ALTERNATE FOOTING DESIGN 02052015 ' �`'�.` 1015 East 4th Avenue
INSIGHT GEOLOGIC, INC. of Wash� Olympia, Washington 98506
� ��0 � f Telephone: (360) 754-2128
� 7 Fax: (360) 754-9299
MEMORANDUM
TO: Sound Built Homes �%, �'° 89G� '` �
�
FROM: William Halbert , LEG d
DATE: February 5, 2015 Wi! � . Halbert
SUBJECT� Footing Drains, Tahoma Terra Phases 5/6
Insight Geologic evaluated subsurface conditions on Lot 175 of the Tahoma Terra subdivision in
Yelm, Washington on January 13, 2015. We understand that ponded water within an adjacent
homesite excavation prompted the City to have concerns regarding possible high groundwater
conditions that could affect new homes.
We excavated an exploratory test pit on the street side af Lot 175 to evaluate subsurFace soil
and groundwater conditions. We found approximately 1.5 feet of fine to coarse gravel fill with
silt and fine sand overlying 1.0 feet of dark brown silty gravel containing a high fraction of
organics which we interpret to be the former ground surface at the site. Underlying the silty
gravel layer we encountered 1.5 feet of brown fine sand with silt and 2.5 feet of dark brown silt
with sand overlying dense glacial till. No groundwater seepage was observed in the test pit.
It is our opinion that the water obsenred in the adjacent footing excavation is surface water
runoff from recent heavy rains and does not represent a high groundwater condition in the area
since no groundwater seepage was observed in our test pit only a few feet from the area of
standing water. Additionally, during our investigation of the area in January 2005 consisting of
over 50 soil test pits, we observed groundwater seepage at a depth of 8 to 9 feet below ground
surface in fewer than 5 of the test pits. Based on this information, our opinion is that footing
drains are not needed in this area. r
We have reviewed Sound Built Homes' proposed redesign of the crawlspace completion for
those lots with crawlspaces at, or below, adjacent street grade. They propose increasing the
elevation of the crawlspace surface with pea gravel to a point at, or above, the top of the footing
and covering with an appropriate vapor barrier and eliminating footing drains. The increase in
the crawlspace elevation using pea gravel will provide a level of insurance against water
ponding in the crawlspace. In all cases, soil and landscaped areas around the foundations
shall be sloped to drain. C i� �� �e I m� V�V
Apprav��
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Cit� �fi Yelm, ���
Approved
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2x6 STUDS
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R-3m INSULATIO
15" UNDERLAYMENT
P.T. PLATE
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BLACK BARRIER 24' O.G., Tl'P.
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TYPICAL FOOTI NG
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