HomeMy WebLinkAboutGEO2009-00058-Revised for BLD2010-00479 - GEO Geological Review - 8/5/2009 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
(360)427-9670
Geotechnical ReportReview Acceptance Letter
August 05, 2009 TO BE KEPT IN THE
TERESA GAULD PARCEL FILE
2341 NW 96TH ST
SEATTLE WA 098117 �N 222 33— 5Z—Doi Q
Case No.: GE02009-00058
Parcel No.: 222335200901
Proiect Description: GEO REVIEW FOR RESIDENTIAL DEVELOPMENT
The Geotechnical Report for TERESA GAULD has been received and reviewed by the Planning
Department. The report was prepared by Glen Coad dated 6/30/2008.
Based on the certification provided by the licensed engineer/geologist, the referenced
Geotechnical Report was prepared in general accordance with the requirements in the Mason
County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.5. Mason County considers
the review valid until such time as scope of project, site conditions, and/or regulations change.
Should the scope of work, site conditions, and/or regulations change after the original review, then
an addendum from the original author of the report may be required to address these changes.
The report would only be re-reviewed if a permit for development were submitted after these
changes occur. Mason County does not certify the quality of the work done in this Geotechnical
Report.
Please contact me at (360) 427-9670, ext. 363 if you have questions.
Sincerely,
Kell J. McAboy
Land Use Planner
Mason County Planning Department
Comments: Recommendations made in the Geotechnical Report shall become conditions of the
future building permit.
8/5/2009 Page 1 of 1 GE02009-00058
Mason County Review Checklist
For a Geotechnical Report
Instructions:
This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report
is reviewed for completeness with respect to the Resource Ordinance. If an item is found to be not
applicable,the Report should explain the basis for the conclusion.The Report is also reviewed for clarity
and consistency. If the drawings, discussion, or recommendations are not understandable,they should be
clarified. If they do not appear internally consistent or consistent with the application or observations on
site,this needs to be corrected or explained. If resolution is not achieved with the author,staff should refer
the case to the Planning Manager or Director.
Applicant's Name: �C SsC) �"loly
Permit# CT d 2 Parcel# 27_?.g ^92—
Date(s)of the Document(s)reviewed:
(1) (a)A disc sion of general geologic conditions in the vicinity of the proposed development,
OK? Comment:
(b) A dis ssion of specific soil types
OK? Comment:
(c) A dis ssion of ground water conditions
OK? Comment:
(d) A disc sion of the upslope geomorphology
OK?Comment:
(e) A disc sion of the location of upland waterbodies and wetlands
OK?Comment:
(f) A discussion of history of landslide activity in the activity in the vicinity,as available in the
OK?refere ed maps and records
Comment:
(2) A site pl which identifies the important development and geologic features.
OK? V Comment:
(3) Locations�and logs of exploratory holes or probes.
OK? ✓ Comment:
(4) The area of the proposed development,the boundaries of the hazard,and associated buffers and
setbagks,�hall be delineated(top,both sides,and toe),on a geologic map of the site.
OK? V Comment:
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile,and
which inco orates the details of proposed grade changes.
OK?Comment:
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions.Analysis should examine worst case failures.The analysis should include the
Simplified Bishop's Method of Circles.The minimum static safety factor is 1.5,the minimum
seismic safety factor is 1.1.and the quasi-static analysis coeffients should be a value of 0.15.
OK? Comment:
(7) (a)Appropriate restrictions on placement of drainage features
OK? Nj Comment:
(b) Appropriate restrictions on placement of septic drain fields
OK? V Comment:
(c) Appro riate restrictions on placement of compacted fills and footings
OK? V Comment:
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Page 1 of 2 Form Effective June 2008
toi i�i�wa� micnaei iwacaems - ueoiecnnicai Kepori Keview unec►cusi b-Uu.aoc rage z
/
OK? ✓ Comment:
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
othef slopes on the property.
OK? V Comment:
(8) Recommendations for the preparation of a detailed clearing and grading plan which specifically
identifies vegetation to be removed,a schedule for vegetation removal and replanting,and the
method/ f vegetation removal.
OK? �/ Comment:
(9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies
the specific mitigating measures to be implemented during construction to protect the slope from
erosion landslides and harmful construction methods.
OK? V Comment:
(10) An analy is of both on-site and off-site impacts of the proposed development.
OK? Comment:
(11) Specifications of final development conditions such as,vegetative management, drainage,
erosion ontrol,and buffer widths.
OK? Comment:
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigatioy�.
OK? ✓✓ Comment:
(13) A site drawn to scale showing the property boundaries,scale, north arrow,and the location
and n t re of existing and proposed development on the site.
OK? Comment:
Are the Documents signed and stamped?\/es .
Type and#of License: sL P F /
If not approved,what is the next action/recommendation for further action?
Reviewed by on
Time spent in review:—(. S
SECOND REVIEW/UPDATE:
Reviewed by on
Time spent in second review:
THIRD REVIEW/UPDATE:
Reviewed by on
Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment
Page 2 of 2 Form Effective June 2008
Mason County Department of Community Development
Submittal Checklist For a Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain
the basis for the conclusion.
Applicant/Owner K Ness ie, G a-1d Parcel# 222--33S
Site Address .J0� ( fas-t K%.O r\ bake-- 0 r;vz Eu Sf
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) '2-
(b) A discussion of specific soil types
Located on page(s) 2-
(c) A discussion of ground water conditions
Located on page(s) 3
(d) A discussion of the upslope geomorphology
Located on page(s) '2-
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) 2-
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps and record
Located on page(s) 2 d 3
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) F!gvr<- 2
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) LocaEv, ri Z-
baq
s G;9vrt ('0
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and
setbacks shall be delineat d (top, both sides, and toe)on a geologic map of the site.
Located on Map(s) �Q��a
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details of proposed grade changes.
Located on Map(s) -
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions. Analysis should examine worst case failures. The analysis should include the
Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
Located on page(s) -]
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) -,
(b) Appropriate restrictions on placement of septic drain fields
Located on page(s) -1
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s) (0 6-7
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
l
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) 9
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on thWroperty.
Located on page(s) `1
(8) Recommendations for the preparation of a detailed clearing and grading plan which specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method of vegetation removal.
Located on page(s) (a/-1 8 1�
(9) Recommendations for the preparation of a detailed temporary erosion control plan which
identifies the specific mitigating measures to be implemented during construction to protect the
slope from erosion, landslides and harmful construction methods.
Located on page(s)
(10) An analysis of both on- ite and off-site impacts of the proposed development.
Located on page(s)_ _
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and b ffer widths.
Located on page(s)
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s)
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location
and nature of existing and proposed development on the site.
Located on Map(s) Giauit—
u
1, hereby certify under penalty of
perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of
geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of
Washington with special knowledge of the local conditions. I also certify that the Geotechnical
Report, ted V aQ?� , and entitled �IiS� Qe ee ,A T_ Ir
A41V meets all the requirements of the Mason
County Resource Ordi e, L d i e Hazard Section, is complete and true, that the assessment
demonstrates conclusive y th t isks posed by the landslide hazard can be mitigated through the
included geotechnical design recommendations, and that all hazards are mitigated in such a manner as
to prevent harm to property and pu health and safety. (Signature and Stamp)
`?Shz
0
NM
ErgineeringGeologis
2228
`ictOhce
d
�RADLEY P.BIGGERSTAFF
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
TT L TT
a L
eoResources, C
Ph. 253-896-1011 5007 Pacific Hwy. E., Suite 20
Fx. 253-896-2633 Fife, Washington 98424-2462
November 8, 2007
Revises! June 30, 2008
Ms. Tessie Gauld
2341 NW 961h Street
Seattle, WA 98117
(206) 782-8547
Revised Geotechnical Report
Proposed Single-Family Residence
3041 East Mason Lake Drive East
Mason County, WA
PN: 222335200901
Job: Gauld.EMasonLakeDrE.GR
INTRODUCTION
This geotechnical report summarizes the results of our geotechnical engineering
services for the proposed single family residence and rockery to be replaced at 3041 East
Mason Lake Drive East in the Mason Lake area of Mason County, Washington. The
approximate location of the site is shown on the Site Vicinity map, Figure 1.
