HomeMy WebLinkAboutRevised OWTS Design Packet 07.01.2026129 Cains Lane
Carbondale, CO 81623
970.309.5259
carla.ostberg@gmail.com
July 1, 2026 Project No. C1900
Mike Premich
Whiteriverconstructionco@gmail.com
Subsurface Investigation and Onsite Wastewater Treatment System Design
4-Bedroom Residence
Lot 23, Homestead Estates
Garfield County, Colorado
Mike,
CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system
(OWTS) design for the subject residence. The 10.069-acre property is located outside of Glenwood
Springs, in an area where OWTSs and wells are necessary. An additional subsurface investigation was
conducted on June 1, 2026 with larger equipment due to digging refusal in our previous Test Pits
excavated with smaller equipment. Changes from our June 4, 2026 design include only the required
separation in the proposed partial mounds. No other changes were made.
Legal Description: Section: 24 Township: 6 Range: 88 Subdivision: HOMESTEAD EST. Lot: 23
Parcel ID: 2187-243-00-023
SITE CONDITIONS The property is currently undeveloped. A 4-bedroom residence is proposed.
The residence will be served by a private well on the property. The well is located to the northeast of the
proposed residence. The well is located greater than 50-feet from the proposed septic tank and greater
than 100-feet from the proposed soil treatment area (STA).
The proposed soil treatment area (STA) location has an approximate 5 to 6 percent slope to the
southeast. The proposed area is vegetated with sage and native grasses.
There should be no traffic or staging of material over the future STA site to avoid compaction of soils
prior to construction of the STA.
SUBSURFACE
The subsurface was investigated on June 28, 2024 by digging three soil profile test pit excavations (Test
Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.1
The materials encountered in Test Pit #1 consisted of medium brown clay loam topsoil to 3.0-feet where
digging refusal was encountered on a large boulder. No bedrock or groundwater was encountered.
1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile
Evaluation of Soils Training.
Page 2
The materials encountered in Test Pit #2 consisted of medium brown clay loam 4.0-feet, underlain by
medium brown clay loam with pockets of reddish brown clay to a maximum depth explored of 5.0-feet
where practical digging refusal was encountered. No bedrock or groundwater was encountered.
A sample of the soil was taken from Test Pit #1 at 3-feet below grade. Soil structure grade was
moderate. The soil formed a ball and a ribbon 1 to 2-inches in length before breaking. Soil structure
shape was blocky and consistence was friable. Soil texture was both gritty and smooth.
We also viewed a previously excavated Test Pit near the house foundation. It was excavated to a maximum
depth explored of 7.0-feet. We have labeled this Test Pit #3, but it is described in Kumar and Associate’s
report (enclosed) as Pit 7. A gradation was performed on a sample from Pit 7 and is described below.
The subsurface was investigated by Kumar and Associates, Project No. 23-7-2024 and is documented in a
report dated July 15, 2024. Seven Test Pits were excavated surrounding the proposed foundation.
The gradation on a sample taken from Pit 4 at 4.5 to 5.5-feet consisted of 40% gravel, 30% sand, and 30%
silt and clay.
A gradation on a sample taken from Pit 5 at 3.0 to 4.0-feet consisted of 14% gravel, 48% sand, and 38% silt
and clay.
A gradation on a sample taken from Pit 7 at 4.5 to 5.5-feet consisted of 31% gravel, 22% sand, and 47% silt
and clay. Pit 7 profile consisted of topsoil (clay, silty, slightly sandy, organics, firm, slightly moist to moist,
gray) to 2.0-feet, underlain by clay (sandy, scattered gravely to gravelly, stiff to hard, slightly moist to moist,
brown) to 4.0-feet, underlain by gravel and cobbles (sandy, clayey, occasionally silty with boulders, basalt
rock, dense to very dense with depth, moist, dark brown) to a maximum depth explored of 7.0-feet. No
bedrock or groundwater was encountered.
We have researched soils in the area through USGS Web Soil Survey. The report is enclosed. The area of
the proposed STA is identified by map unit symbol 19. The map unit name is Cochetopa-Antrobus
association, 25 to 50% slopes. Typical soil profile from 0 to 3-inches consists of loam, 3 to 38-inches
consists of clay loam, and 38 to 60-inches consists of gravelly clay loam.
An additional subsurface investigation was performed on June 1, 2026 by digging two Test Pits.
Substantially larger equipment was used to dig the pits due to encountering refusal with the previous
excavation.
