HomeMy WebLinkAbout1.04 Appendix D - Grading & Drainage Reports
IHC SCOTT RIFLE PIT #1
GRADING AND DRAINAGE REPORT
RIFLE PIT #1
IHC SCOTT (SCOTT CONTRACTING INC.)
MARCH 2021
Prepared by
118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004
970.945.5948 fax
IHC Scott – Rifle Gravel Pit #1 Grading and Drainage Report March 2021
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TABLE OF CONTENTS
1.0 Site Map 1
2.0 Drainage Structures 1
2.1 Locations of Existing Drainage Features 1
2.2 Existing Drainage Features 1
Wetlands 1
Geology 1
Drainage and Stormwater Conveyances 1
Irrigation Infrastructure 7
2.3 Locations of Proposed Drainage Features 7
2.4 Preliminary Engineering Design and Construction Features 9
Floodplain Modeling and Site Drainage 9
Access Road and I-70 N Frontage Road Drainage 9
3.0 Topography 9
4.0 Grading and Drainage Plan 9
5.0 Soil Stockpile and Snow Storage Areas 9
6.0 Equipment Storage Areas 9
7.0 Temporary Roads 12
8.0 Areas of Steep Slope 12
9.0 Construction Schedule 12
10.0 Mining Plan 13
10.1 Site Development and Grading (Phase 1) 13
Topsoil and Overburden Handling 13
Water Handling and Dewatering 14
Stormwater Management 14
Dewatering 15
Mining Preparation (Phase 2) 15
Water Handling and Dewatering 16
Schedule of Operations 16
Explosives 16
10.2 Mining Extraction (Phase 3 – in 2 Stages) 16
Stockpiling and Overburden Handling 16
11.0 Permanent Stabilization and Post-Mined Conditions (Reclamation, Revegetation and
Soil Plan) 17
IHC Scott – Rifle Gravel Pit #1 Grading and Drainage Report March 2021
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11.1 Description and Types of Reclamation, Revegetation, and Soil Plan 17
11.2 Post-Mining Land Use 17
12.0 Implementation of the Reclamation Plan 19
12.1 Topsoil Segregation, Preservation, and Replacement 19
12.2 Final Grading 19
12.3 Seeding 19
Temporary Seed Mix 19
Long-Term/Permanent Seed Mix 19
13.0 Erosion Control Measures 20
14.0 Estimated Cost 20
15.0 Calculations 21
15.1 Floodplain Analyses 21
16.0 Neighboring Areas 21
17.0 Stormwater Management 22
17.1 Stormwater Management Plan (SWMP) 22
18.0 Reclamation, Revegetation, and Soil Plan 22
18.1 Weed Management Plan 22
18.2 Revegetation Security 23
19.0 Hydraulic Calculations 23
20.0 Maintenance Requirements 23
21.0 Spill Prevention Control and Countermeasures Plan (SPCC) 23
22.0 Signature Block 24
LIST OF TABLES
Table 1. Estimated Areas of Disturbance to Support Gravel Mining 12
Table 2. Estimated Timetable for Stages 1 & 2 Activities 14
Table 3. Estimated Reclamation Costs 21
IHC Scott – Rifle Gravel Pit #1 Grading and Drainage Report March 2021
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LIST OF FIGURES
Figure 1. Site Map including Existing and Proposed Water Features 2
Figure 2. Existing Conditions Site Map 3
Figure 3. NWI Wetlands Map 4
Figure 4. Initial Wetlands Mapping (SGM, July 17, 2019) 5
Figure 5. November 19, 2020 (SGM) Wetlands Mapping to inform Dewatering Pipeline Alignment 6
Figure 6. Existing I-70 N Frontage Road Drainage Features and Proposed Access Road and Drainage
Improvements 8
Figure 7. Stage 1 Mining Plan Details, Perimeter Berm Detail and Stockpile Locations 10
Figure 8. Stage 2 Mining Plan Details, Perimeter Berm Detail and Stockpile Locations 11
Figure 9. Post-Mining and Reclaimed Conditions 18
LIST OF APPENDICES
Appendix A
SPCC Plan
1
This Grading and Drainage Plan describes the information required in Section 4-203.E of
the Garfield County Land Use and Development Code (LUDC) for the IHC Scott (Scott)
[formerly Scott Contracting, Inc. (SCI)] Rifle Pit #1 Major Impact Land Use Permit
application.
1.0 Site Map
Figure 1 depicts the existing site conditions and structures, waterbodies and hydrologic
features, wetlands and the 100-year floodplain boundaries for the Rifle Pit #1 property.
2.0 Drainage Structures
2.1 Locations of Existing Drainage Features
Figures 1 and 2 depict the locations of existing and proposed drainage structures affecting
site drainage on the site and within 10 feet adjacent to the site boundary.
2.2 Existing Drainage Features
Wetlands
The National Wetlands Inventory (NWI) for the Rifle Pit #1 property indicated that most of
the area is wetlands (Figure 3). Site visits and delineations were performed by SGM on July
17, 2019 and November 19, 2020 and generally confirmed that this parcel contains large
areas of wetlands, although not as extensive as suggested by the NWI (Figure 4 and Figure
5). The wetland areas are concentrated on the west end of the property and are well-
developed and relatively high-quality from a biological and functional perspective. The east
end is mesic pasture meadow rather than jurisdictional wetlands, and development of the
gravel resources in this area could be accomplished without Section 404 permits.