Our understanding of the project is based on our discussions with you, our review
of the preliminary septic design and Mason County review comments, our September 10,
2007 and October 11, 2007 site visits, and our experience in the area. We understand the
proposed development includes demolishing the existing residence and constructing a new
single family residence within the existing foundation footprint area. We anticipate that the
residence will be wood-framed and supported on new conventional spread footings and
may include a basement configuration. In addition to the residence, ancillary site
development items will include removing the concrete wall east of the existing residence
and replacing it with a rock wall. Based on comments by Mason County dated August 28,
2006 we understand a Geotechnical Report is required by Mason County to address
geologic hazards and slope stability at the site.
SCOPE
The purpose of our services was to evaluate site conditions as a basis for
addressing the potential slope stability, seismic, landslide and erosion hazard issues at the
site according to the Mason County environmental policies provided in the Mason County
Code, and to provide geotechnical recommendations and design criteria for design and
construction the proposed residential structure. Specifically, the scope of services for this
project included the following:
1. Conducting a geologic reconnaissance of the site area.
2. Addressing the appropriate geotechnical regulatory requirements for the proposed
site development, including erosion, landslide and seismic hazards.
3. Exploring the subsurface conditions at the site by advancing 2 hand augers on the
slope at the site.
4. Performing a slope stability analysis in accordance with Mason County Code on
slopes that exceed 40 percent with a vertical height of at least 10 feet.
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 2
SITE CONDITIONS
Surface
The site is located at 3041 East Mason Lake Drive East in the Mason Lake area of
Mason County, Washington. The site is in an area of existing residential development. The
site is rectangular in shape, measure 175 feet north to south by 65 feet east to west, and
encompasses approximately 0.25 acres. The site is bounded by existing residential
development on the north and west, East Mason Lake Drive East on the south and Mason
Lake on the east. The site is currently developed with an existing single family residence,
several small out buildings, several stable rock masonry and rock walls including a
concrete wall between the residence and Mason Lake shoreline, and a dock extending
onto Mason Lake. The site is protected from shoreline erosion with an existing rock
bulkhead in good condition.
The site is located at the end of a narrow point, on the northeast portion of
Mason Lake. The point has less than 35 feet of relief between the highest elevation
and Mason Lake and tapers down towards the north and terminates at the site. The
upper portion of the site slopes down to the northeast at inclinations of 5 to 15 percent to
the top of the slope area. This area slopes steeply down towards Mason Lake at
inclinations of 45 to 60 percent with a total vertical relief of 12 feet. The site slope area is
currently protected with a series of rock walls, rockeries and a concrete wall. The site
flattens out, for approximately 14 horizontal feet, adjacent to the shoreline of Mason Lake.
The site is protected from shoreline erosion by an existing mason rock bulkhead. Total
vertical relief across the site is on the order of 15 feet.
Vegetation at the site generally consists of landscaped shrubs with scattered
mature conifers and native shrubs. No upland water bodies or wetlands were observed
within 300 feet of the site. No evidence of surficial erosion or instability was observed at
the time of our site visit.
Site Soils
The USDA Natural Resource Conservation Service (NRCS) web soil survey for
Mason County maps the site soils as Alderwood gravelly sandy loam (Ab) that forms on 5
to 15 percent slopes. The Alderwood soils are generally derived from sandy glacial till and
are listed as having "moderate" potential for erosion. A copy of the NRCS soils map for the
site is included as Figure 3.
As previously discussed, no evidence of surficial erosion was observed at the time
of our site visit.
Geology
The Geologic Map of Washington State, by Eric Schuster, dated 2005, shows soils
in the vicinity of the site consisting of Pleistocene Continental Glacial Drift (Qgd). These
soils are described as undifferentiated glacial till and outwash sand and gravel. These
soils were deposited during the Vashon Stade of the Fraser Glaciation, approximately
12,000 to 15,000 years ago. The glacial till consists of a heterogeneous mixture of clay,
silt, sand, and gravel that was deposited and overridden by the continental ice mass. As
such, the till is considered overconsolidated and provides high strength and low
compressibility characteristics. The outwash deposits consist of a poorly stratified mixture
of sand and gravel that were deposited by meltwater streams and rivers emanating from
Gauld.EMaSonLake®rE.GR.r
June 30, 2008
Page 3
the continental ice mass. An excerpt of the above reference geologic map is included as
Figure 4.
We also reviewed the Relative Slope Stability of the Southern Hood Canal Area,
Washington by Smith and Carson dated 1977. The site, located on the southeastern
shoreline area of Hood Canal, is in an area mapped as "Class 1" for stable, based on
slopes less than 15 percent with localized small slopes on very stable glacial till mantled by
outwash sands.
Subsurface Explorations
On October 11, 2007 the subsurface conditions at the sites were evaluated by
observing the excavation of 2 hand auger holes with a hand auger to maximum depths of 6
1/2 feet below the existing ground surface. We continuously monitored and logged the
subsurface soil and groundwater conditions while digging our hand auger explorations in
general accordance with the system described in Figure 5. Copies of our hand auger
explorations are included as Figure 6.
Our hand auger holes were backfilled with the excavated soils upon completion.
Because the soils encountered in our hand auger holes were generally consistent with the
mapped stratigraphy, it is our opinion that no further explorations are required to evaluate the
subsurface conditions at the site.
Subsurface Conditions
Our hand auger holes encountered fairly uniform subsurface conditions that
confirmed the mapped stratigraphy. Our hand auger holes encountered 6 inches of topsoil
mantling 12 to 30 inches of brown sand, overlying gray silty sand. We interpret the gray silty
sand layer to be glacial till deposits. These soils were encountered to the full depth explored
in both hand auger holes.
No groundwater was encountered in our shallow explorations at the time of our site
visit. However, we anticipate that the site is prone to a "perched" groundwater condition.
Perched groundwater develops when the vertical infiltration of run-off through a shallow,
more permeable soil is slowed at depth by a deeper, less permeable soil type. Throughout
the year, groundwater levels would likely fluctuate in response to changing precipitation
patterns, off-site usage, nearby construction activities, and site utilization.
Groundwater Conditions
No groundwater seepage was observed in any of our explorations at the time of
our site visit. However, the soils encountered below 2 feet in HA-2 were observed to be
wet. This level correlates to the level of the Mason Lake, located less than 5 feet from
HA-2. Perched groundwater typically develops when the vertical infiltration of
precipitation through a more permeable soil is slowed at depth by a deeper, less
permeable soil type. We expect that perched groundwater may develop seasonally
atop the deeper and denser glacial till. Based on the observed mottling and nature of
the near surface soils, we anticipate that fluctuations in the local groundwater levels
will occur in response to precipitation patterns, off-site construction activities, and
site utilization.
Water well logs from the Washington State Department of Ecology web-site
and the USGS Groundwater Level of Washington State web-site were reviewed to
evaluate the static water levels in the vicinity of the site. Wells mapped in the near
vicinity of the site had static water levels of approximately 44 feet to 75 feet below
the ground surface. Based on the general elevation and locations of these wells and
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 4
the well log for the site, we anticipate the static water level to be approximately 45
feet below the site. The site specific well log is attached.
