HomeMy WebLinkAboutGEO2011-00015 for BLD2011-00124 - GEO Geological Review - 2/4/2011 -FT IN THE
Mason County Review Checklist IT 0 C.
For a Geological Assessment AR' IF I i..E
Instructions:
This checklist is intended to assist Staff in the review of a Geological Assessment. The
Assessment 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
Assessment 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:
Permit# 307411 Parcel#
ax t s- �Q
Date(s)of the Document(s) reviewed: ! � , ?fit t
(1) A discussion of geologic conditions in the general vicinity of the
proposed development, with geologic unit designation based
on referen d maps.
OK?Comment:
(2) (a)A discu on of the ground water conditions at the site,
OK? Comment:
(b) A discussion of the estimated depth to water Q
OK? ✓ Comment:
q7
(c) A discu sion of the quantity of surface seepage
OK=Comment:'
(d) A disc ion of the upslope geomorphology
OK?Comment:.
(e) A disc sion of location of upland waterbodies and wetland
OK?Comment:
(3) The appro ate depth to hard or dense co petent soil, e.g. glacial till or outwash sand.
OK?Comment: fl/ 7
(4) A discussion of any geomorphic exp ession of past slope instability(presence of
hummocky ground or ground cracks,terraced topography indicative of landslide block
mover5anT, bowed or arched trees in icatiQg downslope movement, etc.).
OK? Comment: S
(5) A discussion of the history of lands tide activity in the vicinity, as available in the
reference aps and records. S Q
OK? V Comment: 10 [.'
(6) An opinion on whether the propose d/
elopment is within the landslide hazard area or
its associated buffer or setback and the poten ial for landslide activity at the site in light of
the proposed velopment.
OK? omment: 1
(7) A recommendation by the preparer whether a Geotechnical Report should be required to
further ev ate site conditions and the pro o eyi development of the subject property.
OK? Comment: G6(
(8) If the presence of a hazard is determine within 300 feet of the proposed development,
then the following are delineated on a geolog Va /site map:
(a) the are f the proposed development.
OK?
Page 1 of 2 Form Effective June 2008
(b) the boundaries of the landslide hazard area (top, both sides, and toe),
OK? Comment: i ��—
(c) the associated buffers (top, both sides, and toe) A � ^
OK? Comment:
(d) building or other setbacks (top, both sides, and toe).
OK? Comment:
(9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the
location an ature of existing and proposed development on the si .
OK? VComment: t k.--A--
Are the.Document(s)signed and stamped?
Type and #of License: 3 0Oil-
If not approved, what is the next action/recommendation for further action?
OLvv �
Reviewed by , on
Time spent in review:
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
�c0 2oiI - W615
Mason Countv Department of Community Development
Submittal Checklist For a Geological Assessment
Instructions:
This checklist must be submitted with a Geological Assessment and completed, signed, and
stamped by the licensed professional(s) who prepared the Geological Assessment 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 TM MAW Parcel# 22331 50 00030
Site Address 931 C-0l/1119 L-aA&-- Dr;,ie�
(1) A discussion of geologic conditions in the general vicinity of the
proposed development, with geologic unit designation based
on referenced maps.
Located on page(s) .S
(2) (a) A discussion of the ground water conditions at the site,
Located on page(s) 7
(b) A discussion of the estimated depth to water
Located on page(s) -7
(c) A discussion of the quantity of surface seepage
Located on page(s) 7
(d) A discussion of the upslope geomorphology
Located on page(s) 3
(e) A discussion of location of upland waterbodies and wetlands.
Located on page(s) 3
(3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
Located on page(s) C
(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.).
Located on page(s) 3
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and records.
Located on page(s) �3, 9
(6) An opinion on whether the proposed development is within the landslide hazard area or
its associated buffer or setback and the potential for landslide activity at the site in light of
the proposed development.
Located on page(s)
(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.
