a half graben chiefly due to removal of evaporite from beneath the valley by dissolution. In the
lower cross section, the Spring Valley structure is shown as a pull-apart feature caused by evaporite flow toward the Roaring Fork River valley.
Location of cross section shown on Figure 2.
model, the sediment deposited in the Spring Valley structure
would directly overlie evaporite.
Strain along the southern margin of thehypothesizedrafted
block may be largely lateral shearing. The strain would occur
as sinistral-strike slip or oblique slip along a narrow, arcuate
fault zone that starts in the southeast corner of the structure,
bends to a nearly west trend, and disappears into the evaporitic
rocks that crop out beneath the volcanic rocks on the east wall
of the river valley (Fig. 2). Lateral strain on thenorthernmargin
of a rafted Spring Valley structure would in part be accom-
modated by thenarrow grabenthatextendsnorthwestwardfrom
Spring Valley and in part by the complex fault swarm between
the graben and the river valley.
Minor structures.Several small synclinal sags deform the
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.92
Figure 17. Oblique aerial photograph of Shippes Bowl sag (SBS), looking south. Basalt Mountain forms the skyline on the left side of the
photograph, and Spring Park Reservoir is in the middle distance between the sag and the base of Basalt Mountain. Margin of collapse center,
immediately below the top of Basalt Mountain, shown by dashed line with tick marks.
volcanic bedrock in the Carbondale collapse center (Fig. 2).
They include the Los Amigos sag, Polaris sag, Shippes Bowl
sag, Shippes Draw sag, and Ti-Ke-Ki sag (Kirkhametal.,1996,
1998, 2001b). ThepreviouslydescribedHeuschkelParksaghas
sharp walls and considerable structural relief, but others have
broad, relatively flat limbs with only meters or tens of meters
of structural amplitude.
Los Amigos sag is a 1500-m-long, slightly arcuate, north-
west-trending feature adjacent and parallel to the Roaring Fork
River valley. Polaris sag, Shippes Bowl sag, and Shippes Draw
sag are 1.6- to 2.6-km-long, northeast- or east-trending struc-
tures in the northeastern part of the collapse area (Fig. 2). They
lie on a nearly horizontal structuralbenchunderlainbyMiocene
volcanic rocks between Cottonwood monocline and Cattle
Creek (Fig. 7). Topographically, the Polaris sag and Shippes
Draw sag are broad, shallow depressions, but a prominent,240-
m-deep, nearly circular topographic depression is associated
with Shippes Bowl sag (Fig. 17). Basalt flows are drapedacross
the eastern, northeastern, and perhaps westernflanksofShippes
Bowl sag, but are absent on other flanks. The 2.4-km-long Ti-
Ke-Ki sag formed in basalt flows on the interfluve between the
valleys of the Roaring Fork and Crystal Rivers.
Within the east-central part of the collapse center the ba-
saltic flows are highly broken, fractured, and jostled. Kirkham
and Widmann (1997) described these deposits as collapse de-
bris. Individual structures within the collapse debris are typi-
cally too complex to map at a scale of 1:24000. Collapsedebris
locally includesvaryingamountsofunconsolidatedsurficialde-
posits that have collected over or between the blocks of broken,
locally rubbly bedrock. Much of the Missouri Heights area is
underlain by collapse debris (Fig. 2).
Ten closed, or nearly closed, linear topographic depres-
sions were identified in Pleistocene terraces along the Roaring
Fork and Crystal Rivers (Fig. 2). These depressions, whichpar-
allel the subjacent river channels, are interpreted as subsidence
troughs resulting from bending due to roof collapse into dis-
solution cavities formed in evaporite beneath the terraces.Sink-
holes are associated with many of the troughs.
The Barbers Gulch trough southwest of Carbondale (Fig.
2), which formed in a middle Pleistocene terrace west of the
Crystal River, is 3.5 km long, 0.6 km wide, and 12 m deep;
it is the largest subsidence trough in the area. In addition to
locally derived alluvium and colluvium, the trough contains a
bed of Lava Creek B ash that lies 73 m above the Crystal
River (Kirkham and Widmann, 1997). A subsidence trough
likely existed at this location prior to deposition of the 0.64 Ma
ash (Lanphereet al.,2002),astopographicdepressionsaregood
environments in which to preserve tephra deposits. The ash bed
appears to be slightly tilted (Kirkham and Widmann, 1997),
which suggests trough subsidence also postdates tephra depo-
sition.
Other notable subsidence troughs include the Crystal ter-
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 93
Figure 18. Distribution and minimum preserved thickness of late Ce-
nozoic syn-collapse sediments. Contour interval 100 m.
race trough, Blue Creek trough, and Leon trough along the
Roaring Fork River (Fig. 2). Crystal terrace trough is a well-
preserved, symmetrical depression on a late Pleistocene terrace
east of Carbondale. The axis of the trough is 10 m lower than
the edges of the terrace. Blue Creek trough is a narrow depres-
sion formed on theouterorvalley-wallsideofalatePleistocene
terrace north of El Jebel. Blue Creek makes a sharp, nearly
right-angle bend as it enters the trough and flows roughly par-
allel to the Roaring Fork River for nearly 1700 m. Leon trough
is south of El Jebel. Collapse of this nearly circular depression
involves a latest Pleistocene terrace that was dropped to the
level of the Holocene valley-fill deposits. Holocene fluvial sed-
iments may partially fill Leon trough. A slightly smallertrough,
adjacent to and northeast of Leon trough, lies on the outer edge
of the valley floor. This trough, in which a lake for water skiing
was recently built, is separated from the Leon trough by a to-
pographic high that likely is a narrow remnant of the original
terrace tread.
Sinkholes are prevalent throughout the collapse area
(Mock, this volume). They occur in outcrops of evaporite and
in bedrock and surficial deposits that overlie evaporite. Sink-
holes are most numerous along the Roaring Fork diapir, where
on average there is one known sinkhole every 3.9 km
2. The
sinkholes provide direct evidence of evaporite dissolution.
Some sinkholes may be thousands of years old, butdozenshave
disrupted the ground surface during the past few years or de-
cades.
Most known sinkholes that formed during historic time are
associated with irrigated fields, irrigation ditches, ponds, and
lakes. This coincidence may be due to the relatively abundant
supply of fresh water found in these areas, which can cause or
enhance sinkholes by evaporite dissolution and can induce roof
collapse of underground voids by piping. Also, the close atten-
tion paid to agricultural fields and water-supply systems could
accountformorecompletereportingofsinkholesinthoseareas.
Spring Park Reservoir, an irrigation reservoir between Carbon-
dale and Basalt Mountain (Fig. 2), was rapidly drained twice
during the twentieth century when sinkholes developed in the
floor of the reservoir (Steve Callicotte, 1996, personal com-
mun.). Open, sinuous voids are present in many exposures of
evaporite. Sinkholes and open voids may be interconnected,
forming groundwater flow paths with very high transmissivity.
A spring with high discharge flows from an open void 1.3
km north of El Jebel. Individual sinkholes may be very large;
one in a basalt flow that overlies evaporite near Colorado
Mountain College (Fig. 1) is 70 m wide.
COLLAPSE-RELATED SEDIMENTARY DEPOSITS
Syn-collapse sedimentary deposits accumulated in four
major structural depressions formed in bedrock: Thepreviously
described Spring Valley structure and Cottonwood bowl, the
Sopris bowl on the north side of Mount Sopris, and the Cattle
Creek bowl along the east-central part of the collapse area (Fig.
2). Both the Spring Valley structure and Cottonwood bowl are
topographically well expressed, but Sopris bowl and Cattle
Creek bowl were recognized chiefly by the preserved remnants
of sediments originally deposited within them.
The thickest and laterally most extensive syn-collapsesed-
imentary deposits fill Sopris bowl (Kirkham and Widmann,
1997; Kirkham et al., 1998; Streufert et al., 1998; Streufert,
1999). Large remnants of these deposits are found on the in-
terfluve between the Roaring Fork and Crystal Rivers and in
the hills on the west side of the Crystal River (Fig. 18). The
sediments include gravelly clast-supported fluvial deposits and
matrix-supported debris-flow deposits. Clast lithologies indi-
cate an ancestral Crystal River provenance for deposits in the
western part of the basin and an ancestral Roaring Fork River
provenance in the eastern part. The paleovalley exposed on
Light Ridge (Figs. 2 and 18) probably accommodated the an-
cestral Roaring Fork River.