Landslide Hazard Indicators per Mason County Resource Ordinance 17.01.100
According to the Mason County Resource Ordinance 17.01.100, the purpose of the
landslide hazard assessment is to identify areas that present potential dangers to public
health and safety, to prevent the acceleration of natural geological hazards, to address off
site environmental impacts, and to minimize the risk to the property owner or adjacent
property owners from development activities. The following shall be classified as Landslide
Hazard Areas:
a. Areas with any indications of earth movement such as debris slides, earthflows,
slumps and rock falls.
b. Areas with artificial oversteepened or unengineered slopes, i.e. cuts or fills.
c. Areas with slopes containing soft or potentially liquefiable soils.
d. Areas oversteepened or otherwise unstable as a result of stream incision,
stream bank erosion, and undercutting by wave action.
e. Slopes greater than 15% (8.5 degrees) and having the following:
I. Hillsides intersecting geologic contacts with a relatively permeable
sediment overlying a relatively impermeable sediment or bedrock (e.g.
sand overlying clay); and
ii. Springs or groundwater seepage.
f. An area with a slope of fort percent or steeper and with a vertical relief of t Y p Y p p en
or more feet except areas composed of consolidated rock. A slope is delineated
by establishing its toe and top and measured by averaging the inclination over at
least ten feet of vertical relief.
In addition, the following information may be used as a guide by the County to indicate
areas that have a higher likelihood of meeting the classification criteria above:
a. The areas identified on the Mason County Soil Survey Map as having slopes
greater than 15%.
b. The areas identified on the Coastal Zone Atlas, Volume 9, of Mason County,
Washington as:
I. Unstable - "U"
ii. Unstable Old Slides - "UOS"
iii. Unstable Recent Slides - "URS"
iv. Intermediate Slopes - "I"
v. Modified Slopes - "M"
c. The areas identified as Class 2, 3, 4, or 5 of the maps: "Relative Slope Stability
of the Southern Hood Canal Area, Washington", by M. Smith and R.J. Carson,
Washington State Department of Natural Resources, Division of Earth
Resources, 1977; and `The Geological Map of North Central Mason County,
Washington", by R.J. Carson, 1976, U.S. Geologic Survey OFR 76-2;
d. Areas mapped as landslide deposits (Map Unit Qls) on the: Geologic map of
the Longbranch 7.5-minute quadrangle, Thurston, Pierce, and Mason Counties,
Washington, by R. L. Logan, T. J. Walsh, and Michael Polenz. 1 sheet, scale
1:24,000, 2003; Geologic map of the Squaxin Island 7.5-minute quadrangle,
Mason and Thurston Counties, Washington, by R. L. Logan, Michael Polenz, T.
J. Walsh, and H. W. Schasse. 1 sheet, scale 1:24,000, 2003; Geologic map of
the Shelton 7.5-minute quadrangle, Mason and Thurston Counties, Washington,
by H. W. Schasse, R. L. Logan, Michael Polenz, and T. J. Walsh. 1 sheet, scale
GauId.EMasonLakeDrE.GR.r
June 30, 2008
Page 5
1:24,000, 2003; and Geologic map of the Summit Lake 7.5-minute quadrangle,
Thurston and Mason Counties, Washington, by R. L. Logan and T. J. Walsh. 42 x
36 in. color sheet, scale 1:24,000, 2004.
Seismic Hazard Areas per Mason County Resource Ordinance 17.01.102
The purpose of the Seismic Hazard Section is to identify areas that present
potential dangers to public health and safety, and to prevent the acceleration of manmade
and natural geological hazards, and to neutralize the risk to the property owner or adjacent
properties from development activities. The following shall be classified as Seismic Hazard
Areas:
1. Areas susceptible to ground failure including the following:
a. Mapped geologic faults until proven inactive;
b. Deep road fills and areas of poorly compacted artificial fill;
c. Areas with artificially steepened slopes (i.e. old gravel pits);
d. Postglacial stream, lake or beach sediments;
e. River deltas;
f. Areas designated as potential Landslide Hazard Areas;
g. bluff areas;
In addition, the following criteria may be used as a guide by the County to indicate areas
that have a higher likelihood of meeting the classification criteria above:
a. Areas identified on the Coastal Zone Atlas of Washington, Volume 9,
Mason County as Af, Qa1, Qa2, Qvc, Qls, Qos and Op.
b. Areas identified on the Mason County Soil Survey Map as having slopes
greater than 15 percent.
c. Faults identified on "Map Showing Known or Suspected Faults With
Quaternary Displacement in the Pacific Northwest", A.M. Rogers, T.J.
Walsh, W.J. Kockelman and G.R. Priest, US Geologic Survey, 1996; or
described in "Active Faulting Investigations on the Canyon River Fault,
Southern Olympic Range, Washington", T.J. Walsh and K.G. Neal, U.S.
Geologic Survey, 1997.
Although the site has slopes greater than 15 percent and areas designated a
potential landslide hazard areas based on greater than 40 percent slopes on the site, no
other seismic hazard area indicators are located on the site.
Based on the subsurface units mapped at the site, we interpret the structural site
conditions to correspond to a seismic Site Class "C" in accordance with Table 1615.1.1 in
the 2003 IBC (International Building Code) documents. This is based on the likely range of
equivalent SPT (Standard Penetration Test) blow counts for the soil types observed in the
site area. These conditions were assumed to be representative for the conditions based
on our experience in the vicinity of the site.
Liquefaction is a phenomenon where there is a reduction or complete loss of soil
strength due to an increase in water pressure. The increase in pore water pressure is
induced by seismic vibrations. Liquefaction mainly affects geologically recent deposits of
loose, fine-grained sands that are below the groundwater table. Based on the density and
well graded nature of the glacially derived soils observed on the site, and the lack of a
groundwater table encountered in our subsurface exploration, it is our opinion that the risk
for liquefaction to occur at this site during an earthquake is negligible.
Erosion Hazards per Mason County Resource Ordinance 17.01.104
The purpose of the Erosion Hazard Section is to identify areas that present
potential dangers to public health and safety, and to prevent the acceleration of natural
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 6
geological hazards, and to neutralize the risk to the property owner from development
activities. The following shall be classified as Erosion Hazard Areas:
Areas in Mason County underlain by soils which are subject to severe erosion when
disturbed. Such soils include, but are not limited to, those for which potential for
erosion is identified in the Soil Survey of Mason County, USDA Soil Conservation
Service, 1960, or any subsequent revisions or addition to this source. These soils
include, but are not limited to, any occurrence of River Wash ("Ra") or Coastal
Beaches ("Cg") and the following when they occur on slopes 15% or steeper:
a. Alderwood gravelly sandy loam ("Ac" and "Ad")
b. Cloquallum silt loam ("Cd")
c. Harstine gravelly sandy loam ("Hb")
d. Kitsap silt loam ("Kc")
The USDA Natural Resource Conservation Service Web Soil Survey for Mason
County indicates the soils on the site consist of Alderwood gravelly sandy loam (Ab).
Therefore the site does not fit the criteria of an erosion hazard area.
Slope Stability Methodology
The computer program WinStabl was used to determine the overall stability of the
site in its current configuration and for both static and seismic conditions in the post-
development configuration. Slope failure surfaces were analyzed using the Bishop
Method, which is a circular failure force equilibrium method. All calculations were
performed by the computer model WinStabl, which requires user input of the topographic
surface, soil strength properties, groundwater information, and other loads, including
seismic and building loads. The surface data was provided by the Mason County aerial
map with topographic contours and our observations in the field. The soil parameters used
in the analysis are interpreted, estimated, and/or assumed based on the visual
observations, field and laboratory testing, empirical correlations, and experience with
similar soil and groundwater conditions.
Once the parameters have been determined, the critical failure surfaces and
associated factors of safety for the modeled slope and development conditions can be
calculated. The critical surface is the surface or plane most likely along which the soil
mass will slide. The factor of safety is the ratio of the sum of moments resisting movement
over the sum of moments driving movements. Accordingly, a slope with a factor of safety
less than 1.0 has more driving forces than resisting forces, while a factor of safety greater
than 1.0 has more resisting forces than driving forces. Industry standard requires that a
site have a factor of safety of 1.5 and 1.1 against failure for static and seismic conditions,
respectively.
CONCLUSIONS
Based on a review of the available geologic information, our site reconnaissance,
and slope stability analysis it is our opinion that the site is currently stable under the
existing conditions. Based on our observations, subsurface explorations, and engineering
analysis, it is our opinion that the proposed development is feasible from a geotechnical
standpoint. The structures may be supported on new conventional spread footings or floor
slabs bearing on competent native soils or on structural fill placed above these native soils.
