HomeMy WebLinkAboutGeological Assessment for BLD2008-00165 - GEO Geological Review - 3/7/2008 ALKAI CONSULTANTS, LLC.
Environmental Engineering • Geotechnical Engineering • Wetland Consulting
March 7,2008 10126
Mason County Department of Community Development
P.O.Box 279
Shelton,WA 98584
Attn: Tammi Wright
Geological Assessment Review
Permit#BLD 2008-00165
Applicant: Reis
Dear Ms. Wright
At your request, ALKAI CONSULTANTS have reviewed a Geological Assessment for the above referenced
permit. The report was prepared by Envirotech Engineering dated December 31, 2007. The assessment was
signed and stamped by Michael Staten(License#43045).
It is ALKAI's opinion that the assessment contains the information required in the Mason County Code 8.52.140
Section 5 (D), for a Geological Assessment. ALKAI therefore recommends that Mason County accept the
Geological Assessment for the referenced permit.
Should you have any questions or concerns, or if we may be of additional assistance, please call our office at
(360)613-2407 or contact us by e-mail at Jim@alkai.net.
Sincerely,
Donald Balmer, L.G. } James Harding,E.LT
Senior Hydrogeologist ' Project Engineer
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Attachments: Geo Tech Work Order
Geotechnical Report by EE
Mason County Requirements Checklist
9465 Provost Road NW, Suite 202 • Silverdale, Washington 98383 • (360) 613-240 • Fax: (360) 613-2408
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MASON COUNTY PLANNING
GEO TECH WORK ORDER
CONSULTANT
ALKAI CONSULTANTS, LLC
9465 PROVOST ROAD NW, SUITE 202
SILVERDALE, WA 98383
PERMIT # cog - Go I(p
APPLICANT
DATE MAILED
PLANNER Wx2�G�-F—T'
AMOUNT BILLED
ADDITIONAL COMMENTS
"Please fill out the cost of the review and return this form
and the report to us with your recommendations.
Reis Single Family Residence Project 10126 1
Mason County Requirements
For Geotechnical Assessment
Mason County Code 8.52.140 section 5 (D)
1) A discussion of geologic conditions in the general vicinity of the proposed development,
with geologic unit designation consistent with terminology used in the Coastal Zone Atlas
(Washington Department of Natural Resources, 1980) or in applicable U.S. Geologic
Survey maps (See page 2 for examples of maps). Use of soil conservation service soil
layer terminology is considered inappropriate for this assessment
X❑ 2) A discussion of the groundwater conditions at the site, including the estimated depth to
water and the quantity of surface seepage and the upslope geomorphology and location of
upland waterbodies and wetlands.
X❑ 3) The approximate depth to hard or dense competent soil, e.g., glacial till or outwash sand
X❑ 4) A discussion of any geomorphic expression of past slope instability(presence of
hummocky ground or ground cracks, terraced topography indicative of landslide block
movement, bowed or arched trees indicating downslope movement, etc.).
X❑ 5) A discussion of the history of landslide activity in the vicinity, as available in the Coastal
Zone Atlas, the map of"Relative Slope Stability of the Southern Hood Canal Area,
Washington" by M. Smith and R.J. Carson, 1977 (More examples listed on page 2) and the
landslide records on file with the Mason County Department of Community Development.
X❑ 6) ❑ An opinion on whether the proposed development is within the landslide hazard area or
its associated buffer or setback.
XD 7) A recommendation by the preparer whether a geotechnical report should be required to
further evaluate site conditions and the proposed development of the subject property.
X❑ 8) If the presence of a hazard is determined within three hundred feet of the proposed
development, then the area of proposed development, the boundaries of the hazard, and
associated buffers and setbacks shall be delineated (top, both sides, and toe) on a
geologic map/site map.
v 9) 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.
Reis Single Family Residence Project 10126 2
Examples of accepted maps:
Geological Map of North Central Mason County, by R.J. Carson, 1976, U.S. Geologic Survey OFR
76-2). Also to be used as applicable are: 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. one sheet, scale 1:24,000, 2003; Geologic map of the Squaxin Island 7.5minute quadrangle,
Mason and Thurston Counties, Washington, by R.L. Logan, Michael Polenz, T.J. Walsh, and H.W.