The exposed thickness of syn-collapse deposits in Sopris
bowl exceeds 450 m in the central part of the bowl (Fig. 18).
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.94
Figure 19. Map of the Roaring Fork diapir, Quaternary depositsfolded
by evaporite diapirism, and seismic reflection lines used to interpret
the diapir and collapse center (modified from Kirkham et al., 2001b).
Refer to Perry et al. (this volume) for interpretation of the seismic
lines. BT—Bershenyi terrace.
The base of the syn-collapse deposits is concealed beneath the
ground surface in most of the bowl. Where exposed west of
Basalt, the basal contact of the syn-collapse sediments slopes
into Sopris bowl with an apparent dip of 9 to the northwest
(Streufert et al., 1998). This suggests the maximum preserved
thickness of these syn-collapse deposits greatly exceeds 450 m.
Seismic reflection data collected from the southwestern part of
Sopris bowl suggest the syn-collapsedepositsattainapreserved
thickness of 1100 m (Perry et al., this volume).
An ash-flow tuff underlies the syn-collapse sediments in
the southeast corner of Sopris bowl (Fig. 2). The tuff dips 20
to the northeast (Streufert et al., 1998) and contains sanidine
dated at 35.21 0.03 Ma (Kunk et al., 2001). Deformation
associated with Sopris bowl must have begun sometime after
eruption of the ash-flow tuff. Basalt flows west of El Jebel
(groups 12a and 12b) with an average age of 13.3 Ma (Table
1) are stratigraphically at or near the top of the syn-collapse
sedimentary sequence, which indicates Sopris bowl continued
to fill with sediments until near the end of the middle Miocene.
Since the 13.3 Ma flows are tilted and are at elevations sub-
stantially lower than other middle Miocene flows found outside
the collapse area, major subsidence continued in Sopris bowl
after 13.3 Ma. The proximity of Sopris bowl to Mount Sopris
stock, and age relationships between the formation of the bowl
and emplacement of the stock, suggest increased geothermal
gradients and other hydrologic changes associated with the
stock may have caused or enhanced evaporite dissolution.
A laterally extensive but relatively thin remnant of syn-
collapse sediments deposited in Cattle Creek bowl is preserved
on the drainage divide between Cattle Creek, MissouriHeights,
and Spring Park Reservoir (Fig. 18). A west-flowing stream
deposited these sediments in fluvial, deltaic, and lacustrine en-
vironments. Coarse-grained, sandy, silty, cobble and pebble
gravel eroded from the mountains east of the collapse area was
deposited in the eastern and central parts of Cattle Creek bowl.
Fine-grained sediments found farther west in the bowl suggest
that collapse created closed topographic depressions favorable
for lacustrine and deltaic deposition.
The syn-collapse sediments in Cattle Creek bowl uncon-
formably overlie ca. 10 Ma group 1b volcanic rocks, although
in places the group 1b volcanic rocks crop out in hills that are
topographically higher than adjacent syn-collapse sediments.
As the syn-collapse sediments were first deposited, these hills
of volcanic rock formed islands that rose above the streamsand
lakes in which the sediments accumulated. The sediments in
Cattle Creek bowl also locally overlie 7.75 Ma volcanic rocks,
but stratigraphic relationships with the Pliocene (3.05 0.04
Ma) group 6c rocks are equivocal.
EVAPORITE FLOW
Evidenceof evaporiteflowinthelowerRoaringForkRiver
valley includes valley-centered anticlines, diapiric contacts be-
tween evaporite and overlying rocks, and folded Quaternary
deposits. The Cattle Creek anticline, first described by Mallory
(1966),underliestheRoaringForkRivervalleyfromGlenwood
Springs to near Carbondale (Fig. 1). Evaporite in the core of
this anticline is at least locally diapiric (Figs. 4 and 19). This
structure coincides with the upper limb of the Laramide Grand
Hogback monocline in much of the lower Roaring Fork River
valley. Evaporite flowed toward the upper limb of the mono-
cline during the Laramide orogeny (Perry et al., this volume).
The valley-centered anticline was enhanced by subsequent late
Cenozoic evaporite flow and diapirism related to the Roaring
Fork diapir. Over 100 m of diapiric piercement by the Eagle
Valley Evaporite into overlying beds in the Middle and Upper
Pennsylvanian EagleValleyFormationisapparentinthepromi-
nent exposure on the east valley wall of the Roaring Fork River
immediately south of Cattle Creek (Fig. 20).
Quaternary outwash terraces are deformed by evaporite
flow at four locations in the lower Roaring Fork River valley
between Glenwood Springs and Carbondale (Fig. 19). These
tilted deposits dip away from the axis of the valley, even where
the deposits are adjacent to the valley wall. This folding prob-
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 95
RED TABLE MOUNTAIN
CATTLE CREEK BOWL
Diapir
Margin
ROARING FORK DIAPI
R
Figure 20. Photograph of Roaring Fork diapir. View is to east. Note diapiric contact between the Eagle Valley Evaporite and overlying Eagle
Valley Formation (shown by arrows). Outcrop is on east side of the Roaring Fork River valley between Cattle Creek and the town of
Carbondale.
ably resulted from upward evaporite flow in the Roaring Fork
diapir during or after the middle Pleistocene, because Quater-
nary deposits that sag or collapse into subsidence troughs al-
ways dip into the subsided area. Unruh et al. (1993) described
terraces deformed by evaporite flow along the west wall of the
Roaring Fork River valley southwest of Basalt. These deposits
appear to be uparched in an anticlinal structure that is oblique
to the valley axis, which also is suggestive of deformation by
upwelling evaporite.
At Bershenyi terrace, near the northern end of the Roaring
Fork diapir (Figs. 5, 19, and 21), a Quaternary terraceandover-
lying deposits are deformed by evaporite flow. The middle
Pleistocene Bershenyi terrace (Piety, 1981) is overlain by a
wedge-shaped layer of debris-flow deposits that is thickest at
the fan head (Kirkham et al., 1996, 1997). Where closest to the
river, these deposits are folded upward and dip away from the
river. The downstream (northern) end of the terrace is uparched
such that debris-flow deposits at the distal end of the fan are
now 30 m higher in elevation than correlative deposits at the
original fan head. The adjacent late Pleistocene airport terrace
(“AT” on Fig. 21), is not visibly affected by evaporite tecton-
ism. Measurable evaporite flow last occurred at this location
after deposition of the middle to upper Pleistocene debris-flow
deposits and prior to deposition of the undeformed, adjacent
upper Pleistocene terrace deposits.
Seismic reflection data interpreted by Perry et al. (this vol-
ume) support our conclusion that evaporite flow and diapirism
locally created evaporite-cored valley anticlines and uparched
Quaternary terraces and associated deposits along the valley
axis. The interpreted seismic lines suggest the evaporitic strata
are thin beneath the Grand Hogback monocline and in the area
east of the Roaring Fork River valley but up to 1.5 km thick in
the ends of the intrusive diapir under the valley. The evaporite
apparently withdrew from the adjacent upland areas and flowed
into the valley-centered diapir. The interpretation of Perry et al.
(this volume) suggests that the Roaring Fork diapir may locally
pierce as much as a kilometer of overlying strata.
Evaporite flow may also be responsible for the Spring Val-
ley structure and Heuschkel Park synclinal sag, which were
previously described. Large, relatively intactblocksofrockthat
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.96
BT AT
Figure 21. Photograph of Bershenyi terrace (BT, in the left center of photograph) looking north. The downstream end of this middle
Pleistocene outwash terrace and the distal (northern) end of an overlying debris-flow fan are upwarped by evaporite flow. The adjacent late
Pleistocene airport terrace (AT) is not deformed by evaporite flow. Location of terraces shown in Figures 5 and 19.
overlie the evaporitic strata between these structures and the
river valley may be rafting into the valley as the underlying
evaporite flows toward the valley.
TIMING OF COLLAPSE
Available data indicate that the rate of evaporite-related
collapse has varied temporally and spatially. The earliest rec-
ognized evidence of post-Laramide evaporite collapseoccurred
between 35.21 Ma and 13.3 Ma when a deep, but localized
dissolution basin formed immediately north of Mount Sopris.
Collapse during this time period apparently was restricted to
the area north of Mount Sopris.
Major subsidence across the entire collapse center began
sometime after 10 Ma (Fig. 22), but its precise initiation is
poorly constrained. In some areas, ca. 10 Ma volcanic rocks are
downdropped more than the 7.7 Ma flows, suggesting some of
the regional collapse occurred between ca. 10 Ma and 7.7 Ma.
