HomeMy WebLinkAboutGEO2009-00066 Assessment - GEO Geological Review - 9/18/2009 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
914 (360)427-9670
Geotechnical Assessment Review Acceptance Letter
September 18, 2009
VIRGIL ELKINTON
1518 10TH ST
BREMERTON WA 98337-1308
Case No.: GE02009-00066
Parcel No.: 123094260000
Proiect Description: NEW MANUFACTURE HOME
The Geotechnical Assessment for VIRGIL ELKINTON has been received and reviewed by the
Planning Department. The assessment was prepared by Michael Staten dated 8/6/2009.
Based on the certification provided by the licensed engineer/geologist, the referenced Geological
Assessment was prepared in general accordance with the requirements in the Mason County
Resource Ordinance, Landslide Hazard Areas 17.01.100.E.4. 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 assessment may be required to address these changes.
The assessment 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 Geological
Assessment.
Please contact me at (360) 427-9670, ext. 365 if you have questions.
Sincerely, ) �
Allan Borden
Land Use Planner
Mason County Planning Department
Comments:
9/18/2009 Page 1 of 1 GE02009-00066
Mason County Review Checklist
For a Geological Assessment
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:
[��()`'L If t,
Permit# ' c� �") ,C r, Parcel #C3
Date(s)of the Document(s) reviewed: I ,
(1) A discussion of geologic conditions in the general vicinity of the
proposed development,with geologic unit designation based
on referenced maps.
OK? Comment:
(2) (a)A discussion of the ground water conditions at the site,
OK? Comment:
(b) A discussion of the estimated depth to water
OK? Comment:
(c) A discussion of the quantity of surface seepage
OK? Comment:
(d) A discussion of the upslope geomorphology
OK? Comment:
(e) A discussion of location of upland waterbodies and wetlands.
OK? Comment:
(3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
OK? Comment:
(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.).
OK? Comment:
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and records.
OK? Comment:
(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. KA,p /�`
OK? Comment: y . _fI !�� /
(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.
OK? Comment:
(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 development
OK? Comment: al °`" Md
Page 1 of 2 Form Effective June 2008
f
(b) the boundaries of the landslide hazard area (top, both sides, and toe),
OK? Comment:
(c) the associated buffers (top, both sides, and toe)
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 and nature of existing and proposed development on the site.
OK? Comment:
Are the Document(s)signed and stamped? V
Type and #of License: i
If not approved, what is the next action/recommendation for further action?
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
Mason County 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 ItY o% EI ki�1TfIhI Parcel# 1 Z 30") +7- C'(�CCC
Site Address ��� /12
Y" rt t �t l�✓t fly c�
(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) Q"
(2) (a)A discussion of the ground water conditions at the site,
Located on page(s)
(b) A discussion of the estimated depth to water
Located on page(s) S
(c) A discussion of the quantity of surface seepage
Located on page(s) S
(d) A discussion of the upsle geomorphology
Located on page(s)
(e) A discussion of location of upland waterbodies and wetlands.
Located on page(s) Z
(3) The approximate depth to hard or dense competent soil,e.g.glacial till or outwash sand.
Located on page(s) +
(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 er arched trees indicating downslope movement,etc.).
Located on page(s) Z_
(5) A discussion of the history of landslide activity in the vicinity,as available in the referenced
maps and records.
Located on page(s) 6 0-7
(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
(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 June 2008
Located on page(s) 10
(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 proposedgvelopment,
Located on Map(s)
(b) the boundaries of the landslide hazard area(top, both sides, and toe),
Located on Map(s) N'/A
(c) the associated buffers(top both sides,and toe)
Located on Map(s) _n
(d) building or other setbacks op,both sides,and toe).
Located on Map(s) f1/
(9) A site map drawn to scale showing the property boundaries,scale,north arrow,and the
location and nature of exis'ng an roposed development on the site.
Located on Map(s) AM A
I, / " i G k,e I c ly 4 1 hereby certify under penalty
of perjury that I am a civil engineer licensed in the State of Washington with specialized
knowledge of geotechnicaVgeological engineering or a geologist or engineering geologist licensed
in the State of Washington with special know�lLe�dgee of the local conditions. 1 also certify
that the Geological Assessment,dated c / 0 and entitled
4n- Apr'-�� meets all the requirements of the
Mason County R�eso�.rce Ordinarice, Landslide Hazards Sion,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)
CLYDE S
OF VvASy��
� J
�.n F(G/ST6R� �('
FSSION AL
Disclaimer: Mason County does not certify the quality of the work done in this Geological
Assessment.