The native soils at the site are moisture sensitive and contain a relatively high
percentage of fines (silt and clay-size particles), which will make them difficult to compact
as structural fill in wet weather conditions. We understand that grading at the site will be
minimal, and will consist primarily of excavating the footings for the proposed residence and
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 7
site utilities. If grading activities will take place during the winter season, the owner should
be prepared to import free-draining granular material for use as structural fill and backfill.
Any slow drainage system, such as a septic drainfiield, should be placed at least 10
feet back from the building setback or placed in the gently sloping, south portion of
the site. Proper surface drainage and erosion control measures will reduce the risk for
future erosion and slope instability at the site.
Slope Stability Analysis
To analyze the stability of the site, we performed our analysis on the 45 to 60
percent slope observed between the existing residence and Mason Lake. We encountered
the medium dense sand and gravel mantling dense silty sand in this area. The slope area,
below the concrete wall to be removed, has several existing, interlocking rockeries and
rock walls. Based on our observations, we interpret these elements to increase the stability
of the slope area. Based on our site observations including observed topography, provided
site septic plan, and encountered subsurface soil and groundwater conditions, we
established both dry and saturated unit weight, isotropic strength intercept (cohesion), and
isotropic strength angle (friction angle) for the various soil types.
GeoResources assigned soil unit weight and strength parameters based on our
experience, field explorations accomplished on this site, as well as index laboratory testing
accomplished on this parcel. Based on our review, we conclude the assumed values for
the various soil types appear to fall well within the range of tabulated values in the
literature, and in some instances, the values appear to be conservative. The following
table summarizes our assigned soil strength properties.
ESTIMATED PROPERTIES OF ON-SITE SOILS FOR STABILITY ANALYSIS
Dry Unit Sat. Unit Isotropic Strength Internal Strength
Soil Type Weight Weight Intercept Angle
cf cf) (psf) (de rees
Existing Rockery Areas 115 117 50 36
Brown an and Gravel 115 118 0 36
Gray Silty Sand 120 123 550 39
The site seismic stability conditions were analyzed by applying a horizontal
acceleration equal to one-half of the appropriate peak ground acceleration. Based on
current Mason County Code, we used a design peak ground acceleration of 0.15g for the
site.
Using the Bishop method, we generated several failure surfaces for the pre- and
post-development conditions using both the static and seismic loading conditions. Our
analyses yielded the following safety factors:
Development Condition Factor Of Safety
Pre Development (Static) 1.51
Pre Development with Seismic 1.32
Post Development(Static) 1.53
Post Development with Seismic 1.32
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 8
Graphical output of the WinStabl analysis, indicating the ten most critical failure
planes and corresponding factors of safety for the two post development models are
included as Appendix A.
In our opinion, provided the recommendations presented in this report are
incorporated into the project design and construction, the proposed development, including
removal of the existing concrete wall, will not decrease slope stability at the site and the
risk for such occurrence would be minimal. The analysis indicates removal of the concrete
wall may slightly increase the factor of safety in static conditions.
Erosion Hazards and Control
As stated above the site does not fit the criteria of a landslide hazard area. The
removal of vegetation and grading activity will result in an increased risk for erosion. We
recommend that temporary and permanent erosion control measures be installed and
maintained during and following construction, until permanent erosion control measures or
landscaping is in place.
We recommend that the existing denuded areas be re-vegetated as soon as practical
with native type vegetation or other slope stabilizing landscaping.
During wet weather conditions, erosion control measures may include but should not
be limited to berms and swales to channel surface water runoff, and ground cover/protection
in exposed or disturbed areas. Temporary ground cover/protection such as jute matting,
excelsior matting, wood chips or clear plastic sheeting should be used during wet weather
conditions until permanent erosion protection is established. Silt fences should be utilized
where appropriate.
Graded or disturbed areas should be shaped to avoid concentrations of runoff onto
the site slopes or other erosion-sensitive areas. Stormwater from the site should be
collected, tightlined and dispersed away from the slope, beyond the toe.
Landslide Hazard Classification
Based on our observations of the site and review of published information, no
evidence of past or ongoing earth movement, or landslide activity was observed. No
significant areas of fill constructed or over steepened slopes were observed, nor were
slopes with areas containing soft or potentially liquefiable soils observed. We did not
observe areas oversteepened or unstable as a result of stream incision, stream bank
erosion, or undercutting by wave action. The site is currently protected from shoreline
erosion by the existing bulkhead which appeared stable at the time of our site visit. No
areas with 15 percent slopes and seeps or intersecting contacts were observed on the site
at the time of our site visit. We did observe areas of greater than 40 percent slopes with
12 feet of vertical relief between the existing residence and the shoreline of Mason Lake.
This slope area appeared stable at the time of our site visit and through our slope stability
analysis.
Although portions of the site meet the technical criteria of a Landslide Hazard area
(slope greater than 40 percent with more than 10 vertical feet), it is our opinion that the site
soils are in a stable condition based on our slope stability analysis and observations.
Furthermore, the proposed residence will be located within the existing foundation
footprint and may have a basement configuration. This may reduce the height of the
slope and therefore eliminate the landslide hazard classification from the site.
Gauld.EMason Lake DrE.GR.r
June 30, 2008
Page 9
Buffers per Mason County Resource Ordinance 17.01.100.D.6
We understand Mason County Resource Ordinance 17.0100.D.6a requires a
50 foot buffer of undisturbed, natural vegetation around a landslide hazard area
unless otherwise stated by a geotechnical engineer. The slope area nearest the
proposed residence has inclinations greater than 40 percent and approximately 12
feet of total relief. Therefore the slopes with 40 percent or greater and 10 or more
vertical feet meet the criteria of a Landslide Hazard area. The required 50-foot buffer
would encompass the existing building and eliminate a possible building envelope.
We understand a reduction of the buffer around the Landslide Hazard Area is
permitted as stated in the Mason County Resource Ordinance 17.0100.D.6c.
However, as demonstrated by our slope stability modeling, the slope does have a
factor of safety greater than the required minimum by Mason County. Provided the
recommendations in the report are followed; we anticipate a reduction or elimination
of the buffer should be allowed, to facilitate the proposed development.
Again, based on our subsurface explorations and our slope stability analysis, it
is our opinion the slope near the proposed residence location appears stable in both
its current and proposed conditions.
Recommended Setback
The Mason County building department may require a building setback in
accordance with IBC standard requirements. The IBC requires a building setback from
slopes that are greater than 30 percent unless evaluated and reduced, and/or a structural
setback is provided, b a licensed eotechnical engineer. The setback distance is
p Y 9 g
calculated based on the vertical height of the slope. The typical IBC setback from the top
of the slope equals one third the height of the slope while a setback from the toe of the
slope equals one half the height of the slope. Vegetation in the setback area may be
enhanced, if approved/required by the City of Seattle. Clearing, grading and filling within
the setback area is allowed if it can be demonstrated that the existing vegetation will not be
adversely impacted or that it can be mitigated (enhanced).
Based on our site observations, in accordance with UBC/IBC guidelines, we
recommend a building foundation setback distance of at least 5 feet from the slope located
on the eastern portion of the site. Where this setback distance cannot be met, the
foundation elements of the structure can be extended vertically to meet the horizontal
setback distance. Where the foundation is extended vertically, we recommend that the
setback be measured horizontally from the lower outside edge of the foundation element to
the face of the slope. This structural setback is based on the foundation elements
extending to the dense to very dense native soils. Once the final locations of the
residences are determined and the setback criteria cannot be met, we can provide
alternative foundation recommendations to address the setback criteria.
As previously discussed, weathering, erosion and the resulting surficial sloughing
and shallow land sliding are natural processes that affect steep slope areas. As noted, no
evidence of surficial raveling or sloughing was observed at the site. To manage and
reduce the potential for these natural processes, we recommend no drainage of
concentrated surface water or significant sheet flow onto or near the steep slope area. No
additional fill should be placed within the setback area. Grading should be limited to
providing surface grades that promote surface flows away from the top of slope to an
appropriate discharge location.