The materials encountered in Test Pit #4 consisted of medium brown clay loam topsoil to 3.0-feet underlain
by large boulders and clay pockets to a maximum depth explored of 8.0-feet. No bedrock or groundwater
was encountered.
The materials encountered Test Pit #5 were consistent with those encountered in Test Pit #4. No bedrock or
groundwater was encountered. Test Pit #5 was excavated to a maximum depth explored of 7.0-feet.
We are considering the large boulders a restrictive layer at 3-feet below native grade. Three feet of
vertical separation must be achieved. Additionally, the sand filter will be built into and above the topsoil
horizon. See W3.0 / 2 Partial Mound Section for construction details.
Based on these findings, we are proposing a partially mounded sand filter built in the topsoil horizon to
avoid digging into the large boulders. The topsoil is consistent with Soil Type 3, Clay Loam with
moderate structure grade. We are proposing a pressure-dosed, partially mounded sand filter with a
minimum of 2-feet of sand filter material (Secondary Sand). A long-term acceptance rate (LTAR) of
0.65 gallons per square foot will be used to design the STA.
Page 3
Test Pit #1
Test Pit #1
Clay loam topsoil with sporadic large boulders
Page 4
Sieved sample Ribbon 1 to 2-inches in length
Looking toward Test Pit #2 Similar bouldery conditions
Test Pit #2
Page 5
Test Pit #2 Pit 7 (previously excavated)
Page 6
Additional Test Pits excavated June 1, 2026
Test Pit #4 / Large boulders
More large boulders
Page 7
Pockets of clay
DESIGN SPECIFICATIONS
Design Calculations:
Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 75 GPD (4th Bedroom) = 525 GPD
LTAR = 0.65 GPD/SF
525 GPD / 0.65 GPD/SF = 808 SF
(2) 10’ X 40.5’ pressure dosed, partially mounded, unlined sand filters
The OWTS design is based on 4-bedrooms. An average daily wastewater flow of 525 GPD will be used.
For the purposes of this OWTS design, Benchmark Elevation at grade 8756’ has been established as
100’ (Finished Floor). CBO Inc. should be notified of any discrepancies or problems with grade
elevations of proposed components during installation of the OWTS.
Page 8
OWTS Component Minimum Elevation
Primary Tank Inlet Invert Approximate horizontal distance 25’ from residence
/ min. 2% fall / min. 6.25” fall
Approximate horizontal distance 110’ from shop /
min. 2% fall / min. 27.5”
Automatic Distributing Valve Approximate horizontal distance 7’ / min. 1% rise /
min. 0.875” rise
Infiltrative Surface Approximate horizontal distance 65’ to furthest bed
/ min. 1% fall to STA / min. 8.1.25” fall
*Elevations are based upon standard OWTS installation practices. Component elevations may change during
installation due to site conditions. Minimum grade refers to piping between components.
The 4-inch SDR-35 sewer lines exiting the residence and shop must have a double-sweep clean out and
a minimum 2% grade to the septic tank.
The system installation will include a 15000-gallon, two-compartment Valley Precast concrete septic tank
with an Orenco® Biotube Pump Vault and an Orenco® PF3005 pump in the second compartment of the
septic tank. Minimum Schedule 40 sewer line must be used at least 5-feet before entering and after
existing the septic tank. Safety grates must also be placed in each accessible riser. The floats should be
set to dose approximately 71 gallons each pump cycle, allowing approximately 1 gallon of drain back.
The control panel for the pump must be located within line of sight of the septic tank. An electrician will be
responsible for wiring the pumping system and the contractor will be responsible for connecting the
plumbing. This office should be contacted for start up of the system to verify its functioning and to perform a
squirt test prior to use of the system.
Pump Table
Dose Range Max = 101 gal. (20 gal x 5 + 1 gal
drain back)
Min. 61 gal. (20 gal x 3) + 1 gal
drain back
Dose Setting 71 gallons/dose 1 gallon drain back (7’ / 1.5”
diameter pump line)
Float Separation 1500 gallon, two-compartment
Valley Precast concrete septic
tank
7” on/off float separation
Pump Criteria 32.5 gallons per minute (GPM) 26.8 feet total dynamic head
(TDH)
Effluent will be pressure dosed through a 1.5-inch diameter pump line to two partially mounded, unlined sand
filters. The sand filters will be 10’ x 40.5’, constructed in accordance with details provided on W3.0/1 and 2.