Geology
The Rifle Pit #1 site is underlain by river gravels which are saturated and in direct contact
with the water table. The surface soil is generally an alluvial silty clay loam, with areas of
heavy clay. Boring logs and direct observation suggest that many areas of wetland
vegetation are underlain by a clay aquitard layer at a depth of approximately 3 feet.
The July 2019 site visit (SGM) and supplemental subsurface documentation suggests that
the wetlands are supported primarily by surface water discharge onto the property via
pooling of that water on the shallow clay aquitards. Shallow groundwater may be
supplementing the wetland hydrology in some areas, but drilling data suggest that the water
table is approximately seven feet below the surface across most of the property, and that 3
or 4 feet of dry gravel underlies the clay pans and wetlands.
Drainage and Stormwater Conveyances
There are no street gutters nor storm sewers on nor adjacent to the site. There is an existing
concrete valley pan that intercepts drainage from the east within the roadway ditch that
conveys it to a 30” culvert and carries it under the existing gravel frontage road to the south.
2 Figure 1. Site Map including Existing and Proposed Water Features
3 Figure 2. Existing Conditions Site Map
4 Figure 3. NWI Wetlands Map
5 Figure 4. Initial Wetlands Mapping (SGM, July 17, 2019)
6
Figure 5. November 19, 2020 (SGM) Wetlands Mapping to inform Dewatering Pipeline
Alignment
7
There is also a roadway ditch that intercepts drainage from the I-70 N Frontage road and
conveys it to the west (Figure 1).
Irrigation Infrastructure
In general, surface water reaches the property exclusively via artificially excavated channels
off the Last Chance Ditch. This includes the large lateral/tailwater ditch that bisects the
property from east to west, and several smaller ditches that discharge underneath the
interstate and onto the southern boundary of the property (Figure 1).
SGM conducted two phone interviews to better understand the irrigation practices. SGM
interviewed Joey Shideler, who is the president and ditch rider for the Rising Sun Ditch and
one of the lessees of the Ranch. Joey Shideler and his brother Chris Shideler have been
leasing the Ranch for approximately 15 years for cattle grazing. SGM also interviewed Jim
Snyder, president of the Loesch & Crann Ditch Company (operates the Last Chance Ditch
which is also known as the Loesch & Crann Ditch).
During a July 17, 2019 site visit, SGM observed a concrete irrigation system on the property
that is fed by two culverts under I-70. The two culverts lead to an open concrete irrigation
lateral along the southern edge of the property with turnouts approximately every 100 feet to
irrigate the field to the north of the lateral. This infrastructure is shown on Figure 1. SGM did
not follow these culverts to their headgates, but interviews with Mr. Shideler and Mr. Snyder
both agree that these culverts are laterals currently diverting from the Last Chance Ditch,
not the Rising Sun Ditch.
Mr. Snyder understands that there is currently no infrastructure in place to deliver water to
the property from the Rising Sun Ditch, though he understands that there was historically a
lateral delivering water to the property from the Rising Sun Ditch (which crossed over the
Last Chance Ditch, as the Rising Sun Ditch is located above the Last Chance Ditch).
2.3 Locations of Proposed Drainage Features
The proposed perimeter berm will serve as stormwater control for any water generated on-
site as a result of precipitation events, specifically containing any stormwater runoff off the
site during mining activities. The interception trench will also redirect the tailwater from the
east along the eastern and northern edges of the property to the Colorado River.
Based on this understanding of the hydrology, if the tailwater seepage and direct discharge
onto the property are stopped (by closing headgates, re-routing and/or piping the ditches, or
other similar methods), the primary water source for the wetlands could be removed. Scott,
however, will not disturb the tailwater channel in its existing location and implement Best
Management Practices (BMPs) to prevent mining operations from discharging into or
comingling with these waters. Scott will install a low-water crossing at the existing tailwater
culvert crossing or collect the water in a pipe. The combination of pit dewatering adjacent to
the wetlands, could remove the hydrology supporting the wetlands throughout the site, and
will likely result in the loss of wetland status within two growing seasons. Scott has installed
piezometers to measure the groundwater to inform the jurisdictional determination of these
wetlands. Groundwater modeling also suggests that pit dewatering activities in adjacent
upland areas (east) will significantly and rapidly depress groundwater levels throughout the
Parcel, further isolating the wetlands from groundwater hydrology.
8 Figure 6. Existing I-70 N Frontage Road Drainage Features and Proposed Access Road and Drainage Improvements
9
2.4 Preliminary Engineering Design and Construction Features
There were two primary preliminary engineering analyses conducted for purposes of the site
development and controlling developed drainage conditions: 1) Floodplain and flood control
and 2) the access road.