Schasse. One 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. one sheet, scale 1:24,000, 2003; and the Geologic map of the Summit Lake 7.5-minute
quadrangle, Thurston and Mason Counties, Washington, by R.L. Logan and T.J. Walsh. forty-two by
thirty-six in. color sheet, scale 1:24,000, 2004.
Examples of accepted Landslide maps:
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. one sheet, scale 1:24,000, 2003;
Geologic map of the Squaxin Island 7.5-minut quadrangle, Mason and Thurston Counties,
Washington, by R.L. Logan, Michael Polenz, T.J. Walsh, and H.W. Schasse. One 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. One sheet,
scale 1:24,000, 2003; and the Geologic map of the Summit Lake 7.5-minute quadrangle, Thurston
and Mason Counties, Washington, by R.L. Logan and T.J. Walsh. forty-two by thirty-six in. color
sheet, scale 1:24,000, 2004;
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Geological Assessment
for
Reis Single Family Residence
Parcel No. 32232-5049017
Mason County, Washington
December 31, 2007
Project#0764
Prepared For:
Deborah Reis
PO BOX 4 �Po wn y�T9T�
Union, Washington 98592
Prepared By:
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Envirotech Engineering '0�0 43045
,o ER
74 NE Hurd Road �sS�GIST
1
Belfair, Washington 98528
Phone: 360-275-9374 F EXPIRES JAN 10,2009
Fax: 360-275-4789
TABLE OF CONTENTS
1.0 INTRODUCTION...........................................................................................................................1
1.1 PROJECT INFORMATION............................................................................................................... 1
1.2 PURPOSE OF INVF.STIGATION........................................................................................................ 1
1.3 SCOPE OF WORK........................................................................................................................... 1
2.0 SURFACE CONDITIONS..................................................»..........................................................3
2.1 GENERAL OBSERVATIONS............................................................................................................3
2.2 TOPOGRAPHY.......................................................................................................................••......3
2.2.1 Upslope Geomorphology....................................................................................................... 3
2.2.2 Downslope Geomorphology..................................................................................••••............ 3
2.3 SURFACE DRAINAGE.....................................................................................................................
2.4 SLOPE AND EROSION OBSERVATIONS...........................................................................................4
3.0 SUBSURFACE INVESTIGATION.................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING........................................................................5
3.2 GEOLOGIC CONDITIONS...............................................................................................................5
3.3 SPECIFIC SUBSURFACE CONDITIONS.............................................................................................6
3.3.1 Groundwater......................................................................................................................... 6
3.4 SOILS TESTING.............................................................................................................................6
3.4.1 Visual Classification............................................................................................................. 7
4.0 ENGINEERING CONCLUSIONS..................................................................................................8
4.1 LANDSLIDE HAZARDS...................................................................................................................8
4.L I Septic Drainfield Impacts..................................................................................................... 9
4.1.2 Surface and Subsurface Drainage........................................................................................ 9
4.1.3 Off-site impacts...................................................................................................••••.._......... 10
4.2 EROSION HAZARDS..................................................................................................................... 10
4.3 SEISMIC E[AGARDs...................................................................................................................... 10
5.0 CLOSURE..................................................................................................................................... 12
Appendix A- Site Plan
Appendix B - Soil Information
Soil Logs
Well Reports
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1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geological assessment for a vacant
property identified as parcel number 32232 50 49017 located in Mason County,
Washington (Project). As presented herein, this report includes information pertaining to
the Project in this Introduction Section; observations of the property and surrounding
terrain in the Surface Conditions Section; field methods and soils descriptions in the
Subsurface Investigation Section; and, assessments for landslides, erosion and seismic
hazards in the Conclusions Section.
