HomeMy WebLinkAboutSoils Report for Foundation DesignMarch 20, 2025
(revised May 6, 2025)
Brian L. Sperry
2877 Loma Place
Boulder, CO 80301
Attention: Brian L. Sperry
Subject: Revised Site and Soil Evaluation
Sperry Residence
5811 County Road 320
Garfield County, Colorado
Project No. GS06951.000-132-L1 R
CTLIThompson, Inc. (CTLIT) was retained to perform a site and soil evaluation for
design of an on -site wastewater treatment system (OWTS) for the Sperry Residence proposed
at 5811 County Road 320 in Garfield County, Colorado. Design of the OWTS will be done by
other consultants. Our site and soil evaluation was conducted in accordance with the Garfield
County Onsite Wastewater Treatment System Regulations published by the Garfield County
Public Health Department.
The subject site is an approximately 9.92-acre parcel accessed by County Road 320 to
the east. A vicinity map with the location of the site is included on Figure 1. A shed and trailer
are present on the site. A new residence is planned on the west side of the lot on a terrace
about 15 feet above the Colorado River. An aerial photograph of the site is shown on Figure 2.
Trees and hydrophilic vegetation are present on the lot near the river with dryland shrubs and
grass at the central and eastern portions of the lot. An existing water well is located east of the
planned residence. The proposed soil treatment area (STA) is located in the south-central part
of the property to the south of the proposed residence location. A preliminary site plan with
proposed location of the STA is shown on Figure 3.
Ryan R. Barbone, P.E., of CTLIT visited the property on February 26, 2025, to perform a
site and soil evaluation. The ground surface in the proposed STA area is generally flat and
slopes down to the west at grades less than 5 percent. The "slope shape"
variable for the STA
classifies as "LL", pursuant to the EPA's Onsite Wastewater Treatment Systems Manual.
CTLIT investigated subsurface conditions in the proposed STA areas by observing two
profile pits (P-1 and P-2) that were excavated with a trackhoe at the approximate locations
shown on Figures 2 and 3. Subsoils exposed in our profile pits consisted of approximately fl-
inches of topsoil over sandy loam with gavel and loamy sand to the total excavated depth of 8
feet. Graphic logs of subsurface conditions found in our profile pits are shown on Figure 4.
We did not find limiting layers in the subsoils. Groundwater was not encountered in our
profile pits at the time of excavation. No redoximorphic features were observed in the pits. We
observed that the soil had weak to no structure per the USDA Soil Structure — Shape and was
considered "massive" per USDA Soil Structure — Grade.
C T L Thom son Inc.
Deaver, Fort Collins, Colorado Springs, Glenwood Springs, Pueblo, Summit County — Colorado
Cheyenne, Wyoming and Bozeman, Montana
We performed grain -size analysis on two samples of soils obtained from our profile pits.
The soils encountered in our profile pits classified as sandy loam with gravel (Soil Type R-1,
Matrix Soils Type 2A) and loamy sand (Soil Type 1). We found a maximum gravel (>2mm)
content of 42 and 26 percent in P-1 and P-2, respectively. Descriptions of these soil types are
summarized on Table 10-1 and Table 10-1A of the OWTS design regulations published by
Garfield County. Gradation test results are included as Figure 5.
We are available to discuss the contents of this letter. If you have questions or need
additional information, please call.
CTLITHOMPSON, ..
Kimberly Talbert
Staff Geologist
kt2lbert@ct[thompson.com
Attachments Figure 1 — Vicinity Map
Figure 2 — Aerial Photograph
Figure 3 — Proposed OWTS
Figure 4 — Summary Logs of Profile Pits
Figure 5 — Gradation Test Results
Via email: brianIspeEy@gmajI.com
Reviewed by:
Ryan R. Barb
Division Man,,
BRIAN SPERRY Page 2 of 2
SPERRY RESIDENCE
CTLIT PROJECT NO. GS06951.000-132-L1R
0 50 100
SCALE: 1' = 100'
LEGEND:
P-1 APPROXIMATE LOCATION OF
PROFILE PIT
NOTE: SATELLITE IMAGE FROM GOGGLE EARTH
(DATED JUNE 23, 2023)
Aerial
BRIAN SPERRY
SPERRY RESIDENCE Photograph
CTL/T PROJECT NO. GS06951.000-132-L1
Fig. 2
0 50 100
SCALE: 1" = 100'
LEGEND:
P-1 APPROXIMATE LOCATION OF
PROFILE PIT
NOTE: BASE PLANS PROVIDED BY SGM
(DATED FEBRUARY 07, 2025)
21 zz
Proposed Residence.