Floodplain Modeling and Site Drainage
HEC-RAS was used to model the 100-year floodplain for the existing and construction
phases of the site, including the height of the perimeter berm. Figures 7 and 8 show the site
plan during the Stage 1 and Stage 2 mining activities, including a typical section for the
perimeter berm. The perimeter berm will be constructed as mining proceeds across the
property, in stages, and serve to retain all stormwater and drainage on-site and any
drainage from the access road will be intercepted by the roadway ditch.
Access Road and I-70 N Frontage Road Drainage
Drainage from the access road will be intercepted by the roadway ditch (Figure 6). 2-18”
Corrugated Metal Piping (CMP) culverts will also be installed under the access road to
maintain the flowline along the roadside ditch from east to west.
3.0 Topography
Figure 2 depicts the existing topography for the site. Elevations at the site range from 5,530
feet at the southeastern portion of the property to 5,374 feet at the western portion of the
site. The existing drainage flows east to west across the length of the property and is
generally conveyed to the Colorado River. The slope across the site varies and is generally
<5%.
4.0 Grading and Drainage Plan
Figures 7 and 8 depict the proposed Stage 1 and Stage 2 mining for the site. The only
permanent structure will be a trailer where vehicles check in and out and are weighed prior
to shipping material off-site. The perimeter berm will be constructed as mining proceeds
across the property and serve to retain all stormwater and drainage on-site and any
drainage from the access road will be intercepted by the roadway ditch (Figure 6).
5.0 Soil Stockpile and Snow Storage Areas
Figures 7 and 8 depict probable stockpile locations, by stage during Stage 1 and Stage 2,
respectively. The placement of snow storage areas will also be determined by the mining
stage of mining activity and most likely on the site, away from the excavation activity, and
outside the travel and access on and to the site.
6.0 Equipment Storage Areas
Location of storage areas designated for equipment, fuel, lubricants, chemical, and waste
storage with an explanation of spill containment structures will be identified by mining phase.
Attention to spill control and containment procedures will be part of the identification of these
storage areas during operations. S has a Spill Prevention Control and Countermeasure
10 Figure 7. Stage 1 Mining Plan Details, Perimeter Berm Detail and Stockpile Locations
11 Figure 8. Stage 2 Mining Plan Details, Perimeter Berm Detail and Stockpile Locations
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(SPCC) Plan to cover the storage and transport of fuel and other liquids that are regulated
by the Environmental Protection Agency (Appendix A).
7.0 Temporary Roads
There will be no temporary roads constructed for this project.
8.0 Areas of Steep Slope
There are no existing areas at the site with greater than 20% slopes. The mining excavation
phase will have a 25% (3H:1V) slope at the edge of each pit/area (See Figures 7 and 8 for
typical sections during mining). The perimeter berm will have 50% (2H:1V) slopes and
erosion and sediment control practices will be installed to capture any stormwater runoff at
the edge of the property.
9.0 Construction Schedule
The mining extraction areas associated with Phase 3, Stage 1 and Stage 2, has
approximately 1-2 million tons of minable material that will be extracted over four years.
These materials are anticipated to support various construction projects for future Garfield
County (County) and Colorado Department of Transportation (CDOT) projects. The
estimated area of disturbance during Stage 1 is 18.04 acres and 8.70 acres during Stage 2.
The phases are as follows:
· Site development and grading (Phase 1)
· Mining preparation (Phase 2)
· Mining extraction (Phase 3 – in two stages, Stage 1, and Stage 2, limited to non-
wetland areas)
· Reclamation (Phase 4)
A 12” dewatering pipeline will be installed during Phase 1 to collect water from the
dewatering wells and convey it to the Colorado River. The land disturbance associated with
the dewatering pipeline is temporary and estimated at 0.96 acres (3,622 linear feet with a 5-
foot offset on both sides of the pipeline).
The total estimated planned excavation area is provided in Table 1 and amounts to
approximately 29.30 acres. Appendix C (Land Use Permit Application) includes the
Drawings depicting additional details and information associated with this proposed mining
activity.
Table 1. Estimated Areas of Disturbance to Support Gravel Mining
Mining Operation Stage Area
(acres)
Dewatering Pipeline Construction (temporary disturbance) (Phase 1) 0.96
Stage 1 (Limits of Disturbance) (Phase 3) 18.04
Stage 2 (Limits of Disturbance) (Phase 3) 8.70
Operations Area (Phase 1) 1.6
Total 29.30
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The following table provides the anticipated construction schedule indicating the anticipated
starting and completion time periods of the mining by phase/stage, estimated nature, depth
and thickness of the deposit to be mined and type of overburden to be removed.
The following sub-sections provide additional narrative specific to the grading and/or
installation and removal of erosion and sediment control measures, and the estimated
duration of exposure of each area prior to the completion of temporary erosion and sediment
control measures.
10.0 Mining Plan
10.1 Site Development and Grading (Phase 1)
Topsoil and Overburden Handling
This phase of the project will include minor site grading, vegetation removal and
construction of the site access/driveway. Scott will not disturb the tailwater channel in its
existing location and implement Best Management Practices (BMPs) to prevent mining
operations from discharging into or comingling with these waters. Scott will install a low-
water crossing at the existing tailwater culvert crossing or collect the water in a pipe.
The existing topsoil will be stripped and used for the required berms along the perimeter of
the site. These berms will be placed inside of a 25-foot set back area from the property line.