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 10
Site Preparation
Site clearing and grading in the developed portion of the site should be minimal,
however any areas to be graded should be cleared of deleterious matter including the
existing organic topsoil. Our hand auger explorations indicated thicknesses of organic topsoil
up to 6 inches. If the clearing operations cause excessive disturbance, additional stripping
depths may be necessary. Disturbance to a greater depth should be expected if site
preparation work is done during periods of wet weather. The organic-laden stripping can be
stockpiled on-site and later used for landscaping purposes. Materials which cannot be used
for landscaping should be removed from the project site.
Structural Fill
All fill placed to establish finish grades should be placed as structural fill. The
appropriate lift thickness will depend on the fill characteristics and compaction equipment
used. We recommend that the appropriate lift thickness be evaluated by our field
representative during construction. For planning purposes, we recommend a maximum
loose-lift thickness of 12 inches. We recommend that our representative be present during
site grading activities to observe the work and perform field density tests.
Structural fill should be compacted to at least 95 percent of the soils laboratory
maximum dry density (MDD) as determined in accordance with ASTM D-1557 (Modified
Proctor). The moisture content of the soil at the time of compaction should be within two
percent of its optimum, as determined by this same ASTM standard.
The suitability of material for use as structural fill will depend on the gradation and
moisture content of the soil. As the amount of fines (material passing the No. 200 sieve)
increases, soil becomes increasingly sensitive to small changes in moisture content and
compaction becomes more difficult to achieve. During wet weather, we recommend using
a well-graded sand and gravel with less than 5 percent (by weight) passing the No. 200
sieve based on that fraction passing the 3/4-inch sieve. If prolonged dry weather prevails
during the earthwork and foundation installation phase of construction, a slightly higher (up
to 10 to 12 percent) fines content may be acceptable.
Material placed for structural fill should be free of debris, organic matter, trash and
cobbles greater than 6 inches in diameter. The moisture content of the fill material should
be adjusted as necessary for proper compaction.
Suitability of On-Site Materials as Fill
Our study indicates the majority of the soils at the site are moisture sensitive and
contain a significant percentage of fines (silt and clay-size particles), which will make them
difficult to compact as structural fill in wet weather conditions. Accordingly, the ability to
use the native soils from site excavations as structural fill will depend on their moisture
content and the prevailing weather conditions when site grading activities take place.
If structural fill will be imported to the site and grading activities are planned during
the wet winter months, or if they are initiated during the summer and extend into fall and
winter, the owner should be prepared to import a wet weather structural fill. For this
purpose, we recommend importing a wet weather structural fill as described in the
"Structural Fill" Section of this report.
Permanent Slopes
We recommend a maximum slope of 2H:1 V for permanent cut and fill slopes.
Where 2H:1 V slopes are not feasible, retaining structures should be considered. Fill
placed on slopes that are steeper than 5H:1 V should be placed as an engineered fill and
Gauld.EMasonLakeDrE.G R.r
June 30, 2008
Page 11
"keyed" into the undisturbed native soils by cutting a series of horizontal benches. The
benches should be 1'/z times the width of equipment used for grading and a maximum of 3
feet in height. Subsurface drainage may be required in seepage areas. Surface drainage
should be directed away from all slope faces. Some minor raveling may occur with time.
All slopes should be seeded as soon as practical to facilitate the development of a
protective vegetative cover or otherwise protected.
Excavations
All excavations at the site associated with confined spaces, such as utility trenches
and retaining walls, must be completed in accordance with local, state, or federal
requirements. Based on current Washington State Safety and Health Administration
(WSHA) regulations, the surficial soils and weathered glacial till on the site would be
classified as Type C soils.
According to WSHA, for temporary excavations of less than 20 feet in depth, the
side slopes in Type C soils should be laid back at a slope inclination of 1.5H:1 V
(Horizontal: Vertical) or flatter from the toe to the crest of the slope. All exposed slope
faces should be covered with a durable reinforced plastic membrane during construction to
prevent slope raveling and rutting during periods of precipitation. These guidelines
assume that all surface loads are kept at a minimum distance of at least one half the depth
of the cut away from the top of the slope and that significant seepage is not present on the
slope face. Flatter cut slopes will be necessary where significant raveling or seepage
occurs, or if construction materials will be stockpiled along the slope crest.
This information is provided solely for the benefit of the owner and other design
consultants, and should not be construed to imply that GeoResources assumes
responsibility for job site safety. It is understood that job site safety is the sole
responsibility of the project contractor.
Foundations
The proposed residence may be supported on new conventional spread footing
foundations that bear on competent native soils or on structural fills placed above these
native soils. Foundation subgrade areas should be prepared as recommended in the "Site
Preparation" section of this report.
Perimeter foundations exposed to the weather should bear at a minimum depth of
18 inches below final exterior grades for frost protection. Interior foundations can be
constructed at any convenient depth below the floor slab. We recommend a minimum
width of 18 inches for isolated spread footings and 16 inches for continuous footings. With
footings founded as recommended, we recommend they be designed for an allowable soil
bearing capacity of 2,500 pounds per square foot (psf) for combined dead and long-term
live loads. The weight of the footing and any overlying backfill should be neglected. The
allowable bearing value may be increased by one-third for short-term loads such as those
induced by seismic events or wind loads. With the anticipated loads and this bearing
stress applied, building settlements should be less than one inch total and one-half inch
differential. All footing areas must be evaluated by a representative of GeoResources prior
to placement of forms.
For designing foundations to resist lateral loads, a base friction coefficient of 0.35
can be used. Passive earth pressures acting on the sides of the footings can also be
considered. We recommend calculating this lateral resistance using an equivalent fluid
weight of 300 pounds per cubic foot (pcf). We recommend not including the upper 12
inches of soil in this computation because it can be affected by weather or disturbed by
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 12
future grading activity. This value assumes the foundations will be constructed neat
against competent native soil or backfilled with structural fill, as described in the
"Structural Fill" section of this report. The values recommended include a safety factor of
1.5.
Subgrade Foundation/Retaining Walls
Based on the slopes between the existing residence and Mason Lake on the site,
we anticipate that the proposed residence may also include a basement in addition to
replacing the existing concrete wall.
The lateral pressures acting on subgrade foundation and retaining walls (such as
basement walls) will depend upon the nature and density of the soil behind the wall. It is
also dependent upon the presence or absence of hydrostatic pressure. If the walls are
backfilled with granular well-drained soil, the design active pressure may be taken as 35
pcf (equivalent fluid density). This design value assumes a level backslope and drained
conditions as described below.
Positive drainage which controls the development of hydrostatic pressure can be
accomplished by placing a zone of coarse sand and gravel behind the walls. The granular
drainage material should contain less than 5 percent fines. The drainage zone should
extend horizontally at least 18 inches from the back of the wall. The drainage zone should
also extend from the base of the wall to within 1 foot of the top of the wall. The drainage
zone should be compacted to approximately 90 percent of the MDD. Over-compaction
should be avoided as this can lead to excessive lateral pressures.
A perforated PVC pipe with a minimum diameter of 4 inches should be placed in the
drainage zone along the base of the wall to direct accumulated water to an appropriate
discharge location. We recommend that a non-woven geotextile filter fabric be placed
between the drainage material and the remaining wall backfill to reduce silt migration into
the drainage zone. The infiltration of silt into the drainage zone can, with time, reduce the
permeability of the granular material. The filter fabric should be placed such that it fully
separates the drainage material and the backfill, and should be extended over the top of
the drainage zone.
Lateral loads may be resisted by friction on the base of footings and as passive
pressure on the sides of footings and the buried portion of the wall.
Rockeries
Based on our slope stability analysis, it is our professional opinion that removing the
concrete wall will not greatly decrease the slope stability of the site. However, the existing
retaining wall along the back of the residence can be removed and replaced with a rockery.
