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GARFIELD COUNTY OWTS REPORT
306 COUNTY ROAD 340
PARACHUTE, COLORADO
September 2021
Prepared by
118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004
970.945.5948 fax
306 County Road 340 September 2021
OWTS Engineering Report 2
306 COUNTY ROAD 340
PARACHUTE, COLORADO
“I hereby affirm that this report for the Onsite Wastewater Treatment System (OWTS) for 306
County Road 340, Garfield County, Colorado was prepared by me or under my direct supervision
for the Owners thereof in accordance with the provisions of Garfield County’s Land Use and OWTS
Regulations and approved variances and exceptions listed thereto. I understand the County does
not and will not assume liability for OWTS facilities designed by others.”
______________________________________ License No. ____________________
Licensed Professional Engineer, State of Colorado (Affix Seal)
PREPARED BY:
TERRY BENDETTI, P.E.
SGM Project # 2018-271.002
09/08/2021
306 County Road 340 September 2021
OWTS Engineering Report 3
TABLE OF CONTENTS
1.0 Introduction 5
2.0 Preliminary Investigation 5
2.1 Property Information 5
2.2 Public Health Agency Records 5
2.3 Topography 6
2.4 Soil Data 6
2.5 Location of Physical Features 6
2.6 Additional Information 6
2.7 Landscape Position 6
2.8 Natural and Cultural Features 6
2.9 Current and Historic Land Use 6
3.0 Detailed Soil Investigation 7
3.1 Visual Evaluation 7
3.2 Tactile Evaluation 7
4.0 Recommendations 8
306 County Road 340 September 2021
OWTS Engineering Report 4
Appendix
Drawing 1
Drawing 2
NRCS Soils Map
NRCS Absorption Field Soils Data
TP-1 Trench Photo
TP-1 Trench Photo
TP-2 Trench Photo
TP-2 Trench Photo
SGM Soil Observation Logs
SGM Soil Texture by Feel
306 County Road 340 September 2021
OWTS Engineering Report 5
1.0 Introduction
A new 3-bedroom residential structure is being proposed for construction on the subject property. To
treat wastewater from the residence, an onsite wastewater treatment system (OWTS) will be installed.
This report describes the results of a preliminary investigation, reconnaissance, and detailed soil
evaluation to support design of the OWTS for the subject property, in addition to presenting design
of the system to be compliant with Garfield County’s “On Site Wastewater Treatment System
Regulations”, hereinafter referred to as Reg43.
SGM personnel contributing to this report are:
· Terry Bendetti - PE/CPOW Certified Competent Technician/NAWT Certified Designer
2.0 Preliminary Investigation
2.1 Property Information
Physical Address: 306 County Road 340, Parachute, Colorado.
Legal Description: Section 3 Township:7 Range: 95; Subdivision Morrisania Ranch. Account No.
R270100, Parcel 240703400010.
Existing Structures: An existing residential structure, shop and outbuilding are presently located
on the subject property. According to County documents the following information for the home
was obtained.
· Building permit issued in April of 1980.
· The home has 1,370 square feet of floor area.
· The home has two bedrooms.
· The home has one story.
· A sunroom was added in July of 1982.
Domestic Water: Provided by a well in the southeast portion of the subject property. The well is
located greater than the minimum setback requirement of 100 feet, Table 7-1 of Reg43.
2.2 Public Health Agency Records
Search of Garfield County’s Public Records found there is an existing ISDS permit for this
residence. The permit indicates the size of the septic tank is 1,000 gallons and the absorption
area has 330 square feet.
The existing system is functioning. No issues of concern have been expressed by the Owner of
the subject property.
Since the subject property has multiple OWTSs, it needs to be established whether the systems
are considered as one or as separate systems. According to WQSA-6 (Water Quality Site
Application Policy), multiple systems are considered separate if the horizontal influence area
(HIA) of each system does not overlap and each system has a daily capacity less than or equal
to 2,000 gpd.