These berms will be roughly 5-feet in height and 23-feet wide at the bottom and will help
control noise produced during operation. These berms will serve many purposes but specific
to drainage and erosion control they will prevent runoff of stormwater and intercept
groundwater off site and protect the operations from the influence and flooding by the
Colorado River.
Note overburden materials across the site vary. The boring holes indicate the overburden
depth can vary from 1 foot to 2.5 feet.
The mine will use conventional earth moving equipment to stockpile topsoil and gravel
including, but not limited to a bulldozer, track-hoe, and a 35-ton haul truck.
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Table 2. Estimated Timetable for Stages 1 & 2 Activities
Phase/Stage Anticipated Start Estimated
Duration Estimated Depth Type of
Overburden
Pre-Site
Development Ground
Water Monitoring
(Piezometers)
February 2021 Phases 1-3
(Stages 1 & 2)
Install at 10-12-
foot depth N/A
Phase 1
Site Development &
Grading
May
2021
May – June 2021
(1-2 months) Approx. 0.5 feet
Clay and silt; about
6” of topsoil,
medium stiff,
slightly moist,
brown
Phase 2
Mining Preparation
May
2021
May – August
2021
(2-4 months)
N/A
No additional
overburden will be
removed during
this phase
Phase 3
Mining Extraction
July
2021
July 2021 –
December 2025
(4 years)
17 – 22 feet Varies
Stage 1 July
2021
July 2021 – July
2023
20 feet
(gravel layer
thickness)
See Boring 3.
Remove estimated
5.5 feet to 6 feet of
clay and silt; gravel
layer estimated at
7 feet to 27 feet
below surface.
Stage 2 July
2023
July 2023 – July
2025
21 feet
(gravel layer
thickness)
See Boring 4
Remove estimated
6” of clay and silt;
gravel layer
estimated at 1 foot
to 22 feet below
surface.
Phase 4
(Reclamation) July 2025 July 2025–
December 2027 Not Applicable Not Applicable
Water Handling and Dewatering
Stormwater Management
Scott will apply for coverage under Permit No. COR400000, CDPS General Permit (for)
Stormwater Discharges Associated with Construction Activity at least 10 days prior to the
commencement of construction activities disturbing greater than or equal to 1 acre. This
permit has several requirements that address water quality and stormwater management,
including monitoring and reporting, and the development and implementation of a
Stormwater Management Plan (SWMP).
During the initial stages of mining, Scott will not disturb the tailwater channel in its existing
location and implement BMPs to prevent mining operations from discharging into or
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commingling with these waters. Scott will install a low-water crossing at the existing tailwater
channel crossing or collect the channel in a pipe.
Dewatering
Scott will also apply for coverage under Permit No. COG603000 (Discharges Associated
with Subterranean Dewatering or Well Development) or Permit No. COG608000
(Discharges to Surface Water from Well Development and Pumping Test Activities) to
manage dewatered water. The specific permit will be determined once the water is sampled
and analyzed.
Scott negotiated a temporary license agreement with the owner of the neighboring Shideler
property (Parcel 217908100527) to the east that will allow Scott to bury a 12” dewatering
pipeline that will collect and convey pumped dewatered water to the Colorado River
(Appendix C Drawings in the Land Use Permit Application). This pipeline will have an
energy dissipation structure upstream of the discharge point to the Colorado River and an
armored outfall to prevent erosion and sedimentation discharges into the Colorado River.
The trenching and installation of the proposed dewatering pipeline will create temporary
impacts to federally jurisdictional wetlands located on the Shideler property (Parcel
217908100527), and will also require a permanent outfall structure on the bank of the
Colorado River, which will constitute a permanent impact to that jurisdictional water. A range
of alternatives has been considered for this project and every effort has been made to avoid
the discharge of dredged or fill material into waters of the United States. However, there are
no practicable alternatives that avoid a minor and temporary filling of wetlands, which have
been minimized to the extent possible by careful selection of the proposed pipeline route.
An aquatic resources report and wetland delineation will be submitted to the Army Corps of
Engineers (ACOE) in support of a nationwide permit application 39 (NWP 39) for
Commercial and Institutional Developments. The NWP 39 application will encompass the pit
mining stages (Stages 1-2) and the dewatering pipeline. All impacts from the dewatering
pipeline are temporary; in accordance with NWP 39 conditions, during installation in wetland
areas heavy equipment will work on mats to minimize surface disturbance, and topsoil will
be segregated and reapplied following pipeline installation. No changes are proposed to the
existing hydrologic conditions on the Shideler property; therefore, the wetland conditions will
quickly re-establish in the pipeline route. The NWP 39 will be acquired prior to construction.
Coverage under a Nationwide Permit No. 7 will also be obtained for the outfall to the
Colorado River. Scott submitted a Watershed Permit Application to the City of Rifle to
address the dewatering discharge within their Watershed Protection Area.
Mining Preparation (Phase 2)
This phase of the project will include mobilization of the heavy equipment, work trailer,
screening and wash equipment, and major site grading to prepare the site for mining
activities. This phase of the project will include additional minor site grading and vegetation
removal, as needed. Equipment for this phase will include, but not be limited to, a bulldozer,
track-hoe, and a 35-ton haul truck.