The rockery should be constructed in accordance with the recommendations provided in
this report and the Standard Rock Wall Construction Guidelines established by the
Associated Rockery Contractors (ARC). All rock used in the rockery construction should
meet Washington State Department of Transportation (WSDOT) requirements presented
in their standard specifications 9-13.7, Rock for Rock Wall. The rockery at the site should
be provided with adequate drainage from behind the rocks. The rockery contractor should
provide you with the appropriate documentation verifying rock quality prior to bringing any
rock onto the site.
The rockery should be constructed against a cut into the medium dense soils
encountered in our subsurface exploration northeast of the existing residence, and have a
maximum height of no more than 6 feet. We recommend installing a continuous drain
behind the rockery. The rockery drain should be tightlined to an approved point of
controlled discharge. Subsurface drains must be laid with a gradient sufficient to promote
Gauld.EMasonLakeDrE.GR.r
June 30, 2003
Page 13
positive flow to the point of discharge. All drains should be provided with cleanouts at
easily accessible locations. These cleanouts should be serviced at least once every year.
A recommended typical Cut Rockery Detail is attached as Figure 8.
GeoResources should verify soil and bearing conditions, and the rock and drain
placement during construction.
Site Drainage
Final exterior grades should promote free and positive drainage away from the
building area. Surface water must not be allowed to flow uncontrolled over the crest of the
site slopes and embankments. Surface water should be directed away from the slope
crests to an appropriate discharge location.
LIMITATIONS
We have prepared this report for use by Ms. Tessie Gauld and other members of the
design team for use in evaluating a portion of this project. This report may be made
available to regulatory agencies or others, but this report and conclusions should not be
construed as a warranty of the subsurface conditions. Subsurface conditions can vary
over short distances and can change with time.
When the design is finalized, we recommend that the design and specifications be
reviewed by our firm to see that our recommendations have been interpreted and
implemented as intended. The scope of our services does not include services related to
environmental remediation and construction safety precautions. Our recommendations are
not intended to direct the contractor's methods, techniques, sequences or procedures,
except as specifically described in our report for consideration in design.
Within the limitations of scope, schedule and budget, our services have been
executed in accordance with generally accepted practices in this area at the time this
report was prepared. No other conditions, expressed or implied, should be understood.
Gauld.EMasonLakeDrE.GR.r
June 30, 2008
Page 14
We have appreciated the opportunity to work with you on this project. Please do not
hesitate to call at your convenience is you have any questions or require additional
assistance.
Respectfully submitted,
GeoResources, LLC
Renee M. Hadley
Staff Geologist
GIL,
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EXPIRES
Brad Bi rstaff, 2 Glen Coad, PE
Princip Principal
BPB:GC:rmh
DocID:Gauld.EMasonLakeDrE.GR.r
Attachments: Figure 1:Site Vicinity Map
Figure 2:Site Plan
Figure 3:NRCS Soils Map
Figure 4:USGS Geology Map
Figure 5:Soil Classification System
Figure 6: Hand Auger Logs
Figure 7:Cross-section
Well Log
Grain Size Analysis
Slope Stability Analysis
W A T E W E L L R E F3 R T Start Card No. 064615
R
.TATE OF WASHINGTON deter,Right Permit Noass==.=_.=..a=== ,-
(1) OWNER:-NsmaxTE5s19G(yJLD9 Address�•1e2823 N.V. 70TH '0 SEATTLE, VA_ 98117-
CL x=====_== - v.x..ve=e.veev=exv..........se...=a=xxl c= ,==___.._______x____-sx________-_s===a=a=...=save
_________ _____ __________
W 12) LOCATION OF WELL; Conty KASOM _ sW 1/4- Nu 1/4 Sec 34 T 22 M., R 2 t4twN
(2a) STREET ADDRESS OF WELL (or nearest address)MASON LAKE
G) (3). �aa�xx..:xx..x:.===,_,__=..-.s:xsx.xxxs
P •PROPOSED USE: DOMESTIC `10)=WELLLOGxIIQ6¢®®a=--•------------s-- - - _----_•---
W (4) TYPE OF WORK: Owner's Number of well Formation: Describe by color, character, size of isetorfal
(If more then one) and structure, and show thickness of aquifers and the kind
S NEW WELL Method: ROTARY and nature of the material in each stratum penetrated, with
a+
.............. .................:...::..= at least one entry for each change in formation.
_ (5)DIMENSIONS: Diameter of well 6 inches ............._------------------------------------_________..._
O Drilled 85 ft. Depth of completed well 85 ft. MATERIAL FROM TO
1_ .=.=a....=s...................vs.........___ .v.............. LOAM GRAVEL BROWN 0 4
® (6) CONSTRUCTION DETAILS: HARD PAN BROW 4 16
—` casing installed: 6 " Dim. from 0.5 ft. to e5 ft. HARD PAN GRAY 16 21
CU WELDED "Die. from ft. to ft. CLAY i GRAVEL SOFT GRAY 21 46
` "Dim. from ft. to ft. HARD PAN GRAY 46 56
O ••`•••-------"•^---•••................•••----__._...._.. CLAY GRAY 56 60
w— Perforations: Mo CLAY HARD GRAY 60 63
C Type of perforator used CLAY SOFT GRAY 63 71
a SIZE of perforations in. by In. SAND R GRAVEL HARD GRAY 71 8o
perforations from ft. to ft. GRAVEL i WATER 8o 85
perforations from ft. to ft.
L perforations from ft_ to ft.
O •----------------------------•••-•---•-••_...._••---------
l7 Screens: NO
Manufacturer's Name
Type Model No.
f0 Diem. slot size from It. to ft.
Diem, slot size from ft. to ft.
ca
Q ...................._..............._............
a Gravel packed: NO Size of gravel
S Gravel placed from ft. to ft.
Surface meet: YES To what depth? 20 ft.
+�' Material used in seal RENTONITE
Did any strata Contain unusable water?NO
Type of water? Depth of strata ft.
d Method of staling strata off
R ...........e................ es===.=__._—........._
? (7) PUMP: Msnufacturer'e Monte
Type M.P.
O _________________x___......=.........
__cc_Y5
eVATER LEVELS:� land surface elevation
Z (8)
above mean sea level ft.
U) static level 45 ft. below top of well Date 06/15/91
a Artesian Pressure lbs. per square inch Date
0 Artesian water controlled by
Work started 06/15/91 Coapleted 06/15/91
� �•a ........a_________
(9)�WELL�TESTS; Drawdownis amount water level Is lowered below WELL CONSTRUCTOR CERTIFICATION:
O static level. 1 constructed end/or accept responsibility for con-
6 Was a pump test made? NO If yes, by whom? struction of this well, and Its compliance with sit
V Yield: gel./min with ft_ drewdown after hrs. Washington well construction standards. Materiels used
LU and the information reported above are true to my best
O knowledge and belief.
Recovery date
+' Time Water Level Time Water Level Time Water Level NAME ARCADIA DRILLING INC.
C
ac (Parent, firm, or corporation) (Type or print)
EADDRESS SE 170 WALKER PARK RD
RDate of test
CU Bailer test gel/min. ft. drowdown after hrs. [SIGNED] �l u•.-�_ii ��=l cense No. 1445
a Air test 20 gal/min. w/ stem set at 80 ft. for 1 hrs.
Artesian flow 9.p.m. Date Contractor's
Temperature of water Was a chemical analysis made?NO Registration No. ARCADDe147K1 Date 06/17/91
________•_______________.............__,.._____......===x.x===.......______
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Approximate Site Location
Not to Scale
GeoResources LLC
Site Vicinity Map
5007 Pacific Highway East, suite 20 Fife, Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: Gauld.EMasonLakeDrE.SVM October 2007 Figure 1
b�AWN i0 5HOW-H PMOXIMME WCAWN Of M%NC r
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Scale f.20'
APPROXIMATE LOCATION OF HAND AUGER HA-1 • Site drawing prepared by Pioneer Digging, Inc.