Definitive evidence of collapse during this time, such as greatly
deformed older flows overlain by less-deformed flows, how-
ever, was not observed. Rates of river incision probably in-
creased ca. 10-8 Ma, and greatly accelerated during the past 3
m.y. (Kirkham et al., 2001a). This incision in turn decreased
lithostatic pressures on the evaporitic rocks beneath the valleys
and triggered or enhanced evaporite flow. As the rivers cut
deeper, fresh groundwater circulated to greater depths in the
evaporite and promoted dissolution and collapse.
Along the eastern margin of the collapse area, near Spring
Park Reservoir, a 2.90 Ma cinder cone and associated volcanic
flow (group 6b ) are tilted approximately the same amount by
the Basalt Mountain monocline as are nearby ca. 10 Ma group
4b basaltic rocks. Therefore most of the collapse of the Basalt
Mountain monocline occurred after ca. 3 Ma (Kirkham et al.,
2001b). Major Pliocene and younger collapse can also be in-
ferred from data in the northeastern part of the collapse area.
Preserved remnants of the 3.17 0.02 Ma eruptive center at
Buck Point (group 6b ) are at an altitude of 2680 m (Streufert
et al., 1997), and the 3.97 0.08 Ma eruptive center at Little
Buck Point (group 6b) is at 2620 m (Kirkham et al., 1995).
Both of these Pliocene eruptive vents are within the collapse
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Figure 22. Schematic east-west cross sections (F–F) showing the generalized evolution of the Carbondale collapse center in the lower
Roaring Fork River valley (adapted from Kirkham et al., 2001b). Approximate line of section (shown by dashed line in Figure 7)
follows an irregular path from Sunlight Peak to Basalt Mountain.
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
R.M. Kirkham et al.98
center, yetthey areonly slightlylowerthanorequalinelevation
to the 7.75 Ma flows on Little Grand Mesa, which are at an
altitude of 2680–2745 m and are outside of the Carbondale
collapse center. If significant collapse occurred between 7.75
and ca. 3 Ma, then these younger eruptive vents would have
been constructed on a ground surface that was lower in the
landscapethanLittleGrandMesa.Thesedatasuggestthatmuch
of the evaporite collapse in the lower Roaring Fork Rivervalley
occurred during the past 3 million years, which closely mirrors
incision rates (Kirkham et al., 2001a; Kunk et al., this volume).
Historic sinkholes and high salinity loads in rivers and thermal
springs document active dissolution and deformation.Thepres-
ence of thick evaporite beneath much of the collapse area por-
tends continuing collapse. Future collapse rates likely will fluc-
tuate as climate and rates of incision and uplift vary.
SUMMARY
Dissolution and flow of Pennsylvanian evaporitic rocks
during the late Cenozoic have created a regional collapse area
in the lower Roaring Fork River valley in west-central Colo-
rado. Abundant and well-preserved evidence of this evaporite
tectonism is widespread in the collapse area. The lateral extent
and amount of vertical collapse, as well as the timing and style
of deformation, are well constrained by upper Cenozoic vol-
canic rocks that were correlated using field mapping,
40Ar/39Ar
geochronology, geochemistry, and paleomagnetism. These vol-
canic rocks are downdropped as much as 1220 min thecollapse
area. Syn-collapse sedimentary deposits accumulated in struc-
turally controlled topographic depressions along the margins of
the collapse center and within its interior.
Local collapse initiated during the Oligocene or early Mio-
cene. Collapse became widespread between ca. 10 Ma and 7.7
Ma, and it greatly accelerated during the past 3 million years,
largely in response to river incision. When the Roaring Fork
River began to downcut through a broad, low-relief erosion
surface during the late Miocene, rocks overlying the evaporite
beds were eroded from the valley. This created differentiallith-
ostatic pressures, which triggered flow of the evaporite from
beneath adjacent upland areas where pressures remained high,
toward the Roaring Fork River valley where the pressureswere
reduced. River incision also allowed relatively fresh ground-
water to circulate to progressively greater depths, a processthat
increased dissolution rates. Since thick evaporite still underlies
much of the collapse area, continued subsidence is likely.
ACKNOWLEDGMENTS
The National Cooperative Geologic Mapping Program sup-
ported most of our geologic mapping; the U.S. Forest Service
and Bureau of Land Management also provided financial and
logistical support. Nancy Bauch, Bruce Bryant, Chris Carroll,
Jim Cappa, Paul Carrara, Nancy Driver, Francisco Gutie´rrez,
Ken Hon, Karl Kellogg, Dave Lidke, Bill Lorah, Dave Merritt,
Ralph Mock, Bob Scott, Ralph Shroba, Tom Steven, Dan Un-
ruh, Robin VerSchneider, Paul Von Guerard, and Beth Wid-
mann shared information and ideas that contributed to our
study. Kenneth S. Johnson and James T. Neal reviewed the
manuscript for the Geological Society of America; WilliamPat
Rogers, Ren Thompson, Francisco Gutie´rrez, Bruce Bryant,
and Vince Matthews reviewed earlier versions of this manu-
script. We appreciate their thorough and insightful reviews.
Larry Scott prepared the digital graphics.
REFERENCES CITED
De Voto, R.H., Bartleson, B.L., Schenk, C.J., and Waechter, N.B., 1986, Late
Paleozoic stratigraphy and syndepositional tectonism, northwestern Col-
orado,in Stone, D.S., ed., New interpretations of northwest Colorado
geology: Denver, Colorado, Rocky Mountain Association of Geologists,
Symposium, p. 37–49.
Freeman, V.L., 1971, Permian deformation in the Eagle Basin, Colorado: U.S.
Geological Survey Professional Paper 750-D, p. D80–D83.
Freeman, V.L., 1972, Geologic map of the Woody Creek quadrangle, Pitkin
and Eagle Counties, Colorado: U.S. Geological Survey Geologic Quad-
rangle Map GQ-967, scale 1:24000.
Kirkham, R.M., and Streufert, R.K., 1996, Neogene deformation in the Glen-
wood Springs-Carbondale-Gypsum area, Colorado: Geological Society
of America Abstracts with Programs, v. 28, no. 7, p. A-517.
Kirkham, R.M., and Widmann, B.L., 1997, Geologic map of the Carbondale
quadrangle, Garfield County, Colorado: Colorado Geological Survey
Open-File Report 97-3, scale 1:24000.
Kirkham, R.M., Streufert, R.K., and Cappa, J.A., 1995, Geologic map of the
Shoshone quadrangle, Garfield County, Colorado: Colorado Geological
Survey Open-File Report 95-4, scale 1:24000.
Kirkham, R.M., Streufert, R.K., Hemborg, H.T., and Stelling, P.L., 1996, Geo-
logic map of the Cattle Creek quadrangle, Garfield County, Colorado:
Colorado Geological Survey Open-File Report 96-1, scale 1:24000.
Kirkham, R.M., Streufert, R.K., and Cappa, J.A., 1997, Geologic map of the
Glenwood Springs quadrangle, Garfield County, Colorado: Colorado
Geological Survey Map Series 31, scale 1:24000.
Kirkham, R.M., Widmann, B.L., and Streufert, R.K., 1998, Geologic map of
the Leon quadrangle, Eagle and Garfield Counties, Colorado: Colorado
Geological Survey Open-File Report 98-3, scale 1:24000.
Kirkham, R.M., Kunk, M.J., Bryant, B., and Streufert, R.K., 2001a, Constraints
on timing and rates of incision by the Colorado River in west-central
Colorado: A preliminary synopsis,in Young, R.A., and Spamm, E.E.,
eds., The Colorado River: Origin and evolution: Grand Canyon, Arizona,
Grand Canyon Association Monograph 12 (in press).
Kirkham, R.M., Streufert, R.K., Budahn, J.R., Kunk, M.J., and Perry, W.J.,
2001b, Late Cenozoic regional collapse due to evaporite flow and dis-
solution in the Carbondale collapse center, west-central Colorado: The
Mountain Geologist, v. 38, no. 4, p. 193–210.
Kunk, M.J., and Snee, L.W., 1998,
40Ar/39Ar age-spectrum data of Neogene
and younger basalts in west-central Colorado: U.S. Geological Survey
Open-File Report 98-243, 112 p.
Kunk, M.J., Winick, J.A., and Stanley, J.O., 2001,
40Ar/39Ar age-spectrum and
laser-fusion data for volcanic rocks in west-central Colorado: U.S. Geo-
logical Survey Open-File Report 01-472, 94 p.