An initial geological/geotechnical evaluation of the Project was conducted by Envirotech
with the property owner, Deborah Reis, on December 18, 2007. It was previously
determined that slopes between 15% and 40% were present within 300 feet of the
planned development, and subsequently will require a geological assessment pursuant to
landslide hazard areas of the Mason County Resource Ordinance (MCRO). During the
evaluation and site visit by Envirotech, surface and subsurface conditions were assessed.
After completion of the field work and applicable Project research, Envirotech prepared
this geological assessment.
1.1 Project Information
Information pertaining to the Project was provided by the property owner, and general
assumptions typical of this type of development. The Project is accessed from a paved
road (E McReavy Road) linking State Route 106. See the vicinity map on the following
page of this report. The new development is expected to consist of an approximate 1200
square feet single family residence with a loft, driveway, and on-site septic features.
Construction is expected to consist of a typical wood frame, with concrete footings, and
slabs-on-grade. Footings are expected to be 16 inches wide and placed at a minimum
depth of 12 inches below the ground surface. Clearing of vegetation is expected, and
minor stormwater control.._may be utilized. Minor earthwork is expected_to.-achieve
- T __....
positive .dtaln�ge. Approximate building footprint with relation to site features are
illustrated in the Site Map in Appendix A.
1.2 Purpose of Investigation
The purpose of this geological assessment was to evaluate the Project in order to confirm
that the proposed development is outside of any landslide hazard area and its associated
buffers and setbacks as determined in the MCRO. The investigation included
characterizing the general Project surface and subsurface conditions, and evaluating the
suitability of the soils to support the planned site development.
1.3 Scope of Work
In order to fulfill the purpose of investigation, the geological/ geotechnical program
completed for the proposed improvements of the Project include-
Envirotech Engineering Geological Assessment
Ph. 360-275 9374 page I Parcel 32232 50 49017
Fat: 360-275-4799 Mason County. Washington
December 3 i, 2ti07
• Review project information provided by the Project owner/developer;
• Conduct a site visit to document the site conditions that may influence the
construction and performance of the proposed improvements;
• Define the general subsurface conditions of the site by observing two existing
excavations within the Project, observing one test pit near the planned building
footprint, and review well logs from existing wells near the Project;
• Perform soils testing to determine selected index properties of the soils that
includes 2 visual classifications;
• Complete an engineering assessment supported by planned site alterations, and
the surface and subsurface conditions that were identified by the field
investigation, soil testing, and applicable Project research; and,
• Establish engineering conclusions based on findings and anticipated development.
Project
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Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page 2 Parcel 32232 50 49017
Fax: 360-275-4789 Mason County, Washington
December 31, 2007
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on
December 18, 2007 by Michael Staten, geotechnical engineer with Envirotech. During
the site visit, site features were documented, soil samples were collected from selected
locations, and near-surface soils were visually classified. This Surface Conditions Section
provides information on general observations, vegetation, topography, drainage and
slope/ erosion conditions for the Project and surrounding areas that may impact the
Project.
2.1 General Observations
The Project is currently undeveloped land as previously mentioned, and surrounded on
three sides by Mcreavy Road and 41" Street. Residential development of moderate density
exists beyond the property lines. Vegetation on the property consists dense alders,
maples, cedars, ferns, blackberry, ivy, Oregon grape, and other trees and shrubbery
common to this area of the Pacific Northwest. An aerial photo of the project and
immediate vicinity is provided on the following page.
2.2 Topography
The Project is situated within and near moderate terrain. The building envelope location
appears to be on relatively flat ground. The topographic information provided in this
section was extrapolated from a public lidar source, and incorporated observations and
field measurements. See the Site Map in Appendix A for an illustration of the general
slope indicators with respect to the planned development.
2.2.1 Upslope Geomorphology
Ascending grades are located to the south of the planned development beyond 4`h
Street. This slope is as much as 25% with a vertical relief of over 200 feet.
Ascending 2:1 grades exist on the property abutting 4 h Street with a vertical relief
of about 5 feet. There are no apparent water bodies or wetlands located upslope
from the planned development.
