HomeMy WebLinkAboutGeological Assessment for BLD2005-01985 - BLD Engineering / Geo-tech Reports - 1/17/2006 _STATFo�
P M 0 MASON COUNTY
° H N z PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER
V y Shelton, Washington 98584
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DATE: January 17, 2006
INTER-DEPARTMENTAL COMMUNICATIONS
TO: Chuck McCoy-Planning PARCEL #12331-51-00071
FROM: Patricia C. — PW BUILDING PERMIT NUMBER: BLD2005-01985
SUBJECT: Geological Assessment NAME: Michael Boltz
Hi Chuck;
The Geological Assessment prepared for the proposed Single Family residence 261 Jolly
Roger Lane NE, Belfair has been received and reviewed by Public Works.
We are asking for a Geotechnical report. E3RA firm stated the slopes are about 15-45
percent. This is indicates according to Title 17 in 17.01.00 Landslide Hazard Areas "any
slope of forty percent or steeper" needs to have a Geotechnical report. It is felt that we do
not have enough information to adequately evaluate the area properly.
Please feel free to contact me at 619 or Bob Thuring ext. 452 if you have any questions
regarding these comments, or if you feel any features need further discussion or attention.
Sincerely,
u
Patricia Carroll
TOTAL.ALL .....,..r......
3), 81LUD DATEINY0. PAIDVATB R90A
PO Box 44890
Tacoma WA 98444
253-537-9400
253-537-9401 fax
E3RA
January 3,2006
T05385 0
Mike Boltz
11315 Crescent Valley Drive
Gig Harbor, Washington 98332 00(1
Subject: Geological Assessment Letter
Parcel#42331-1 0071'
261 Jolly Roger Lane NE
Belfair, Washington
Dear Mike:
E3RA is pleased to submit this Geological Assessment Letter for your residential lot at 261 Jolly Roger
Lane NE in Belfair, Washington, The purpose of our assessment is to address Title 17 of Mason County
Critical Areas Ordinances as they relate to landslide hazards on the site. Plans call the construction of a
single-family residence on the south part of the site.
Our scope of work is limited to surface observations, geotechnical research, and letter preparation. This
report has been prepared for the exclusive use of Mike Boltz and his consultants, for specific application
to this project,in accordance with generally accepted geotechnical practice.
PROJECT DESCRIPTION
The project site is an irregularly-shaped parcel that treasures 40 feet on the north boundary at Jolly Roger
Lane NE, 120 feet on the south boundary, and extends 134 to 157 feet south from Jolly Roger Lane NE.It
is located in the Lynch Cove area west of.Belfair,Washington.
Plans call for the construction of a residence on the south part of the parcel.
SITE CONDITIONS
During our reconnaissance of the site and nearby areas on December 29, 2005, we observed site grades
have been modified somewhat_ The largest modification is the engineered roadway belnn constructed to
support Jolly.Roger Lane'NM- on the north part of the site. There the engineered berm desacnds from the
roadway about 15 feet at grades of about 45 percent. The other modification is a small cut made on the
gently-sloping south part of the site to provide a level building area for the planned residence. The cut is
a few feet deep and was made in area where original slopes appear to have measured less than 15 percent.
Original slopes onsite appear to have been about 25 percent on the north thud of the site and 15 percent or
less on the south two thirds of the site,whcra construction is to occur.
An asphalt driveway extends down from the engineered berm of Jolly Roger Lane NE, crosses the north
port of the site, and continues to the adjacent parcel to the west.
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January 3, 2006 ORA, Inc.
T05385/ Boltz Landslide Letter
Soils onsite are exposed in a utility excavation and consist of medium dense Vashon recessional glacial
outwash comprised of gravelly sand with few fines. Excavations nearby the site are also of this soil type.
No groundwater was observed in the onsite excavation or in nearby excavations. No surface expressions
of groundwater, such as seeps or springs,were observed onsite or nearby off-site. No streams, streambeds,
or other hydrologic features indicating surface flow were observed.
We did not observe indications of ancient, recent, or incipient slope instability, such and hummocky
terrain, scarps, landslide blocks,tension cracks,or any other features indicating unstable slopes on the site
or nearby offsite. The Coastal Zone Atlas maps slopes on the south two thirds of the site as S, Stable.
The same reference maps the north third of the site as either I, Intermediate or as S. Stable. Intermediate
slopes are generally steeper than 15 percent,have no known slope failures, and include slopes of sand and
gravel, till,or thin soils over bedrock.
Much of the site has been cleared during preparation for construction. Vegetation currently consists of
weeds and sparse grass_
CONCLUSIONS AND RECOMMENDATIONS
Groundwater conditions do not adversely affect slope stability on the site,and groundwater will probably
not be encountered during site development.
Sufficiently consolidated soils, adequate for foundation support, were, in general, observed at shallow
depths onsite.
In our opinion, the proposed development will not create unstable slope conditions onsite or nearby
offsite.
In our opinion, no further geologic or geotechnical study is necessary to further evaluate site conditions
and the proposed development of the subject property.
CLOSURE
The conclusions and recommendations presented in this report are based, in part, on our interpretations
and assumptions regarding subsurface conditions; therefore, if variations in the site conditions are
observed at a later time, we may need to modify this report to reflect those changes.
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January 3, 2006 E3RA, Inc.
T05385/ Boltz Landslide Letter
We appreciate the opportunity to be of service on this project. If you have any questions regarding this
report or any aspects of the project,please feel free to contact our office.
Respectfully submitted,
E3RA, Inc.
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Fred Ernest Pennebaum
Fred Rcnnebaum, L.B.G_
Senior Geologist,MRA
P.O Box 44890
Tacoma, Wasbiington 984"
(253)53 7-9400
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