HomeMy WebLinkAboutObservation of Pit Excavations, Stairway, and Deck Additions 10.30.18*s/¿¿ctr'J+€s77
H-PVKUMAR
Geotechnical Engineering I Engineering Geology
Materials Testing I Environmental
5020 County Road 154
Glenwood Springs, C0 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email : hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
October 30, 2018
Go Handy Andy
Attn: Andy Womack
600 East Street
Rifle, Colorado 81650
gohand)¡andyqo @ gmail. com
Project No. 18-7-631
Subject:Observation of Pit Excavations, Stairway and Deck Additions, Lot 15, Cerise
Ranch, 389 Larkspur Drive, Garfield County, Colorado
Gentlemen
As requested, a representative of H-P/Kumar observed the excavation at the subject site on
October 24,2018 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation design are presented in this report. The
services were performed in accordance with our agreement for professional engineering services
to Go Handy Andy, dated October 18, 2018. Hepworth-Pawlak Geotechnical (now HP/Kumar)
previously conducted a subsoil study for the residence foundation design at the site and presented
the findings in a report dated July 10, 2006, Job No. 106 0474.
Piers for the stairway and deck supports have been constructed and it is desired to evaluate the
suitability of the bearing soils for foundation support. Spread footings placed on the natural soils
and sized for an allowable bearing pressure of 1,200 psf were designed for support of the piers.
At the time of our visit to the site, four pit excavations had been made next to existing "Bigfoot"
piers each cut to a depth of4 feet below the adjacent ground surface. The soils exposed in the
bottom of the excavations consisted of silty sandy clay with fine gravel. Results of swell-
consolidation testing performed on a sample taken from the site, shown on Figure 1, indicate the
soils are slightly to moderately compressible under conditions of light loading and wetting. The
laboratory test results of samples taken from the pits and their locations are summarized in Table
1. A fourth pit with similar soil conditions had been dug at grid 13 & D but the soils were not
tested. No free water was encountered in the excavations and the soils were moist to very moist.
Considering the conditions exposed in the pit excavations and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of I,200 psf should be adequate for support of the proposed stairway and
deck piers. The clay soils tend to compress under load and there could be post-construction
settlement of the foundation depending on the actual bearing conditions and foundation loading.
Go Handy Andy
October 30, 2018
Page 2
The recommendations submitted in this letter are based on our observation of the soils exposed
within the pit excavations and do not include subsurface exploration to evaluate the subsurface
conditions within the loaded depth of f'oundation influence. This study is based on the
assumption that soils beneath the footings have equal or better support than those exposed.
Possible variations in the subsurface conditions could increase the risk of future settlement.
If you have any questions or need further assistance, please call our office.
Sincerely,
H-P* KUM.AR
Steven L. Pawlak, P.E.
SLPlksw
Attachments: Figure 1 -Test Results
Table I - Summary of Laboratory Test Results
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1 8-7-631 H-PryKU]VIAR SWELL_CONSOLIDATION TEST RESULTS Fig. 1
H-P*KUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No. 18-7-631NATURALMOISTURECONTENTNATURALDRYDENSlTYPERCENTPASSINGNO.200SIEVEBERG LIMITSUNCONFINEDCOMPRESSIVESTRENGTHBottom of PitExcavation/GridGRAVELSANDLIQUIDLIMITPLASTICINDEXsotL oRBEDROCK TYPE(%t%t-O.sA & 9t4.510760Silty Sandy Clay withGravel-0.6A & 10.510.6111Silty Sandy Clay withGravelSilty Sandy Clay',rrithGravel6248I9919.4F&13