The HIA associated with the existing system is 56 feet, for the proposed system 74 feet. There is
no overlap of the HIA calculated for each system. In addition, each system has a daily wastewater
306 County Road 340 September 2021
OWTS Engineering Report 6
capacity less than 2,000 gpd; 300 gpd for the existing system and 450 gpd for the proposed
system. Therefore, these systems are separate systems. The HIA for each system is shown on
sheet 1.
2.3 Topography
Topography in the vicinity of the OWTS slopes from south to the north at grades of between 4.5
to 8.0 percent. Grades in the east/west direction are flat and continuous, not broken by
irregularities in the ground surface.
2.4 Soil Data
According to the Web Soil Survey for the Natural Resources Conservation Service (NRCS), soils
associated with this subject property are classified as map unit 56, Potts loam. Potts loam has
grades of between 6 to 12 percent, which agrees with field observation.
Pots loam also has a very limited rating for septic tank absorption fields due to the slow movement
of water. However, plotting of percentages of clay, sand and silt given for this soil unit on the
USDA Textural Triangle indicates the soils would classify as soil type 2 or 2A. Soils having a
classification type of 2 or 2A are very suitable for absorption fields, having long term application
rates (LTAR) of 0.6 and 0.5 gallons per day per square foot of area (gpd/ft2), respectively.
2.5 Location of Physical Features
Physical features on the subject property that will require minimum horizontal setbacks are shown
in the following Table. All distances are in feet.
Potable
Water
Structure with
Basement, Crawl
Space, Footing Drains
Property Lines, Piped
Irrigation
Septic
Tank
Septic Tank 50 5 10 --
Effluent Line 50 N/A 10 --
STA 100 20 10 5
2.6 Additional Information
a. Easements: There is a 12.0’ easement at the west side of the property for Garfield County
Road 340.
b. Floodplain Maps: According to FEMA (Federal Emergency Management Agency), there is
no flood mapping for the area where the OWTS will be located.
2.7 Landscape Position
The landscape position for the STA is considered summit and will not be impacted by stormwater
drainage. The slope shape is linear – linear (LL) towards the northwest property corner.
2.8 Natural and Cultural Features
No natural or cultural features were identified in the site reconnaissance.
2.9 Current and Historic Land Use
306 County Road 340 September 2021
OWTS Engineering Report 7
The subject property is in Garfield County’s Rural zone district, which is for Agricultural and other
uses. Current and historic land use has been agricultural, its future use is expected to also be
agricultural.
3.0 Detailed Soil Investigation
A detailed soil investigation to determine the depth to the limiting layer, if any, and properly classify
the soil type was conducted on May 18, 2021. Visual evaluation of two soil profile test pits were
conducted in the field and samples collected from each test pit. The samples were taken to SGM’s
Office to classify the soil type that will receive the effluent waste using the soil texture by feel method.
Test pits were excavated adjacent to the proposed location for the STA, see sheet 1 for locations.
Visual evaluation of both test pits was conducted under adequate light conditions, with the soil being
in an unfrozen state.
3.1 Visual Evaluation
The Client excavated two soil profile test pits, TP-1 and TP-2, with SGM personnel being on site.
Both test pits were excavated to an approximate depth of 6 feet, with no groundwater nor bedrock
being encountered.
Both test pits exhibited topsoil with a root zone for the first 8 to 10 inches. One layer horizon from
the bottom of the topsoil zone to the bottom of each pit was observed. Rocks were not
encountered in either test pit.
Excavation was terminated at a depth of 6 feet for the following reasons:
· A limiting layer was not encountered.
· The in-situ soils to treat effluent will begin at 2 feet from the surface, which with the 4 feet
of required vertical separation between the infiltrative surface and a limiting layer can be
met.
Soil observation logs and photos can be found in the Appendix.
All measurements are from ground surface.
3.2 Tactile Evaluation
SGM conducted a Soil Texture by Feel test on the soil samples collected from each test pit per
CPOW’s methodology.
Gravels were not present in either sample, therefore Table 10-1, Section 43.10 of Reg43 was
used to determine soil type and applicable LTAR.
306 County Road 340 September 2021
OWTS Engineering Report 8
Results of the soil texture by feel tests are shown in the following table.