Page 1 of 2 Form Effective dune 2008
Located on page(s)
(8) If the presence of a hazard is determined within 300 feet of the proposed development,
then the following are delineated on a geologic map/site map:
(a) the area of the proposed d velopment,
Located on Map(s) 6UA
(b) the boundaries of the laJ� slide hazard area (top, both sides, and toe),
Located on Map(s) /V
(c) the associated buffers��(�op both sides, and toe)
Located on Map(s).__�_/f}
(d) building or other setbacks (top, both sides, and toe).
Located on Map(s) /1/f/�
(9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the
location and nature of existing %,, proposed development on the site.
Located on Maps) an Ci9��,��
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 1,[
that the//Geological Assessment, dated )"--e� 2O " �, and entitled �xo�ea,,u �55essn�eirr
r Sid�/?d /°fa y meets all the requirements of the
Mason County Reso rce Ordinance, Landslide Hazard Se tion, is complete and true,that the
assessment demonstrates conclusively that the risks 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 public health and safety.
(Signature and Stamp)
CLY
AL�G��v
Disclaimer: Mason County does not certify the quality of the work done in this Geological
Assessment.
Pane 2 of 2 Form Effective June 2008
TO BE- KEEPT IN F F IE
PARCE7'_ FILE
Geological Assessment
for
Walker Single Family Residential Property
931 Collins Lake Drive
Parcel No. 2233150 00030
Mason County, Washington
February 4, 2011
Project#1109
Prepared For:
Jim Walker
PO Box 125 ti CLYDF S
Keyport, Washington 98345 ��� oFWAsy��c�-���
Prepared By: Z/IO/
Envirotech Engineering .� 43045 q�
PO Box 984 0• ��c�S
Belfair, Washington 98528 �SS1pNALE�G`
Phone: 360-275-9374
Fax: 360-275-4789
TABLE OF CONTENTS
1.0 INTRODUCTION...........................................................................................................................1
1.1 PROJECT INFORMATION............................................................................................................... 1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK..................................................................... 1
2.0 SURFACE CONDITIONS..............................................................................................................3
2.1 GENERAL OBSERVATIONS............................................................................................................ 3
2.2 TOPOGRAPHY............................................................................................................................... 3
2.3 SuRFACEDRAINAGE..................................................................................................................... 3
2.3.1 Upslope Geomorphology and Upland Water Bodies.............................................................. 3
2.4 SLOPE AND EROSION OBSERVATIONS........................................................................................... 3
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
3.31 Groundwater......................................................................................................................... 7
3.4 SOILS TESTING.............................................................................................................................7
3.4.1 Usual Classisi f cation............................................................................................................. 7
4.0 ENGINEERING CONCLUSIONS..................................................................................................8
4.1 LANDSLIDE HAZARDS...................................................................................................................8
4.1.1 Landslides and Slope Stability Analysis................................................................................ 9
4.1.2 Surface and Subsurface Drainage........................................................................................ 9
4.2 EROSION HAZARDS.......................................................................................................................9
4.3 SEISMIC HAZARDS...................................................................................................................... 10
4.4 OTHER CONSIDERATIONS........................................................................................................... 10
5.0 CLOSURE..................................................................................................................................... 11
Appendix A-Site Plan
Appendix B- Soil Information
' t
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed this geological assessment for a residential
property located 931 NE Collins Lake Dr., identified as parcel number 2233150 00030 in Mason
County, Washington (Project). As presented herein, this assessment 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, seismic hazards, and
other considerations in the Conclusions Section.
An initial geological/ geotechnical evaluation of the Project was conducted by Envirotech with
the property owner Jim Walker on January 28, 2011. It was determined that natural slopes
between 15%and 40%were present within 300 feet of the Project. Due to these slope grades, a
geological assessment is required pursuant to landslide hazard areas of the Mason County
Resource Ordinance (MCRO). Due to these slope grades, a geological assessment is required
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 in order to determine if further geotechnical studies are required. 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 observations from
a field visit by Envirotech. The property is accessed from NE Collins Lake Dr., a paved roadway
in Mason County,Washington. The proposed development is expected to consist of a new single
family residence. All drainage collected from foundations, roofs and/ or retaining walls are
expected to have a protected outfall located downslope from the proposed structures.
