HomeMy WebLinkAboutGEO2014-00041 for BLD2014-00727 - GEO Geological Review - 7/30/2014 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
P10
(360)427-9670
Geotechnical Assessment Review Acceptance Letter
August 27, 2014
SEAN DEREK-ALLEN
331 E KUHN
UNION WA 98592
Case No.: GE02014-00041
Parcel No.: 322325050035
Proiect Description: REPLACE SFR WITH MANUFACTURED HOME
The Geotechnical Assessment for SEAN DEREK-ALLEN has been received and reviewed by the
Planning Department. The assessment was prepared by M Staten dated 7/30/2014.
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.EA. 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:
8/27/2014 Page 1 of 1 GE02014-00041
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
intemally 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: �ore(c, lal
Z0� �07 Permit# e2 Parcel # J2Z32 5Dd
' _t1
Date(s)of the Document(s) reviewed: �J
(1) A discussion of geologic conditions in the general vicinity of the
proposed development,with geologic unit designation based
on referenc maps.
OK? Comment:
(2) (a)A discu ion of the ground water conditions at the site,
OK? Comment:
(b) A di scu ion of the estimated depth to ater
OK?_ Comment: �1
(c) A discu ion of the quantity of s ce seepage
OK?Comment:'
(d) A discussion of the upslope geomorphology
OK?��Comment:
(e) A disc sion of location of upland waterbodies and wetlands.
OK?Comment:
(3) The appro mate 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 Ound or ground cracks,terraced topography indicative of landslide block
movemen , bowed or arched trees indicating downslope rPovement, etc.).
OK? V Comment:
(5) A discussion of the history of landslide activity in the vicinity, as available in the
reference¢/maps and records.
OK. V Comment:
(6) An opinion on whether the props 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 pronnAed development.
OK? VV Comment:
(7) A recommendation by the prepare whether a Geotechnical Report should be required to
further evaluate site conditions and th ropo d development of the subject property.
OK? Comment: pq
(8) If the presence of a hazard is determirfedlLwIthin 300 feet of the proposed development,
then the follo ing are delineated on a geologic map/site map:
(a) the are of the proposed develop t,
OK? Comment:
Page 1 of 2 Form Effective June 2008
► (b) the bou daries of the landslide hazard area (top, both sides, and toe),
OK? Comment:
G� r� (c) the ass fated buffers (top, both sides, and toe)
OK? L.1 Comment:
(d) building r other setbacks (top, both sides, and toe).
OK? Comment:
(9) A site map dra n to scale showing the property boundaries,scale, north arrow, and the
location and ature of existing and proposed development on the site.
OK? Comment: aAf
Are the.Document(s)signed and stamped? r�
Type and#of License: �I/ 0 Q� J
If not approved, what is the next actionlrecommendation for further action?
2 /
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
�2DIq- fl
Geological Assessment
for
Derek Single Family Residential Property
320 E Kuhn Ave.
Union, WA
Parcel No. 32232-50-50035
Mason County, Washington
July 30, 2014
Project#1492
Prepared For:
Sean Derek
5321 Tyrone Ave. `G4P�oF wASys�9
Sherman Oakes, CA 91401 4
Prepared By: 045
�A STVI
Envirotech Engineering �sSIONALE�'G�
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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 S Dlzle'k Pa�rc)el# 32 Z 3 Z' .6-0 -500 35
Site Address .32 C /�a h n A✓� C/n,on
(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) 5
(e) A discussion of location of upland waterbodies and wetlands.
Located on pages) 3
(3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
Located on page(s) 9
v
(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) �f
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and records.
Located on page(s) 0
(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) f'
(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)
(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,
Located on Map(s) A✓1,4
(b) the boundaries of the landslide hazard area (top, both sides, and toe),
Located on Maps) &IIA
(c) the associated buffers (to both sides, and toe)
Located on Map(s)
(d) building or other setbacks (top, both sides, and toe).
Located on Maps)
(9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the
location and nature of e)dst�:r� nd proposed development on the site.