SAMPLE
Depth from
Ground
Surface (ft)
Does Soil
Form a Ball
(yes/no)
Does Soil
Form a
Ribbon
(yes/no)
*Type of Ribbon
Formed (Weak,
Moderate,
Strong)
How Does the Soil Feel
(Gritty/Smooth/Neither)
TP-1 4.0 Yes Yes Strong Very Smooth
TP-2 4.0 Yes Yes Strong Very Smooth
*Weak < 1 inch; Moderate 1-2 inches; Strong > 2 inches.
Results shown in the above table indicate a USDA soil classification of Silty Clay, soil type 4 or
4A.
To determine the proper soil type, 4 or 4A, the USDA soil structure type and grade were used.
The following Table shows the soil’s USDA structure type and grade determined for each sample.
SAMPLE
USDA Soil
Structure
Type
USDA Soil
Structure
Grade
TP-1 Blocky Moderate
TP-2 Blocky Moderate
According to Table 10-1, section 43.10 of Reg43, both soil types 4 and 4A can have a blocky
structure type, but only soil type 4 can have a moderate soil structure grade. As such, the soil
to receive the effluent waste is classified as soil type 4, having a LTAR of 0.20 gpd/ft2 for
treatment level 1 (TL1).
The USDA soil classification based on NRCS data for clay, sand and silt percentages in
subsection 2.4 above does not support this conclusion. However, the NRCS data for absorption
fields does agree with the soil test by feel results.
SGM’s worksheets for the Soil Observation Logs, Soil Texture by Feel and STA LTAR by Soil
Texture, Soil Structure and Treatment Level can be found in the Appendix.
4.0 Recommendations
An OWTS as a wastewater treatment system is suitable for this site. At a minimum The OWTS shall
have:
· A septic tank.
· A trench type STA.
· Category 3 distribution media in the STA.
· A distribution box.
· 4” diameter distribution laterals.
· 4” diameter service lines.
Effluent from the residence will be conveyed through service lines, by gravity, to a new septic tank.
From the septic tank the effluent will be conveyed through service lines to a distribution box, effluent
flow will be by gravity. The distribution box will divide the effluent flow into equal volumes for each
distribution lateral. Each lateral will convey its volume of effluent to its associated STA trench, effluent
flow will be by gravity.
306 County Road 340 September 2021
OWTS Engineering Report 9
The proposed residence will be a 3-bedroom single family residence. Per Table 6-1 of the County’s
OWTS Regulations the design flow rate will be 450 gpd (gallons per day).
# Bedrooms Occupancy (# of
Persons)
Wastewater Flow per
Person Design Flow (gpd)
3 6 75 450
The site of the proposed STA for the OWTS will be north of the proposed residence. The septic tank
will be installed in the vicinity shown on sheet 1. The proposed residence is expected to have a crawl
space, basement, a foundation drain or a combination thereof. To comply with setback requirements
stated in Table 7-1 of Reg43, the Owner will need to construct the proposed residence at least 20
feet from where the STA is located. The OWTS STA site elevation is approximately 5,941 feet above
sea level (NAVD 88).
Sewer Pipe: Sewer service pipe shall be 4-inch SDR-35 PVC pipe installed with a minimum grade
of 1%, maximum grade of 8%. Joints shall be solvent welded. Cleanouts are required:
1) Within 5 feet of the existing building.
2) At spacing not to exceed 50 feet.
3) Upslope of two or more bends closer than 10 feet.
All 90 degree bends shall be constructed using two 45 degree fittings. The pipe shall be properly
bedded per the typical trench detail presented on sheet 2.
Septic Tanks: One new 1,500 gallon septic tank with two bays is recommended for the possibility for
future expansion. The tank must be on the Colorado Department of Public Health and Environment’s
accepted septic tank list. The tanks and lids shall conform to current County OWTS regulations and
be traffic rated. The tanks shall be installed with insulated, watertight access risers having lids that
can be secured. Risers shall meet the tank manufacturer’s requirements for type and installation.
The effluent filter handle shall extend to within twelve inches of the lid.