The excavation for the sand filter will begin 2.0-feet below native grade on the uphill side. A minimum of 2-
feet of sand filter material will be installed in the over-excavated footprint, resulting in mounding of topsoil cap
above native grade on the uphill side of the mound and approximately 1-foot of sand filter above native
grade on the downhill side of the mound, tapering sand filter material out approximately 6-feet beyond the
primary infiltrative area to accommodate the linear loading rate of 10 GPD/lineal foot (see enclosed Mound
System Design Spreadsheet). Sand filter material must be clean, coarse sand, all passing a screen having
four meshes to the inch. The sand must have an effective size between 0.15 and 0.60 mm. The uniformity
coefficient must be 7.0 or less. Material meeting ASTM 33, for concrete sand, with three percent or less
fines passing 200 mesh sieve may be used. A gradation of the sand media must be provided.
Effluent will be pumped through a 1.5-inch diameter pump line from the pump chamber to an Orenco®
automatic distributing valve (ADV), model 6402. This pump line must have a minimum 1% grade for proper
drain back into the tank after each pump cycle. The ADV must be placed at a high point of each zone in an
Page 9
insulated riser with access from grade. Screened rock must be placed below the ADV to support the ADV
and to assure the clear pipes exiting the ADV remain visible for future inspection and maintenance.
Level, 1.5-inch diameter manifolds will connect laterals in each bed (see W3.0/1 Mounded Sand Filter Plan).
Laterals must be 1.5-inches in diameter with 5/32-inch diameter orifices facing down, spaced 2.5-feet on
center, installed on the GeoMat™ with the filter fabric over the laterals. Laterals should be placed 2-feet
from the edges of the bed leaving 3-feet between center of lateral. Three 39” wide GeoMat™ sheets must
be placed on each10-foot wide bed. All material associated with the GeoMat™ installation must be
proprietary products associated with the GeoMat™, including orifice shields and geotextile fabric.
Manufacturer instructions must be followed regarding installation of the GeoMat™.
Each 1.5-inch diameter lateral must end in a sweeping ell facing up with a ball valve for flushing. Laterals
must be covered by the gray Geomat™ soil separation fabric and at least 1-foot of topsoil or other suitable
soil able to support vegetative growth. There shall be no cobble-sized (2.5”) or greater rock in final cover
over the GeoMat™. Inspection ports must be placed into the sand filter material on each corner of the beds.
The mound must have a minimum 3:1 slope (horizontal:vertical); therefore, the sand fill will extend
approximately 6-feet beyond the sand filter on the downhill side of the mound and another 3-feet further with
the topsoil cap to catch downgradient grade. Soils in the sloped perimeter areas of the mound must be well
draining and able to support vegetative growth. This soil must be approved by this office prior to
installation. The mound must be crowned in a manner to promote drainage off the STA. With the second
partially mounded sand filter further down gradient, a consistent slope must be established for proper
drainage and tie into existing grade naturally. Separation between the partially mounded sand filters must be
a minimum of 30-feet.
COMPONENT SPECIFICATIONS
The component manufacturers are typical of applications used by contractors and engineers in this area.
CBO Inc. must approve alternative components prior to installation of the OWTS. Requests must
be submitted, in writing, to our office for approval prior to installation. Component technical data
sheets are available upon request.
COMPONENT MANUFACTURER MODEL NO. COMMENTS
Septic Tank Valley Precast Item # 1500-2CP-HH
1500-gallon, two-
compartment concrete
septic tank with HH pump
in second compartment
Pump Orenco® PF300511 ½ HP
120 Volt
Biotube ProPak Pump Package Orenco® BPP30DD Vault, Filter, Control Panel (demand dose)
Tank Risers and Lids Orenco® Double-walled PVC Risers and Lids (24” diameter)
Safety Grate Infiltrator® EZ Snap Safety Star 2400 Substitutions may be necessary / risers must fit with safety grate ADV Orenco® V6402A 1.5” Inlet and Outlets
ADV Riser and Lid Orenco® Double-walled PVC Risers
and Lids (30” diameter) Orifice Shields Orenco® OS150 1.5 inch diameter (90 total) Flushing Assembly Orenco® 1.5” diameter (2) 45° or 90° long sweep only (6 total) GeoMat™ GeoMatrix Systems, LLC 243’ GeoMat™ (39”)
Page 10
Construction must be according to the jurisdiction’s adopted On-Site Wastewater Treatment System
Regulations, the OWTS Permit, and this design.