Located on Maps) //VV
hereby certify under
penalty of perjury that 1 13m a civil engineer licensed in the State of Washington with specialized
knowledge of geotechnical/geological engineering or a geologist or engineering geologist
licensed in the State of Washington with special knowledge of the local conditions. I also certify
that the Geological Assessment, dated a 39 201 , and entitled 114-c k
z;ine/'t' vti;'� kc-5;kOhu 1 01�7e-r l meets all the requirements of the
Mason ounty Resource Ordinance, Landslide H zard tection, 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)
. (1
o ,p 43045 lisp
TSq
oNA,L��v
Disclaimer: Mason County does not certify the quality of the work done in this Geological
Assessment.
Page 2 of 2 Form Effective June 2008
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
2.2.1 Upslope Geomorphology.............................................................................................................3
23 SURFACE DRAINAGE...........................................................................................................................3
2.3.1 Upland Water Bodies..................................................................................................................3
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...............................................................................................................................7
4.0 ENGINEERING CONCLUSIONS.......................................................................................................8
4.1 LANDSLIDE HAzARDS.........................................................................................................................8
4.L I Landslides and Slope Stability Analysis...................................................................................10
4 L2 Surface and Subsurface Drainage...........................................................................................11
4.2 EROSION HAZARDS...........................................................................................................................11
4.3 SEISMIC HAZARDS............................................................................................................................11
4.4 OTHER CONSIDERATIONS.................................................................................................................12
5.0 CLOSURE............................................................................................................................................13
Appendix A- Site Plan
Appendix B-Soil Information
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed this geological assessment for a residential
property located at 320 E Kuhn Ave Union, Washington , identified as parcel number 32232-50-
50035 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 without
the property owner or owner's representative on July 15, 2014. 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).
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's representative, and
observations from a field visit by Envirotech. The property consists of an existing house to be
demolished, driveway, and on-site septic features. The proposed development is expected to
consist of a new single family residence and other common ancillary features. 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 Derek Geological Assessment
Ph.360-275-9374 page 1 Parcel 32232-50-50035
Fax: 360-2754789 Mason County,Washington
July 30,2014
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Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 2 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on July 15,
2014 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 consists of a house and existing drainfield and is surrounded by rural
residential development. E Kuhn Avenue extends along the south side of the property, and Hood
Canal is located over 900 feet to the north.Vegetation on and near the property consists primarily
of maples, firs, 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 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 on and beyond the property. Except for modified
slopes, average slope grades are approximately 24% with a vertical relief of approximately 80
feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the south 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 hillside. Landforms are
primarily of glacial origin with centuries of weathering overburden. Additional
geomorphology that is pertinent to both upslope and downslope areas are provided in the
Subsurface Investigation Section of this report.
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.
23.1 Upland Water Bodies
There are no apparent water bodies or wetlands located upslope from the planned
development that would significantly influence the Project.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 3 Parcel 32232-50-50035
Fax: 360-275-4789 Mason County,Washington
July 30,2014
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,
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 Photo from Mason County Website
i
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 4 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
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 15, 2014 by Michael Staten,
geotechnicai 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 probing anticipated
foundation areas with hand tools, and observing soils within test pit excavations and/ or earth
cuts. 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.
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.
The"Geologic Map of the Skokomish Valley and Union 7.5-minute Quadrangle, Mason County,
Washington' by Michael Polenz, Katelin Alldritt, Nicholas J. Hehemann, Isablle Y. Sarikhan,
and Robert L.Logan,July 2010,provides the following caption(s)for the project area:
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 5 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
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Vahon advance outwash—Pebbles,cobbles_and sand-,gray to tan;generally compact,but
commonly cohesionless;clasts well rounded,well sorted,clean;very thinly to thickly bedded-
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 ttie soft, susceptiDnity for potential tanasitaes, erosion anu seismic
hazards may be assessed.
Except where fill is present, competent bearing soils were encountered at 12 inches below the
existing native ground surface in locations where the ground was probed. For engineering
purposes,these native soils consist of distinguishable layers,as presented below.
Soils within the upper 5 feet of natural ground were observed to be primarily moist, brown silty
sand with gravel (SM). Soils below the upper SM layer were observed to be a dense outwash of
predominantly sand and gravel with few fines. 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.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 6 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
According to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Conservation Service (SCS), the site soils are described as Alderwood gravelly
sandy loam, A, with 15% - 30% slopes. See the soil map below, and the applicable SCS soil
profile(s)in Appendix B of this report.