Page 2 of 2 Form Effective June 2008
Geological Assessment
for
Elkinton Single Family Residential Property
100 Bear Creek Dewatto Road
Parcel No. 12309 42 60000
Mason County, Washington
August 6, 2009
Project#0964
Prepared For:
Virgil Elkinton
742 S Summit Avenue Ptiti cL S as ST
Bremerton, Washington 98312 �~G�roe w y
Prepared By: �� x
Envirotech Engineering 43045 w�
74 NE Hurd Road
Belfair, Washington 98528 sS'ONAL' �
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..............................................................................................................2
2.1 GENERAL OBSERVATIONS............................................................................................................2
2.2 TOPOGRAPHY...............................................................................................................................2
2.3 SURFACE DRAINAGE.....................................................................................................................2
2.3.1 Upland Water Bodies............................................................................................................ 2
2.4 SLOPE AND EROSION OBSERVATIONS...........................................................................................2
3.0 SUBSURFACE INVESTIGATION.................................................................................................4
3.1 FIELD METHODS,SAMPLING AND FIELD TESTIN(i........................................................................4
3.2 GEOLOGIC CONDITIONS...............................................................................................................4
3.3 SPECIFIC SUBSURFACE CONDITIONS.............................................................................................4
3.11 Groundwater......................................................................................................................... 5
3.4 SOILS TESTING.............................................................................................................................5
3.4.1 Visual Classi,ficadon............................................................................................................. S
4.0 ENGINEERING CONCLUSIONS.................................................................................................6
4.1 LANDSLIDE HAZARDS...................................................................................................................6
4.1.1 Landslides and Slope Stability Analysis................................................................................ 7
4.1.2 Septic Drainfidd Impacts......................................................................................................8
4.1.3 Surface and Subsurface Drainage........................................................................................8
4.1.4 On-Site and Off-Site Impacts................................................................................................ 8
4.2 EROSION HAZARDS.......................................................................................................................8
4.3 SEISMIC HAZARDS........................................................................................................................8
4.4 OTHER CONSIDERATIONS.............................................................................................................9
5.0 CLOSURE..................................................................................................................................... 10
Appendix A-Site Plan
Appendix B-Soil Information
Soil Logs
Well Reports
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed this geological assessment for a previously
developed property located at 100 Bear Creek Dewatto Road, identified as parcel number 12309
42 60000 located 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's representative, Virgil Elkinton, on July 31, 2009. It was determined that
natural slopes between 15% and 40% were present within 300 feet of the Project. Due to these
slope grades and other geological factors, 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. 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 with general
assumptions by Envirotech that are typical of this type of development. The property is
approximately 3 acres, and is accessed from Bear Creek Dewatto Road, a paved road connecting
Old Belfair Highway. Building construction is expected to consist of a manufactured home with
continuous runners or isolated pads, typical for this type of development. 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
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.
Envirotech Engineering Elkinton Geological Assessment
Ph. 360-275-9374 page 1 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on July 31,
2009 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 developed land as previously mentioned, and surrounded by low density
residential development.The existing structure has been abandoned. Bear Creek Dewatto Road
extends along the southwest side of the property, and a stream (Bear Creek) runs near the
northwest property line. Vegetation on and near the property consists primarily of older growth
cedars, firs, alders 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 sloping 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.
Maximum slope grades on the property and within 300 feet of the Project were measured to be
36%. Isolated slopes near 40%with vertical reliefs of less than 10 feet were probable within the
hillside. This slope is located primarily on the eastern half of the property, and consists of a
vertical relief of about 25 feet.
2.3 Surface Drainage
The majority of the stormwater runoff originating upslope from the anticipated development is
expected to be minimal to moderate. The stream appears to collect the majority of the upslope
runoff. Although Bear Creek is known to scour and cause excessive sedimentation, significant
scour,erosion and sediment transport was not apparent outside the stream channel.