The septic tank shall:
1) Be located down gradient of the home.
2) Have a covering of no more than 4-feet in depth.
3) Be at a location accessible for pumping and maintenance.
The installer must coordinate with the Owner as to the elevation of the tank’s inlet invert stub out for
connection to the service line from the residence. A septic tank having a thicker cover than 4-feet will
not be allowed.
Distribution Box: The distribution box shall be centered as shown on sheet 1 in a manner to distribute
effluent equally to the trenches. The Engineer should be contacted if alignments or locations change
in order to verify regulation requirements are maintained. The box, as shown, should be capable of
one inlet pipe having an insertion point a minimum of 1-inch above outlet openings and 6 outlet
openings.
Soil Treatment Area: The soil treatment area is sized using criteria found in section 43.10 of Reg43
for a 3-bedroom residential home, using trenches for the soil treatment area, effluent application by
gravity and chambers for the distribution media. The following table summarizes sizing of the STA.
306 County Road 340 September 2021
OWTS Engineering Report 10
No.
Bedrooms
Daily
Design
Flow (gpd)
LTAR
Method of
Application
Adjustment Factor
Distribution Media
Adjustment
Factor
STA
Size
(sf)
No. Chambers
(12sf/chamber)
3 450 0.2 1.0 0.7 1,575 131
The STA shall be excavated as field conditions require using the following guidelines.
1. Six trenches, 5 having 22 infiltrators and 1 having 21 infiltrators.
2. Trenches shall be no wider than 3-feet.
3. Trench lengths shall be no greater than 88-feet.
4. A minimum of 4-feet, measured sidewall to sidewall, shall separate trenches.
5. The infiltrative surface shall be no greater than 3-feet from the surface.
6. Trench floors shall be level.
7. Chambers shall be placed per the manufacturer’s directions.
Chambers shall have a minimum of 10.8 square footage area per regulation requirement 43.13.
The STA configuration shown on sheet 1 may be modified or changed in the field as long as guidelines
2, 4, 5,6 and 7 are maintained and setbacks in section 2.5 can be met. Other setbacks per Table 7-
1 of Reg43 may be required, so review of Table 7-1 should be completed prior to relocating the STA.
In addition, the Engineer should be consulted prior to relocating the STA.
The STA shall have a final soil cover as described on sheet 2. This may mean that the STA cover
will need to be 16-inches +/- when initially placed to allow for settlement over the freeze-thaw of a
winter season. The surface of the STA shall be seeded after installation of the system. A native,
upland seed mix should be used. These mixes do not require irrigation and develop a growth 10 to
15 inches high. No automatic sprinkler system shall be installed over the STA. Vehicular traffic and
livestock shall be kept off of the STA. No landscaping, impervious surfaces or plastic sheeting can
be installed over the STA, which will reduce its performance.
306 County Road 340 September 2021
OWTS Engineering Report 11
Appendix
Sheet 1
Sheet 2
NRCS Soils Map
NRCS Absorption Field Soils Data
TP-1 Trench Photo
TP-1 Trench Photo
TP-2 Trench Photo
TP-2 Trench Photo
SGM Soil Observation Logs
SGM Soil Texture by Feel
Graphic ScaleIn Feet: 1" = 40'0204080Title:OWTS PlanRevision#Dwg No.Jablonsky OWTS
306 County Road 340,
Parachute, ColoradoJob No.Drawn by:Date:File:PE:QC:2021-455.001TLB07/13/21TLBOWTS-BMXX118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004 www.sgm-inc.com
Date By:1 2Of :DRAFTProject Milestone:09/08/20211,500 GAL. SEPTIC TANK
···········Title:OWTS DetailsRevision#Dwg No.Jablonsky OWTS
306 County Road 340,
Parachute, ColoradoJob No.Drawn by:Date:File:PE:QC:2021-455.001TLB07/13/21TLBOWTS-BMXX118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004 www.sgm-inc.com
Date By:2 2Of :DRAFTProject Milestone:QUICK4 STANDARD MULTIPORT END CAPINFILTRATOR SYSTEMS INC.QUICK4 STANDARD CHAMBERINSPECTION PORT(EFFECTIVE)34"12"09/08/2021
NRCS Soils Map
Soil Map—Rifle Area, Colorado, Parts of Garfield and Mesa Counties