PERMIT APPLICATION INSTRUCTIONS
An OWTS Permit Application must be submitted to Garfield County Environmental Health Department.
https://www.garfield-county.com/environmental-health/filesgcco/sites/16/OWTS-Application-Complete-
Packet-Dec.-2019.pdf. If the OWTS Permit Application will be submitted with a Building Permit
Application, it should be submitted directly to Garfield County Building Department.
All questions regarding permit submission can be directed to Garfield County Environmental Health
Department, 970-945-6614 x8150.
INSTALLATION CONTRACTOR
CBO Inc. expects that the installer be experienced and qualified to perform the scope of work outlined in this
design. The installer must review this design thoroughly and coordinate with our office in advance of
installation. Any additional conditions in this design or county permit must be completed and documented
prior to final approval of the OWTS installation. Communication between the installer and this office is
expected throughout the installation.
INSTALLATION OBSERVATIONS CBO Inc. must view the OWTS during construction. The OWTS observation should be performed before
backfill, after placement of OWTS components. Septic tanks, distribution devices, pumps, dosing
siphons, and other plumbing, as applicable, must also be observed. CBO Inc. should be notified 48 hours
in advance to observe the installation.
In an effort to improve the accuracy of the record drawing, we request that the installer provide a
sketch of the installation, including path of the sewer lines, water line installation (if applicable),
septic tank location, STA location, and measurements from building corners or another fixed
objects on the property. This sketch is most easily provided on Sheet W2.0 of the OWTS Design
Packet. Photographs of the installation and final cover are also requested to supplement our installation
documentation.
REVEGETATION REQUIREMENTS
An adequate layer of good quality topsoil capable of supporting revegetation shall be placed over the entire
disturbed area of the OWTS installation. A mixture of native grass seed that has good soil stabilizing
characteristics (but without taproots), provides a maximum transpiration rate, and competes well with
successional species. No trees or shrubs, or any vegetation requiring regular irrigation shall be placed over
the STA. Until vegetation is reestablished, erosion and sediment control measures shall be implemented
and maintained on site. The owner of the OWTS shall be responsible for maintaining proper vegetation
cover.
OPERATION INFORMATION AND MAINTENANCE
The property owner shall be responsible for the operation and maintenance of each OWTS servicing the
property. The property owner is responsible for maintaining service contracts for manufactured units,
alternating STAs, and any other components needing maintenance.
Geo-fabrics or plastics should not be used over the STA. No heavy equipment, machinery, or materials
should be placed on the backfilled STA. Machines with tracks (not wheels) should be used during
construction of the STA for better weight distribution. Livestock should not graze on the STA. Plumbing
Page 11
fixtures should be checked to ensure that no additional water is being discharged to OWTS. For example, a
running toilet or leaky faucet can discharge hundreds of gallons of water a day and harm a STA.
If an effluent filter or screen has been installed in the OWTS, we recommend this filter or screen be cleaned
annually, or as needed. If the OWTS consists of a pressurized pump system, we recommend the laterals be
flushed annually, or as needed.
The homeowner should pump the septic tank every two years, or as needed gauged by measurement of
solids in the tank. Garbage disposal use should be minimized, and non-biodegradable materials should not
be placed into the OWTS. Grease should not be placed in household drains. Loading from a water softener
should not be discharged into the OWTS. No hazardous wastes should be directed into the OWTS.
Mechanical room drains should not discharge into the OWTS. The OWTS is engineered for domestic waste
only.
ADDITIONAL CONSTRUCTION NOTES If design includes a pump, weep holes must be installed to allow pump lines to drain to minimize risk of
freezing. The pump shall have an audible and visual alarm notification in the event of excessively high-
water conditions and shall be connected to a control breaker separate from the high-water alarm breaker
and from any other control system circuits. The pump system shall have a switch so the pump can be
manually operated.
Excavation equipment must not drive in the excavation of the STA due to the potential to compact soil.
Extensions should be placed on all septic tank components to allow access to them from existing grade.
Backfill over the STA must be uniform and granular with no material greater than minus 3-inch.
LIMITS: The design is based on information submitted. If soil conditions encountered are different from conditions
described in report, CBO Inc. should be notified. All OWTS construction must be according to the county
regulations. Requirements not specified in this report must follow applicable county regulations. The
contractor should have documented and demonstrated knowledge of the requirements and regulations of
the county in which they are working. Licensing of Systems Contractors may be required by county
regulation.
Please call with questions.
Sincerely,
CBO Inc.
