HomeMy WebLinkAbout2012-09-18 Planning Board Supplemental Materials (32) !_5r 5"
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ENGINEERING, ZNG.
May 24,2012
Mr.Richard Keller
Keller Construction
8 Fosters Pond Road
Andover,MA 01810
RE: Foundation Inspection
Site Address: 40 Red Gate Road
North Andover,MA
Mr.Keller,
Martel Engineering,Inc. is pleased to provide you this letter following our site visit and investigation into
the boulder retaining wall at the above reference site. The wall was constructed prior to the engineer site
visit, but photos of its construction were made available for review. The engineer was also able to talk to
the operator that installed the Wali to gather more information about its construction. A geotechnical
engineer was contacted as an expert in the construction of this type of wall in this material to assist in the
review of the stability of the wall.
The wall was constructed with varying sizes of boulders that were 4 feet.deep or larger at the base and
decreased in size as the wall went up. The maximum height of the wall is 6 feet at its mid-point and has a
2 to 1 slope from the top of the wall back. The boulders at the top of the wall had a minimum depth of 3
feet. A drainage swate was installed at the top of the slope to divert water away from the wall. A filter
fabric was also installed against the existing material and backfilled with inch and a half stone between
the boulders and fabric.
The construction of this wall is adequate to support the soil behind the wall. The wall must be maintained
to allow water to flow out from behind the boulders to relieve the water pressure behind the wall. The
one foot backfill at the base of the wall must also maintain in place.
Should you have any questions regarding this subject,please feel free to contact our office.
Sincerely, neeng44
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MARTEL EN IN INS, IN 1 HAEL E..
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Michael E. Martel, P.E. _ — exp k'FcIsre0� w�Q� e
President o,,p�/O1NA
44 Partridge Road e Windham,NH o (978)204-3753