HomeMy WebLinkAboutGEO Geological Review - 3/7/2007 MASON COUNTY PUBLIC WORKS WORK ORDER
Permit#: � O(� QQI 21
Date: �—
Requested by: z�n
Authorized by; 4,i/t 4 V
Type of Work: CULLW eo
Public Works
employee in charge: o C S
CHARGE TO: riwycef.
Name: f" d4rd' Cf ►c-�(/�C ?i23 Zs" 03 cos--
Billing Address:
Phone:
WORK PERFORMED:
Employee:
Date:
Hours:
Hourly Rate:
Total:
ACCOUNTS RECEIVABLE INFO:
Billed Date:
Invoice #:
Amount Billed:
Receipt #
Date:
Amount Paid:
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GEOLOGICAL ASSESSMENT
171 NE RAINBOW LANE
BELFAIR, WASHINGTON
PREPARED FOR
HAROLD RICE
BY
GEOTECHNICAL TESTING LABORATORY
OLYMPIA, WASHINGTON
MARCH 7, 2007
GEOTECHNICAL TESTING LABORATORY
CONTACT INFORMATION
PREPARER INFORMATION
GTL PROJECT NUMBER: 07-0103
CONTACT: LANCE LEVINE
ADDRESS: 10011 BLOMBERG STREET SOUTHWEST
OLYMPIA,WASHINGTON 98512TELEPHONE: (360)754-4612
FACSIMILE: (360)754-4848
EMAIL ADDRESS: GEOTESTLAB@COMCAST.NET
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CLIENT INFORMATION
ICLIENT: HAROLD RICE
ITELEPHONE: (360)692-4253
IMAILING ADDRESS: 1080 HUCKLE DRIVE
BREMERTON,WASHINGTON 98311
I SITE ADDRESS: 171 NE RAINBOW LANE
BELFAIR,WASHINGTON 98528
1 PARCEL NUMBER: 223255003005
IGPS LOCATION: N47°27.189' W122°51.891'
10011 Blomberg Street SW, Olympia, WA 98512 2
Phone #: (360) 754-4612 Fax #: (360) 754-4848
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GEOTECHNICAL TESTING LABORATORY
SCOPE OF UNDERSTANDING
HAROLD RICE
1080 HUCKLE DRIVE
BREMERTON,WASHINGTON 98311
RE: GEOLOGICAL ASSESSMENT
SITE INFORMATION: 171 NE RAINBOW LANE
BELFAIR,WASHINGTON 98528
GPS LOCATION: N47°27.189' W122°51.891'
PARCEL NUMBER: 223255003005
Mr. Rice:
As per your request, we have conducted a geological assessment and analysis for the above-mentioned parcel. A
site reconnaissance was performed on February 27, 2007. The results of this investigation are to be found in the
following assessment. We have provided three copies for your review and distribution.
• We are also a full service laboratory that can meet all your building, testing (soils compaction, asphalt, concrete,
resteel), and other inspection needs. We appreciate this opportunity to be of service to you and we look forward
to working with you in the future. If you have any questions concerning the above items, the procedures used, or
if we can be of any further assistance please call us at the phone number listed below.
Respectfully Submitted,
>e of Was17 GEOTECHNICAL TESTING LABORATORY
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`• Harold Parks, L.G., L.E.G.
`, nGeologist
�� •IRswi Senior Engineering Geologist
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I HAROLD PARKS
eIS 7-31-07
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1001 1 Blomberg Street SW, Olympia, WA 98512 3
Phone #: (360) 754-4612 Fax #: (360) 754-4848
GEOTECHNICAL TESTING LABORATORY
TABLE OF CONTENTS
CONTACT INFORMATION 2
SCOPE OF UNDERSTANDING 3
TABLE OF CONTENTS 4
PURPOSE 5
SITE CONDITIONS 5
GEOLOGIC CONDITIONS 6
GROUNDWATER CONDITIONS 8
DEPTH TO COMPETENT SOIL 8
PAST SLOPE INSTABILITY 9
HISTORY OF LANDSLIDE ACTIVITY 9
POTENTIAL FOR LANDSLIDE ACTIVITY 10
RECOMMENDATIONS I I
VICINITY MAP 12
SITE PLAN 13
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10011 Blomberg Street SW, Olympia, WA 98512 4
Phone#: (360) 754-4612 Fax #: (360) 754-4848
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GEOTECHNICAL TESTING LABORATORY
PURPOSE
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The objective of the geological assessment is to assess the surface and subsurface conditions prevalent at the
subject site according to Mason County Critical Areas Ordinance 17.01.100.E4. We understand the parcel will be
developed by constructing a single-family residence. At the proposed building location, the slope is
approximately 2 percent. The steepest slope measured near the site is approximately 50 percent. The steep slope
is approximately 105 feet from the proposed building location.