Carla Ostberg, MPH, REHS
Pump Selection for a Pressurized System - Single Family Residence Project
PREMICH
Parameters
Discharge Assembly Size
Transport Length Before Valve
Transport Pipe Class
Transport Line Size
Distributing Valve Model
Transport Length After Valve
Transport Pipe Class
Transport Pipe Size
Max Elevation Lift
Manifold Length
Manifold Pipe Class
Manifold Pipe Size
Number of Laterals per Cell
Lateral Length
Lateral Pipe Class
Lateral Pipe Size
Orifice Size
Orifice Spacing
Residual Head
Flow Meter
'Add-on' Friction Losses
1.25
7
40
1.50
6402
65
40
1.50
2
6
40
1.50
6
38.5
40
1.50
5/32
2.5
5
None
0
inches
feet
inches
feet
inches
feet
feet
inches
feet
inches
inches
feet
feet
inches
feet
Calculations
Minimum Flow Rate per Orifice
Number of Orifices per Zone
Total Flow Rate per Zone
Number of Laterals per Zone
% Flow Differential 1st/Last Orifice
Transport Velocity Before Valve
Transport Velocity After Valve
0.68
48
32.5
3
1.0
5.1
5.1
gpm
gpm
%
fps
fps
Frictional Head Losses
Loss through Discharge
Loss in Transport Before Valve
Loss through Valve
Loss in Transport after Valve
Loss in Manifold
Loss in Laterals
Loss through Flowmeter
'Add-on' Friction Losses
7.4
0.4
7.8
3.9
0.1
0.1
0.0
0.0
feet
feet
feet
feet
feet
feet
feet
feet
Pipe Volumes
Vol of Transport Line Before Valve
Vol of Transport Line After Valve
Vol of Manifold
Vol of Laterals per Zone
Total Vol Before Valve
Total Vol After Valve
0.7
6.9
0.6
12.2
0.7
19.7
gals
gals
gals
gals
gals
gals
32.5
26.8
gpm
feet
0 5 10 15 20 25 30 35 40
0
50
100
150
200
250
300
Net Discharge (gpm)
PumpData
PF3005 High Head Effluent Pump
30 GPM, 1/2HP
115/230V 1Ø 60Hz, 200V 3Ø 60Hz
PF3007 High Head Effluent Pump
30 GPM, 3/4HP
230V 1Ø 60Hz, 200/460V 3Ø 60Hz
PF3010 High Head Effluent Pump
30 GPM, 1HP
230V 1Ø 60Hz, 200/460V 3Ø 60Hz
PF3015 High Head Effluent Pump
30 GPM, 1-1/2HP
230V 1Ø 60Hz, 200/230/460V 3Ø 60Hz
Legend
System Curve:
Pump Curve:
Pump Optimal Range:
Operating Point:
Design Point:
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
July 15, 2024
Mike Premich
P.O. Box 3858
Basalt, Colorado 81621
whiteriverconstructionco@gmail.com
Project No. 23-7-662
Subject: Subsoil Study for Foundation Design, Proposed Residence and Shop, Parcel No.
218724300023, 4799 Homestead Road, Garfield County, Colorado
Dear Mike:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was conducted in accordance with our agreement for geotechnical
engineering services to Mike Premich dated November 16, 2024. The data obtained and our
recommendations based on the proposed construction and subsurface conditions encountered
are presented in this report.
Proposed Construction: The proposed residence will be a single-story wood-frame residence
with attached garage located on the site as shown on Figure 1. Ground floors will be structural
over crawlspace or slab-on-grade. Cut depths are expected to range between about 2 to 5 feet.
Foundation loadings for this type of construction are assumed to be relatively light and typical
of the proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The subject site was vacant at the time of our field investigation. The ground
surface was relatively flat with a gentle slope down to the south. The proposed building area was
graded to remove brush. Vegetation consists of grass with sagebrush and oak brush around the
building area. There were basalt boulders visible on the surface around the site.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating
7 exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about 1½ to 2½ feet of topsoil, consist
of nil to 2½ feet of stiff to hard, sandy clay with scattered gravel. Below the clay, dense to very
dense gravel and cobbles with boulders in a clayey sand matrix was encountered down to the
maximum explored depth of 7½ feet. Results of swell-consolidation testing performed on
relatively undisturbed samples of sandy clay, presented on Figures 4 and 5 indicate low
compressibility under existing moisture conditions and light loading and a low expansion
potential when wetted. Results of a gradation analysis performed on a sample of clayey gravel
(minus 3-inch fraction) obtained from the site are presented on Figures 6 and 7. No free water
was observed in the pits at the time of excavation and the soils were slightly moist to moist.