2.2.2 Downslope Geomorphology
Descending grades of approximately 19% begin at several feet beyond the
location of the planned development in a northerly direction. This vertical relief is
approximately 50 feet. This average grade increases at a distance just over 300
feet from the planned development.
2.3 Surface Drainage
The majority of the stormwater runoff originating upslope from the anticipated
En irotech Engineering Geological Assessment
Ph. 360-275-9374 Page 3 Parcel 32232 50 49017
Fav 360-275-4789 Mason CountN. Washington
December 31. 2007
development is expected to be collected in the drainage channel on the south side of 41'
Street. Some of this stormwater may flow over the roadway if the channel is blocked or
during long durations of intense rainfall. Significant.surface._runoff does not appear to
enter the Proje ., new the, proposed deve o1 pmpnt. Excessive scour, erosion or other
indications of past drainage problems were not observed at or near the planned
development. However, surface drainage was impeded during the time of the site visit
due to an abundance of subsurface water.
2.4 Slope and Erosion Observations
The existing, moderate slopes near the Project signal a potential landslide or erosion
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hazard area. Some indicators thatay suggest past slope movements include:
• Outwash of sediments near the bottom of the slope,
• Fissures, tension cracks or naturally stepped land masses on the face or top of the
slope, and parallel to the slope,
• Fine, saturated subsurface soils,
• Old landslide debris,
• Significant bowing or leaning trees, or,
• Slope sloughing or calving.
Significant mass wasting on the property or within the general vicinity of the Project
were not observed or discovered during research. Indications of past landslides, current
unstable slopes, deep-seated slope problems, or surficial slope failures were not observed
during the site visit.
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Aerial Photo from Mason County Website
Envirotech Engineering Geological Assessment
Ph. 360-275 9374 page 4 Parcel 32232 50 49017
Fax: 360-275-4789 Mason Count. Washington
December 3l, 2007
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the Project was gathered during
research and the site visit on December 18, 2007 by Michael Staten, geotechnical
engineer with Envirotech. Specific information on field methods, sampling, field testing,
subsurface conditions, and results from soil testing are presented in this section of the
report. Appendix B has pertinent information on subsurface conditions for the Project,
including two test pit logs representative of the bearing soils of the building, and one
water well report.
3.1 Field Methods, Sampling and Field Testing
Information on subsurface conditions for the Project was accomplished by observing
soils within existing test pit excavations near the planned building footprint of up to
approximately 4 feet below the existing ground surface. Information on subsurface
conditions also included reviewing water well reports originating from nearby properties.
One bulk sample was collected at the Project site at approximately 1.5 feet below the
existing ground surface near the anticipated building location. The soil sample collected
was secured and transported for possible laboratory testing.
Envirotech measured the relative density of the in-situ soils by gauging the resistance of
hand tools. Field testing results generally indicated medium dense soils in the upper 1
foot within the testing locations, and dense to very dense soils from 1 foot below ground
surface to the depth of terminus.
3.2 Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The
geologic conditions as presented in the "Geologic Map of Washington," compiled by J.
Eric Schuster, 2002 indicates Quaternary sediments, Qg. Quaternary sediments are
generally unconsolidated deposits, and dominantly deposited from glacial drift, including
alluvium deposits. This project is located within the Puget Lowland. Typically, "lower
tertiary sedimentary rocks unconformably overlie the Crescent Formation." as revealed in
the Geologic Map. Initial sedimentary rocks were formed from shales, sandstones and
coal deposits from rivers. During the Quaternary period, the Puget Lowland was covered
by numerous ice sheets, with the most recent being the Fraser glacier with a peak of
approximately 14,000 years ago. Upon the glacial retreat, the landscape was formed by
glacial erosion glacial drift deposits.
According to the "Geologic Map of the Shelton 1:100,000 Quadrangle, Washington," by
Robert L. Logan, 2003, the site soils are subgrouped as Alpine Glacial Deposits. Specific
units for this Project include alpine outwash, pre-late Wisconsinan (Pleistocene), Qapo.
