HomeMy WebLinkAboutGEO2017-00052 BLD2017-00521 - BLD Engineering / Geo-tech Reports - 6/27/2017 C-y�� 2�►�� baosa
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RECEIVED
AUG 18 2017
615 W. Alder Street
Geological Assessment
for
Anderson Single Family Residential Property
E Stretch Island Road N
Parcel No. 12108-75-00070
Mason County, Washington
June 27, 2017
Project#1798
Prepared For:
Don Zech
PO Box 432 P�ti CL ST
Grapeview, Washington 98584wa S
Prepared By:
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Envirotech Engineering �o� '�Fc. ' �ww�
PO Box 984 �'PSI NALtiNG`
Belfair, Washington 98528
Phone: 360-275-9374
Fax: 360-275-4789
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 Terrie Anderson Parcel# 12108-75-00070
Site Address XXX E Stretch Island Road N, Grapeview
(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) 5
(2) (a)A discussion of the ground water conditions at the site,
Located on page(s) 6
(b) A discussion of the estimated depth to water
Located on page(s) 6
(c) A discussion of the quantity of surface seepage
Located on page(s) 6
(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) 6
(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) 4
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and records.
Located on page(s) 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) >>
(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) n/a
(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/a
(d) building or other setbacks(top, both sides, and toe).
Located on Map(s) n/a
(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.
Located on Map(s) Site Plan(app.A)
I, Michael C. Staten hereby certify under
penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized
knowledge of geotechnical/geological engineering or a geologist or engineering geologist
licensed in the State of Washington with special knowledge of the local conditions. I also certify
that the Geological Assessment, dated June 27, 2017 , and entitled Anderson
Single Family Residential Property meets all the requirements of the
Mason County Resource Ordinance, Landslide Hazard Section, 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)
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06/27/17
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
2.3 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...............................................................................................................................6
4.0 ENGINEERING CONCLUSIONS......................................................................................................7
4.1 LANDSLIDE HAZARDS.........................................................................................................................7
4.1.1 Landslides and Slope Stability Analysis.....................................................................................9
4.L2 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
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed this geological assessment for a residential
property located on E Stretch Island Road N, identified as parcel number 12108-75-00070 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 June 23, 2017. 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 proposed development is expected to consist of
a new single family residence, septic system and other ancillary features typical of 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 Anderson Geological Assessment
Ph.360-275-9374 page I Parcel 12108-75-00070
Fax: 360-2754789 Mason County,Washington
June 27,2017
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Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 2 Parcel 12108-75-00070
Fax:360-275-4789 Mason County,Washington
June 27,2017
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on June 23,
2017 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 vacant land, and surrounded by rural residential development. Stretch
Island Road extends along the west side of the property, and Case Inlet is located about '/4 mile to
the west and east of the planned residence.Vegetation on and near the property consists primarily
of 2°d growth 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.
Slopes are variable on the property, and generally descend to a natural drainage swale in the
middle of the parcel. Steepest slope grades are approximately 17% with a vertical relief of
approximately 20 feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the northeast 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 gentle 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.
2.3.1 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 Anderson Geological Assessment
Ph. 360-275-9374 page 3 Parcel 12108-75-00070
Fax: 360-275-4789 Mason County, Washington
June 27,2017
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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Envirotech Engineering Anderson Geological Assessment
Ph. 360-275-9374 page 4 Parcel 12108-75-00070
Fax: 360-275-4789 Mason County,Washington
June 27,2017
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 June 23, 2017 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 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, Q8. 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 Vaughn 7.5-minute Quadrangle, Pierce and Mason Counties,
Washington" by Robert L.Logan and Timothy J. Walsh, December 2007,provides the following
caption(s)for the project area:
Vashon till—Unstratified to moderately stratified,compact,unsorted mixture of clay,silt,sand,
and gravel deposited directly by glacial ice;gray to tan;nearly everywhere in sharp contact with
underlying units;does not drain well as permeability and porosity are low;sand and finer grains
in matrix are very angular;pebble-to boulder-size clasts are commonly striated and faceted,
having angular and(or)rounded edges;boulders are generally disseminated and relatively rare;
may contain interbeds of sand and gravel.The surface of this unit is characterized by streamlined
drumlins,striations,and flutes that are generally hundreds to thousands of feet long.Angular to
subrounded glacial erratic boulders,consisting mostly of plutonic or metamorphic rock,are
common but disseminated on the surface of this unit.Unit may be capped by a few feet of
unsorted and stained ablation sand and gravel or by unit Qgos.Vashon till locally crosscuts older
sediments,forming angular unconformities.Drag folding and horizontal shearing may occur at
the base of the till or internally between layers of till,especially in thick deposits.Unit Qgt
ranges in thickness from 0 to at least 50 ft.