Approximate site development with relation to existing site features are illustrated in the Site Map
in Appendix A.
1.2 Purpose of Investigation and Scope of Work
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. In order to fulfill the purpose of investigation, the geological/
geotechnical program completed for the proposed improvements of the Project include:
• Review project information provided by the Project owner's representative;
• Conduct a site visit to document the site conditions that may influence the construction
and performance of the proposed improvements;
• Define general subsurface conditions of the site by observing soils within test pit
excavations, review well logs from existing wells near the Project, and evaluate
geological maps depicting the site geology for the vicinity of the Project;
• Perform soils testing, such as visual classifications,to determine selected index properties
of the soils;
• Complete an engineering assessment supported by planned site alterations and the surface
Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 1 Parcel 3322150 00030
Fax: 360-2754789 Mason County,Washington
February 4,2011
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 Project.
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Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 2 Parcel 33221 50 00030
Fax: 360-275-4789 Mason County,Washington
February 4,2011
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on January
28, 2011 by Michael Staten, geotechnical engineer with Envirotech. During the site visit, site
features were documented that may influence construction or reveal potential geological hazards.
This Surface Conditions Section provides information on general observations, vegetation,
topography,drainage and slope/erosion conditions for the Project and surrounding areas.
2.1 General Observations
The Project is currently partially developed land with a motor home and on-site septic system,
and surrounded by rural residential development. Collins Lake Dr. extends along the north side of
the property,and Collins Lake is located along the south property line. Vegetation on and near the
property consists primarily of 2nd growth firs 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 topographic information provided in
this section was extrapolated from a public lidar source, and incorporated observations and field
measurements. Where necessary, slope verification included measuring slope lengths and
inclinations with a cloth tape and inclinometer. See the Site Map in Appendix A for an illustration
of the general slope indicators with respect to the planned development.
Descending slopes exceeding 15% are located immediately downslope of the proposed
development. This slope is approximately 25%with a vertical relief of approximately 32 feet.
2.3 Surface Drainage
The majority of the stormwater runoff originating upslope from the anticipated development is
expected to be minimal to moderate. Significant scour, erosion and sediment transport was not
apparent near the Project.
2.3.1 Upslope Geomorphology and Upland Water Bodies
Ascending grades are generally located to the north of the planned development. This
slope is relatively minor within 300 feet of the Project, with no apparent slope grades of
at least 15%. The upland area of the property is situated on a crest. Additional
geomorphology that is pertinent to both upslope and downslope areas are provided in the
Subsurface Investigation Section of this report.
There are no apparent water bodies or wetlands located upslope from the planned
development that would significantly influence the Project.
2.4 Slope and Erosion Observations
The existing moderate slopes near the Project signal a potential landslide or erosion hazard area.
Some indicators that may suggest past slope movements include:
Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 3 Parcel 3322150 00030
Fax: 360-275-4789 Mason County, Washington
February 4.2011
• 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.
The above mentioned indicators, or other signs of 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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2009 Aerial Pholo from USDA Website
Envirotech Engineering Walker Geological Assessment
Ph 360-275-9374 page 4 Parcel 3322150 00030
Fax:360-275-4789 Mason County,Washington
February 4,2011
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the Project was gathered during research and a
site reconnaissance. The site visit was accomplished on January 28, 2011 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
test pit log(s) representative of the site soils, and water well report(s)originating from the subject
property and/or nearby properties.
3.1 Field Methods,Sampling and Field Testing
Information on subsurface conditions for the Project was accomplished by observing soils within
test pit excavations of up to approximately 3 feet below the existing ground surface. Information
on subsurface conditions also included reviewing geological maps within the Project vicinity,and
water well reports originating from nearby properties. No soil samples were collected for this
Project.