From this geologic map, QaW is "stratified sand, gravel and cobbles; in the Quinault
basin, clasts consist of sandstone and less-abundant basalt from the Olympic Mountains
Envirotech Engineering Geological Assessment
Ph. 360-275 937=4 page 5 Parcel 32232 50 49017
Fax: 360-275-4789 Mason County. Washington
December 31. 2007
core and peripheral rocks; in streams draining the southern and southeastern Olympics,
clasts consist primarily of Crescent Formation basalt with less-abundant Olympic-core
sandstone; may include pleat, silt, and clay, and may be capped by weathered loess; clasts
are generally more rounded than those in till and lack facets and striations; poorly to
moderately sorted; gray to subtle yellow with wispy orange weathering."
3.3 Specific Subsurface Conditions
The following subsurface conditions are estimated descriptions of the Project subgrade
utilizing information from the depth of penetration at all testing, sampling, observed and
investigated locations. Soils for this project were described utilizing the Unified Soil
Classification System (USCS). Using the USCS in conjunction with estimated relative
densities and other anticipated engineering properties of the soil, susceptibility for
potential landslides, erosion and seismic hazards may be assessed.
The Project is composed of native soils beneath an organic/ soil mixture of about 12
inches, with no indications of borrowed fill. For engineering purposes, these native soils
consist of distinguishable layers, as presented below.
Soils within the upper.3.to,4 feet of natural ground are very moist to wet, medium dense
to dense brown silty sand with gravel (SM). Gravels are primarily well-graded, and
subrounded to subangular. Sand content was primarily coarse, and the fines contend/
exhibited low to medium plasticity.
Soils beginning at 3 feet to 4 feet below the ground surface to an unknown depth is very
dense, moist, brown silty sand with gravel (SM). Gravel content was primarily
subrounded and well-graded. Sand content was primarily medium and coarse, and the
fines content exhibited none to low plasticity.
According to the well reports, the very dense gravel, sand, and silt soils may extend to
depths of over 20 feet blow the ground surface.
3.3.1 Groundwater
From the water well report and knowledge of the general area, permanent
groundwater is expected to be greater than 100 feet directly below the property at
the building pad location. Seepage and significant groundwater was evident in the
upper 3 to 4 feet of soils. Overall, the upper subsoil consists of a moderate
permeable stratification due to the soil classification and relative density.
3.4 Soils Testing
The soil samples obtained at the Project site during the field investigation were preserved
and transported for possible laboratory testing. Visual classification of soils was
performed in the field. The following soil tests were performed in accordance with the
Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page 6 Parcel 32232 50 49017
Fax: 360-275-4799 Mason Country. Washington
December 3 I. 2007
American Standards for Testing and Materials (ASTM)-
2 Visual Classifications(ASTM D2488)
3.4.1 Visual Classification
The general results from the visual classification are presented above in the
Subsurface Conditions Section at depths of up to 6 feet below the natural ground
surface. Specifically, soils within the.upper 3 to 4 fecQnsisted of approximately
_ 20%,gravel, 50%-sand-stied soils; and-30%.low to medium plastic fines. Minor
variations observed during the visual classification of particle size content (i.e.
gravel, sand, fines), or isolated pockets within the soil stratification were
insignificant in relation to the overall engineering properties of the soil.
Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page 7 Parcel 32232 50 49017
Fax: 360-275-4789 Mason County, Washington
December 31,2007
4.0 ENGINEERING CONCLUSIONS
The following sections present engineering assessments and conclusions concerning the
proposed development of the Project. These conclusions have been made available based
on the planned improvements as outlined in the Introduction Section of this report;
general observations of drainage and topography as summarized in the Surface
Conditions Section; and, soil conditions that were identified by the field investigation and
soils testing as outlined in the Subsurface Investigation Section. Conclusions for the
Project that is provided herein, includes pertinent information for landslide, erosion and
seismic hazards.
4.1 Landslide Hazards
Landslides and erosion are natural processes, and structures near slopes possess an
inherent risk of adverse settlement, sliding or structural damage due to these processes.
These risks cannot be eliminated for any site with moderate to steep sloping grades.
