HomeMy WebLinkAboutObservation of Excavation
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
June 30, 2023
DM Neuman Construction
Attn: Jason Neuman
P.O. Box 2317
Glenwood Springs, Colorado 81601
jmn@dmneuman.com
Project No. 18-7-692.A
Subject: Observation of Swimming Pool Excavation, 2808 County Road 117, Garfield
County, Colorado
Gentlemen:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on June 27, 2023 to evaluate the soils exposed for foundation support. The findings
of our observations and recommendations for the foundation design are presented in this report.
We previously conducted a subsoil study for design of foundations at the site, report dated
October 19, 2021, Project No. 18-7-692 and observed the residence excavation, report dated
July 22, 2022, Project No. 18-7-692A.
The proposed pool will be a fiberglass shell placed on a drain gravel layer connected to a sump
pit. The residence foundation was placed on structural fill consisting of a mixture of onsite soil
and imported materials. It is proposed to sub-excavate the pool area down to the same sub-
excavation level of the residence and replace the full depth with Class 6 ¾-inch base course.
At the time of our visit to the site, the pool area had been excavated down in one level from
about 5 to 8 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavation consisted of existing structural fill closest to the residence and native sandy silty clay
in the remaining area. The results of classification testing performed on the soils exposed are
summarized in Table 1. No free water was encountered in the excavation and the soils were
moist to very moist in the natural soil area.
The soil conditions exposed in the excavation are generally consistent with those previously
encountered on the site. The natural clay soils should be excavated down around 3 feet and
replaced with structural fill. Loose disturbed soils should be moistened and compacted and the
structural fill should be monitored for proper compaction. We recommend an impervious
membrane such as 30 mil PVC pond liner be placed below the drain gravel layer of the entire
pool footprint to help contain possible leakage from the pool works. Other recommendations
presented in our previous report which are applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the pool excavation and the previous subsurface exploration at the site. Variations in the
subsurface conditions below the excavation could increase the risk of foundation movement. We
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 18-7-692.A
Pool Excavation
SAMPLE LOCATION NATURAL MOISTURE
CONTENT
NATURAL DRY
DENSITY
GRADATION
PERCENT PASSING NO. 200 SIEVE
ATTERBERG LIMITS UNCONFINED COMPRESSIVE
STRENGTH
SOIL OR BEDROCK TYPE
BOTTOM OF POOL EXCAVATION
GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%)
(%) (pcf) (%) (%) (PSF)
Natural Soil 21.3 98 68 Sandy Silty Clay
Fill Soil 14.0 112 61 Sandy Silty Clay with
Gravel