2.3.1 Upland Water Bodies
Other than the stream that runs from a northeast to southwest direction as shown on the
Site Plan,there are no major water bodies located upslope from 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:
• 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,
Envirotech Engineering Elkinton Geological Assessment
Ph. 360-275-9374 page 2 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
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.
1�
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Soil Survey From USDA Natural Resources Conservation Service
Envirotech Engineering Elldnton Geological Assessment
Ph. 360-275-9374 page 3 Parcel 12309 42 00000
Fax: 360-2754789 Mason County,Washington
August 6,2009
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 July 31, 2009 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
existing test pit excavations of up to approximately 2 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 m-situ soils by gauging the resistance of hand
tools. Field testing results generally indicated medium dense soils in the upper 24 inches below
the ground surface.
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 "Interactive Geologic Map, 1:100,000 Quadrangle," as depicted by the
Department of Natural Resources, this Project consists mostly of glacial till, Qg,,. Glacial Till is
usually described as "unsorted, unstratified, highly compacted mixture of clay, silt, sand, gravel,
and boulders deposited by glacial ice of the Puget lobe; gray; may contain interbedded stratified
silt, and gravel; sand-size fraction is very angular and contains abundant polycrystalline quartz,
which distinguishes this unit from alpine till;cobbles and boulders are commonly striated and(or)
faceted; although unweathered almost everywhere, may contain cobbles or small boulders of
deeply weathered granitic rock."
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
Envirotech Engineering Elkinton Geological Assessment
Ph. 360-275-9374 page 4 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
(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 2 to 6 inches.
Competent bearing soils were encountered at about 18 inches below the ground surface. For
engineering purposes,these native soils consist of distinguishable layers,as presented below.
Soils within the upper 2 feet of natural ground were observed to be moist,brown silty sand(SM)
with some gravel. A very dense glacial till surface is believed to be within the upper 6 feet of the
ground surface,and extend to depths of greater than 10 feet.
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 Everett gravelly loamy
sand,Ed,with 0%-5%slopes and Everett gravelly sandy loam,Ek,with 15%-30%slopes.
3.3.1 Groundwater
From the water well report, permanent groundwater is expected to be greater than 100
feet directly below the properties near the planned building pad locations. Seepage or
other perched groundwater at shallow depths was not observed on site. However,
groundwater flow could increase during wet months due to groundwater flowing above
hardpan.
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 2 feet to the depth of terminous in
the testing location consisted of approximately 5%gravel,45%sand-sized soils,and 50%
low-medium plastic silt. 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 Elkinton Geological Assessment
Ph. 360-275-9374 page 5 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
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 fiuther surficial or deep seated slope movements that may be damaging to life or
party.
According to the Resource Map from the Washington State Department of Natural Resources
(DNR),the Project is within terrain labeled`highly unstable' or `highly erodible' relating to soils.
DNR did not indicate previous landslide activity near the Project. DNR labeled portions of this
project as medium and high 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:
Envirotech Engineering Elkinton Geological Assessment
Ph. 360-275-9374 page 6 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
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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. Although DNR designated slope instability, 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. Based on the observed soils and
topography, 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.
Envirotech Engineering Elldnton Geological Assessment
Ph 360-275-9374 page 7 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
4.1.2 Septic Drainfield Impacts
The approximate locations of the future 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. 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 from the
proposed drainfield location.
4.1.3 Surface and Subsurface Drainage
Other than the limits of Bear Creek,this Project does not appear to experience significant
subsurface drainage, surface runoff or water flow. It is our opinion that groundwater or
surface drainage is not a limiting factor for this Project.
The 1998 FEMA flood map indicates potential flooding from Bear Creek to a distance of
over 90 feet from the center of the channel. However, indications of past flooding on the
property were not observed during the site visit, and the proposed residence is located
outside the potential flood hazard with relation to FEMA mapping. For development
other than what is outlined in this report,finished floor elevations should be at least 2 feet
above the high water flood elevation.
4.1.4 On-Site and Off-Site Impacts
From a geotechnical perspective, it is Envirotech's opinion that the Project and adjacent
properties, both upslope and downslope from the planned site alterations should not be
negatively impacted. Existing stable slopes, best management practices during
construction, and anticipated post-development stable slopes does not warrant on-site or
off-site concerns.
