HomeMy WebLinkAboutGeotechnical Review 09.08.2025Bomar & Assawates, Inc.® 5020 County Road 154
Geotechnical and Materials Engineers Glenwood Springs, CO 81601
1(+Aand Environmental Scienusis phone: (970) 945-7988
email: kaglenwood@kumarusa.com
www.kumarusa.com
An Employee Owned Company
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
September 8, 2025
Updated October 15, 2025
Ziska Childs
284 County Road 102
Carbondale, Colorado 81623
ziska ziiskachjlds.com
Project No. 25-7-546
Subject: Geotechnical Review for Proposed Garage, 284 County Road 102, Garfield
County, Colorado
Ms. Childs:
As requested, Kumar & Associates has conducted a geotechnical review for design of the
proposed garage at the subject site. A visit was made on September 3, 2025 to observe the
site for geotechnical conditions. The findings of our observations and recommendations for
building site development and foundation design are presented in this report. The review was
conducted in accordance with our agreement for professional services with you dated August
21, 2025. Hepworth-Pawlak Geotechnical (now Kumar & Associates) previously conducted a
subsoil study for foundation design of the existing studio building at the site and presented the
findings in a report dated April 24, 1997, Job No. 197 217.
Site Conditions: The proposed garage is located across the driveway to the west of the studio
building. The ground surface drops steeply down around 5 feet off the driveway into the garage
site then slopes gently to the west. The steep slope is an embankment fill for the driveway
access into the property from County Road 102 and has recently been covered with end
dumped fill of mixed rocky soil and concrete fragments ranging up to around 3 feet in size. The
natural ground of the garage site is vegetated with grass, weeds and sage brush with scattered
basalt rocks.
Proposed Construction: The planned development is to elevate the garage building site
around 6 feet to have a relatively level access from the driveway with a parking apron in front
of the garage. The stockpile of soil next to the studio was sampled as a possible source of
material to fill the garage site. The results of laboratory testing are presented on Figures 1 and
1A which indicated the stockpile soil can be used as structural fill in the proposed building site.
The proposed garage will be a single -story pole type structure with slab -on -grade.
Design Recommendations: Considering the subsurface conditions encountered at the studio
building and our observations of the proposed garage site, we recommend the pole supports be
founded on footing pads bearing on the natural soils or properly compacted structural fill. The
existing end -dumped fill and organics should be removed from the garage building site. The
exposed soils should then be moistened to near optimum and compacted. Structural fill should
be placed in thin lifts and compacted to at least 98% of standard Proctor density within 2% of
optimum moisture content, The embankment slope away from the building footprint should be
graded at 2 horizontal to 1 vertical or flatter and be protected against erosion. The ground
surface next to the building should have a minimum slope of 5% for 5 feet in miscellaneous
graded areas and 2% in paved areas. Concrete floor slab and driveway slab should be
Ziska Childs
September 8, 2025
Project No. 25-7-546
Page 2
supported on structural fill compacted to at least 95% of standard Proctor density at near
optimum moisture content. For passenger vehicle loading, we recommend a minimum 4-inch
thick concrete slab supported on 4 inches of CDOT Class 6 aggregate base course.
The design and construction criteria presented below should be observed for a footing
foundation system.
1) Footings placed on the undisturbed natural soils or compacted structural fill should be
designed for an allowable bearing pressure of 1,500 psf. Based on experience, we
expect settlement of footings designed and constructed as discussed in this section will
be about 1 inch or less. Settlement of embankment fill could be another 1 inch, around
2% of the fill depth.
2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet
for isolated pads.
3) Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement of
foundations at least 36 inches below exterior grade is typically used in this area.
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 12 feet.
5) All existing fill, topsoil and any loose or disturbed soils should be removed from the
building area including the exterior slope around the building footprint. The exposed
soils should then be moistened and compacted prior to placing structural fill.
6) A representative of the geotechnical engineer should observe the building excavation
prior to placing structural fill for bearing conditions.
The recommendations submitted in this letter are based on our observation of the site
conditions and the previous subsurface exploration at the studio building site. Variations in the
subsurface conditions could increase the risk of foundation movement. 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.
If you have any questions or need further assistance, please call our office.
Sincerely,
Kumar & Associates, Inc
Steven L. Pawla , E15222 x
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Attachments: Figur mpaction Test Report
Figure 1 ize Distribution Report
cc: Confluence Architecture — Angela Loughry (an ela confluencearchitecture.com)
Kumar & Associates, Inc.
COMPACTION TEST REPORT
110
1
Ld
108
106
U
a
W
C
N
�
I
104
102
ZAV for
Sp.G. _
100
2.50
13 14.5 16 17.5 19 20.5 22
Water content, %
e - Rock Corrected -o- - Uncorrected
Test specification: ASTM D 698-12 Method B Standard
ASTM D4718-15 Oversize Corr. Applied to Each Test Point
Elev/
Depth
Classification
Nat.
Moist.
Sp.G.
LL
35
PI
% >
3/8 in.
%
No.200
USCS
AASHTO
SM
A-4(1)
10
12.0
43.0
ROCK CORRECTED TEST RESULTS
UNCORRECTED
MATERIAL DESCRIPTION
Maximum dry density = 106.3 pcf
Optimum moisture = 16.1 %
102.5 pcf
18.2 %
Silty Clayey Sand with Gravel
Project No. 25-7-546 Client: Ziska Childs
Project: 284 County Road 102, Garfield County, Colorado
Date: 9/3/2025
0 Location: On Site Stockpile Sample Number: 263-25
Remarks:
See Figure IA for classification results.
Figure 1
Kumar & Associates, Inc.
Glenwood Springs, Colorado
Tested By: KO Checked By: SLP
Tested By: KO Checked By: SLP