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 5 Parcel 12108-75-00070
Fax:360-275-4789 Mason County,Washington
June 27,2017
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 primarily composed of undisturbed,native soils,without
indications of substantial fill. 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 4 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 an SM hardpan. The
hardpan is believed to extend to depths of at least 50 feet. This is based on nearby well reports,
site geology, and/ or knowledge of the general area. 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 (SCS), the site soils are described as
Lystair sandy loam,La,with 0%- 5% slopes,Bellingham silt loam, Bd,with 0%-3% slopes,and
Harstine gravelly sandy ashy loam, Hb, with 15% - 30% slopes. See the soil map below, and the
applicable SCS soil profile(s)in Appendix B of this report.
Soil Survey From USDA Natural Resources Conservation Service
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. Surface seepage
or perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports.However, some seasonal groundwater is expected to flow directly above the
hardpan on occasion.
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 6 Parcel 12108-75-00070
Fax:360-2754789 Mason County,Washington
June 27,2017
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' regarding potential landslide activity. Stable slopes are generally not
prone to landslides due to small grades and accommodating geology. A Stability Map from the
Coastal Zone Atlas for the general area of this Project may be found below.
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 7 Parcel 12108-75-00070
Fax:360-2754789 Mason County,Washington
June 27,2017
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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 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:
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 8 Parcel 12108-75-00070
Fax:360-2754789 Mason County,Washington
June 27,2017
Project
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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.
4.1.2 Surface and Subsurface Drainage
Except for the natural swale away from the development, 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 MR, as provided above,
the Project is not within terrain labeled `highly erodible.' This Project is within an erosion hazard
area as deemed 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
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 9 Parcel 12108-75-00070
Fax: 360-275-4789 Mason County,Washington
June 27,2017
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).
Per the MCRO,temporary and permanent erosion control measures are required.
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 Westem Washington,"prepared by the Washington State Department of
Ecology Water Quality Program.
43 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 Tacoma Fault Zone. This fault is a Class `A,` and is located approximately 2 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
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 Anderson Geological Assessment
Ph. 360-275-9374 page 10 Parcel 12108-75-00070
Fax:360-275-4789 Mason County,Washington
June 27,2017
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.
PV /4
.
Michael Staten,P.E.
Geotechnical Engineer
Envirotech Engineering Anderson Geological Assessment
Ph.360-275-9374 page 11 Parcel 12108-75-00070
Fax:360-2754789 Mason County,Washington
June 27,2017
APPENDIX A
SITE PLAN
SCALE- I INCH = 100 FEET
0 25 50 100
PROPERTY LINE
790 FT t
l,
IVEWAY
PO
PROPOSED
SINGLE FAMILY
RESIDENCE
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TP1
0
N
PO
WET AREA
SEPTIC
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VET AREA
air
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PROJECT/ OWNER/ LOCATION
SINGLE FAMILY PROPERTY
GEOLOGICAL ASSESSMENT
ANDERSON
NOTES E STRETCH ISLAND ROAD N
1. SLOPE INDICATORS WERE FIELD MEASURED BY ENVIROTECH, AND/ OR PARCEL 12108-75-00070
EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE WHERE APPROPRIATE. MASON COUNTY, 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, TPIO TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geological Assessment DATE OF LOG: 06/23/2017
PROJECT NO: 1798 LOGGED BY: MCS
CLIENT: Anderson/Zech EXCAVATOR: N/A
LOCATION: Parcel 12108-75-00070 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 ILL PI CURVE
AND TEST DATA DEPTH N 10 30 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
Light brown, low moisture, very dense
4 'hardpan'
Excavation terminated at approximately
4.0 feet
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.