4.2 Erosion Hazards
Based on the USCS description of the Project soils, the upper soils are considered to have a
moderate to high erodibility factor. DNR designated a high erosion hazard on the ascending
slopes. Based on the proximity and nature of the development,temporary erosion is not necessary
for this Project. The gentle grades will perform as a vegetated filter strip during light construction
activities. Permanent erosion protection should consist of standard water outflow protection and
energy dissipation from roof runoff and other pipe outlets.
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.
Envirotech Engineering Elkinton Geological Assessment
Ph 360-275-9374 page 8 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
There are no known faults beneath this Project. The nearest Class `A' or 'B' fault to this property
is the Tacoma Fault Zone. This fault is a Class `A,` and is located approximately 7 miles to the
south 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
Site development that significantly deviates from the anticipated improvements presented in this
report may require geotechnical design recommendations.
Emvirotech Engineering Elkinton Geological Assessment
Ph. 360-275-9374 page 9 Parcel 12309 42 00000
Fax:360-2754789 Mason County,Washington
August 6,2009
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,
Enviroteck Engineering
Michael Staten, P.E.
Geotechnical Engineer
Envirotech Engineering Elkinton Geological Assessment
Ph 360-275-9374 page 10 Parcel 12309 42 00000
Fax:360-275-4789 Mason County,Washington
August 6,2009
APPENDIX A
SITE PLAN
SCALE, 1 INCH IN FEET
GR
0 25 50 100
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Q
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APPRX
LOCATION OF
EXISTING
BUILDING
Tel rl7
TP2
A
AREA OF
PROPOSE] PROPOSE
SINGLE SEPTIC
HF FAMILY DRAINFI LD
B<4p �5�/ RESIDENCE
cRFFk !� CAPPRX>
R�
PROJECT/ OWNER/ LOCATION
ELKINT❑N
GE❑L❑GICAL ASSESSMENT
VIRGIL ELKINTON
100 BEAR CREEK DEWATTO ROAD
PARCEL NO 12309 42 60000
MASON COUNTY WASHINGTON
ENGINEER-
LEGEND ENVIROTECH ENGINEERING
74 NE HURD ROAD
2/.t SLOPE INDICATOR BELFAIR, WASHINGTON 99529
360-275-9374
TPI a TEST PIT
SITE PLAN
APPENDIX B
SOIL INFORMATION
W A T 6 R W E L L R E P O R T Start Card No W124793
Unique Well I D # AFB183
G C3 Z STATE op WASHINGTON Water Right Permit No
Q '1) OWNE."Name NELSON -KERN= MARnOUy(=J====3 Ad ------" _ ` ` �is= --
r. Address BEAR CR/DBWATIO3D BELFJLIR, WA 99528�"'iiY-=-6E=:.:.:__..
;2) LOCATION OF WELL County MASON - B] 1/4 SE 1/4 Sec 9 T 23N N , R 1W 'nM
(2a) STREET ADDRESS of WEAL (or nearest address) NJ 211 BEAR CK/DEWATrO RD, BELPAIR
____'.................._________==__......... _..________-----=a=`-------------'
4) ;3) PROPOSED USE DOMESTIC I (10) WELL LOG
---------------------------------------------------------------
;4) 7YP6 OP WORK Owner's Humber of well I Formation Describe b color character, size of material
H (IE more then one) I and structure, and show thickness of aquifers and the Lind
S NEW WELL Method CABLE I and nature of the material in each stratum penetrated, with
ir ..........__________.. ...•........... at least one entry for each change in formation
C ;5) DIMENSIONS Diameter of well 6 inches I---------------------------------------------------------------
G Drilled 173 ft Depth of completed well 273 ft I MATERIAL I FROM I TO
r_ .............:..a=...._.________•'•......................_.......I TOP SOIL AND GRAVEL I 0 13
Q -6) CONSTRUCTION DETAILS I BROWN CEMEKTIM GRAVEL CLAY 13 ( 21
r Casing installed 6 Dia from +1 5 Et to 169 5 ft I BROWN CLAY AND GRAVEL 121 [ 35
WELDED CASING • Dia from ft to ft I BROWN CLAY SAND SOME GRAVEL 135 1127
Diaf omftto ft I GRAY CLAY FINS SAND WET 127 1171
