HomeMy WebLinkAboutObservation of Excavation 08.24.2020l(+rlm,mm;ffü'.*
An Ëmployac Oryvnsd Compony
5020 Cor.rnty Road 154
Clcnwood Springs, CO 8ló01
phone: (970) 945-7988
fax: (970) 945-8454
emai I : kaglenwood(@k urnalusa.corn
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Office l-ocations: Denver (llQ). Parker, Colorado Springs, Fort Collir¡s. Glelrvood Springs, and Sun¡¡riî County, [--olorado
August 24,2020
Richard Dooley
P.O. Box 519
Tabernash, Colorado 80478
ri chard. dool eylrdsrn ai1. com
Project No. 20-7-198
Subject: Observation of Excavation, Proposed Residence, LotST,Ironbridge Subdivision,
272River Bank Lane, Garfield County, Colorado
Dear Richard:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on August 20,2020 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 and
presented our findings in a report dated April 6,2020, Project No. 20-7-198.
At the time of our visit to the site, the foundation excavation had been cut in multiple levels up to
I 1 feet below the adjacent ground surface. The soils exposed in the bottom ofthe excavation
consisted of mostly medium dense, silty sand and gravel with cobbles. A small section of the
proposed westem garage wall footing area appeared to be on about 2 feet of sandy silty clay.
Water was observed seeping into the lower level of the excavation on the south side and flowing
toward the 'îet well" where the water was being pumped out at about an estimated l0 gpm.
Screened rock had been spread across the excavation bottom to help facilitate the dewatering.
Outside of the wetted areas, the soils were slightly moist.
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site. The natural gravel soils are suitable for support of spread footings designed for the
recommended allowable bearing pressure of 2,500 psf. The small footing section on the clay
soils can probably be left as is, assuming that area is lightly loaded and the footing design
bearing pressure is less than 1,000 psf. Loose and disturbed soils should be removed in the
footing areas to expose the undisturbed natural soils. The interior subdrains should be placed to
collect and route the water seepage from below slab areas through the excavation and under or
through the interior footings via piping and screened rock to the'lvet well" pump for temporary
dewatering. The completed foundation drains should discharge by gravity flow. Water seepage
should be diverted away from the footing areas and any softened soils and mud removed before
concrete placement. Other recommendations presented in our previous report which are
applicable, including moisture barriers below slab-on-grade, should also be observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and the previous subsurface exploration at the site. Variations
Richard Dooley
Augrrst 24,202A
Page2
in the subsurface conditions below the excavation could increase the risk of foundation
movement. We should be advised of any variations encountered in the excavation conditions for
possible changes to recommendations contained in this letter. Our services do not include
determining the presence, prevention or possibility of motd 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 & Associateso Inc.
Daniel E. Hardin, P.
Rev. by: SLP
DEH/kac
Kumar & Associates, lnc. o Project No.20-7.198