Map Unit Description: Lystair sandy loam,0 to 5 percent slopes--Mason County,Washington
Mason County, Washington
Ld—Lystair sandy loam, 0 to 5 percent slopes
Map Unit Setting
National map unit symbol: 2hlz
Elevation: 0 to 750 feet
Mean annual precipitation: 60 to 90 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 140 to 170 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Lystair and similar soils: 100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Lystair
Setting
Landform: Kames, outwash plains
Parent material: Outwash or sandy till
Typical profile
H1 -0 to 4 inches: ashy sandy loam
H2-4 to 16 inches: ashy sandy loam
H3- 16 to 60 inches: sand
Properties and qualities
Slope: 0 to 5 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Somewhat excessively drained
Capacity of the most limiting layer to transmit water(Ksat): High
(1.98 to 5.95 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available waterstorage in profile: Low(about 5.0 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: A
Other vegetative classification: Droughty Soils (G002XN402WA)
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 12, Sep 9, 2016
Natural Resources Web Soil Survey 6/24/2017
Conservation Service National Cooperative Soil Survey Page 1 of 1
Map Unit Description: Bellingham silt loam,0 to 3 percent slopes--Mason County,Washington
Mason County, Washington
Bd—Bellingham silt loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2hjj
Elevation: 0 to 490 feet
Mean annual precipitation: 35 to 60 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 150 to 210 days
Farmland classification: Prime farmland if drained
Map Unit Composition
Bellingham and similar soils: 100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Bellingham
Setting
Landform: Depressions
Parent material., Alluvium, lacustrine deposits and loess
Typical profile
H1 - 0 to 8 inches: silt loam
H2- 8 to 60 inches: clay
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Poorly drained
Capacity of the most limiting layer to transmit water(Ksat):
Moderately low to moderately high (0.06 to 0.20 in/hr)
Depth to water table: About 0 to 12 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Very high (about 12.1 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 5w
Hydrologic Soil Group: C/D
Other vegetative classification: Wet Soils(G002XN102WA)
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 12, Sep 9, 2016
tii).\ Natural Resources Web Soil Survey 6/24/2017
4911i_0 Conservation Service National Cooperative Soil Survey Page 1 of 1
Map Unit Description:Harstine gravelly ashy sandy loam, 15 to 30 percent slopes—Mason
County,Washington
Mason County, Washington
Hb—Harstine gravelly ashy sandy loam, 15 to 30 percent
slopes
Map Unit Setting
National map unit symbol: 2rtvk
Elevation: 200 to 390 feet
Mean annual precipitation: 30 to 55 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 180 to 200 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Harstine and similar soils: 90 percent
Minor components: 10 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Harstine
Setting
Landform: Ridges
Landform position (two-dimensional): Backslope
Landform position (three-dimensional): Side slope
Down-slope shape: Linear
Across-slope shape: Convex
Parent material: Sandy glacial drift with an influence of volcanic
ash over dense glaciomarine deposits
Typical profile
Oi- 0 to 0 inches: slightly decomposed plant material
Oe- 0 to 1 inches: moderately decomposed plant material
Bw1 - 1 to 6 inches: gravelly ashy sandy loam
Bw2- 6 to 14 inches: gravelly ashy sandy loam
Bw3- 14 to 22 inches: gravelly ashy sandy loam
Bw4- 22 to 32 inches: gravelly ashy sandy loam
2Cd1 -32 to 38 inches: gravelly loamy sand
2Cd2-38 to 61 inches: gravelly loamy sand
Properties and qualities
Slope: 15 to 30 percent
Depth to restrictive feature: 20 to 39 inches to densic material
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat): Very
low(0.00 to 0.00 in/hr)
Depth to water table: About 24 to 37 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low (about 4.2 inches)
i)\ Natural Resources Web Soil Survey 6/24/2017
o� Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description:Harstine gravelly ashy sandy loam, 15 to 30 percent slopes—Mason
County,Washington
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: C
Other vegetative classification: Limited Depth Soils
(G002XN302WA)
Hydric soil rating: No
Minor Components
Neilton
Percent of map unit. 5 percent
Landform: Outwash terraces
Landform position (three-dimensional): Riser
Down-slope shape: Linear
Across-slope shape: Linear
Hydric soil rating. No
Indianola
Percent of map unit. 5 percent
Landform: Eskers, kames, terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 12, Sep 9, 2016
I."w' Natural Resources Web Soil Survey 6/24/2017
�� Conservation Service National Cooperative Soil Survey Page 2 of 2
GEO
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:
�
Permit 2,34�" 0,0 Parcel#'s: �Z�0 R70
Date(s)of the Document(s) reviewed: SU nC'
1. A discussion of geologic conditions in the general vicinity of the proposed development,with geologic unit
designation Z:7Comment:
n referenced maps.
OK?
2. (a) A discussions of the ground water conditions at the site,
OK? ✓ Comment:
(b) A discussion of the estimated depth to water,
OK? .,.—/ Comment:
(c) A discussion the quantity of surface seepage,
OK? Comment:
(d) A discussion/�f the upslope geomorphology,
OK? '✓ Comment:
(e) A discussion of location of upland waterbodies and wetlands.
OK?_ Comment:
3. The approximated th 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 m7Comment:
nt, etc.).
OK?
5. A discussion of th istory of landslide activity in the vicinity, as available in the referenced maps and records.
OK? N Comment:
6. An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or
setback and the po ntial for landslide activity at the site in light of the proposed development.
OK? Comment:
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:
Page 1 of 2 Form Effective June 2008
(a) the area of the proposed development,
OK? Comment:
(b) the bou aries 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 pro sed development on the site.
OK? Comment:
Are the Documents signed and stamped? By whom? 6`Q
License#: L} J cj License type: r2_g .
FIRST REVIEW Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by 1` 0 , on �� Time spent in review:
SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by on . Time spent in second review:
THIRD REVIEW/UPDATE ❑ Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
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