Envirotech measured the relative density of the in-situ soils by gauging the resistance of hand
tools. Field testing results generally indicated loose to medium dense soils in the upper 36 inches,
and dense soils from 36 inches below the ground surface to the depth of terminous.
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 Lake Wooten 7.5-minute Quadrangle, Mason County,
Washington"by Robert E. Derkey,Nicholas J. Hehemann,and Katelin Alldritt, 2009,this Project
consists of Vashon Till(Pleistocene), and provides the following caption for this Project:
Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 5 Parcel 3322150 00030
Fax: 360-275-4789 Mason County,Washington
February 4,2011
Vashon till(Pleistocexe�-Unstratif•:ed to moderately stratified.compact,unsorted mixture of
Ogt ciay,silt. sand.and gravel deposited directly by glacial ice;consists of sediment rtca to
northern-provenance clasts;gray.tan_or brown;nearly every-where in sharp contact with
underlying units:does not drain weiL as permeability and porosity are lour;sand and imer grains
in matrts are very angular;pebble-to boulder-size clasts are commonh striated and faceted.
hating angular and(or)rounded edges:boulders are eeneraily disseminated and re:atively rare,
may contain interbeds of sand and gravel: ground surface for this unit characterized by
streamlined drumlins,striations.and flutes that are generally hundreds to thousands of feet lon=:
angular to subrounded glacial erratic boulders consist mostly of plutonic or metamorphic rock;
unit may be capped by a few feet of unsorted and stained ablation sand and gravel: localh-
crosscuts older--ediment.. Forming angular unconformities;drag folding and horizontal--hearing
may occur at the base of the till or internally between layers of till,especially in thick deposits;
trait ranges in thickness from 0 to more than 5C ft.
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 with indications of fill. Competent bearing soils were
encountered at 18 inches below the bottom of the fill. For engineering purposes, the native soils
consist of distinguishable layers,as presented below.
Soils within the upper 3 feet of natural ground were observed to be moist, brown silty sand with
gravel(SM).
Soils below the upper 3 feet layer were observed to be brown and grey silty sand and gravel
(SM), and are locally described as hardpan. Soils below the observed depth are believed to be
hardpan for a depth of at least 50 feet below the ground surface. This is based on nearby well
reports, site geology,and/or knowledge of the general area.
The relative densities of the soil are provided above in Section 3.1. Expanded and specific
subsurface descriptions, other than what is provided in this section, are provided in the soil logs
located in Appendix B of this report.
According to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Conservation Service, the site soils are described as Alderwood gravelly sandy
loam, Ae, with 5% - 15% slopes. According to this soil survey, "the surface soils consist of a
friable, brown, gravelly sandy loam 8 to 13 inches deep. It has a weak granular structure and
contains numerous rounded shot. Below the surface soil,to depths ranging from 18 to 24 inches,
is a pale-brown gravelly sandy loam that is very fiiable, is single-grained, and contains small to
moderate amounts of shot. Between this layer and the cemented till is a 3- to 10-inch layer of
very pale brown gravelly sandy loam. It contains no shot and is firmer but has the same texture as
the layer above. The cemented till consists of light gray, gravelly sandy loam, and it normally
occurs at depths ranging from 24-to 32-inches It is impermeable to roots, and slow permeable to
Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 6 Parcel 3322150 00030
Fax:360-275-4789 Mason County,Washington
February 4,2011
water. Below this, to a depth of many feet, the till is uniformly cemented, fairly uniform light
gray.The cemented substratum tends to restrict the rapid downward movement of moisture."
3.3.1 Groundwater
From the water well report(s)and knowledge of the general area,permanent groundwater
is at least 50 feet directly below the property at the building pad location. Seepage or
perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports. However,the owner reported seepage within an earth cut to the north of the
development.