Lanphere, M.A., Champion, D.E., Christiansen, R.L., Izett, G.A., and Obra-
dovich, J.D., 2002, Revised ages for tuffs of the Yellowstone Plateau
volcanic field: Assignment of the Huckleberry Ridge Tuff to a new geo-
magnetic polarity event: Geological Society of America Bulletin (in
press).
Larson, E.E., Ozima, M., and Bradley, W.C., 1975, Late Cenozoic basic vol-
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Evaporite tectonism in the lower Roaring Fork River valley, west-central Colorado 99
Printed in the U.S.A.
canism in northwest Colorado and its implications concerning tectonism
and origin of the Colorado River system,in Curtis, B.F., ed., Cenozoic
history of the southern Rocky Mountains: Boulder, Colorado, Geological
Society of America Memoir 144, p. 155–178.
Mallory, W.W., 1966, Cattle Creek anticline, a salt diapir near Glenwood
Springs, Colorado: U.S. Geological Survey Professional Paper 550-B,
p. B12–B15.
Mallory, W.W., 1971, The Eagle Valley Evaporite, northwest Colorado—A
regional synthesis: U.S. Geological Survey Bulletin 1311-E, 37 p.
Murray, F.N., 1966, Stratigraphy and structural geology of the Grand Hogback
monocline, Colorado [Ph.D. thesis]: Boulder, Colorado, University of
Colorado, 219 p.
Murray, F.N., 1969, Flexural slip as indicated by faulted lava flows along the
Grand Hogback monocline, Colorado: Journal of Geology, v. 77, p. 333–
339.
Peale, A.C., 1876, Report on the valleys of Eagle, Grand, and Gunnison Rivers,
Colorado: Annual Report of the United States Geological and Geograph-
ical Survey of the Territories, 8th Annual Report, p. 73–180.
Piety, L.A., 1981, Relative dating of terrace deposits and tills in the Roaring
Fork valley, Colorado [M.S. thesis]: Boulder, Colorado, University of
Colorado, 209 p.
Stover, B.K., 1986, Geologic evidence of Quaternary faulting near Carbondale,
Colorado, with possible associations to the 1984 Carbondale earthquake
swarm,in Rogers, W.P., and Kirkham, R.M., eds., Contributions to Col-
orado seismicity and tectonics—A 1986 update: Colorado Geological
Survey Special Publication 28, p. 295–301.
Streufert, R.K., 1999, Geologic map of the Mount Sopris quadrangle, Garfield
and Pitkin Counties, Colorado: Colorado Geological Survey Open-File
Report 99-7, scale 1:24000.
Streufert, R.K., Kirkham, R.M., Widmann, B.L., and Schroeder, T.J. II, 1997,
Geologic map of the Cottonwood Pass quadrangle, Eagle and Garfield
Counties, Colorado: Colorado Geological Survey Open-File Report 97-
4, scale 1:24000.
Streufert, R.K., Widmann, B.L., and Kirkham, R.M., 1998, Geologic map of
the Basalt quadrangle, Eagle, Garfield, and Pitkin Counties, Colorado:
Colorado Geological Survey Open-File Report 98-1, scale 1:24000.
Tweto, O., 1977, Tectonic history of west-central Colorado,in Veal, H.K., ed.,
Exploration frontiers of the central and southern Rockies: Denver,
Colorado, Rocky Mountain Association of Geologists, Symposium, p.
11–22.
Unruh, D.M., Budahn, J.R., Siems, D.F., and Byers, F.M., 2001, Major- and
trace-element geochemistry; lead, strontium, and neodymium isotopic
compositions; and petrology of late Cenozoic basaltic rocks from west
central Colorado: U.S. Geological Survey Open-File Report 01-477, 90 p.
Unruh, J.R., Wong, I.G., Bott, J.D., Silva, W.J., and Lettis, W.R., 1993,Seismo-
tectonic evaluation, Rifle Gap Dam, Silt Project, Ruedi Dam, Fryingpan–
Arkansas Project, northwestern Colorado: Report prepared by William R.
Lettis and Associates and Woodward-Clyde Consultants for U.S. Bureau
of Reclamation, 154 p.
MANUSCRIPT ACCEPTED BY THE SOCIETY APRIL 12, 2002
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
Downloaded from http://pubs.geoscienceworld.org/gsa/books/book/510/chapter-pdf/967736/i0-8137-2366-3-366-0-73.pdfby Colorado School of Mines useron 31 March 2022
ROCKY MOUNTAIN | MIDWEST | SOUTHWEST | TEXAS
909 Colorado Avenue Glenwood Sp ring s , CO 81601 | Office: 970-945-6777 | LREWATER.COM
SPRING VALLEY RANCH
Physical Water Supply Report
Prepared for: Roaring Fork Engineering
Date 3/8/2023
Project Number 21667SVRD02
The following members of the LRE Water staff contributed to the preparation of this report.
Angela Schenk, Senior Project Hydrogeologist
March, 2023 – Project # 2167SVRD02
TABLE OF CONTENTS
Section 1: Introduction ................................................................................................................. 1
Section 2: Background ................................................................................................................. 1
Section 3: Physical Water Supply ................................................................................................... 1
3.1 SV Well No. 1 ..................................................................................................................... 2
3.2 ASR Well No. 16 fka Gamba 8 ................................................................................................ 4
3.3 Well 36567-MH ................................................................................................................... 7
3.4 Well 36596-MH ................................................................................................................. 10
3.5 SVR Well No. 20 fka Gamba 1 .............................................................................................. 12
3.6 ASR Well No. 15 ............................................................................................................... 15
3.7 ASR Well No. 14 ............................................................................................................... 17
3.8 SVH Well 10 ..................................................................................................................... 20
Section 4: Water Quality Results .................................................................................................. 23
LIST OF FIGURES
Figure 1: SVR Well 1 (86630-F) Pump Test .................................................................................................................. 3
Figure 2: SVR Well 1 (86630-F) Recovery ..................................................................................................................... 4
Figure 3: ASR Well No. 16 (86629-F) Pump Test .......................................................................................................... 6
Figure 4: ASR Well No. 16 (86629-F) Recovery Analysis .............................................................................................. 7
Figure 5: Well 36567-MH Pump Test ............................................................................................................................. 9
Figure 6: Well 36567-MH Recovery Analysis ............................................................................................................... 10
Figure 7: Well 36569-MH Pump Test ........................................................................................................................... 11
Figure 8: Well 36569-MH Recovery Analysis ............................................................................................................... 12
Figure 9: SVR Well No. 20 (86628-F) Pump Test ........................................................................................................ 14
Figure 10: SVR Well No. 20 (86628-F) Recovery Analysis .......................................................................................... 15
Figure 11: SVR Well No. 15 (MH-36760) Pump Test ................................................................................................... 16
Figure 12: SVR Well No. 15 (MH-36760) Recovery Analysis ...................................................................................... 17
Figure 13: SVR Well No. 14 (66299-F) Pump Test ...................................................................................................... 19
Figure 14: SVR Well No. 14 (66299-F) Recovery Analysis .......................................................................................... 20
Figure 15: SVR Well No. 10 (MH-33819) Pump Test ................................................................................................... 21
Figure 16: SVR Well No. 10 (MH-33819) Recovery Analysis ...................................................................................... 22
March, 2023 – Project # 2167SVRD02
LIST OF TABLES
Table 1: Summary of Spring Valley Ranch Wells Pump Test Analysis .......................................................................... 2
Table 2: Regulated Water Quality Results ................................................................................................................... 24
Table 3: Additional Water Quality Parameters ............................................................................................................. 25
LIST OF ATTACHMENTS
Attachment 1: Well Location and Current Production Rate Map
Spring Valley Ranch Page 1 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
SECTION 1: INTRODUCTION
LRE Water, Inc. (LRE) was retained to perform 24 hour well pumping test with 24 hour recovery
period on the wells located on Spring Valley Ranch (SVR). In addition to the well pumping tests,
water quality samples were collected and analyzed by a State of Colorado certified laboratory that
follows accepted industry standards and quality assurance/quality control procedures. This report
describes the results of the pumping test and physical groundwater supply; the water quality
results; and provides recommendations for treatment.
SECTION 2: BACKGROUND
The Spring Valley Ranch Planned Unit Development (PUD) is an approximately 5,900 acre
planned development. The property consists of four parcels located in the Roaring Fork Valley
on the western end of Missouri Heights between the towns of Carbondale and Glenwood Springs
in Garfield County. A location map is included in Attachment 1.