(309 County Road 340)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 1 of 3437170043718004371900437200043721004372200437230043724004372500437170043718004371900437200043721004372200437230043724004372500243500243600243700243800243900244000244100
243500 243600 243700 243800 243900 244000 244100
39° 27' 52'' N 107° 58' 54'' W39° 27' 52'' N107° 58' 27'' W39° 27' 23'' N
107° 58' 54'' W39° 27' 23'' N
107° 58' 27'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,250 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Rifle Area, Colorado, Parts of Garfield and
Mesa Counties
Survey Area Data: Version 13, Jun 5, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Dec 31, 2009—Oct
12, 2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—Rifle Area, Colorado, Parts of Garfield and Mesa Counties
(309 County Road 340)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 2 of 3
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
34 Ildefonso stony loam, 25 to 45
percent slopes
17.2 21.5%
56 Potts loam, 6 to 12 percent
slopes
62.7 78.5%
Totals for Area of Interest 79.9 100.0%
Soil Map—Rifle Area, Colorado, Parts of Garfield and Mesa Counties 309 County Road 340
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 3 of 3
NRCS Absorption Field Soils Data
Septic Tank Absorption Fields—Rifle Area, Colorado, Parts of Garfield and Mesa Counties
(309 County Road 340)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 1 of 5437170043718004371900437200043721004372200437230043724004372500437170043718004371900437200043721004372200437230043724004372500243500243600243700243800243900244000244100
243500 243600 243700 243800 243900 244000 244100
39° 27' 52'' N 107° 58' 54'' W39° 27' 52'' N107° 58' 27'' W39° 27' 23'' N
107° 58' 54'' W39° 27' 23'' N
107° 58' 27'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,250 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
Very limited
Somewhat limited
Not limited
Not rated or not available
Soil Rating Lines
Very limited
Somewhat limited
Not limited
Not rated or not available
Soil Rating Points
Very limited
Somewhat limited
Not limited
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Rifle Area, Colorado, Parts of Garfield and
Mesa Counties
Survey Area Data: Version 13, Jun 5, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Dec 31, 2009—Oct
12, 2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Septic Tank Absorption Fields—Rifle Area, Colorado, Parts of Garfield and Mesa Counties
(309 County Road 340)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 2 of 5
Septic Tank Absorption Fields
Map unit
symbol
Map unit name Rating Component
name (percent)
Rating reasons
(numeric
values)
Acres in AOI Percent of AOI
34 Ildefonso stony
loam, 25 to 45
percent slopes
Very limited Ildefonso (90%)Slope (1.00)17.2 21.5%
Large stones
(1.00)
56 Potts loam, 6 to
12 percent
slopes
Very limited Potts (85%)Slow water
movement
(1.00)
62.7 78.5%
Slope (0.04)
Totals for Area of Interest 79.9 100.0%
Rating Acres in AOI Percent of AOI
Very limited 79.9 100.0%
Totals for Area of Interest 79.9 100.0%
Septic Tank Absorption Fields—Rifle Area, Colorado, Parts of Garfield and Mesa Counties 309 County Road 340
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 3 of 5
Description
Septic tank absorption fields are areas in which effluent from a septic tank is
distributed into the soil through subsurface tiles or perforated pipe. Only that part
of the soil between depths of 24 and 60 inches is evaluated. The ratings are
based on the soil properties that affect absorption of the effluent, construction
and maintenance of the system, and public health. Saturated hydraulic
conductivity (Ksat), depth to a water table, ponding, depth to bedrock or a
cemented pan, and flooding affect absorption of the effluent. Stones and
boulders, ice, and bedrock or a cemented pan interfere with installation.
Subsidence interferes with installation and maintenance. Excessive slope may
cause lateral seepage and surfacing of the effluent in downslope areas.
Some soils are underlain by loose sand and gravel or fractured bedrock at a
depth of less than 4 feet below the distribution lines. In these soils the absorption
field may not adequately filter the effluent, particularly when the system is new.
