HomeMy WebLinkAboutObservation of ExcavationK3nf;ffififfiHfnlri**
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
email: kaglenwood@kumarusa.com
www.kumarusa.com
An Employ** Owned Compony
Ofiice Locations; Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
July 7,2025
Number 1 Construction
Attn: Lukas Stuemke
62 Sweetgrass Drive, Suite A
Carbondale, Colorado 81623
lukasl roofins@qmail. com
Subject:
Projec,t No.25-7-455
Observation of Excavation, Proposed Accessory Dwelling Unit (ADU) and
Garages, Lot 11, Coryell Ranch,69 Spirit Mountain Drive, Garfield County,
Colorado
Dear Lukas:
As requested, a representative of Kumar & Associates observed the excavation at the subject
site on July 3, 20251o evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation support are presented in this report. The
services were performed in general accordance with our agreement for professional engineering
services to Number 1 Construction dated July 1 ,2025.
The proposed buildings will be single-story, wood-frame structures with a combination of slabon-
grade and structural over crawlspace ground floors. The buildings have been designed to be
supported on spread footing foundations sized for an assumed allowable bearing pressure of
1,500 psf.
At the time of our visit to the site, the foundation excavations were each cut to 1 level from 2 to
STzteet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted primarily of relatively dense, silty sandy gravel with cobbles. Silty sand and clay was
exposed in the north corner of the smaller 2-car garage excavation. The results of a gradation
analysis performed on a sample of silty sandy gravel with cobbles (minus S-inch fraction) obtained
from the site are presented on Figure 1. No free water was encountered in the excavation and
the soils were slightly moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable soil
bearing pressureof 1,500 psf should beadequateforsupportof theproposed buildings. The
exposed soils tend to compress when wetted and there could be some post-construction
settlement of thefoundation if the bearing soils becomewet. Footings should be a minimum width
of 16 inches for continuous walls and 2 feet for columns. Loose disturbed soils in footing areas
should be removed and the bearing level extended down to the undisturbed natural soils. Exterior
footings should be provided with adequate soil cover above their bearing elevations for frost
protection. Continuous foundation walls should be well reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 12 teet. Foundation walls
acting as retaining structures should also be designed to resist a lateral earth pressure based on
an equivalent fluid unit weight of at least 50 pcf for on-site soil as bacKill. Structural fill placed
Number 1 Construction
July 7,2025
Project No. 25-7-455
Page 2
within floor slab areas can consist of the on-site soils compacted to at least 95o/o of standard
Proctor density at a moisture content near optimum. Backfill placed around the structure should
be compacted and the surface graded to prevent ponding within at least 10 feet of the building.
Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads should not be
located within 10 feet of the foundation.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and do not include subsurface exploration to evaluate the
subsurface conditions within the loaded depth of foundation influence. This study is based on the
assumption that soils beneath the footings have equal or better support than those exposed. The
risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. ln order to reveal the nature and extent of variations in
the subsurface conditions below the excavation, drilling would be required. lt is possible the data
obtained by subsurface exploration could change the recommendations contained in this letter.
Our services do not include determining the presence, prevention or possibility of mold or other
biologicalcontaminants (MOBC) developing in the future. lf the client is concerned about MOBC,
then a professional in this special field of practice should be consulted.
lf you have any questions or need further assistance, please call our office.
Sincerely,
[.ti l* I ",'l* s' t\ A**-l r-'{.: i;r}.{,:rs,
James H. Parsons, P
Rev. by: DEH
JHP/kac
attachments Figure 1 - Particle Size Distribution Report
Kumar & &s*o*iaies, ln*,@
Particle Size Distribution Report
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GRAIN SIZE - mm.
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o/o +3"7o Gravel %Sand % Fines
Coarse Fine Coarse M€dium Fine silr clay
7.0 22.0 10.0 4.4 13.,5 155 28-0
(no specifi cation providul)
Location: Spoil Pile
Sample Number: 168-25 Date: 712/2025
SIEVE
slzE
PERCENT
FINER
SPEG.*
PERCENT
PASS?
(X=NO)
5
3
1.5
.75
.375
#4
#8
#t6
#30
#50
#100
#200
100.0
93.0
82.0
71.0
66.0
61.0
58.0
53.0
47.0
40.0
34.0
28.0
Soil Description
Clayey Sandy Gravel with Cobbles
PL=
Ddn= 62.6423
DXX= 0.s300
Di6=
USCS=
Atterberg Limits
LL=
Coefficients
Dqc= 45.9131
DXX= 0.0945neYvg-
Classification
AASHTO=
Remarks
Pl=
D6O= :.t:Se
Prg=wC-
Kumar & Associates, lnc.
Glenwood Sprinqs, Golorado
Glient: Number I Construction
Project: Lot I l, Coryell Ranch, 69 Spirit mountain Road, Garfield County,
Colorado
Proiect No: 25-7-455 Fiqure I
Tested By:KO Checked By:JHP