SECTION 3: PHYSICAL WATER SUPPLY
LRE conducted a constant-discharge pump test at eight wells located on SVR. A map of the well
locations is included in Attachment 1. The pumps test were performed to evaluate the current
pumping capacities of the wells under current aquifer conditions. Additionally, these tests were
performed during the period of the year when groundwater is seasonally lower because there is
minimal recharge occurring.
All of the wells produce from unconfined aquifers, which largely recharge from snowmelt run-off,
precipitation, and irrigation occurring on the ranch. Currently, only a small area of the lower valley
is irrigated.
Table 1 provides a summary of the current static water levels, pumping capacities results from
the 24-hour pumping tests, drawdown of the wells evaluated, and calculated well production rates.
The individual well tests and results are described in more detail below.
Spring Valley Ranch Page 2 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Table 1: Summary of Spring Valley Ranch Wells Pump Test Analysis
Well Production Rate, Static Water Levels, and Max Drawdown
Well Name
Permit/
Decreed
Rate
(gpm)
Permit
No.
Pump Test
Date
Pump Test
Production
Rate
(gpm)
Static
Water
Level
(ft)
Max
Drawdown
Measurement
(ft)
Max
Drawdown
(ft)
Well
Production
Rate
(gpm)
SV Well No. 1 300 86630-F 9/29/2022 300 22 161.53 139.53 550
ASR Well No. 16
fka Gamba 8 100 86629-F 10/12/2022 54.3 20.25 231.42 211.17 60
36567-MH 100 36597-MH 10/18/2022 7.7 89 219.37 130.37 10
36596-MH 100 36596-MH 10/19/2022 100 19.55 91.01 71.46 195
SVR Well No. 20
fka Gamba 1 300 86628-F 10/31/2022 51.6 113 169.9 56.9 95
ASR Well No. 15 100 36760 MH 11/14/2022 79 112.8 149.58 36.78 225
ASR Well No. 14 100 66299-F 11/30/2022 10 143.6 154 10.4 19
SVH Well 10 40 33819 MH 12/14/2022 11.4 95.7 340.78 245.08 12
TOTAL 614 1,166
3.1 SV WELL NO. 1
LRE conducted a 24-hour constant discharge pumping test at SV Well No. 1 on September 29,
2022. The temporary well pump was set at 180 ft. The perforated portion of the well casing is
from 85 ft to 285 ft below the ground surface. The pressure transducer was installed at 175 ft and
was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
The static water level prior to the test was measured to be 22 ft below the top of the well casing
(TOC). With the pump set at 180 ft below the ground surface, there was approximately 158 ft of
available drawdown in the aquifer. The pump was initially set to 100 gpm increased to 300 gpm
36 minutes after starting the test. On average, LRE Water calculated a pumping rate of 298.4
PUMPING TEST RESULTS
Spring Valley Ranch Page 3 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
gpm over the 24 hour pumping period, with a maximum pumping rate of 300 gpm. The pump was
intentionally operated to run at or near this rate based on the permitted rate.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 131 ft within 40 minutes (six minutes after achieving 300
gpm), then incrementally dropped over the 24-hour test. The maximum water level drawdown
occurred at the end of the pump test with a water level depth of 161.53 ft below TOC (139.53 feet
of drawdown compared to static water levels). Figure 1 graphically shows the water depth
measurements that were taken both manually and electronically by the pressure transducer.
Figure 1: SVR Well 1 (86630-F) Pump Test
Depth from Top of Casing (TOC)
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first six minutes from a depth of 161.53 ft to a depth of 47.85 ft. Figure 2 depicts the water level
Static Water Level (ft)Notes: 1.) Initial Water Level = 22.0 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 161.53 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =305 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.00.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 22.0 ft.
Average Pumping Rate= 300 gpm
Spring Valley Ranch Page 4 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
recovery in the well and demonstrates the well recovered to 96% after 24 hours of the pump being
shut off.
Figure 2: SVR Well 1 (86630-F) Recovery
Depth from Top of Casing (TOC)
The aquifer drawdown and recovery data support that SV Well No. 1 can produce at the permitted
rate of 300 gpm and experienced a 96% recovery in 24 hours. Setting the pump at the deepest
elevation in the well results in approximately 260 ft of allowable drawdown of the aquifer. Using
an average pump rate of 300 gpm and total drawdown of 139.53 ft, the specific capacity of the
well was calculated to be 2.14 gpm per foot. Using the specific capacity of the well and 260 ft of
available drawdown, LRE estimates SV Well No. 1 can currently produce at 550 gpm.
3.2 ASR WELL NO. 16 FKA GAMBA 8
LRE conducted a 24-hour constant discharge pumping test at ASR Well No. 16 on October 12,
2022. The temporary well pump was set at 240 ft. The perforated portion of the well casing is
from 150 ft to 180 ft below the ground surface. The pressure transducer was installed at 235 ft
and was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
Static Water Level (ft)
Residual Drawdown (ft)
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 22.0 ft.
Spring Valley Ranch Page 5 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
The static water level prior to the test was measured to be 20.25 ft below the top of the well casing
(TOC). With the pump set at 140 ft below the ground surface, there was approximately 120 ft of
available drawdown in the aquifer. The well has a permitted rate of 100 gpm, so the pump was
initially set to 100 gpm. The pumping rate was decreased over the 24-hour pumping test due to
the rate of drawdown and available water in the well. On average, LRE Water calculated a
pumping rate of 54.3 gpm over the 24 hour pumping period.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 93.32 ft within 10 minutes and continued to decline at a
steady rate until the flow rate was reduced to 82 gpm. The well recovered approximately 50 ft
after the flow rate was reduced, but then the aquifer level began to steadily decline until the flow
rate was reduced to a lower rate. A flow rate reduction was performed a couple more times
throughout the test. The maximum water level drawdown occurred at the end of the pump test
with a water level depth of 231.42 ft below TOC (211.17 feet of drawdown compared to static
water level). Figure 3 graphically shows the water depth measurements that were taken both
manually and electronically by the pressure transducer.
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first 10 minutes from a depth of 231.42 ft to a depth of 150.9 ft, equal to approximately an 80 ft
rise in the aquifer level. Figure 4 depicts the water level recovery in the well and demonstrates
the well recovered to 70% after 24 hours of the pump being shut off
Spring Valley Ranch Page 6 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 3: ASR Well No. 16 (86629-F) Pump Test
Depth from Top of Casing (TOC)
Static Water Level (ft)Notes: 1.) Initial Water Level = 20.25 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 222.67 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =260 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
20.0
40.0
60.0
80.0
100.0
120.00.0
50.0
100.0
150.0
200.0
250.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 20.25 ft.
Average Pumping Rate= 54.3 gpm
Spring Valley Ranch Page 7 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 4: ASR Well No. 16 (86629-F) Recovery Analysis
Depth from Top of Casing (TOC)
Using an average pump rate of 54.3 gpm and total drawdown of 211.17 ft, the specific capacity
of the well was calculated to be 0.26 gpm per foot. This is a conservative estimate since the
pump was pumped at higher rates for the first seven hours of the test, which could result in a
higher amount of drawdown than if the pump had been set at 54.3 gpm throughout the 24-hour
pumping period. Using the specific capacity of the well and 235 ft of available drawdown, LRE
estimates ASR Well No. 16 can currently produce at 60 gpm.
3.3 WELL 36567-MH
LRE conducted a 4-hour constant discharge pumping test at Well 36567-MH on October 18, 2022.
The temporary well pump was set at 240 ft. The perforated portion of the well casing is from 180
ft to 250 ft below the ground surface. The pressure transducer was installed at 25 ft and was set
to record pressure and temperature reading every minute. Barometric pressure can impact water
levels in unconfined aquifers; therefore, all pressure values were corrected for changes in
barometric pressure. LRE relied on this dataset to analyze drawdown within the well over the
course of the pumping test. In addition, a turbine flowmeter was then connected between the
outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
Static Water Level (ft)
Residual Drawdown (ft)
0.0
50.0
100.0
150.0
200.0
250.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 20.25 ft.