As a result, the ground water may become contaminated.
The ratings are both verbal and numerical. Rating class terms indicate the extent
to which the soils are limited by all of the soil features that affect the specified
use. "Not limited" indicates that the soil has features that are very favorable for
the specified use. Good performance and very low maintenance can be
expected. "Somewhat limited" indicates that the soil has features that are
moderately favorable for the specified use. The limitations can be overcome or
minimized by special planning, design, or installation. Fair performance and
moderate maintenance can be expected. "Very limited" indicates that the soil has
one or more features that are unfavorable for the specified use. The limitations
generally cannot be overcome without major soil reclamation, special design, or
expensive installation procedures. Poor performance and high maintenance can
be expected.
Numerical ratings indicate the severity of individual limitations. The ratings are
shown as decimal fractions ranging from 0.01 to 1.00. They indicate gradations
between the point at which a soil feature has the greatest negative impact on the
use (1.00) and the point at which the soil feature is not a limitation (0.00).
The map unit components listed for each map unit in the accompanying
Summary by Map Unit table in Web Soil Survey or the Aggregation Report in Soil
Data Viewer are determined by the aggregation method chosen. An aggregated
rating class is shown for each map unit. The components listed for each map unit
are only those that have the same rating class as listed for the map unit. The
percent composition of each component in a particular map unit is presented to
help the user better understand the percentage of each map unit that has the
rating presented.
Other components with different ratings may be present in each map unit. The
ratings for all components, regardless of the map unit aggregated rating, can be
viewed by generating the equivalent report from the Soil Reports tab in Web Soil
Survey or from the Soil Data Mart site. Onsite investigation may be needed to
validate these interpretations and to confirm the identity of the soil on a given
site.
Septic Tank Absorption Fields—Rifle Area, Colorado, Parts of Garfield and Mesa Counties 309 County Road 340
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 4 of 5
Rating Options
Aggregation Method: Dominant Condition
Aggregation is the process by which a set of component attribute values is
reduced to a single value that represents the map unit as a whole.
A map unit is typically composed of one or more "components". A component is
either some type of soil or some nonsoil entity, e.g., rock outcrop. For the
attribute being aggregated, the first step of the aggregation process is to derive
one attribute value for each of a map unit's components. From this set of
component attributes, the next step of the aggregation process derives a single
value that represents the map unit as a whole. Once a single value for each map
unit is derived, a thematic map for soil map units can be rendered. Aggregation
must be done because, on any soil map, map units are delineated but
components are not.
For each of a map unit's components, a corresponding percent composition is
recorded. A percent composition of 60 indicates that the corresponding
component typically makes up approximately 60% of the map unit. Percent
composition is a critical factor in some, but not all, aggregation methods.
The aggregation method "Dominant Condition" first groups like attribute values
for the components in a map unit. For each group, percent composition is set to
the sum of the percent composition of all components participating in that group.
These groups now represent "conditions" rather than components. The attribute
value associated with the group with the highest cumulative percent composition
is returned. If more than one group shares the highest cumulative percent
composition, the corresponding "tie-break" rule determines which value should
be returned. The "tie-break" rule indicates whether the lower or higher group
value should be returned in the case of a percent composition tie. The result
returned by this aggregation method represents the dominant condition
throughout the map unit only when no tie has occurred.
Component Percent Cutoff: None Specified
Components whose percent composition is below the cutoff value will not be
considered. If no cutoff value is specified, all components in the database will be
considered. The data for some contrasting soils of minor extent may not be in the
database, and therefore are not considered.
Tie-break Rule: Higher
The tie-break rule indicates which value should be selected from a set of multiple
candidate values, or which value should be selected in the event of a percent
composition tie.
Septic Tank Absorption Fields—Rifle Area, Colorado, Parts of Garfield and Mesa Counties 309 County Road 340
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/12/2021
Page 5 of 5
TP-1 Trench Photos
TP-2 Trench Photos
SGM Soil Observation Logs
SGM Soil Texture by Feel
TP-1
TP-2