Geotechnical and geological engineering provides an acceptable factor of safety for
building near sloping site conditions. These factor of safeties are based on engineering
judgment, and engineering standards accumulated from years of academic and
professional research by individuals in the field of geotechnical and geological
engineering.
Surface sloughing or other types of surficial slope movements usually do not affect the
deep-seated structural capability of the slope. However, excessive and/or repeated
surficial slope movements, if not repaired, may represent a threat to the structural
integrity of the slope. With appropriate drainage and erosion control provisions for this
Project during and after construction, it is unlikely that this Project will experience
excessive surficial movements. However, maintenance of the slope should be completed
if the situation does arise in order to prevent the possibility of further surficial or deep
seated slope movements that may be damaging to life or property.
It is
Envirotech's opinion that the proposed development is not within 300 feet of a Ji
landslide hazard area or its associated buffer or setback as defined in the MCRO.
According to the Coastal Zone Atlas of Mason County, Washington, the Project is within
and near terrain labeled `Intermediate' regarding potential landslide activity. Historically,
Intermediate terrains have no known landslides. A Stability Map from the Coastal Zone
Atlas for the general area of this Project may be found on the following page of this
report.
Past landslide activity near the proposed development was not revealed during the Project
research. In addition, detrimental landslide activity was not observed during the site visit
as outlined in the Surface Conditions Section of this report. Considering the planned
construction as summarized in the Introduction Section of this report, it is our opinion
that the proposed site alterations will not encourage a landslide hazard.
Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page R Parcel 32232 50 49017
Fax: ,60.275-4789 Mason Count}. Washington
December 31. 200"/
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4.1.1 Septic Drainfield Impacts
The approximate locations of the planned septic drainfields are presented on the
Site Plan in Appendix A of this report. The drainfields are not expected to
adversely influence moderate slopes within the vicinity of the septic components,
or affect the stability of the planned building structure. This determination is
partly based on the behavior and characteristics of the Project soils under
saturated conditions, in addition to the relatively moderate grades located
immediately upslope and downslope from the proposed drainfield location.
4.1.2 Surface and Subsurface Drainage
This Project experiences significant subsurface drainage, and minor surface runoff
originating from upslope properties. Substantial seasonal groundwater is
apparently confined to within the upper 4 feet of the subsurface. It is our opinion
that groundwater is not a limiting factor for slope stability or foundations if
construction is completed as expected per the information in the Introduction
Section of this report. Curtain drains would perform exceptional for this property
Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page 9 Parcel 32232 50 49017
Fax: 360-275-4789 Mason County, Washington
December 31,2007
les-groundwater was desired for this Project. If utilized, curtain drains should
extend along contours, and upslope from where groundwater is desired to be
lowered. These drains should penetrate the hardpan, and use appropriate drain
rock, drain pipe, and filter fabric typical of these systems. It is suggested that
outlets are established downslope and over 10 feet away from structures.
4.1.3 Oft-site impacts
Potential off-site impacts are limited for this Project. It is Envirotech's opinion
that adjacent properties, both upslope and downslope from the planned site
alterations, should not be negatively impacted from a geotechnical perspective.
Existing stable slopes, good stormwater collection systems downslope from the
property, and anticipated stable slopes after construction does not warrant off-site
concerns for this Project.
4.2 Erosion Hazards
Based on the USCS description of the Project soils, the upper soils are considered
moderately erodible. Temporary and/ or permanent erosion control measures may be
required for any site when land disturbance is involved. Erosion control will mostly
depend on the timeliness of construction, moisture content of the soil, and amount of
rainfall during construction. Soil erosion typical to the existing conditions and planned
disturbance of this Project include wind-borne silts during dry weather, and sediment
transport during prolonged wet weather. Sediment transport of disturbed soils could be
from stormwater runoff or tracking off-site with construction equipment. Erosion control
measures may need to be employed if excessive erosion occurs or required by the County
or other prevailing agencies.
Erosion control information and specifications may be found in the "Stormwater
Management Manual for Western Washington," prepared by the Washington State
Department of Ecology Water Quality Program.