P-2
4�v
P-1
Proposed STAY
ER LN
P.—I R,
SC4n�R R05E.;
BRIAN SPERRY Proposed
SPERRY RESIDENCE OWTS Fig. 3
OTLfr PROJECT NO. GS06951.000-132-Ll
w
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t
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a
w
w
P-1
P-2
LEGEND:
EL.5242
EL.5241
TOPSOIL, CLAY, SANDY, ORGANICS, MOIST TO
5245
5245
VERY MOIST, SOFT, DARK BROWN.
SANDY LOAM AND LOAMY SAND WITH GRAVEL,
F
WEAK TO STRUCTURELESS GRADE, LOOSE
CONSISTENCY, MOIST, TAN. (SOIL TYPE R-1,
SOIL TYPE 1)
5240
5240
INDICATES A BULK SAMPLE FROM EXCAVATED
w
SOILS.
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a
NOTES:
w
5235
5235
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1.
PROFILE PITS WERE EXCAVATED WITH A
TRACKHOE ON FEBRUARY 26, 2025. THE PITS
WERE BACKFILLED IMMEDIATELY AFTER
EXCAVATION OPERATIONS WERE
COMPLETED.
2.
SOIL EVALUATION CONDUCTED BY RYAN
L5230
BARBONE, P.E. (CPOW SOILS CERTIFIED)
5230
3.
GROUNDWATER WAS NOT ENCOUNTERED IN
PROFILE PITS AT THE TIME OF EXCAVATION.
REDOXIMORPHIC FEATURES WERE NOT
OBSERVED IN PROFILE PITS.
4.
ELEVATIONS WERE ESTIMATED FROM
GROUND SURFACE ELEVATION CONTOURS ON
FIGURE 3.
5.
THESE LOGS ARE SUBJECT TO THE
EXPLANATIONS, LIMITATIONS, AND
CONCLUSIONS IN THIS LETTER.
Summary Logs of
Profile Pits
BRIAN SPERRY
SPERRY RESIDENCE FIG. 4
CTLjT PROJECT NO. GS06951.000-132-1-1
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Sample of SANDY LOAM WITH GRAVEL_- SOIL TYPE R-1 GRAVEL 35 % SAND 42 %
From P-1 AT 3-4 FEET SILT & CLAY 23 % LIQUID LIMIT %
PLASTICITY INDEX %
HYDRdMETERANALY&S SIEVE ANALYSIS
25 HR. 7 HR. TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
45 MIN. 15 MIN. 60 MIN. 19 MIN. 4 MIN. 1 MIN. '20D '100 -50 '40 '30 -16 '10 -B '4 3!6" 3/4" 1'/:" 3" 5"6" 80"
100_
-
-
-
10
90
- -
-
-
80
20
30 w
Z D
m
00
-
40
K
r
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50 w
LL50
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70
30xi
^
20
80
90
10
100
_
-
0
.001
0.002 .005 .009 .019 .037 .074 .149 .297 .590 1.19 2.0 2.38 4.76 9.52 19.1 36.1 76.2 12152200
0.42
DIAMETER OF PARTICLE IN MILLIMETERS
CLAY (PLASTIC) TO SILT (NON -PLASTIC)
SANDS
GRAVEL
FINE MEDIUM COARS
FINE COARSE COBBLES
Sample Of LOAMY SAND WITH GRAVEL -SOIL TYPE 1
From P-2 AT 3-4 FEET
GRAVEL 20 % SAND 64 %
SILT & CLAY 16 % LIQUID LIMIT %
PLASTICITY INDEX %
BRIAN SPERRY Gradation
SPERRY RESIDENCE
PROJECT NO. GS06951.000-132-L1 Test Results
FIG. 5