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Project
Soil Survey From USDA Natural Resources Conservation Service
33.1 Groundwater
From the water well report(s)and knowledge of the general area,permanent groundwater
is over 50 feet directly below the property at the building pad location. Surface seepage
or perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports.
Envirotech Engineering Derek Geological Assessment
Ph. 360-275-9374 page 7 Parcel 32232-50-50035
Fax:360-275-4789 Mason County,Washington
July 30,2014
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 of 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. This
conclusion is based on the contents provided in this report.
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 Coastal Zone Atlas of Mason County, Washington, the Project is within and
near terrain labeled `Stable' and `Intermediate' regarding potential landslide activity. Stable
..1,. ,.11. ,.t p. ♦.. 1...,,7..1:,7„ .7, tC -11 —A— —A nni.�+r+m��ntin.r noi+lnns.
Historically, intermediate terrains have no known landslides. A site specific analyses and
conclusions concerning the slopes are presented herein. A Stability Map from the Coastal Zone
Atlas for the general area of this Project may be found below.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 8 Parcel 32232-50-50035
Fax:360-275-4789 Mason County,Washington
July 30,2014
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Map from Washington State Department of Ecology Website
According to the Department of Natural Resources (DNR) "LHZ— Final A-1 Map — Landslide
Inventory—Mason Watershed, by Sarikhan, et. al., May 2007,"previous landslide activity is not
recorded near the project. Per the Resource Map from DNR, the Project is not within terrain
labeled `highly unstable' or `highly erodible' relating to soils. DNR labeled portions to the north
of this project as medium to nigh slope mstamuty witn relation to slopes. i nis 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 Derek Geological Assessment
Ph.360-275-9374 page 9 Parcel 32232-50-50035
Fax:360-275-4789 Mason County,Washington
July 30,2014
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4.1.1 Landslides and Slope Stability Analysis
Past landslide activity or high slope instability indicators 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 and Subsurface Conditions Sections of this report. Due to these factors, and
existing/proposed conditions,a slope stability analysis was not deemed necessary for this
Project. Considering the planned construction as summarized in the Introduction Section
of this report; the aforementioned surface and subsurface conditions for the Project; the
slope stability assessment provided herein; and the Engineering Conclusions provided
later in this report, it is our opinion that the Project is not within a landslide hazard area,
and that the proposed site alterations will not encourage a landslide hazard.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 10 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
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 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), Harstine Gravelly
Sandy Loam on slopes 15%or greater(Hb),and Kitsap Silt Loam on slopes 15%or greater(Kc).
Since the project is within an erosion hazard area as defined by the MCRO,an engineered erosion
control plan may be required by the County. Although the site meets the definition of an erosion
hazard, it is our understanding that work will be performed on slopes of less than 15%, which is
more conducive of an Ab soil type.
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
• , rr_ _� r_.__i --_7. 17--- IrL:- l..4 .. 1-1 - 6D G n..� :n l..nµ+o.l n ,.nv:mntAly 1 C mil-C to
1J UIV I1VVu\-,Wlal 1 UUU.L MMI. 11110 1aa1u 1u u—.-.a ✓, = ..,1.,.. ... ..YY..,...... ...J - .-
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.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 11 Parcel 32232-50-50035
Fax:360-2754789 Mason County, Washington
July 30,2014
4.4 Other Considerations
The existing house and deck are partially located on fill soils. It is our understanding that the
proposed home will be located outside of any fill material. If the proposal changes, and any
structures are located within the footprint of the existing fill, additional geotechnical studies are
required.
Conclusions in this report are based on the type and location of the anticipated development, and
existing on-site and off-site conditions. Site development that significantly deviates from the
anticipated improvements presented in this report, or nearby development that influences this
Project may require geotechnical design recommendations.