4.3 Seismic Hazards
Soils immediately below the expected foundation depth for this Project are generally
Type D, corresponding to the International Building Code (IBC) soil profiles. Type C
soils may be assumed for soils below 4 feet in depth. According to the IBC, the regional
seismic zone is 3 for this Project. The estimated peak ground acceleration ranges from
0.50g to 0.60g. This estimation is based on the United States Geological Survey (USGS)
National Seismic Hazard Project in which there is an estimated 2% probability of
exceedance within the next 50 years.
There are no known faults beneath this Project. The nearest Class `A' or 'B' fault to this
property is the Hood Canal Fault Zone. This fault is a Class `B,` and the distal end is
En irotech Engineering Geological Assessment
Ph. 360-275-9374 page 10 Parcel 32232 50 49017
Fax: 360-275-4799 Mason County. Washington
December 31. 2007
approximately 3 miles to the west of the Project. This information is supported by the
USGS Quaternary Fault and Fold Database for the United States.
The potential for liquefaction and other earthquake induced hazards are believed to be
very low for this Project. This is based on subsurface conditions such as soil
characteristics and the lack of a permanent shallow water table. Subgrade characteristics
that particularly contribute to problems caused by seismic events include submerged and
confined, poorly-graded granular soils. Although gravel- and silt-sized soil particles
could be problematic, fine and medium grained sands are typically subjected to these
types of seismic hazards. Significant sand stratifications are not anticipated to be within
the upper 50 feet of the subsoils, and permanent groundwater is expected to be greater
than 50 feet below the ground surface for this Project.
Envirotech Engineering Geological Assessment
Ph. 360-275-9374 page 11 Parcel 32232 50 49017
Fax: 360-275-4789 Mason County. Washington
December 31,2007
5.0 CLOSURE
Based on the project information and site conditions as presented in this report, it is
Envirotech's opinion that additional geotechnical studies are not required to further
evaluate this Project.
Due to the inherent natural variations of the soil stratification and the nature of the
geotechnical subsurface exploration, there is always a possibility that soil conditions
encountered during construction are different than those described in this report.
Therefore, it is recommended that a qualified engineer observes and documents the
construction, or Envirotech is promptly notified if project and subsurface conditions
found on-site are not as presented in this report so that we can re-evaluate our
recommendations.
This report presents a geological/ geotechnical assessment, and is intended only for the
owner, or owners' representative. Furthermore, this report is only valid for the project
information and location described herein.
The services described in this report were prepared under the responsible charge of
Michael Staten, a professional engineer with Envirotech. Michael Staten has appropriate
education and experience in the field of geotechnical engineering in order to assess
landslide hazards, earthquake hazards, and general soil mechanics.
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or
require additional information.
Sincerely,
Envirojecp Engineering
Michael Staten, P.E.
Geotechnical Engineer
Envirotech Engineering Geological Assessment
Ph. 360-27.5 9374 page 12 Parcel 32232 50 49017
Fax: 360-275-4789 Mason CoLmty, Washington
December 3 i, 2007
APPENDIX A
SITE PLAN
SCALE I INCH 30 FEET
APPR❑XIMATE m
L❑CATI❑N OF
PROPOSED
DRAINFIELD
8p PROPOSED
P1 P2v F� DRIVEWAY
I-)-
APPROXIMATE
LOCATION OF APPR❑XIMATE
PROPOSED LOCATION OF
RESIDENCE PROPOSED GARAGE
+IN
IL
o e
TP3 -H
PROPERTY LINE RE ATIVELY FLAT AT dOU F
AND GARAGE LOCATION u-)
co
2:1 SL PES, 5 FT VERTICAL RELIEF ALONG ROADWAY
100 FT f
E 4TH STREET
x
In
of
PROJECT/ OWNER/ LOCATION,
REIS
GEOLOGICAL ASSESSMENT
DEBORAH REIS
PARCEL NO 32232 50 49017
MASON COUNTY, WASHINGTON
ENGINEER.