3.4 Soils Testing
Laboratory testing of soil samples were not performed for this Project. Visual classification of
soils was performed in the field. The following soil tests were performed in accordance with the
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. Specifically, soils within the upper 3 feet in the testing location
consisted of approximately 40%coarse gravel,401/6 sand-sized soils,and 20%low plastic
silty clay. 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 Walker Geological Assessment
Ph. 360-275-9374 page 7 Parcel 3322150 00030
Fax: 360-275-4789 Mason County, Washington
February 4, 2011
4.0 ENGINEERING CONCLUSIONS
The following sections present engineering assessments and conclusions concerning the Project.
These conclusions have been made available based on the planned construction activities 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
For the planned development, as provided in the Introduction Section, surface and subsurface
conditions as presented in this report, it is Envirotech's opinion that the proposed development is
not subjected to or cause adverse impacts to a landslide hazard area or its associated buffer or
setback as defined in the MCRO.
Landslides are natural geologic processes, and structures near slopes possess an inherent risk of
adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering
cannot eliminate these risks for any site with sloping grades because gravity is constantly
inducing strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will
exacerbate these strains. Geotechnical engineering considers excessive wet weather and `design'
earthquakes in order to provide an acceptable factor of safety for developing on or near sloping
terrain. These factors of safeties are based on engineering standards such as defining engineering
properties of the soil,topography,water conditions, seismic acceleration and surcharges.
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.
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.
According to the Resource Map from the Washington State Department of Natural Resources
(DNR), the Project is not within terrain labeled `highly unstable' or `highly erodible' relating to
soils. In addition, DNR did not indicated previous landslide activity near the Project. DNR
labeled portions of this project as medium slope instability with relation to slopes. This
delineation is primarily dependent upon slopes and convergence. Secondly, lithology and
precipitation are modeled within this delineation. In summary, this designation is based on
mapping without field observations or knowledge of the specific site geology or soils. A resource
map from DNR is provided below:
Emrirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 8 Parcel 3322150 00030
Fax: 360-275-4789 Mason County.Washington
February 4,2011
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4.1.1 Landslides and Slope Stability Analysis
Past landslide activity near the proposed development was not revealed during the Project
research. In addition, detrimental landslide activity or potential high landslide indicators
were not observed during the site visit as outlined in the Surface Conditions Section of
this report. Therefore, a slope stability analysis was not deemed necessary for this
Project. Considering the planned construction as summarized in the Introduction Section
of this report; surface and subsurface conditions for the Project; and, the slope stability
assessment provided herein, it is our opinion that the proposed site alterations will not
encourage a landslide hazard.
4.1.2 Surface and Subsurface Drainage
This project does not appear to experience significant subsurface drainage or surface
runoff. It is our opinion that groundwater or surface drainage is not a limiting factor for
this Project.
4.2 Erosion Hazards
Based on the USCS description of the Project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,
the Project is not within terrain labeled `highly erodible.' This Project is not within an erosion
hazard area as defined by the MCRO. Erosion hazard areas are those with USDA SCS
designations of River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on
slopes 15% or greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd),
Envirotech Engineering Walker Geological Assessment
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Fax:360-275-4789 Mason County,Washington
February 4,2011
Harstine Gravelly Sandy Loam on slopes 15% or greater (Hb), and Kitsap Silt Loam on slopes
15%or greater(Ke).
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. Although
an engineered erosion control plan is not warranted for this project, Best Management Practices
(BMP's) should be employed during and after construction. Ordinary BMP's includes silt
fencing, protection of drainage outlets and vegetating denuded areas.
Erosion control information and specifications may be found in the applicable "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. 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 is located approximately 5 miles to
the northwest 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 low for
this Project. This is based on subsurface conditions such as soil characteristics and the lack of a
permanent and substantial 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.