The Mason County Resource Ordinance Geologically Hazardous Areas(12-27-2006)contains the following:
17.01.100 Landslide Hazard Areas
E. Special Reports
1.Applicability
Category c.
•
Development proposed within 100 feet of areas of oversteepened or otherwise potentially unstable
slopes as a result of stream incision, stream bank erosion, and undercutting by wave action will
require a Geotechnical Report. If the proposed development is 100 feet or more from these areas,
but not more than 300 feet from them, then a Geological Assessment is required and a
Geotechnical Report may be required based on findings of the assessment.
The proposed building location will be 105 feet from the potential landslide area. Hence, Mason County requires
a geological assessment.
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SITE CONDITIONS
The subject site (0.33 acres) is located approximately 1.75 miles west of the center of Belfair, Washington. The
parcel is located in an area of heavy residential development; see the Vicinity Map (Figure 1) following this
report. The site is currently bounded by residential parcels to the west, north, and south sides. Rainbow Lane
borders the parcel to the east. Access will occur from a proposed driveway from the eastern portion of the site.
Slope angles on this site range from 0 to 2 percent at the proposed building location. Offsite to the west,the slope
approaches 48 percent.
The lot is mostly vegetated with sword ferns, bracken ferns, huckleberry, blackberry, salal, holly, Oregon grape,
rhododendron as well as hemlock,cedar, madrone,and fir trees. Surface water was not observed onsite. No slope
instability was observed at or around the proposed building location. Onsite and surrounding trees are straight
and vertical.
10011 Blomberg Street SW,Olympia, WA 98512 5
Phone#: (360) 754-4612 Fax #: (360) 754-4848
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GEOLOGIC CONDITIONS •
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The Soil Survey of Mason County, Washington, USDA Soil Conservation Service (1960) has incorrectly mapped
the site soils. The western site soils are an Indianola loamy sand, slopes 15 to 30 percent slope (Ic) and is
described as follows:
This soil generally occupies short, steep slopes in association with the Everett and the
Alderwood soils and Indianola loamy sand, 5 to 15 percent slopes. The surface layer is thinner
than that of the less strongly sloping Indianola loamy sand, and the depth to sand varies more.
Where Indianola loamy sand, 15 to 30 percent slopes, is closely associated with the Everett or
the Alderwood soils, gravel occurs in lenses or is scattered throughout the profile.
The Soil Survey of Mason County, Washington, USDA Soil Conservation Service (1960) should have mapped
the eastern site soils as Indianola loamy sand, 5 to 15 percent slopes(Ib)around the proposed building site.
This is the dominant soil of the Indianola series. It is associated with other Indianola soils and
the Everett and Alderwood soils. Forested areas have a 1- to 2-inch surface layer of organic
litter consisting of partly decomposed needles, leaves, twigs, roots, and moss. The surface soil,
to a depth of 5 inches, is brown, very friable, single-grain loamy sand that contains a few
rounded shot and many roots. The upper 2 or 3 inches of surface soil contains intermittent,firm
or slightly hard, irregular aggregates stained with iron. The surface soil is dark brown when
moist. The next 10 inches of soil, a transitional layer, is slightly lighter in color than the surface
layer and contains fewer shot. The subsoil, a pale-brown loamy sand, begins at 15 inches and
continues to depths of 26 to 30 inches. It is dark yellowish brown when moist. This loamy sand
is massive but readily crushes to loose, single grains. Yellow and olive colored sands are
•
common. The subsoil gradually changes to the substratum, which is gray and dark-gray sand.
The substratum is massive but crumbles readily to single grains when removed. It contains some
light-gray,yellow, and yellowish-brown sand. A few pebbles are scattered throughout the profile
where this soil merges with the Everett or Alderwood soils. The reaction is medium to strongly
acid and is less acid with depth.