Spring Valley Ranch Page 8 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
The static water level prior to the test was measured to be 89 ft below the top of the well casing
(TOC). With the pump set at 240 ft below the ground surface, there was approximately 151 ft of
available drawdown in the aquifer. The pump was set to 8 gpm. On average, LRE Water
calculated a pumping rate of 7.7 gpm over the 24 hour pumping period, with a maximum pumping
rate of 8 gpm.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 130.86 ft within 10 minutes. A rise in the water level
occurred in the well when the flow rate dropped to 6 gpm. When the flow rate was adjusted back
to 8 gpm around minute 100 the aquifer steadily declined, but experienced brief periods of
recharge. The maximum water level drawdown occurred at the end of the pump test with a water
level depth of 219.37 ft below TOC (130.37 feet of drawdown compared to static water level).
Figure 5 graphically shows the water depth measurements that were taken both manually and
electronically by the pressure transducer.
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first 10 minutes from a depth of 219.37 ft to a depth of 191.79 ft. Figure 6 depicts the water level
recovery in the well and demonstrates the well recovered to 91.5% after 4 hours and 100% after
16 hours of the pump being turned off.
The aquifer drawdown and recovery data support that Well 36567-MH can currently produce 7.7
gpm and with 91.4% recovery occurring in 4hours and 100% recovery experienced in 16 hours.
Setting the pump at the deepest elevation in the well results in approximately 165 ft of allowable
drawdown of the aquifer. Using an average pump rate of 7.7 gpm and total drawdown of 130 ft,
the specific capacity of the well was calculated to be 0.06 gpm per foot. Using the specific capacity
of the well and 165 ft of available drawdown, LRE estimates Well 36567-MH can currently produce
at 10 gpm.
Spring Valley Ranch Page 9 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 5: Well 36567-MH Pump Test
Depth from Top of Casing (TOC)
Static Water Level (ft)Notes: 1.) Initial Water Level = 89.0 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 219.37 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =264 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.00.0
50.0
100.0
150.0
200.0
250.0
110100
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 89.0 ft.
Average Pumping Rate= 7.7 gpm
Spring Valley Ranch Page 10 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 6: Well 36567-MH Recovery Analysis
Depth from Top of Casing (TOC)
3.4 WELL 36596-MH
LRE conducted a 24-hour constant discharge pumping test at Well 36596-MH on October 19,
2022. The temporary well pump was set at 150 ft. The perforated portion of the well casing is
from 80 ft to 150 ft below the ground surface. The pressure transducer was installed at 145 ft and
was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
The static water level prior to the test was measured to be 19.55 ft below the top of the well casing
(TOC). With the pump set at 150 ft below the ground surface, there was approximately 130 ft of
available drawdown in the aquifer. The pump was set to 8 gpm, based on the expected yield of
the well. On average, LRE Water calculated a pumping rate of 99.9 gpm over the 24 hour
pumping period.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
Static Water Level (ft)
Residual Drawdown (ft)
0.0
50.0
100.0
150.0
200.0
250.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 89.0 ft.
Spring Valley Ranch Page 11 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
pump test started the aquifer dropped 50 ft within 10 minutes, then incrementally dropped over
the 24-hour test. The maximum water level drawdown occurred at the end of the pump test with
a water level depth of 91.01 ft below TOC (71.46 feet of drawdown compared to static water
levels). Figure 7 graphically shows the water depth measurements that were taken both manually
and electronically by the pressure transducer.
Figure 7: Well 36569-MH Pump Test
Depth from Top of Casing (TOC)
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first 10 minutes from a depth of 91.01 ft to a depth of 36.74 ft, equal to approximately a 17.19 ft
rise in the aquifer level. Figure 8 depicts the water level recovery in the well and demonstrates
the well recovered to 97% after 24 hours of the pump being shut off.
Static Water Level (ft)Notes: 1.) Initial Water Level = 19.55 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 88.75 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =163 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 19.55 ft.
Average Pumping Rate= 99.9 gpm
Spring Valley Ranch Page 12 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 8: Well 36569-MH Recovery Analysis
Depth from Top of Casing (TOC)
The aquifer drawdown and recovery data support that 36596-MH can currently produce at the
permitted rate of 100 gpm and experience a 97% recovery in 24 hours. At the end of the 24 hour
pumping test, 61 ft of water in the aquifer remained in the well. Using an average pump rate of
99.9 gpm and total drawdown of 135 ft, the specific capacity of the well was calculated to be 1.45
gpm per foot. Using the specific capacity of the well and 135 ft of available drawdown, LRE
estimates 36596-MH can currently produce at 195 gpm.
3.5 SVR WELL NO. 20 FKA GAMBA 1
LRE conducted a 24-hour constant discharge pumping test at SVR Well No. 20 on October 31,
2022. The temporary well pump was set at 180 ft. The perforated portion of the well casing is
from 110 ft to 219 ft below the ground surface. The pressure transducer was installed at 175 ft
and was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
Static Water Level (ft)
Residual Drawdown (ft)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 19.55 ft.
Spring Valley Ranch Page 13 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
The static water level prior to the test was measured to be 113 ft below the top of the well casing
(TOC). With the pump set at 180 ft below the ground surface, there was approximately 67 ft of
available drawdown in the aquifer. The well has a permitted rate of 300 gpm. The pump was set
initially to produce at a constant rate of 70 gpm with the intent to increase to 100 gpm shortly after
the test began. The pumping rate was decreased over the 24-hour pumping test due to the rate
of drawdown and available water in the well. On average, LRE Water calculated a pumping rate
of 51.6 gpm over the 24 hour pumping period.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 56.9 ft within 5 minutes, so the flow rate was reduced to
and then increased to approximately 80 gpm. The aquifer level began to steadily decline until the
flow rate was reduced to a lower rate. A flow rate reduction was performed a couple more times
throughout the test. The maximum water level drawdown occurred within the first five minutes of
the test with a water level depth of 151.44 ft below TOC occurring at the end of the 24-hour
pumping period. Figure 9 graphically shows the water depth measurements that were taken both
manually and electronically by the pressure transducer.
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first six minutes from a depth of 151.44 ft to a depth of 121.13 ft, equal to approximately an 30 ft
rise in the aquifer level. Figure 10 depicts the water level recovery in the well and demonstrates
the well recovered to 90% after 24 hours of the pump being shut off.
Using an average pump rate of 51.6 gpm and total drawdown of 56.9 ft, the specific capacity of
the well was calculated to be 0.91 gpm per foot. This is a conservative estimate since the pump
was pumped at higher rates for the part of the test, which could result in a higher amount of
drawdown than if the pump had been set at 51.6 gpm throughout the 24-hour pumping period.
Using the specific capacity of the well and 105 ft of available drawdown, LRE estimates SVR Well
No. 20 is capable of currently producing at 95 gpm if the pump was set at the deepest elevation
in the well.
Spring Valley Ranch Page 14 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 9: SVR Well No. 20 (86628-F) Pump Test
Depth from Top of Casing (TOC)
Static Water Level (ft)Notes: 1.) Initial Water Level = 113.0 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 151.44 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =223 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.00.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 113.0 ft.
Average Pumping Rate= 51.6 gpm
Spring Valley Ranch Page 15 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 10: SVR Well No. 20 (86628-F) Recovery Analysis
Depth from Top of Casing (TOC)
3.6 ASR WELL NO. 15
LRE conducted a 24-hour constant discharge pumping test at ASR Well No. 15 on November 14,
2022. The temporary well pump was set at 190 ft. The perforated portion of the well casing is
from 110 ft to 220 ft below the ground surface. The pressure transducer was installed at 185 ft
and was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
The static water level prior to the test was measured to be 112.8 ft below the top of the well casing
(TOC). With the pump set at 190 ft below the ground surface, there was approximately 77 ft of
available drawdown in the aquifer. The pump was set to 100 gpm, based on the expected yield
of the well. The pumping rate was reported as decreasing over the 24-hour pumping test based
on the flow meter, but was not manually decreased because there was still plenty of water level
available in the well to maintain the 100 gpm pumping rate. Based on the reported flow rates,
LRE Water calculated an average pumping rate of 79 gpm over the 24 hour pumping period.
Static Water Level (ft)
Residual Drawdown (ft)
50.0
70.0
90.0
110.0
130.0
150.0
170.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 113 ft.
Spring Valley Ranch Page 16 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 30.36 ft within 5 minutes, then incrementally dropped over
the 24-hour test. The maximum water level drawdown occurred at the end of the pump test with
a water level depth of 149.58 ft below TOC (36.78 feet of drawdown compared to static water
levels). It is worth noting that approximately 40 ft of water in the well was available for additional
drawdown during the pump test. Figure 11 graphically shows the water depth measurements
that were taken both manually and electronically by the pressure transducer.