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Water Handling and Dewatering
Phase 1 dewatering activities will continue throughout this phase. No additional water
diversions nor impoundments will be required during this phase.
Schedule of Operations
The Rifle Gravel Pit #1 will operate from 7 a.m. to 7 p.m. Monday through Friday, and
weekends, as needed. Scott will limit winter operations between the hours of 7 a.m. and 5
p.m. Approximately 3 to 5 employees will be on site during the mining operations. No
nighttime activities are anticipated. Occasional equipment repair, or maintenance may be
conducted at night, but lighting will be kept to a minimum and directed inward; the site will
not have ambient lighting.
Explosives
Explosives will not be used during mining or reclamation of the property.
10.2 Mining Extraction (Phase 3 – in 2 Stages)
Initial mining extraction operations will take place in 2 extraction stages and include the
areas east of the delineated wetlands. Fencing will be installed at least 10-feet away from
the tailwater channel and wetlands to prevent disturbance of these resources.
Stage 1 of the mining extraction operation will start in the southeastern quadrant of the site,
depicted in the Drawings in Appendix C (see also Figure 3). At this location, the crusher will
be placed at existing grade as excavation proceeds down to the lowest elevation of the
gravel. When enough material has been excavated in Stage 1, the crusher will be moved to
the mining pit floor. Stage 2 will take place in the northeastern quadrant of the property (See
Drawings in Appendix C or Figure 4).
Scott will also monitor the response of the delineated wetlands on the property over the
course of Phase 3 to determine if the wetlands are supported entirely by agricultural water
(i.e. non-jurisdictional). If the wetlands are determined to be non-jurisdictional, Scott intends
to submit a minor amendment to the Garfield County Land Use Change Permit to allow for
expanded mining in the future.
It should be noted that the dewatering pipeline on the Shideler property will already be
installed and the associated disturbance will be revegetated during mining extraction.
The location of the mining equipment in the bottom of the pit will support mitigation of the
mining noise and dust. All stockpiling of material at this point also be done at this level.
Stockpiling and Overburden Handling
This phase of the project will include stockpiling of material for screening, washing and
crushing processes. Sheets C5 and C6 in the Drawings (Appendix C of the Land Use Permit
Application) or Figure 7 and Figure 8 to see the approximate location of the stockpiles.
Equipment for this phase will include, but not be limited to, a bulldozer, track-hoe, and a 35-
ton haul truck.
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11.0 Permanent Stabilization and Post-Mined Conditions (Reclamation,
Revegetation and Soil Plan)
Figure 9 depicts the stabilized and post-mining conditions of the property.
Scott plans to reclaim the property as each mining stage commences. Areas disturbed
during development shall be restored with natural-appearing landforms that blend with the
adjacent undisturbed topography within 90 days of completion to meet Garfield County
standards. Scott Contracting will start the reclamation process as soon as mining
progresses throughout the site. After each mining phase is completed, Scott will start
backfilling pits with excess dirt and unused material. The pits will not be filled in completely
as part of the reclamation plan is to create a recreational pond. See Figure 9 for proposed
pond location. The site will be graded to compliment the surrounding topography, and
slopes will be mined and graded.
Area disturbed by grading will be contoured so they can be revegetated and will be
revegetated to stabilize the surface from erosion Trees, shrubs, bushy-type vegetation and
approved grasses will be planted as approved by the Natural Resource Conservation
Service (NRCS) and/or County.
11.1 Description and Types of Reclamation, Revegetation, and Soil Plan
Scott will achieve the required reclamation of the affected land per the Garfield County Land
Use Permitting and seeding regulations using existing and available equipment. The primary
reason for this goal is to minimize dust and erosion of the property and restore the site back
to its natural conditions to the extent practicable.
Figure 9 depicts the amount of acreage proposed for each reclamation activity. All
reclamation will occur with specified equipment and methods for attaining successful
revegetation of the property. It is assumed that an 18.4-acre pond will be present post-
mining.
11.2 Post-Mining Land Use
The adjacent properties are primarily agricultural, county and interstate roadways, oil and
gas well pad and the Colorado River. The post-mining land uses will be like the current land
use and not conflict with adjacent land uses, which are currently comprised of agricultural
uses.
18 Figure 9. Post-Mining and Reclaimed Conditions
19
12.0 Implementation of the Reclamation Plan
12.1 Topsoil Segregation, Preservation, and Replacement
The topsoil excavated, stockpiled and or used for berm construction during Phase 1 will be
used to support the revegetation of the site.
Backfilling and recontouring of the site will occur after the mining and extraction activities
finish. Pit slopes will generally be backfilled with subsoils, overburden, and unmined
materials. This will be placed with a bulldozer and haul trucks. Then the use for a roller for
compaction and sloping will be tracked in. Recontouring to a rough texture will support the
establishment of broadcasted seeds and moisture retention.
Stored topsoil and growth medium will be replaced evenly to a depth of 4-6 inches unless
site conditions preclude this depth. Topsoil will also be left very rough. Soils will not be
worked when wet to avoid mixing, loss of topsoil, and potential erosion issues.