4.4 Other Considerations
Conclusions in this report are based on the type and location of the anticipated development, and
existing surface and subsurface conditions. Site development that significantly deviates from the
anticipated improvements presented in this report may require geotechnical design
recommendations. Foundations must extend beneath fill soils at least 18 inches below the native
ground surface. Alternatively,the fill may be removed and replaced with engineered fill.
Envirotech Engineering Walker Geological Assessment
Ph 360-275-9374 page 10 Parcel 3322150 00030
Fax: 360-275-4789 Mason County,Washington
February 4,2011
5.0 CLOSURE
Based on the project information and site conditions as presented in this report, it is Envirotech's
n t additional geotechnical studies are not required to further evaluate this Project.
opinion that g q
P
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,
Envirotech Engineering
Michael Staten, P.E.
Geotechnical Engineer
Envirotech Engineering Walker Geological Assessment
Ph. 360-275-9374 page 11 Parcel 3322150 00030
Fax: 360-275-4789 Mason County, Washington
February 4,2011
APPENDIX A
SITE PLAN
N
SCALE, I INCH 40 FEET
p 20 40
CpLIINS LAKE DRIVE
60 Ft t
EXISTING _ EXISTING
PRIMARY AND GRAVEL
RESERVE SEPTIC DRIVEWAY
DRAINFIELD AREA
�D
I+
PROPOSED
SINGLE
FAMILY
RESIDENCE
-H OTP1
v
(U (v
PROPERTY LINE
cn
I+
PROJECT/ OWNER/ LOCATIONS
JIM WALKER
GE❑L❑GICAL ASSESSMENT
JIM WALKER
COLLINS LAKE PARCEL NO 22331 50 00030
MASON COUNTY, WASHINGTON
ENGINEER-
LEGEND ENVIROTECH ENGINEERING
2/# PO BOX 984
SLOPE INDICATOR BELFAIR, WASHINGTON 98528
360-275-9374
TP1 TEST PIT
SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geological Assessment DATE OF LOG: 01/28/2011
PROJECT NO: 0909 LOGGED BY: MCS
CLIENT: Jim Walker EXCAVATOR: N/A
LOCATION: Parcel 22331 5000030 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
STANDARD PENETRATION TEST
SOIL STRATA,
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 ..... .... . . .. .
FILL
1
:..
. ................ .. ...................... .... .... . .
2 SM Brown, moist, medium dense SILTY
SAND with GRAVEL. Gravel is coarse
and subrounded. Sand is primarily
3 coarse. Medium plasticity.
Excavation terminated at approximately
3.0 feet
4
5
6
7
8
9
110
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
interpreted as being indicitive of the entire site.
VATBR IIBLL k 9 P 0 & T Start Card No. V031173
Unique Yell I.D. I ABN44
STATE OF VASB[NGTON hater light Permit No. G1-11431 C
(1) OVNBE: Nave COLLINS LALB COMMUNITY CL Addreso PO 1101 113 ULFAIR, VA 11121.
#1) LOCATION OF YELL: County NAM - SE 1/4 S1 1/4 See 31 T 31 N., 3 19 YN
1a) STURT ADDUSS OF YELL (or nearest address) LOT it COLLINS LW, NNLFAII
(3) PROPOSED USE: G4IOUP DOMESTIC - -_ .� 110) YELL LOG
(4) TYPE OF VORS: Owner's Number of well ( Formation: Describe by color character, site of material
{`It more than ore j 1 and Itrmeture, and show thickness of agvifert and the kind
NB1 VBLL Aethod: AIR IWTARi i adsatire of the material in each str0as penetrated, with
at least one entry for each change in formation.