Figure 11: SVR Well No. 15 (MH-36760) Pump Test
Depth from Top of Casing (TOC)
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first six minutes from a depth of 149.58 ft to a depth of 124.83 ft, equal to approximately a 25 ft
rise in the aquifer level and then experienced an incremental rise throughout the monitoring
period. Figure 12 depicts the water level recovery in the well and demonstrates the well
recovered to 80% after 24 hours and 95% after seven days of the pump being turned off.
Static Water Level (ft)Notes: 1.) Initial Water Level = 112.8 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 149.58 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =220 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
20.0
40.0
60.0
80.0
100.0
120.0‐30.0
20.0
70.0
120.0
170.0
220.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 112.8 ft.
Average Pumping Rate= 79 gpm
Spring Valley Ranch Page 17 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 12: SVR Well No. 15 (MH-36760) Recovery Analysis
Depth from Top of Casing (TOC)
Using an average pump rate of 79 gpm and total drawdown of 36.8 ft, the specific capacity of the
well was calculated to be 2.15 gpm per foot. This is a conservative estimate since the pump was
pumped at higher rates for the part of the test, which could result in a higher amount of drawdown
than if the pump had been set at 79 gpm throughout the 24-hour pumping period. Using the
specific capacity of the well and 105 ft of available drawdown, LRE estimates the well can
currently produce at a maximum rate of 225 gpm if the pump was set at the deepest elevation in
the well. This and the unutilized 40 ft of water column in the well during the pump test suggests
that the well can support the 100 gpm permitted rate.
3.7 ASR WELL NO. 14
LRE conducted a 24-hour constant discharge pumping test at ASR Well No. 14 on November 30,
2022. The temporary well pump was set at 160 ft. The perforated portion of the well casing is
from 140 ft to 160 ft below the ground surface. The pressure transducer was installed at 155 ft
and was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
Static Water Level (ft)
Residual Drawdown (ft)
90.0
100.0
110.0
120.0
130.0
140.0
150.0
160.0
1 10 100 1000 10000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 112.8 ft.
Spring Valley Ranch Page 18 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
The static water level prior to the test was measured to be 143.6 ft below the top of the well casing
(TOC). With the pump set at 160 ft below the ground surface, there was approximately 16.4 ft of
available drawdown in the aquifer. The pump was set to 50 gpm based on the expected yield.
The pumping rate was decreased over the 24-hour pumping test due to the rate of drawdown and
available water in the well. On average, LRE Water calculated a pumping rate of 10 gpm over
the 24 hour pumping period.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped below the pressure transducer with in the first minute. The
pumping rate was decreased to 10 gpm and the water level in the well rebounded to 146 ft within
eight minutes. The rate was increased to 16 gpm at 10 minutes and the water level dropped
approximately 4.5 ft in two minutes. 30 minutes after pumping began the rate was decreased to
10 gpm and remained constant throughout the test. The water level depth at the end of the pump
test was 146.85 ft below TOC (3.25 feet of drawdown compared to static water levels). Figure
13 graphically shows the water depth measurements that were taken both manually and
electronically by the pressure transducer.
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first 1 minute from a depth of 146.85 ft to a depth of 143.95 ft, equal to approximately a 2.9 ft rise
in the aquifer level equating to 90% recovery. Figure 14 depicts the water level recovery in the
well and demonstrates the well recovered to 100% after 18 hours of the pump being shut off.
Spring Valley Ranch Page 19 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 13: SVR Well No. 14 (66299-F) Pump Test
Depth from Top of Casing (TOC)
Static Water Level (ft)Notes: 1.) Initial Water Level = 143.6 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 146.85 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =180 ft. from Top of Well Casing
Flow Rate (gpm)
0.0
10.0
20.0
30.0
40.0
50.0
60.0142.0
144.0
146.0
148.0
150.0
152.0
154.0
156.0
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 143.6 ft.
Average Pumping Rate= 10 gpm
Spring Valley Ranch Page 20 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Figure 14: SVR Well No. 14 (66299-F) Recovery Analysis
Depth from Top of Casing (TOC)
The aquifer drawdown and recovery data support that ASR Well No. 14 can currently produce 10
gpm and experience a 100% recovery in 18 hours. Using an average pump rate of 10 gpm and
total available drawdown of 30 ft, the specific capacity of the well was calculated to be 0.63 gpm
per foot. This is a conservative estimate since the pump was pumped at higher rates for the part
of the test, which could result in a higher amount of drawdown than if the pump had been set at
10 gpm throughout the 24-hour pumping period. Using the specific capacity of the well and 30 ft
of available drawdown, LRE estimates ASR Well No. 14 is capable of currently producing at 19
gpm.
3.8 SVH WELL 10
LRE conducted a 24-hour constant discharge pumping test at SVH Well 10 on December 14,
2022. The temporary well pump was set at 350 ft. The perforated portion of the well casing is
from 90 ft to 350 ft below the ground surface. The pressure transducer was installed at 345 ft and
was set to record pressure and temperature reading every minute. Barometric pressure can
impact water levels in unconfined aquifers; therefore, all pressure values were corrected for
changes in barometric pressure. LRE relied on this dataset to analyze drawdown within the well
over the course of the pumping test. In addition, a turbine flowmeter was then connected between
the outflow of the pump and the discharge line. This meter was used to establish and monitor the
pumping rate and volume pumped.
Static Water Level (ft)
Residual Drawdown (ft)
143.4
143.6
143.8
144.0
144.2
144.4
144.6
144.8
145.0
1 10 100 1000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 143.6 ft.
Spring Valley Ranch Page 21 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
The static water level prior to the test was measured to be 95.7 ft below the top of the well casing
(TOC). With the pump set at 350 ft below the ground surface, there was approximately 254 ft of
available drawdown in the aquifer. The pump was set to 50 gpm, based on the expected yield of
the well. The pumping rate was decreased over the 24-hour pumping test due to the rate of
drawdown and available water in the well. On average, LRE Water calculated a pumping rate of
11.4 gpm over the 24 hour pumping period.
Throughout the pumping test, manual readings were collected in the field. In particular, the
drawdown was monitored in order to determine if the pumping rate could be sustained. Once the
pump test started the aquifer dropped 184.78 ft within 5 minutes, so the flow rate was reduced to
to 38 gpm. After 40 minutes of pumping the well had experienced 228.85 ft of drawdown and the
water level was at 324.55 ft below the top of casing. The pumping rate was reduced to 16 gpm
and the water level experienced a 32 ft rise and then the aquifer level began to steadily decline
until the flow rate was reduced to a 12 gpm. A flow rate reduction was performed a couple more
times throughout the test. The maximum water level drawdown occurred at the end of the pump
test with a water level depth of 340.78 ft below TOC (245.08 feet of drawdown compared to static
water levels). Figure 15 graphically shows the water depth measurements that were taken both
manually and electronically by the pressure transducer.
Figure 15: SVR Well No. 10 (MH-33819) Pump Test
Depth from Top of Casing (TOC)
Static Water Level (ft)Notes: 1.) Initial Water Level = 95.7 ft. below Top of Well Casing
Depth of Water from TOC 2.) Final Water Level = 340.78 ft. below Top of Well Casing
Manual Measurements 3.) Well Depth =360 ft. from Top of Well Casing
Flow Rate (gpm)
0
5
10
15
20
25
30
35
40
450
50
100
150
200
250
300
350
400
1 10 100 1000
Fl
o
w
Ra
t
e
(g
p
m
)
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Pumping Time (minutes)
Static Water Level = 95.7 ft.
Average Pumping Rate= 11.4 gpm
Spring Valley Ranch Page 22 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
In addition to monitoring the water level during the pumping test, it is equally important to monitor
the recovery process. The pump and pressure transducer were therefore kept in place at the
conclusion of the test. The water level in the well at the start of recovery rebounded within the
first 5 minutes from a depth of 340.78 ft to a depth of 297.34 ft, equal to approximately a 43.44 ft
rise in the aquifer level. Figure 16 depicts the water level recovery in the well and demonstrates
the well recovered to 99% after 24 hours of the pump being shut off.
Figure 16: SVR Well No. 10 (MH-33819) Recovery Analysis
Depth from Top of Casing (TOC)
The aquifer drawdown and recovery data support that SVH Well 10 can currently produce 11.4
gpm and experience a 100% recovery in 24 hours. Using an average pump rate of 11.4 gpm and
total available drawdown of 254 ft, the specific capacity of the well was calculated to be 0.05 gpm
per foot. This is a conservative estimate since the pump was pumped at higher rates for the part
of the test, which could result in a higher amount of drawdown than if the pump had been set at
11.4 gpm throughout the 24-hour pumping period. Using the specific capacity of the well and 254
ft of available drawdown, LRE estimates SVH Well 10 is capable of currently producing at 12 gpm.