LEGEND ENVIROTECH ENGINEERING
74 NE HURD ROAD
2%t SLOPE DIRECTION BELFAIR, WASHINGTON 98528
360-275-9374
TP1 9 TEST PIT
SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST MT LOG
TEST PIT NUMBER TP-1
PROJECT: Single Family Residence Geological ant DATE OF LOG: 12/18/2007
PROJECT NO: 0764 LOGGED BY: ARCS
CLIENT: Deborah Reis EXCAVATOR: N/A
LOCATION: Parcel 32232 50 49017 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: 2 ft FINAL DEPTH OF WATER: 2 ft
STANDARD PENETMTM TEST
DEPTH
SOIL STRATA, 1JSC3 DESCRIPTION LL PI DEPTH N CURVE
SAMPLERS
AND TEST DATA 10 30 50
0
r :•° ::' SSA Dark brown.motet, medm dares SILTY
:-. SAND wkh gravel.Gravel Is wskVaded
_ and wbsrV"do M broWKW.Sand is
mosay Coarse.Law to medksn plastldty.
Brawn.Dense
2 Wet
y = . hx+'ea*V dmm ty wkh depth
:_ .
Very dense
4
Exwvadon WmiraW at approodrnat*
4.0 feet
- 5
7
t
8
9
10
cro ftr Encountered ENVIROTECH ENGINEERING
Tjo k*m"m Muth aYy b EW eatg and a►m&nor be Geolechmkwl Engineering
TEST NT LOG
TEST PIT NUMBER TP-2
PROJECT: Single Family Residence Geological Assessment DATE OF LOG: 12/18/2007
PROJECT NO: 0764 LOGGED BY: MCS
CLIENT: Deborah Refs EXCAVATOR: N/A
LOCATION: Panel 32232 50 49017 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: 2 ft FINAL DEPTH OF WATER: 2 ft
S RA*M PEW-MUM TEST
DEPTH SOIL MAT& USCS DESCRIPTION LL PI CURVE
AND TEST DATA 10 30 50
0 .... ... ...... ... . . . .
Sm Deck brown,moist,mec&sn dense SILTY
SAND with gravel.GMffl l is w4 9taded
and subenguier to subrotxKed.Send Is
1 mostly coa m.Low to medium phWift.
Brown,Dose
—2 Wet
V� density wkh depth
denis
exwvadw bm*mftd at approximately
3.25 feet
S 41
8 -
9
10
Groundwater Encoun red ENVIROTECH ENGINEERING
Tina krbr:netlnn pxd�k�a aNy 1n ehfs eo►re end aAalfd not bs Geotecftk;W Ergkmwdng
file'pobd as beft mace of rba 008 of
J
TEST MT LOG
TEST PIT NUMBER TP-3
PROJECT: Single Family Residence Geological Assessment DATE OF LOG: 12/18/2007
PROJECT NO: 0764 LOGGED BY: MACS
CLIENT: Deborah Reis EXCAVATOR: N/A
LOCATION: Parcel 32232 5049017 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: 2 ft FINAL DEPTH OF WATER: 1 ft
STANDMW PENETRATION TET
DEPTH SOIL STRATA, USCS DESCRIPTION DEPTH
PI DEPTH � CURVE
SAMPLERAND TEST DATA 10 30 50
0 ..... .. . .. .. . .. .. ..
SM Dark Wown,moist,medli n dense SILTY
SAND with gravel.Gravel is wer-graded
and UbWWW to u&mnds&Sand Is
mocth►coerce.Law tD medlxn pkwfidty.
Brown,Dense
Wet
2 e=wadon terminated at Wroodr.mW 2
feet
3
4
5
r
p_
7
8
9
10
—41
cvaumtwater Encaailered ENVIROTECH ENGINEERING
Geotec mkxl Ergneering
7h*k0 mvAbn pwtsft 0*to fMe boric wW ahaMd not be
iMrrpelod p bsip kxkw i d g►s Was r0.
O '
C STATE OF WASHINGTOk
DEPARTMENT OF CONSERVATION 1
AND RXYS,+(IFXEKT _
LOG
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