10011 Blomberg Street SW,Olympia, WA 98512 6
Phone#: (360) 754-4612 Fax#: (360) 754-4848
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GEOTECHNICAL TESTING LABORATORY
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The Geologic Map of Washington—Northwest Quadrant(2002)has mapped the site geology as advance outwash
I deposits(Qga)of continental glacial origin. The report reads:
Advance outwash — Glaciofluvial sand and gravel and lacustrine clay, silt, and sand deposited
during the advance of glaciers; sandy units commonly thick, well sorted, and fine grained, with
I interlayered coarser sand, gravel, and cobbles; locally contains nonglacial sediments and
deposits mapped as transitional between glacial and nonglacial. Includes the Colvos and
Es.perance Sand Members of the Vashon Drift and part of the Vashon Drift undivided
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GROUNDWATER CONDITIONS
Groundwater seepage was not observed at the proposed •
building location or throughout the site. Wetland vegetation \\ , •1
was not observed at the proposed building location or �/` . .,.
throughout the site. Research of the local wells indicates , 4 : IT? ' 4
that depth to static groundwater is beyond the scope of this �;
report. .' , 1s
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DEPTH TO COMPETENT SOIL
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The building location is underlain by deleterious material to y rT`
a depth of 14 inches (see photo right). Below the disturbed `t' 'fit.: ` J _ {
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surface material is a very competent Vashon glacial advance dr -IF-rin
material. All organic material, garbage, and other +; l
deleterious material must be removed prior to foundation k � --
construction.
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Phone#: (360) 754-4612 Fax#: (360)754-4848
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GEOTECHNICAL TESTING LABORATORY
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PAST SLOPE INSTABILITY
Surrounding the proposed building location, trees were observed to be straight and vertical. No indication of past
instability was discerned at the proposed building location. Active slumping and sliding was not observed along
the western slope. At the building location,the slope is 2 percent.
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HISTORY OF LANDSLIDE ACTIVITY
Slumping and sliding were not observed onsite or the surrounding parcels. At the proposed building location, the
existing structure has been razed in anticipation of the new structure. The western slope is well vegetated with no
indication of previous landsliding. The toe of the western slope has been cut for the neighboring residence. The
cut slope is vertical and approximately 8 feet tall. Minimal to no sloughing was observed. The onsite trees are
straight and vertical.
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1001 1 Blomberg Street SW,Olympia, WA 98512 9
Phone#: (360) 754-4612 Fax#: (360) 754-4848
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IThe Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977)describes the site area
as Class 3. Class 3 is described as:
I Areas inferred to be unstable because slopes, generally greater than 15 percent, are underlain
by weak, unstable materials in which old or recently active landslides have occurred. Includes
areas of sand and gravel on top of impermeable silt and clay, mostly along steep valley sides.
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POTENTIAL FOR LANDSLIDE ACTIVITY
IEven though slopes approach 2 percent at the proposed building location, the potential for landslide activity is
very slight. Steep slopes over 105 feet from the proposed building location will not adversely impact the proposed
1 construction. The onsite and offsite slopes are not a concern for potential landslide activity. The surrounding
area includes moderate slopes that are well vegetated.
The Liquefaction Susceptibility Map of Mason County, Washington by Palmer, Magsino, Poelstra, Bilderback,
Folger,and Niggemann(September 2004)maps the site area as having a very low to low liquefaction potential.
The Site Class Map of Mason County, Washington by Palmer, Magsino, Bilderback, Poelstra, Folger, and
Niggemann (September 2004) maps the site area as site class C to D. Site class C is a very stiff soil or soft rock
and site class D is a stiff soil.
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RECOMMENDATIONS
There is no evidence of soil erosion or deposition onsite to suggest that the site should be included in the Erosion
Hazard Area designation. Proposed activities and site conditions for the development do not warrant a more
comprehensive Geotechnical Report. We recommend no further action is needed unless areas of concern are
unearthed during construction or damage ensues from removing vegetation. To minimize erosion and
sedimentation,we recommend that vegetation remain or be cultivated in areas outside the building location.
If there are any changes in the loads, grades, locations, configurations or types of facilities to be constructed, the
conclusions and recommendations presented in this report may not be fully applicable. If such changes are made,
we should be given the opportunity to review our recommendations and provide written modifications or
verifications,as appropriate.
Changes to the Mason County Code require our firm to revisit the subject site prior to development, if six months
has elapsed,to ensure the conditions are in agreement with our original report.
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I Geotechnical TestingLaboratory
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Geotechnical Services 10011 Blomberg St.SW FIGURE 3
Olympia,WA 98512
I QA/QC Services Plans:(380)754-4812
Testing Services F (380)7s4-4e48 Not to scale DRAINAGE DETAILS