- 2 -
Kumar & Associates, Inc. ® Project No. 23-7-662
Foundation Recommendations: The upper clay soils possess low bearing capacity and low
swell potential when wetted. Considering the subsoil conditions encountered in the exploratory
pits and the nature of the proposed construction, we recommend spread footings placed on
the undisturbed granular soil below the clay designed for an allowable soil bearing pressure
of 3,000 psf for support of the proposed residence. The granular soils appear dense and post-
construction settlement of the foundation should be minor. Footings should be a minimum width
of 16 inches for continuous walls and 2 feet for columns. The topsoil, upper clay soils and loose
disturbed soils encountered at the foundation bearing level within the excavation should be
removed and the footing bearing level extended down to the undisturbed natural granular soils.
Exterior footings should be provided with adequate cover above their bearing elevations for frost
protection. Placement of footings at least 36 inches below the exterior grade is typically used
in this area. Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls
acting as retaining structures should be designed to resist a lateral earth pressure based on an
equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab-on-grade construction. To reduce the effects of some differential movement, floor slabs
should be separated from all bearing walls and columns with expansion joints which allow
unrestrained vertical movement. Floor slab control joints should be used to reduce damage due
to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be
established by the designer based on experience and the intended slab use. A minimum 4-inch
layer of free-draining gravel should be placed beneath basement level slabs to facilitate drainage.
This material should consist of minus 2-inch aggregate with less than 50% passing the No. 4
sieve and less than 2% passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: Although free water was not encountered during our exploration, it has
been our experience in the area and where clay soils are present that local perched groundwater
can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring
runoff can create a perched condition. We recommend below-grade construction, such as
retaining walls, crawlspace and basement areas (if any), be protected from wetting and
hydrostatic pressure buildup by an underdrain system.
The drains should consist of rigid perforated PVC drainpipe placed in the bottom of the wall
backfill surrounded above the invert level with free-draining granular material. The drain should
be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and
sloped at a minimum ½% to a suitable gravity outlet. Free-draining granular material used in the
underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing
the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at
least 1½ feet deep.
- 3 -
Kumar & Associates, Inc. ® Project No. 23-7-662
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction. Drying could increase the expansion potential of the clay
soils.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
Free-draining wall backfill should be capped with about 2 feet of the on-site, finer
graded soils to reduce surface water infiltration.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least
5 feet from the building.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. Our services do not include determining the presence, prevention or possibility of mold
or other biological contaminants (MOBC) developing in the future. If the client is concerned
about MOBC, then a professional in this special field of practice should be consulted. Our
findings include interpolation and extrapolation of the subsurface conditions identified at the
exploratory pits and variations in the subsurface conditions may not become evident until
excavation is performed. If conditions encountered during construction appear different from
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
Kumar & Associates
Kumar & Associates
Kumar & Associates
Kumar & Associates
Kumar & Associates
Kumar & Associates
Kumar & Associates
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 23-7-662
SAMPLE LOCATION NATURAL
MOISTURE CONTENT
NATURAL
DRY DENSITY
GRADATION
PERCENT PASSING NO. 200 SIEVE
ATTERBERG LIMITS UNCONFINED
COMPRESSIVE STRENGTH SOIL TYPE BORING DEPTH GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%)
(ft) (%) (pcf) (%) (%) (psf)
4 3½ 38.3 80 Sandy Clay
4½ - 5½ 31.2 40 30 30 43 18 Clayey Sandy Gravel
5 3 – 4 38.3 14 48 38 53 19 Very Clayey Gravelly Sand
6 2½ 35.5 81 Sandy Clay
7 2 29.3 88 Sandy Clay
4½ - 5½ 36.9 31 22 47 28 NP Gravelly Sandy Silt
Gar eld County, CO
Developed by
Account
Number
R050041
Parcel Number 218724300023
Acres 40
Land SqFt 0
Tax Area 005
Mill Levy 60.9540
Physical
Address
0
GLENWOOD SPRINGS 81601
Owner Address PREMICH, MICHAEL III &
SARAH
PO BOX 3858
BASALT CO 81621
Total Actual
Value
$475,000 Last 2 Sales
Date Price
4/7/2022 $485,000
9/21/1992 $75,000
Date created: 9/5/2024
Last Data Uploaded: 9/5/2024 2:17:38 AM
921 ft
Overview
Legend
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Roads
Parcel/Account
Numbers
Owner Name
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County Boundary
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