Static Water Level (ft)
Residual Drawdown (ft)
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
1101001000
De
p
t
h
fr
o
m
TO
C
(f
e
e
t
)
Recovery Time (minutes)
Static Water Level = 95.7 ft.
Spring Valley Ranch Page 23 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
SECTION 4: WATER QUALITY RESULTS
Wells were sampled for a standard suite of parameters in accordance with CDPHE Regulation
No. 11 – Colorado Primary Drinking Water Regulations. Samples were analyzed by a State of
Colorado certified laboratory that follows accepted industry standards and quality
assurance/quality control procedures. The water quality results are tabulated in Table 2 and
Table 3. Overall, results indicate good water quality for potable consumption and use. The data
indicate the only likely treatment required for the well will be chlorine disinfection if the water will
be used for a community or non-community water system as defined by CDPHE.
ASR Well No. 16 and ASR Well No. 15 have elevated levels of iron and manganese. Results at
Well 36567-MH and ASR Well No. 14 also had elevated iron levels. Iron and manganese are
secondary parameters, so no treatment will be required by CDPHE. Although treatment will not
be required, removal of these contaminants from the water is recommended to maintain the
service life of the water mains and service lines and to provide water to the users without taste
and odor issues.
Toluene was detected in low levels, three and four orders of magnitude below the maximum
allowable amount of contaminant (MCL), in wells ASR Well No. 16, Well 36567-MH, ASR Well
No. 15, and ASR Well No. 14. Toluene is a volatile organic compound and is known to be toxic
for human consumption. LRE spoke with CDPHE about the presence of toluene and concluded
it was probably due to field contamination from the generator operating at the time sampling
occurred.
DI(2-ethylhexyl)phthalate was also detected in wells ASR Well No. 16 and ASR Well No. 15. The
amount detected was three orders of magnitude below the MCL. DI(2-ethylhexyl)phthalate is a
volatile organic compound which is widely used as a plasticizer in manufacturing of articles made
of PVC and also used as a hydraulic fluid. Based on a conversation with CDPHE, it is the opinion
of LRE that the presence of DI(2-ethylhexyl)phthalate was also due to field contamination from
materials used by the pump contractor during testing; PVC piping was used during testing as well
as a hydraulic lift was used to place the pump and PVC piping into the well.
ASR Well No. 16 and Well 36596-MH are located approximately 110 ft and 20ft from Landis
Creek, respectively. It is anticipated that CDPHE will require a that a Groundwater Under the
Influence of Surface Water (GWUDI) evaluation be completed on both wells. The GWUDI occurs
over six months and consists of weekly sampling from both the wells and creek. CDPHE will
require additional treatment if the results of the evaluation indicate that Landis Creek has a direct
influence on the wells.
Spring Valley Ranch Page 24 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Table 2: Regulated Water Quality Results
Regulation 11 Constituents
Name
SV Well
No. 1
ASR Well
No. 16 fka
Gamba 8 36567-MH
SVR Well
No. 20 fka
Gamba 1
ASR Well
No. 15
ASR Well
No. 14
Permit No.86630-F 86629-F 36567-MH 86628-F 36760 MH 66299-F
Parameter Unit MCL Result Result Result Result Result Result
Regulation 11 Constituents
Total Coliform Rule
Total Coliform --------------
E.coli MPN/100mL ------------
Nitrate and Nitrite Rule
Nitrate - N mg/L 10 0.84 ND 0.68 0.53 0.51 0.43
Nitrite - N mg/L 1 ND ND ND ND ND ND
Inorganics Rule
Antimony mg/L 0.006 ND ND ND ND ND ND
Arsenic mg/L 0.01 ND ND ND ND ND ND
Asbestos fibers/L 7 mil fibs/L ND ND ND ND ND ND
Barium mg/L 2 0.36 0.12 0.085 0.16 0.17 0.28
Beryllium mg/L 0.004 ND ND ND ND ND ND
Cadmium mg/L 0.005 ND ND ND ND ND ND
Chromium mg/L 0.1 ND ND 0.0072 ND ND ND
Cyanide mg/L 0.02 ND ND ND 0.0057 ND ND
Fluoride mg/L 4 0.14 ND ND ND ND ND
Mercury mg/L 0.002 ND ND ND ND ND ND
Nickel mg/L ND ND 0.0036 ND 0.002 0.003
Selenium mg/L 0.05 ND ND ND ND ND ND
Thallium mg/L 0.002 ND ND ND ND ND ND
Sodium mg/L 9.3 4.8
ND ND 4.2 5.5
Secondary Parameters Secondary MCL
Aluminum mg/L .05 - 0.2 ND ND 2.4 ND 0.09 ND
Chloride mg/L 250 ND ND ND ND 0.74 1.5
Iron mg/L 0.3 ND 12.1 1.6 0.3 2.1 0.8
Manganese mg/L 0.05 ND 0.18 0.011 0.002 0.087 0.003
pH 6.5-8.5 7.96 8.31 8.11 7.85 7.90 7.77
Silver mg/L 0.1 ND ND ND ND ND ND
Sulfate mg/L 250 4.6 ND 1.4 ND 7.1 2.6
TDS mg/L 500 331 115 248 204 229 266
Zinc mg/L 5 ND ND ND ND ND ND
Radionuclides
Gross Alpha pCi/L 15 ND ND ND ND ND
Gross Beta pCi/L 15 3.8 ND 1
ND 0.02
Combined Radium pCi/L 5 0.9 1 0.8
ND 0.5
SOCs and VOCs (only noting detected compounds)
Toluene mg/L 1 ND 0.004 0.007
ND 0.0003 0.0004
DI(2-ethylhexyl)phthalate mg/L 0.4 ND 0.0005 ND ND 0.0007 ND
Spring Valley Ranch Page 25 of 24
Physical Water Supply
March, 2023 – Project # 2167SVRD02
Table 3: Additional Water Quality Parameters
Name
SV Well
No. 1
ASR Well
No. 16 fka
Gamba 8 36567-MH
SVR Well
No. 20 fka
Gamba 1
ASR Well
No. 15
ASR Well
No. 14
Permit No.86630-F 86629-F 36567-MH 86628-F 36760 MH 66299-F
Parameter Unit MCL Result Result Result Result Result Result
Corrosivity and Hardness
Bicarbonate mg/L as CaCO3 253 91 151 176 185 233
Carbonate mg/L ND 5 ND ND ND ND
Hydroxide mg/L ND ND ND ND ND ND
Total Alkalinity mg/L as CaCO3 253 96 151 176 185 233
Total Hardness mg/L as CaCO3 66.7 137.0 140.0 152.0 198.0
Calcium mg/L 72.6 26.7 53.7 56.2 60.3 79.3
Magnesium mg/L 9.98 6.86 4.60 9.40 9.00 7.90
Additional WQ Paramters
Specific Conductance umhos/cm 520 201 310 355 360 464
Phosphate - Ortho (as P)mg/L as P
Phosphate - Ortho (as PO4)mg/L as PO4
Turbidity NTU 12.00 0.15 10.00
Sodium Adsoprtion Ratio Calc 4 0.271 0.215 0.105 0.146 0.138 0.137
Langelier Index --0.3 0.60 0.40 0.50 0.60
!.
!.
!.
!.
!.
!.
!.
!.!.!.
!.
!.
!.
SV Well No 1
300 gpm
ASR Well No.14
10 gpm
ASR Well No.13
ASR Well No.16 fka Gamba 8
54 gpm
SVR Well No. 2
ASR Well No. 15
79 gpm
SVR Well No. 20 fka Gamba 1
52 gpm
SVH Well No. 10
11 gpm
SVR Well No. 17
SVR Well No. 21
SVR Well No. 3
36596-MH
100 gpm
36567-MH
8 gpm
Landis CreekLandis Creek
Attachment 1Well Location and Current Production Rate MapSpring Valley Holdings, LLC
®
0 2,000 4,0001,000
Feet
Date: 2023-01-20
File: 2166702
Drawn: ABS
Approved:
Source: USDA 2019 NAIP Garfield County
Spring Valley Holdings, LLC
Garfield County Parcels
Streams
Well Locations
!.GPS
!.Alta Survey