12.2 Final Grading
Final grading of the site is depicted in Figure 9. This figure shows the anticipated maximum
slope gradient range for reclamation. The site will need to take on fill dirt for a source of a
disposal area for clean dirt and to fill part of the pit, minimizing the size of the pond and
reducing evaporation potential.
The creation of a pond is planned for the site. Existing ephemeral draws and washes
passing through the mine area will be reestablished or allowed to continue conveyance of
ephemeral flows through the site.
12.3 Seeding
There are different types of seed mixes to support temporary and permanent stabilization
and reclamation of the site.
Temporary Seed Mix
Final seeding is best done in the late fall; therefore, if construction occurs in the summer, it
may be desirable to apply a temporary seed mix to the area to help minimize erosion and
provide some site stabilization. Temporary seed mixes are relatively inexpensive, and the
large seeds germinate quickly.
Long-Term/Permanent Seed Mix
Seeding should occur in the late fall to avoid seeds from germinating in the summer or early
fall, and then either desiccating or freezing. Drill seeding could be utilized on more level
terrain, but broadcast seeding will likely be needed on steeper slopes. Drill seeding will be
the preferred method where equipment access is feasible; seed will be placed in direct
contact with the soil at an average depth of 0.5 inch. For drill seeding applications, small
seeds shall be packaged separately to allow for separate application. The drill seeding rate
is 18 lbs. per acre and the broadcast seeding rate is 25 lbs. per acre.
20
Broadcast seeding will be employed in areas where drill seeding is not possible. Seed will
be uniformly applied over the disturbed areas with manually operated cyclone-bucket
spreaders or mechanical spreaders. Table 1 and Table 2 on Sheet C9 (Appendix C)
provides detail regarding the type of seed mix, form, and application rate.
13.0 Erosion Control Measures
Figures 7 and 8 provide information regarding the erosion and sediment control measures
and approximate locations during the Stage 1 and Stage mining activities, respectively. See
Sections 10 and 11 in this plan for additional narrative describing erosion and sediment
control during and post-mining activities. Sheets C9 and C10 in the Drawings (Appendix C
of the Land Use Permit Application) provide details for the recommended erosion and
sediment control BMPs.
14.0 Estimated Cost
Most of the costs associated with erosion and sediment control are associated with dirt work
as the perimeter berm will serve as a primary Best Management Practice (BMP) for keeping
stormwater and sediment on-site. Other costs for erosion and sediment control BMPs (i.e.,
vehicle tracking control, sweeping, dust control, etc.) are minor in the larger context of these
costs. The worst-case reclamation scenario at the Rifle Gravel Pit will be when the greatest
backfill is required and will occur sometime within the mining process of the north and south
pods and along the dewatering pipeline after mining is completed. These values reflect full
development of the property.
· Backfilling/regrading approximately 42,592 Yds2 (8.8 acres) of mining slopes and the
dewatering pipeline alignment at a cost of $1.50/CY = $63,888.
· Replace topsoil on disturbed areas, assuming excavation areas, materials storage,
and topsoil storage areas, 81,699 Yds2 (16.88 acres) at $1.50/CY = $122,548.
· Seeding and erosion control on 16.88 acres @$700/acre = $11,816.
o This includes the dewatering pipeline
Based on these costs, and a 28% Division of Reclamation Mining and Safety (DRMS) cost
factor, the total bond for the Rifle Gravel Pit will be $253,762.
Table 3 provides more costing information, including the DRMS cost factor.
21
Table 3. Estimated Reclamation Costs
Activity Description Time (Months) Cost ($)
Backfill (includes the dewatering pipeline) 1 $63,888
Replace Topsoil on all disturbed areas 1 $122,548
Seed and mulch all top soiled areas 0.5 $11,816
Sub-Total 2.5 $198,252
DRMS Costs
(28% x direct costs) $55,510
Total Bond Amount $253,762
15.0 Calculations
15.1 Floodplain Analyses
Floodplain modeling analysis was conducted to understand the influence of the proposed
project on the 100-year floodplain. The influence on rainfall on the project will be contained
by the perimeter berm and the dewatering operations to support mining. There are no
sediment basins nor detention/retention facilities included for the project. See the Floodplain
Analysis in Appendix G of the Land Use Permit.
16.0 Neighboring Areas
Per Garfield County submittal requirements, a list of landowners and mineral rights owners
within 200-feet of the proposed project parcel is included with this submittal. Adjacent
landowner addresses were obtained from the Garfield County Assessor’s web-based
database.
There are four adjoining properties with corresponding surface landowners:
· North – Colorado River Ranch, LLC
· West – Rex Robinson Ranch, LLC; Swanson Colorado Trust; Ilgen, Carrol Jeanne;
Rosa, Linda Jane; Robinson, James Dean
· South – Colorado Department of Transportation (CDOT)
· East – Shidelerosa LLP
This information was obtained from the Garfield County Colorado Land Explorer (Garfield
County, March 2021).
North Side: The parcel adjacent to the north is owned by Colorado River Ranch, LLC and is
currently zoned Rural. There aren’t any compatibility issues with the proposed project since
the current use is agricultural.