------------------------ -- ----_-- -- ---_--____-I MEDIUM SAND GRAVEL 6 WATER 1171 I L73
0 Perforations NO I
= '.N pa of perforator used I t
SIZE of perforations in by in I
Z perforations from ft to ft I I ,
perforationa from ft to ft I I I
L perfcratione from ft to ft
O -------------------------------—----------------------I i
Screens YES I
= r9anUfacturer•s Name HOUSTON I [
(a Type SLOTTED Model NO I I [
Diam 5 slot size 014 from 168 ft to 173 ft I I I
.�.� Diam clot size from ft to ft I ( I
R ----------------------------------------E
Gravel packed NO Size of gravel I I
Gravel placed from ft to ft I I I
t ----------------------------------------------------------f
4W Surface seal YES To what depth' 20 ft I
>1 Material used in seal BRMTONITE
= Did any strata contain unusable water' NO I ���`] I I
Type of water' Depth of strata ft I 'r/ iL'-'_'t
L. Method of coaling strata off
tug - ---------------------------------
tu
(7) PUMP Manufacturer's Name � • L B " 2 2001
I
Type H P I I I
v• t s
O 18)`WATER LEVELS =•`6L =' Land-surface elevation j VVa�hln`,to it State I I
Z above mean sea level ft I Depasunent of E«Iogy I I
H Static level 47 ft below top of well Date 01/09/01 I I I
Artesian. Pressure lbe per square inch Date I I I
Arteziar. water contro_led by O I I I
0 I Work started 12/07/00 completed 01/09/01
(9) WELL TESTS 'Drawdown -el amount waterlevel is lowered belowI WELL CONSTRUCTOR CERTIFICATION
O Dtatic lev I I constructed and/or accept responsibility for con-
Was a punp test made', N0 if yes, by whom' I struction of this well, and its compliance with all
C Yield gal /min w-th ft drawdown after hrs I Washington well construction standards Materials Used
V I and the information reported abote are true to m/ best
W I knowledge and belief '
O Recovery data I I
Time Water Level Time Water Level Time Water Level I NAME ARCADIA DRILLING INC
(Person, firm, or corporation) (Type or print)
C I I
ADDRESS SS 170 WALKJy PARK RD
Date of test4.0
L Haller test 8 5 gal/min 77 ft drawdown after 1 hrs I [SIGNEW License No 1992
aAir test gal/min w] stem set at ft for hre I
4) Temperature
flow g p m Data I Contractor's
Q ......
...e_ature of-water
.....___._.=............chemical-ana=]7fl1=made' NO=- =-� Registration ----------i_----- - ARCADDIO SB KI Date......
==-......
W=................
4)
s
H
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Elkinton Geological Assessment DATE OF LOG: 07/31/2009
PROJECT NO: 0903 LOGGED BY: MCS
CLIENT: Manke Lumber Company EXCAVATOR: N/A
LOCATION: Parcel 123094260000 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 . .. .......... . .... .... ...... ..... . .......... . . .. . .
SM-SC Brown, moist, medium dense SILTY
CLAYEY SAND with GRAVEL.
Low-medium plasticity. Sand is mostly
1 fine.
2 Excavation terminated at approximately
2.0 feet
3
4
5
6
7
8
9
10
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.
TEST PIT LOG
TEST PIT NUMBER TP-2
PROJECT: Elkinton Geological Assessment DATE OF LOG: 07/31/2009
PROJECT NO: 0903 LOGGED BY: MCS
CLIENT: Manke Lumber Company EXCAVATOR: N/A
LOCATION: Parcel 123094260000 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
s
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
SM-SC Brown, moist, medium dense SILTY
CLAYEY SAND with GRAVEL.
Low-medium plasticity.
1 Excavation terminated at approximately
1.0 foot
2
3
1
i
t 1
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i
e i I a I
i I
e
5 u
a a
t
1 p I
1 F
« 1 1
f G t
� 6 A I 1
S 1
p I X
1 1 I
t
y 7 e 8
s I
I 1
e i 11
8 I
t 1 1
� t 1
P t
I9
3 1 1
Y
e i
i
i I i
110 a i
a
3
i t
b 1
1
1
No Groundwater Encountered
ENVIROTECH ENGINEERING
This intormation pertains only to this boring and should not be Geotechnical Engineering
interpreted as being indicitive of the entire site.