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March 29,2AZZ
Russell Schweis
P.O. Box 954
Carbondalg Colorado 8 1623
sunrrydS9ftg:yalroo-gcln project No. 2r-?-30r.A
Subject: Observation of Excavation, Proposed Residence, 347 Cooseberry Park Road,
Garfi eld County, Colorado
Gentlemen:
As requested, a representative of Kumar & Associates, lnc. observed the excavatisn at the
subject site on March 29,2022 to evaluate the soils exposd for foundation support. The
findings of our observations and recommendations for the foundation design are presented in this
report. We previously condueted a subsoil study for design of foundations at the site and
presentecl our findings in a report dated May 7,2AZl, Project No. 2l-7-301.
A one to two-story wood framed structure with an attached garage is plamred. The proposed
building has becn designed to be foundecl on spread footings bearing on the natural soils and
bsdrock and sized for an allorvable bearing pr€ssure of 2,000 psf, The current proposed location
is about 200 feet west of the previously proposed location.
At the time of our visit to the site, the foundation excavatisn had been cut in fivc levels up ttr
about l3 feet belotv the adjacent ground surface. The soils exposd in the bottom of the
exc.flvation consisted of slightly sandy clay and clayey, sandy glavel, and wcathered basalt rock.
No frce water lvas cncountered in the excavation and the soils were moist.
Considering the conditions cxposcd in the excavation and the nature of the proposcd
comtruction, spread footings placed on the undisturbed natural soils and rock designed for an
allolvable soil bearing pressure of 2,000 psf can be used for support of the proposed rtxidence'
Footings should be a minimurn width of l8 inches for continuous walls and 2 feet for columns.
Loose and disturbed soils in footing areas should be removed and the bearing level cxtended
down to the undisrurbed basalt rock, sandy clayey gravel or slightly sandy clay. Exterior
footings should be provided with adequatc soil cover above their bearing elevations for frost
protectiein. Placement of footings at least 36 inches belorv the exterior grade is typically used in
this area. Contiluous foundation rvalls should be rcinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at lea-ct l4 feet. Foundation rvalls
acting as retaining structures should also be designcd to resist a lateral earth pressure based on an
equivalerit fluid unit weight of at least 55 pcf for on-site soil as backfill. A perirneter foundation
{rain should be provided to prevent temporary buildup of hydrostatic pressure behind the
Russell Schweis
March 29,2022
Page2
basemenUgarage level walls and prevent wetting of the lower level. The drains should consist of
PVC drainpipe placed in the bottom of the wall backfill surrounded above the invert level with
free-draining granular material. The drain should be placed at each level of excavation and at
least 1 foot below lowest adjacent finish grade and sloped at a minimum %Vo to a suitable gravity
outlet. Free-draining granular material used in the underdrain system should contain less than
2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size
of 2 inches. The drain gravel backfill should be at least lYz feet deep and covered with filter
fabric such as Mirafi 140N or 160N. Structural fill placed within floor slab areas can consist of
the on-site sandy gravel soils compacted to at least 95% 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. Other recommendations
presented in ourprevious 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 foundation excavation and the previous limited subsurface exploration elsewhere on
the site. Variations 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 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.
,{
Mark Gayeski, E.I.T
Reviewed by:
DEH/kac
Kumar & Associates, lnc. o Project No.21-7-301.A