West Side: The Rex Robinson Ranch, LLC, currently owns the property to the west. This
property is zoned Rural. There is currently an oil & gas pad on this property which isn’t
currently being used. The current use of this property is compatible to the proposed mine
project.
South Side: The property to the south is currently owned by CDOT (I-70 N Frontage Road,
also referred to as County Road 346) and is parallel to the property.
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East Side: The property to the east is owned by Shidelerosa LLP and is zoned Rural. This
property is currently used for agricultural purposes and there is one residential driveway
approximately 0.45-mile from the proposed mine property.
All landowners have been notified of the proposed development. The proposed use is
consistent with the predominant existing uses in the surrounding area.
Figure 1 depicts the existing use of the adjacent properties within a 600-foot radius of the
Rifle Pit #1 property.
17.0 Stormwater Management
A description of stormwater management planning concept for the site, including both
structural and non-structural BMPs is mentioned in the Mining Plan (Section 10) and
Reclamation and Post-Mining (Section 11) discussions of this document.
17.1 Stormwater Management Plan (SWMP)
A copy of the SWMP application to CDPHE with date of submittal will be sent to Garfield
County once the Land Use Permit is approved and there is a better idea for when
construction and mining will commence.
18.0 Reclamation, Revegetation, and Soil Plan
Sections 1.10 and 1.11 in this plan address the plant material and seed mix lists for both
temporary and permanent stabilization. Most of the post-mined condition for the Rifle Pit #1
site will be a pond.
On-site stockpile storage for each mining stage will vary depending upon the rate of material
extraction and need of the material from projects. Scott will provide cover for those
stockpiles that may sit exposed for a period of 90 days or more.
18.1 Weed Management Plan
Scott understands that Garfield County requires a Weed Management Plan for all Garfield
County listed noxious weeds and State of Colorado listed noxious weeds that are targeted
for statewide eradication for areas of 1 acre or greater is disturbed for the purposes of site
construction, development or grading but not including areas serving the long-term function
of the site (i.e. building footprint, road surface or permanent parking areas). Scott also
understands that the Weed Management Plan shall include a site-specific map and weed
inventory.
Scott understands that the Weed Management Plan also needs to address the treatment of
all noxious weeds on a biannual basis, with an herbicide application in the spring (late May)
and late summer (late August). Gravel storage piles will also be treated with a bare ground
herbicide if the piles are expected to remain for more than one season. Scott will use a
Colorado-certified herbicide applicator. All work equipment must also be sanitized and have
any existing dirt, vegetation, or seeds from landscaping and operational work removed
before leaving the work area. Prior to bond release, Scott will conduct a noxious weed
inventory and bond release reports developed by third parties for submittal to DRMS and
Garfield County.
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A copy of a Noxious Weed survey representing existing conditions is included in Appendix F
of the Land Use Permit.
18.2 Revegetation Security
Scott understand that a revegetation security may be required if, in the determination of
the County Vegetation Manager, the proposed project has:
· A potential to facilitate the spread of noxious weeds;
· A potential to impact watershed areas;
· A potential for visual impacts from public viewing corridors;
· Steep Slopes 15% or greater or unstable areas; and/or
· Disturbs an area 1 acre or greater where topsoil is exposed for the purposes of site
construction, development or grading but does not comprise the long- term
functioning of the site (i.e. building footprint, road surface or permanent parking
areas).
Scott understands that the County Vegetation Manager will determine the security amount
and that it will be site specific and based on the amount of disturbance. The security shall be
held by the County until vegetation has been successfully reestablished, or for a period
approved by the County Vegetation Manager in any specific land use action, according to
the Reclamation and Revegetation Standards section in the Garfield County Weed
Management Plan. The County Vegetation Manager will evaluate the reclamation and
revegetation prior to the release of the security and shall be subject to all provision of Article
13.
19.0 Hydraulic Calculations
The calculations used to size the drainage facilities and perimeter berm were dictated by the
Floodplain analyses. See the Floodplain Analysis included as Appendix G of the Land Use
Permit document.
20.0 Maintenance Requirements
The Scott on-site staff will be responsible for maintaining the integrity of all BMPs including
the access road and on-site drainage and stockpiling activities. Maintenance activities will
be on-going and an integral part of mining operations to foster safety and compliant
operations.
21.0 Spill Prevention Control and Countermeasures Plan (SPCC)
Scott understands that a SPCC Plan will be required if the Rifle Pit #1 property has the
potential to discharge oil of any kind or in any form including, but not limited to, petroleum,
fuel oil, sludge, oil refuse and oil mixed with wastes, in quantities that may be harmful to
navigable water and adjoining shoreline, per EPA regulations.
A copy of the SPCC Plan is included as Appendix A of this document.
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22.0 Signature Block
I acknowledge the review and acceptance of responsibility for preparing this Grading and
Drainage Plan based upon the existing and available information regarding the Rifle Pit #1
site development.
Angela B. Fowler, P.E.
