HomeMy WebLinkAboutBLD2003-00299 Geotechnical Report e.�� NORTHWESTERN TERRITORIES, INC.
A JLS GROUP COMPANY
,.t- 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362
Engineers Land Surveyors Geologists
NTIConstruction Inspection Materials Testing
(360)452-8491 FAX 452-8498 www.nti4u.corn E-Mail info@nti4u.com � ,^"1 -2, '(I r-V l rii , ;: f
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November 6, 2003 1'-0,a "a 2, 5s� �: ���1
Vince Richey 1Y i{q��// �A�yy-��� ��
263 Blue Jay Lane
Port Ludlow, WA 98365
RE: Geotechnical recommendations for garage foundation at the above referenced
address, located in Section 9, T27N, R1E, W.M. Jefferson County, WA
Dear Mr. Richey:
At your request, Bill Payton of Northwestern Territories, Inc. (NTI) met with you and your
contractor Larry Hovde at the above referenced location on October 20, 2003. The
purpose of this meeting was to observe the soil conditions at the site of the proposed
garage and to provide geotechnical recommendations for the garage foundation. It is our
understanding that the structure will be a lightly loaded 40'x 40' R.V. garage/shop.
The soil at the site appears to be a fined grained silt or clay, mapped by the Soil Survey
of Jefferson County as the Kitsap silt loam. At the time of the site visit, the soil was very
wet due to heavy rains. A spring was flowing down the hill behind the site to the
southwest corner of the proposed garage and then into a drainpipe that ran easterly
under the future garage. Several yards of the native soil had been excavated and
replaced with pit run material in preparation for the garage by another contractor. Upon
further excavation for the footings, outside the limits of the pit run fill, more soft silt/clay
was discovered along with some wood debris.
We offer the following recommendations for the project:
1. Subgrade preparation should consist of removing the loose mucky soil and
wood debris, and replacing with properly placed and compacted crushed rock
structural fill. The entire area should be compacted and then probed for soft
spots using a 1/2" diameter steel rod. Any soft areas should be dug out and
replaced with crushed rock as mentioned above. It may be beneficial to place
geotextile fabric between the fine grained soil and the crushed rock in order to
prevent the silt from migrating up into the crushed rock. Also, it would be
beneficial to allow the site to dry out prior to beginning the work.
2. In order to resist the potential for differential settlement, a mat foundation is
recommended rather than standard strip footings.
3. Footing drains should be utilized. To help dewater the excavation during
construction, it may be beneficial to daylight the downhill side of the footing
trench, and/or to install the footing drains as soon as possible and connect them
to the outlet drainage system.
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4. Gutters, downspouts and drains should be installed so that all runoff is directed
away from the garage. It may be possible to tie this into the pipe that runs under
the garage. However, footing drains and roof drains should be a separate
system in order to reduce the chance of the footing drains becoming surcharged
by roof water in the event of a blockage in the pipe.
5. The spring should be rerouted away from the garage due to the possibility of the
drain becoming clogged and undermining the garage foundation. It would be
best to relocate the spring at least 10 feet away from the garage to allow for
future access by heavy equipment, if needed. The pipe should be about 6" to 8"
diameter to minimize the potential for clogging.
Limitations
This report has been prepared exclusively for use in conjunction with the above
referenced project. The report has not been prepared for use by others or for other
locations. It may be used by others only with the expressed written permission of the
Engineer.
Within the limits of scope, schedule and budget, this report was prepared in general
accordance with accepted professional engineering and geological principles and
practices in this or similar localities at the time the report was prepared. No other
warranty, expressed or implied, is made as to the conclusions and professional advice
included in this report.
The observations, conclusions and recommendations presented in this report were
based on our visual observations of the subject property at the time of our site visit; no
laboratory tests were performed. Soil and geologic conditions can vary significantly
between test holes and/or surface outcrops. If there is a substantial lapse of time,
conditions at the site have changed or appear different than those described in this
report, we should be contacted and retained to evaluate the changed conditions and
make modifications to our report if necessary.
Sincerely, ART A. lF
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NORTHWESTERN TERRITORIES, INC. ` �"
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Robert A. Leach, P.E., MI- EXPIRES 12/30/2004
Principal Engineer _ —.
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Bill Payton, L.E.G.
Engineering Geologist `„,.00' 191�,,, 'r
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G:\Gen\Bill\Reports\RICV0301.9(27-1E).foundation recommendations.( MI i a r71 C. Payton Jr.
Expires 11-06-03
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