40 PERCENT OR GREATER SLOPE AREA Topography is sketched based on field observations by GeoResources, LLC.
GeoResources, LLC Exploration Map
5007 Pacific Highway East, suite 20 Fife, Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: GauId.EMasonLakeDrE.SP October2007 Figure12
ti s
.r
i;
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I
Approximate Site Location
Soil Type Soil Name Slopes Capability
SubClass
Ab Alderwood gravelly sandy loam 5 to 15 percent IVs
Eh Everett gravelly sandy loam 5 to 15 percent VIs
Mg Mukilteo peat 0 to 2 percent IIIw
(N
(W+A.:
Not to Scale
GeoResources, LLC NRCS SCS Soils Map
5007 Pacific Highway East, suite 20 Fife,Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: Gauld.EMasonLakeDrE.SCS October 2007 Figure 3
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5
Approximate Site Location
Not to Scale
GeoResources, LLC USGS Geologic Map
Fife, Pacific Highway East, suite 20 Fife, Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: Gauld.EMasonLakeDrE.USGS October 2007 Figure 4
SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP GROUP NAME
SYMBOL
GRAVEL CLEAN GW WELL-GRADED GRAVEL, FINE TO COARSE
GRAVEL GRAVEL
COARSE GP POORLY-GRADED GRAVEL
GRAINED More than 50%
SOILS Of Coarse Fraction GRAVEL GM SILTY GRAVEL
Retained on WITH FINES
No.4 Sieve
GC CLAYEY GRAVEL
More than 50% SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND
Retained on
No.200 Sieve SP POORLY-GRADED SAND
More than 50%
Of Coarse Fraction SAND SM SILTY SAND
Passes WITH FINES
No.4 Sieve SC CLAYEY SAND
SILT AND CLAY INORGANIC ML SILT
FINE CL CLAY
GRAINED
SOILS Liquid Limit
Less than 50 ORGANIC OL ORGANIC SILT,ORGANIC CLAY
SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY,ELASTIC SILT
More than 50%
Passes CH CLAY OF HIGH PLASTICITY, FAT CLAY
No.200 Sieve Liquid Limit
50 or more ORGANIC OH ORGANIC CLAY,ORGANIC SILT
HIGHLY ORGANIC SOILS PT PEAT
NOTES: SOIL MOISTURE MODIFIERS:
1. Field classification is based on visual examination of soil Dry- Absence of moisture,dry to the touch
in general accordance with ASTM D2488-90.
Moist- Damp,but no visible water
2. Soil classification using laboratory tests is based on
ASTM D2487-90. Wet- Visible free water or saturated, usually soil is
obtained from below water table
3. Description of soil density or consistency are based on
interpretation of blow count data,visual appearance of
soils,and or test data.
GeoResources, LLC Soil Classification System
Fife, Pacific Highway East, suite 20 Fife, Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: Gauld.EMasonLakeDrE October 2007 Figure 5
Hand Auger HA-1
Location: 5'from Top of Wall.
Depth (ft.) Soil Type Description
00"—06" TS Topsoil
06"—36" SP Brown medium/coarse SAND with silt, occasional gravel, roots, loose/medium
dense, moist.
36"—48" SP Lt Brown/Olive SAND with some silt, trace gravel, medium dense, moist.
48"—78" SM Gray silty SAND with occasional gravel, Fe stain, dense/very dense, moist.
" S-1 @ 72"
Hand Auger HA-2
Location: 7'from Toe of Slope.
Depth (ft.) Soil Type Description
00"—06" TS Topsoil
06"—18" SP Brown medium/coarse SAND with silt, occasional gravel, roots, loose/medium
dense, moist.
18"—30" SM Gray silty SAND with occasional gravel, Fe stain, very dense, moist/wet.
S-1 @ 24"
Excavated by: R. O'Rourke(10.11.07)
GeoResources, LLC Hand Auger Logs
5007 Pacific Highway East, Suite 20 Proposed Residential Development
Fife, Washington 98424 3041 E Mason Lake Drive
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
Doc ID:GauldT.EMasonLkDr.HA October 2007 Figure
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5007 Pacific Highway East, Suite 20 Fife, Washington 98424 3041 East Mason Lake Drive East
Phone: 253-896-1011 Mason County, Washington
Fax: 253-896-2633
File: Gauld.EMasonLakeDrE October 2007 Figure 7
LIQUID AND PLASTIC LIMITS TEST REPORT
60 ,
popper iirnk i<aoun:.l;:ary for na',a.arna soils �
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LIQUID LIMIT
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
SLGrey Silty Sand with-Clap--•i)m%-cl 17 15 2 32
Dled bv Renee Hadley on 10/12/2007
Project No. Renee Client: Gauld Remarks:
Project: E.Mason Lake Dr.
•Wash tested on 10/17/2007
Atterberg tested on 10/18/2007
Entered on 10/19/2007
•Depth: 7 ft.depth Sample Number: 070129
GeoResources, LLC
Fife WA Figure 9
Tested By: Tim Bergstrom Checked By: Renee Hadley
Particle Size Distribution Report
C C 0 0 0
C C C C C = W 0 0 O 0 -It0
CO tD M N n \ M # 72 # i_k it N
100 0
I I I I I I I I I I I I I I
90 I I I I I I I I I I 10
I I I I I I I I I I I I I
80 20
I I I I I I I I I I I I I
70 I I I 30
I I I I I I I I I I I I I m
Z 60 40 0
I I I I I I I I I I I Z
Z I I I I I I I I I
50 I I I I I I I I 50 0
I I I I I I I I I I D
a ao I I I I I I I I I I 60 m
I I I I I I I I I I X
30 70
I I I I I I I I I I I I I I
20 I I I I I I I I I 80
I I I I I I I I I I I I I I
10 90
I I I I I I I I I I I I I I
01 1 1 I I I I I I I I I 100
100 10 1 0.1 0.01 0.001
GRAIN SIZE -mm.
Gravel %Sand %Fines
+3 coarse Fine Coarse Medium Fine Silt I Clay
0 9 16 77 13 24 31
SIEVE PERCENT SPEC.* PASS? Material Description
SIZE FINER PERCENT (X=NO) Silty Sand with Gravel
1 100 Sampled on 10/12/2007
3/4 91 Tested by Tim Bergstrom on 10/16/2007
3/8 83
#4 75 Atterberg Limits
#4 68 PL= NP LL= NV Pl=
#20 61 Coefficients
#40 55 D85= 12.2100 D60= 0.7257 D50= 0.3096
#00 39 CU= Cc= D10=
#200 31
Classification
USCS= SM AASHTO= A-2-4(0)
Remarks
Entered on 10/17/2007
(no specification provided)
Sample Number: 070130 Date: 10/17/2007
GeoResources, LLC Client: Gauld
Project: E.Mason Lake Dr.