(3) DINBNSIONS: Diameter of veil 1 inches -----•--------------------------•-•-------------------------
Drilled 117 ft. Depth of completed well 112 ft. 1 NATRRIAL FROM TO
:..:::::.: -.-- PIPE 1TICC-UP l a I
(b)-COMSTRUCTIOM DSTA[LS:.=-._::::::�::��-�-----�::. . 1 PILL `� j
Casingg installed: / ' Dia, from 0 ft. to a/i.l ft. i OW SAM CLAY A GRA 1 13
1BLDRD ' Dia. from It. to ft. I MAY EM SAND A CUY GLAY91, 113 171
! Dia_ fro■ ft. to ft. 1 �� ME 41AVBL 1Nt i 7! 113
--- - - - - - --------•-------------------1 1�� 101 4UVN1. a CLAY I !3 I !1
Perforations: TBS 1 110� UN SAVNL A CLAY SANDY I !1 1117
T�yQQee of perforator used STAR PERFORATOR i 11011 1AGR G AVIL A CLAY 1107 I III
SIi6 of perforations 13 Is. by 1.11 in. 11Ei0R SAND GRAVIL A VATU LENSES OF CLAY i 111 I III
Ill perforations from 311 ft. to 111 ft. 1 R11�1 CLAY I 1:! 1117
130 perforationt from 141 ft. to 371 ft. 111110111 CLAY STIMS/110" SAND 1l7 141
perforations from ft. to It. 11� G1AVU SAID 1141 I In
... - -----------••-••--------------1 110� GRAVEL SAND SOME CLAY 110 117
Screens: NO 111011 ?HILL SAM l If 7 _ 1 I1!
Manufacturer's Nate ( 11011 GRAVEL SAND 11T 1 III t III
Type Model No. 11011 CLAY GRAVEL a ll1N• i 111 11!1
Dias. RIO
Iiot site from ft. to ft. T GRAVEL 1AGR UMW11!1 1241
Dian. slot site from It. to ft. l IGR/1 SAA GRAV1L vim 1144 1111
-
------------------------------------------------•------.i >t10111 aAru SAM & CUT LATBES OF l all 1117
Gravel packed: NO Site of travel 11011 SAND 0AV1L VATU 111 117
Gravel placed fret It. to ft. 1 1 1
----------------------------------------------------------1 l 1
Swrface test: YES To what depth? a1 ft. r I
Material vied in seal BNIITONIT6
Did any strata contain unusable water? NO j
Type of water? Depth of strata ft.
Method of sealing strata off -_ I rn f l
(7) PUMP: Manufacturer's Name------------------------------------� z N
Type R.P. ' aN f I_ _I -
(S) VATULBVBLS: -- - -- Land-svrface elevation. - •-- - _�
above mean sea level .. III* ft.
Static level 141.1 ft. below top of well Date 11113111
Artesian Pressvre lbs. per square inch Date 1
Artesian water controlled by I
York started II/21/01 Completed 13j03/15
(I) VBLL TESTS: Drawdown is amovnt water level is lowered below ' VBLL CONSTRWIf" CUTIFICATION:
static level. i 1 constructed and/or accept responsibility for cos-
Vas a pvmp Lett made? YBS If pew by whom? R A N ( strsetion of this veil, and its compliance with all
Yield: 41.1 gal./min with 11.5 rt. dravdown after 1 hrs. I Vashingtoa well constriction standards. Materials used
41.0 11.71 1 I and the information reported above are true to my best
44.1 13.31 14 ' knowledge and belief.
Recovery data
Time Vater Level Time Vater Level Time later Level 1 NAME N[CNOLSON DR[LLING 1111C
1 143.E 1 143.E II 143.7 1 (Person, firm, or corporation) (Type or print)
30 143.4 10 141.1 11 141./ 1
104 241.4 ADBEESS BOI 113
Date of test 11/(II3/11
Bailer test al/tin. f►. drawdown after hrs. I (SIGNED) Licene No. 0111
Air test gatfmin. v/ stem set at ft. for kirs.1
Artesian flow tt . Date 1 Cestra is
Temperature of water 31p.m Vas a chemical analysis made? TNS ; Registration No. 51 1137ON Date 12/13/I3