HomeMy WebLinkAboutGEOtech Eval - BLD Engineering / Geo-tech Reports - 12/9/2016 EvuVbrotech &vugi,vkeerwA L3
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December 9, 2016
Kenny Che
745 N 199h Street
Seattle, Washington 98133
RE: Geotechnical Evaluation Report for Property Located at 230 E North Bay Road,Mason
County, Washington
Dear Mr. Che,
Envirotech Engineering (Envirotech) has completed this geotechnical evaluation for the above
referenced property. A geotechnical report is not required for this project. We are addressing the
building pad location for the new structure.
A site visit was completed on November 30, 2016, by Robert McNearny, staff engineer with
Envirotech. It was apparent that the building pad is composed of general fill. It is unclear if the
fill is native to the site.The east footing shall be excavated to a minimum of 8' below the building
pad surface. The west footing shall be excavated to a minimum of 12"below the existing building
pad surface. Intermediate foundations may be stepped, and all foundations must be located below
fill soils on competent bearing soils. This is based on compaction tests performed on site.
Compacted Fills and Footings
Unconsolidated fill soils were encountered on-site that would influence building foundations.
Foundations must extend through the fill soils or the fill soils must be removed and replaced as
engineered fill as presented herein.
Existing in-situ soils for this Project indicates that the structure can be established on shallow,
continuous or isolated footings. Foundations shall be established on relatively undisturbed native
soil. Alternatively, foundations may be constructed on selective re-compacted native soil or
compacted engineered fill as described below.
For a bearing capacity requirement of no more than 1500 psf, a minimum continuous footing
width of 12 inches shall be placed at a minimum of 12 inches(15 inches for two story) below the
natural ground surface below existing fill or directly on engineered fill. For a columnar load of no
more than 3 tons, a circular or square isolated foundation diameter or width shall be at least 24
inches. Foundation recommendations are made available based on adherence to the remaining
recommendations that are provided in this report. Alterations to the aforementioned foundation
recommendations may be completed upon a site inspection by a geotechnical engineer after the
foundation excavation is completed.
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Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 1 of 3 230 E North Bay Road
Belfair, Washington 98528 Allyn,Washington
Ph. 360-275-9374 December 9,2016
Total and differential settlement that a structure will undergo depends primarily on the subsurface
conditions, type of structure, amount and duration of pressure exerted by the structure, reduction
of pore water pressure, and in some instances, the infiltration of free moisture. Based on the
expected native soil conditions, anticipated development, and construction abides by the
recommendations in this report, the assumed foundation system may undergo a maximum of 1.0
inch total settlement, and a maximum differential settlement of 0.75 inch.
Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted coarse,
granular material (Retained on U.S. Sieve #10 or greater) that is placed over undisturbed,
competent native subgrade or engineered fill per this report. The recommendations for interior
concrete slabs-on-grade as presented herein are only relevant for the geotechnical application of
this Project. Although beyond the scope of this report, concrete slabs should also be designed for
structural integrity and environmental reliability. This includes vapor barriers or moisture control
for mitigating excessive moisture in the building.
Excavation is recommended to remove existing loose fill soils, and any excessive organic content
or other deleterious material, if present, beneath foundations and to achieve appropriate
foundation depth.Additional sub-excavation will be required for this Project if the soils below the
required foundation depth are loose, saturated, not as described in this report, or otherwise
incompetent due to inappropriate land disturbing, or excessive water trapped within foundation
excavations prior to foundation construction. All soils below the bottom of the excavation shall
be competent, and relatively undisturbed or properly compacted fill.If these soils are disturbed or
deemed incompetent, re-compaction of these soils below the anticipated footing depth is
necessary. Excavations shall be completely dewatered, compacted, and suitable before placement
of additional native soil,engineered fill or structural concrete.
For engineered fill or disturbed native soils that will be utilized as fill material directly beneath
foundations, observation and/or geotechnical testing is required prior to foundation construction.
The following placement and compaction requirements are necessary.
Building pad slopes shall be no steeper than 2:1 for both compacted engineered fill and re-
compacted native soils used as fill.. Stepped fill should be keyed into the subgrade at a minimum
width of 10 feet. All footings shall be located at least 5 feet away from the top of the engineered
fill slope.
Both engineered fill and native soils used as compacted fill should be free of roots and other
organics, rocks over 6 inches in size, or any other deleterious matter. Because of moisture
sensitivity, importing and compacting engineered fill may be more economical than compacting
disturbed native soils. Engineered fill shall include having the soils retained on the No. 4 sieve
crushed(angular),and should consist of the following gradation:
Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 2 of 3 230 E North Bay Road
Belfair,Washington 98528 Parcel 12220-50-19002
Ph. 360-275-9374 December 9,2016
f
•
U.S. Standard Sieve %Finer(by weight)
6" 100
3" 60— 100
No.4 20—60
No. 200 0- 8
Table 1
Partical Size Distribution of Engineered Fill
Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native soils and
engineered fill, respectively. Each lift should be uniformly compacted to at least 95% of the
modified Proctor maximum dry density (ASTM D 1557) and within 3% of optimum moisture
content.Each lift surface should be adequately maintained during construction in order to achieve
acceptable compaction and inter-lift bonding.
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or require
additional information.
Best Regards,
Envirotech Engineering
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Michael Staten,P.E.
Geotechnical Engineer
Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 3 of 3 230 E North Bay Road
Belfair,Washington 98528 Parcel 12220-50-19002
Ph.360-275-9374 December 9,2016