Senior Water Resource Engineer
Appendix A
Appendix A
SPCC Plan
SPILL PREVENTION, CONTROL
AND COUNTERMEASURE PLAN
Scott Contracting, Inc. has prepared a spill control plan to prevent the contamination
of the surrounding environment. Containment structures will be constructed to prevent
spills from entering state waterways, lakes, streams and/or storm sewers. On site spill
control will be used while refueling the equipment and handling hazardous substances.
If a spill occurs, follow the steps below for clean-up procedures and contact
information.
In Case of Leak or Spill:
1. Contact Project Manager or Supervisor immediately. (Contact information is
listed below)
2. Contain spill and start cleanup using the spill control kit located on-site. The kit
will contain a sorbent boom, sorbent rags, absorbent litter and an over-pack
drum to store the material.
3. If a spill occurs that requires emergency response based on the reportable
quantities, use the contact information listed below for clean-up and disposal of
hazardous materials.
Reportable Quantities:
• 25 gallons of engine oil, fuel or hydraulic/brake fluid released to land.
• A visible sheen of engine oil, fuel or hydraulic/brake fluid released to water.
• 100 lbs (13 gallons) of antifreeze released to land.
• 100 lbs of battery acid released to land or water.
• 1 lb of refrigerant released to the air.
• 100 lbs of gasoline released to the air, land or water.
• 100 lbs of engine degreasers released to the air, land or water.
Scott Contracting, Inc. Contacts:
1. Tony Roberts (VP - Operations) 720-490-7405
2. Christian Baumgart (Area Manager) 720-692-4035
3. Dan Spahn (Safety Manager) 720-490-7408
Project Engineer:
1. SGM
Hazardous Substances Contained On-Site:
The following is a list of chemicals we will have on-site, which will be stored in double-
wall tanks, with a berm around the tanks and the entire area will be lined with plastic
for containment purposes.
• 100 Gal Engine oil
• 300 Gal Diesel
• 50 Gal of gasoline
• 30 Gal of Mixed gas
• 2 boxes of marking paint
• On-site fueling of equipment
Equipment Available:
All equipment, not limited to the equipment listed below, necessary to contain or
mitigate a pollutant spill shall be on site within one hour of when the spill occurs.
• Vac Con Combo Jet Truck (2700 gal. Capacity)U This truck can be used to clear
a blockage as well as provide 2700 gallons of storage capacity.
• 8" Diesel Pump w/ 550' of discharge hose This pump and hose will be on standby
and can be delivered and set up quickly to help in the event of primary and
redundant pump failures.
• Excavator This can be used to remove any hazardous material and also any
contaminated soil from the site.
• Loader This can be used to remove any hazardous material and also any
contaminated soil from the site.
Environmentally Sensitive Areas:
The following areas have been identified as being environmentally sensitive. These may
include spillways, channels, and storm drainage that lead directly or indirectly to the
Receiving Waters and/or pose a threat to ground water. Extra care and preventative
measures will be taken to minimize the risk of contamination.
• Last Chance Ditch
• Irrigation/Tailwater Ditch
Notification of Regulatory Agencies:
In the event of a discharge, spill or overflow of pollutants that has the potential to
affect public health or the environment, the following parties shall be notified for non-
hazardous materials:
1. Colorado Department of Public Health and Environment Spill Report Line: 1-877-
518-5608
2. CDOT illicit discharge hotline: 303-512-4426
3. Colorado State Patrol if spill is on a State Highway: 303-239-4501
In the event of a discharge, spill or overflow of pollutants that has the potential to
affect public health or the environment, the following parties shall be notified for
hazardous materials:
1. Local emergency response team: 911
2. Colorado Department of Public Health and Environment Spill Report Line: 1-877-
518-5608
3. CDOT illicit discharge hotline: 303-512-4426
4. Colorado State Patrol if spill is on a State Highway: 303-239-4501
Erosion Control Training:
All employees working on this jobsite have attended and successfully completed a 6-
hour orientation course through Scott Contracting on Safety Procedures and Erosion
Control awareness. Topics covered, among other things, included: BMP identification,
Respect for Installed BMPs and Immediate Notification to Superintendent of Damaged
BMPs.
In addition to the reporting requirements of the paragraph above, Scott Contracting,
Inc. shall notify CDOT in the event of any discharge, spill or overflow to the
environment:
Prepared by:
Scott Contracting, Inc. __________________________________
Signature Date
Approved by:
CDOT __________________________________
Signature Date
By authorized signature below, Scott Contracting, Inc., hereinafter referred to as 'the
Contractor', hereby certifies that this Spill Prevention, Control and Countermeasures
Plan (Plan) complies with and meets applicable Federal, State, and local laws, rules,
regulations and guidelines governing safety, health and sanitation, including but not
limited to the Occupational Safety and Health Act, 29 CFR 1910, 29 CFR 1926, Mine
Safety and Health Administration (MSHA), Title 30 CFR, the "Colorado Work Zone Best
Practices Safety Guide'', national consensus standards, the Drug-Free Workplace Act
(Public Law 100-690 Title V, subtitle D, 41 USC 701 et seq.) and the Colorado
Department of Public Health and Environment. All operations and work practices of the
Contractor will comply with this Plan. The Contractor requires that all subcontractors,
suppliers and Department personnel comply with this Plan.
Signature
Erosion Control Supervisor
Title
Date