Envirotech Engineering Derek Geological Assessment
Ph.360-275-9374 page 12 Parcel 32232-50-50035
Fax:360-2754789 Mason County,Washington
July 30,2014
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
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 Derek Geological Assessment
Ph.360-275-9374 page 13 Parcel 32232-50-50035
Fax:360-275-4789 Mason County,Washington
July 30,2014
APPENDIX A
SITE PLAN
SCALE- 1 INCH = 30 FEET
0 is 0
150FT
X�
cu
N
TPI@
ROPERTY LINE APPRX
EXISTING
SEPTIC
PO
APPROXIMATE LIMITS--,<
OF EXISTING FILL
r
h IEXISTING HOUSE
PROPOSED BUILDABLE
AREA FOR NEW HOUSE
PQ PO 41
X
EXISTING DRIVEWAY
E KUHN AVENUE
M�0
PROJECT/ OWNER/ LOCATIONi
SINGLE FAMILY PROPERTY
GE❑L❑GICAL ASSESSMENT
SEAN DEREK
NOTES- 320 E KUHN AVENUE
1. SLOPE INDICATORS WERE FIELD MEASURED BY ENVIROTECH, AND/ OR PARCEL 32232-50-50035
EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE WHERE APPROPRIATE. UNION WASHINGTON
2. BOUNDARIES ON THIS SITE PLAN WERE NOT PREPARED BY A LICENSED LEGEND ENGINEER,
SURVEYOR. LOCATIONS OF SITE FEATURES AND GEOLOGICAL/ SUBSURFACE ENVIROTECH ENGINEERING
DESIGNATIONS AS SHOWN HERE, WITH RELATION TO THE PROPERTY LINES PO BOX 984
MUST BE VERIFIED BY THE OWNER. THE CONCLUSIONS AND SLOPE INDICATOR BELFAIR, WASHINGTON 98528
RECOMMENDATIONS PROVIDED IN THE GEOTECHNICAL/ GEOLOGICAL REPORT ARE BASED ON GEOLOGIC AND SPECIFIC SUBSURFACE FEATURES THAT MAY Po PROBE 360-275-9374
BE LOCATED ON AND OFF THE PROPERTY, AND ARE NOT NECESSARILY
BASED OFF OF PROPERTY LINES SHOWN ON THIS SITE PLAN. TPIJ@ TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geological Assessment DATE OF LOG: 07/15/2014
PROJECT NO: 1492 LOGGED BY: MCS
CLIENT: Sean Derek EXCAVATOR: N/A
LOCATION: Parcel 32232-50-50035 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI F
URVE
AND TEST DATA
DEPTH N30 50
0 .. . . . . . . . . . . .. . . .. . .. . . ... . . . . . .. .... ...... .
SM Brown, moist, medium dense SILTY
SAND with GRAVEL. Gravel is fine and
subrounded. Sand is primarily coarse.
1 Non plastic.
2
3
4
very dense, granular
Z-5 t:U
Excavation terminated at approximately
5.0 feet
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.
Mason County, Washington
Ac—Alderwood gravelly sandy loam, 15 to 30 percent slopes
Map Unit Setting
• Elevation: 50 to 800 feet
• Mean annual precipitation: 25 to 60 inches
• Mean annual air temperature: 48 to 52 degrees F
• Frost-free period: 180 to 220 days
Map Unit Composition
• Alderwood and similar soils: 100 percent
Description of Alderwood
Setting
• Landform: Drainageways
• Parent material: Basal till with a component of volcanic ash
Typical profile
• H1 -0 to 10 inches: gravelly ashy loam
• H2 - 10 to 28 inches: very gravelly loam
• H3 -28 to 60 inches: gravelly sandy loam
Properties and qualities
• Slope: 15 to 30 percent
• Depth to restrictive feature: 24 to 32 inches to densic material
• Natural drainage class: Moderately well drained
• Capacity of the most limiting layer to transmit water(Ksat): Very low to moderately low
(0.00 to 0.06 in/hr)
• Depth to water table: About 18 to 36 inches
• Frequency of flooding:None
• Frequency of ponding: None
• Available water storage in profile: Low(about 3.4 inches)
Interpretive groups
• Farmland classification: Farmland of statewide importance
• Land capability classification(irrigated): None specified
• Land capability classification(nonirrigated): 4e
• Hydrologic Soil Group: C
• Other vegetative classification: Unnamed (G002XN302WA)