HomeMy WebLinkAboutSoils Report_2.pdf PA/1 iTElg—cel 10
RECEIVED
Ku 5020 County Road 154
MAY 15 2018 Glenwood Springs, CO 81601
Geotechnical Engineering I Engineering Geology Phone: (970)945-7988
Materials Testing I Environmental Town of Vail Fax: (970)945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver(HQ), Parker, Colorado Springs, Fort Coffins, Glenwood Springs, Summit County,Colorado
May 14, 2018
Integrated Landscape Management
Attn: Shelly Mello
P. O. Box 115
Avon, Colorado 81620
shelly@integrated-land.com
Project No. 18-7-253
Subject: Observation of Backhoe Pit, Proposed Site Retaining Wall, Olson Residence,
Lot 6, Lia Zneimer Subdivision, 1726 Buffehr Creek Road, Vail, Colorado
Dear Shell
As requested, a representative of H P/Kumar observed a backhoe excavated at the subject site on
May 1, 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 as part of our agreement for professional engineering services to
Integrated Landscape Management dated April 5, 2018.
The site wall will provide for a stairway to provide access from the garage/parking area to the
upper exterior deck dining level. The wall will be about 10 to 12 feet tall with up to about 6 feet
of wall above grade and about 4 to 6 feet below grade. It is desired to found the wail on a spread
footing. The stairway steps will be covered with stone and somewhat sensitive to settlement.
At the time of our site visit, one backhoe pit (Pit 1) had been excavated in the area of the wall.
The soils exposed in the pit, below about 51/2 feet of fill and topsoil, consisted of medium dense,
clayey silty sand with scattered gravel to the pit depth of 6 feet. Results of swell-consolidation
testing performed on a sample of the natural soils obtained from the bottom of the pit, shown on
Figure 1, indicate the soils are moderately compressible under conditions of loading and wetting.
No free water was encountered in the excavation and the soils were moist to very moist.
Considering the conditions exposed in the pit and the nature of the proposed construction, spread
footings placed on the undisturbed natural soil designed for an allowable bearing pressure of
Integrated Landscape Management
May 14, 2018
Page 2
1,500 psi can be used for support of the proposed wall. The soils may tend to compress some
when loaded and should be further evaluated at the time of excavation to determine if any
removal and replacement with coarse granular soils is needed. The footing(s) should be a
niininiurn width of 2 feet. Prior to the footing construction, all fill, topsoil and any loose or soft
soils removed and the bearing level extended down to firm undisturbed natural soils and the
subgrade compacted. Soft and very moist soils may require subexcavation and replacement with
coarse granular soils to stabilize the subgrade and reduce settlement potential.
Continuous foundation walls should he reinforced top and bottom to span local anomalies such
as by assuming an unsupported length of at least 12 feet. The cantilevered retaining wall, which
we understand will he separate from the residence, is expected to deflect sufficiently to mobilize
the full active earth pressure condition and should he designed for a lateral earth pressure
computed on the basis of an equivalent fluid unit weight of at least 45 pcf for imported granular
backfill. Surcharge pressure from loading other than the soil backfill should be added to lateral
earth pressure value if needed. An underdrain should be provided to prevent hydrostatic pressure
buildup behind wall. The drain can be placed above footing grade, about 1 foot below exterior
grade, to allow gravity flow to outlet. The drain should consist of 4 inch diameter PVC drain
pipe surrounded by drain gravel (11/2 feet deep) and sloped at a minimum 1/2% to outlet.
The wall backfill. should consist of road base (CD(Yl' Class 2, 5 or 6 material) compacted to at
least 98% of standard Proctor density (SPT:)) at a moisture content near optimum. Miscellaneous
backfill should be compacted to at least 90% SPD and the surface graded to prevent ponding
within at least 10 feet of the wall or building foundation. Landscape that requires regular heavy
irrigation, such as sod, and sprinkler heads should not be located within 5 feet of the foundation.
This study has been conducted in accordance with generally accepted geotechnical engineering
principles and practices in this area at this time. We make no warranty either express or implied.
The conclusions and recommendations submitted in this report are based upon the data obtained
from the exploratory pit excavated at the location and to the depth indicated. If conditions
encountered during construction appear different from those described in this report, we should
H-PKUMAR Project No. 18-7-253
Integrated Landscape Management
May 14, 2018
Page 3
be notified at once so re-evaluation of the recommendations may be made. As the project
evolves, we should provide continued consultation and field services during construction to
review and monitor the implementation of our recommendations, and to verify that the
recommendations have been appropriately interpreted. We recommend on-site observation of
excavations and foundation bearing strata and testing of structural fill by a representative of the
geotechnical engineer.
If you have any questions or need further assistance, please call our office.
Sincerely,
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attachment Figure 1, Swell-Consolidation Test Results
H-P�DNMAR Project No. 18-7-253
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1 SAMPLE 01: Gary- Silty Sand
E{2Oh�9: C?ri(rirn of Pit 1 6; 5.5'
INC25 5 %, PD 85.4 per}
ADDITIONAL COMPRES.;fON
UNDER CONSTANT PRESSURE
D ~_ DUE TO WETTING
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18—7-253
'' SWELL--CONSOLIDATION TEST RfaSULTS Fig. 1