Fife WA Project No: Renee Hadley Fi ure
Tested By: Tim Bergstron Checked By: Renee Hadley
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Gauld: pre-development -static Safety Factors
134.57
1 .51
1 .76
107.66 1 .831 .84
1 .86
j 1 .87
80.74 1 .92
1 .94
1 .95
53.83 1 .95
26.91
0
0 26.91 53.83 80.74 107.66 134.57 161 .49 188.40 215.32
134.57 Gauld: pre-devel pment -seismic Safety Factors
Af J 1 .32
'v �� 1 .57
107.66 1 .64
1 .64
1 .65
1 .67
80.74 1 .70
1 .70
1 .74
53.83 1 .74
26.91
0
0 26.91 53.83 80.74 107.66 134.57 161 .49 188.40 215.32
Gauld: post-development -static Safety Factors
134.57 — ----
1 .53
1 .77
107.66 1 .831 83
1 .85
1 .87
80.74 1 .89
1 .94
1 .96
53.83 1 .97
26.91
0
0 26.91 53.83 80.74 107.66 134.57 161 .49 188.40 215.32
Gauld: post-development -seismic Safety Factors
134.57
1 .32
1 .57
107.66 1 .631 .63
1 .63
1 .65
1 .67
80.74 1 .60
1 .70
1 .71
53.83 1 °73
26.91
0
0 26.91 53.83 80.'74 107.66 134.57 161 .49 188.40 215.32
Profile.out
PCSTABL6
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin-Madison
--slope Stability Analysis--
simplified Janbu, simplified Bishop
or spencers Method of slices
PROBLEM DESCRIPTION Gauld: post-development -seismic
BOUNDARY COORDINATES
9 Top Boundaries
16 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Right soil Type
No. (ft) (ft) (ft) (ft) Below Bnd
1 0.00 98.00 1.00 100.00 2
2 1.00 100.00 13.00 100.00 2
3 13.00 100.00 23.00 107.00 1
4 23.00 107.00 26.00 107.00 1
5 26.00 107.00 30.00 114.00 1
6 30.00 114.00 31.00 115.00 1
7 31.00 115.00 37.00 115.00 2
8 37.00 115.00 85.00 115.00 2
9 85.00 115.00 92.00 117.00 2
10 13.00 100.00 23.00 108.00 1
11 23.00 108.00 26.00 108.00 1
12 26.00 108.00 30.00 114.00 1
13 0.00 96.00 13.00 96.00 3
14 13.00 96.00 31.00 110.00 3
15 31.00 110.00 32.00 110.00 3
16 32.00 110.00 92.00 110.00 3
ISOTROPIC SOIL PARAMETERS
3 Type(s) of Soil
Page 1
Profile.out
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 115.0 117.0 50.0 36.0 0.00 0.0 1
2 115.0 118.0 0.0 36.0 0.00 0.0 2
3 120.0 123.0 550.0 39.0 0.00 0.0 3
A Horizontal Earthquake Loading Coefficient
Of0.150 Has Been Assigned
A vertical Earthquake Loading coefficient
Of0.000 Has Been Assigned
Cavitation Pressure = 0.0 psf
BOUNDARY LOAD(S)
1 Load(s) Specified
Load x-Left x-Right Intensit Deflection
No. (ft) (ft) (lb/sgft� (deg)
1 37.00 75.00 2500.0 0.0
NOTE - Intensity Is specified As A uniformly Distributed
Force Acting On A Horizontally Projected surface.
A Critical Failure surface searching Method, using A Random
Technique For Generating Circular surfaces, Has Been Specified.
50 Trial surfaces Have Been Generated.
10 Surfaces Initiate From Each of 5 Points Equally Spaced
Along The Ground surface Between x = 5.00 ft.
and x = 25.00 ft.
Each surface Terminates Between x = 30.00 ft.
and x = 42.00 ft.
Unless Further Limitations were Imposed, The Minimum Elevation
At which A Surface Extends Is Y = 0.00 ft.
3.00 ft. Line segments Define Each Trial Failure surface.
Following Are Displayed The Ten Most Critical Of The Trial
Page 2
Profile.out
Failure surfaces Examined. They Are Ordered - Most Critical
First.
* * safety Factors Are calculated By The Modified Bishop Method * �°
Failure surface specified By 11 coordinate Points
Point x-Surf Y-Surf
No. (ft) (ft)
1 15.00 101.40
2 17.72 102.67
3 20.42 103.98
4 23.09 105.34
5 25.74 106.75
6 28.37 108.20
7 30.97 109.70
8 33.54 111.24
9 36.08 112.83
10 38.60 114.46
11 39.40 115.00
Circle Center At x = -56.2 ; Y = 258.0 and Radius, 172.0
1.323 ***
Failure surface Specified By 12 Coordinate Points
Point x-surf Y-surf
No. (ft) (ft)
1 15.00 101.40
2 17.71 102.69
3 20.41 104.00
4 23.10 105.32
5 25.79 106.65
6 28.47 108.00
7 31.14 109.36
8 33.81 110.74
9 36.47 112.13
10 39.12 113.53
11 41.76 114.95
12 41.86 115.00
Circle Center At x = -231.5 ; Y = 621.7 and Radius, 575.7
*** 1. 570 ***
Failure surface specified By 10 Coordinate Points
Point x-surf Y-Surf
No. (ft) (ft)
Page 3
Profile.out
1 20.00 104.90
2 23.00 104.75
3 25.99 104.98
4 28.92 105.59
5 31.76 106. 58
6 34.44 107.93
7 36.92 109.61
8 39.17 111.60
9 41.14 113.86
10 41.90 115.00
circle center At X = 22.7 ; Y = 128.0 and Radius, 23.2
*** 1.625 ***
Failure surface specified By 10 coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 20.00 104.90
2 23.00 104.74
3 25.99 104.97
4 28.92 105. 58
5 31.76 106. 56
6 34.44 107.91
7 36.93 109. 58
8 39.18 111. 57
9 41.15 113.83
10 41.94 115.00
circle center At X = 22.7 ; Y = 128.0 and Radius, 23.2
*�t* 1.626 *
Failure Surface specified By 9 coordinate Points
Point X-Surf Y-surf
No. (ft) (ft)
1 20.00 104.90
2 23.00 104.88
3 25.97 105.28
4 28.87 106.07
5 31.62 107.26
6 34.19 108.81
7 36.52 110.69
8 38. 57 112.88
9 40.07 115.00
circle center At X = 21.6 ; Y = 126.7 and Radius, 21.9
*** 1.651 ***
Page 4
Profile.out
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-surf
No. (ft) (ft)
1 25.00 107.00
2 27.99 106.70
3 30.97 107.02
4 33.83 107.93
5 36.44 109.40
6 38.71 111.37
7 40. 52 113.75
8 41.12 115.00
Circle Center At X = 27.9 ; Y = 121. 5 and Radius, 14.7
1.673 ***
Failure surface specified By 15 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 5.00 100.00
2 7.97 99. 58
3 10.97 99.41
4 13.96 99.48
5 16.95 99.80
6 19.89 100.37
7 22.78 101.17
8 25.60 102.22
9 28.31 103.49
10 30.92 104.98
11 33.39 106.68
12 35.71 108. 58
13 37.87 110.66
14 39.85 112.92
15 41.39 115.00
circle Center At X = 11.6 ; Y = 135.7 and Radius, 36.3
*** 1.687 ***
Failure surface specified By 12 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 15.00 101.40
2 18.00 101.38
3 20.99 101.68
Page 5
Profile.out
4 23.92 102.29
5 26.78 103.22
6 29.52 104.44
7 32.11 105.94
8 34.53 107.72
9 36.75 109.73
10 38.74 111.98
11 40.49 114.42
12 40.81 115.00
Circle Center At x = 16.7 ; Y = 129.6 and Radius, 28.2
1.704 ***
Failure surface specified By 8 Coordinate Points
Point x-Surf Y-Surf
No. (ft) (ft)
1 25.00 107.00
2 27.97 106. 58
3 30.96 106.78
4 33.85 107.60
5 36. 51 108.99
6 38.81 110.91
7 40.68 113.26
8 41. 54 115.00
Circle Center At x = 28. 5 ; Y = 121.0 and Radius, 14.4
1.711 ***
Failure surface specified By 10 coordinate Points
Point X-surf Y-Surf
No. (ft) (ft)
1 20.00 104.90
2 22.95 104.34
3 25.95 104.26
4 28.92 104.66
5 31.79 105. 53
6 34.49 106.83
7 36.95 108.56
8 39.10 110.64
9 40.90 113.05
10 41.92 115.00
circle Center At x = 25.0 ; Y = 123.1 and Radius, 18.8
1.727 ***
Page 6
a '
Profile.out
Y A x I 5 F T
0.00 26.92 53.83 80.75 107.66 134. 58
x0.00 +---------+---------+---------+-----**--+---------+
7
7
_ **1
. .713
- . . .71*
26.92 + . .73*
. . .73***
321*/1
- . .321
A 53.83 +
x 80.75 +
I 107.66 +
5 134.58 +
161.49 +
F 188.41 +
T 215.32 +
Page 7