HomeMy WebLinkAboutGEO2019-00056 Assessment - GEO Geological Review - 7/18/2019 PL HING
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W AIdor Sh-
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Geological Assessment
for
Pioneer Builders Single Family Residential Property
141-161-171 E Allynview Drive
Parcel No. 12220-58-00007
Parcel No. 12220-58-00008
Parcel No. 12220-58-00009
Mason County, Washington
January 14, 2018
Project#1901
Prepared For:
Pioneer Builders Inc
PO Box 1094
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Port Orchard, Washington 98366 IN
Prepared By: a
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Envirotech Engineering PLLC 43(14s `
PO Box 984 ''
��'�"F 1/14/19
Belfair, Washington 98528•
Phone: 360-275-9374
MASON COUNTY
COMMUNITY SERVICES Geological Assessment
Budding,Planning,Environmental Health.Community Heal!n
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 is found not applicable, the report should explain the basis for the conclusion.
Note: Unless specifically documented, this report does not provide compliance to the International Residential Code Sections
R403.1.7 for foundations on or adjacent to slopes. Section R403.1.8 for expansive soils or section 1808.7.1 of the International
Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Pioneer Builders Parcel # 12220-58-00007 12220-58-00008. 12220-58-00009
Site Address 141 161 and 171 E Allynview Drive
(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) 7
(b) A discussion of the estimated depth to water,
Located on page(s) 7
(c) A discussion of the quantity of surface seepage.
Located on page(s) 7
(d) A discussion of the upslope geomorphology.
Located on page(s) 3
(e) A discussion of location of upland waterbodies and wetlands.
Located on page(s) 3
(3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
Located on page(s) 7
(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) 8
(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) 10
(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.
Rev. February 2016
MASON COUNTY
COMMUNITY SERVICES Geological Assessment
Building.Planning.Environmental Health,Community Health
Located on page(s) 12
(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 (appendix A)
I, Michael 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 Geotechnical
Report, dated January 14, 2019, and entitled Pioneer Builders Single Family Residential Property, meets all the
requirements of the Mason County Resource Ordinance, Geologically Hazardous Areas Section, is complete and true
that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated throuar
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
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Rev. February 2018
Page 2 of 2
Disclaimer:Mason County does not certify the quality of the work done in this Geological Assessment.
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................................................................................I
1.1 Mona 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 Geomorphologv............................................................................................................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............................................................................................................................... 7
4.0 ENGINEERING CONCLUSIONS......................................................................................................8
4.1 LANDSLIDE HAZARDS.........................................................................................................................8
4.1.1 Landslides and Slope Stability Analysis................................................................................... 10
4.1.2 Surface and Subsurface Drainage........................................................................................... 10
4.2 EROSION HAZARDS...........................................................................................................................10
4.3 SEISMIC HAZARDS............................................................................................................................ 11
4.4 OTHER CONSIDERATIONS................................................................................................................11
5.0 CLOSURE............................................................................................................................................12
Appendix A-Site Plan
Appendix B-Soil Information
1.0 INTRODUCTION
Envirotech Engineering, PLLC. (Envirotech) has completed this geological assessment for
adjoining residential properties located at 141, 161.and 171 E Allynview Drive.identified as parcel
numbers 12220-58-00007. 12220-58-00008. and 12220-58-00009 in Mason County,Washington.
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 on
Januart 10.2019. It was determined that natural slopes between 15%and 43%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 proponent of the property, and
observations from a field visit by Envirotech. The proposed development is expected to consist of
a new single family residences and other ancillary features typical of this type of development.
Approximate site development with relation to existing site features are illustrated in the Site Plan
in Appendix A of this report.
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 proiect
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 proponent of the project;
• 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
and hazard 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 development.
Envirotech Engineering, PLLC Pioneer Builders Geological Assessment
PO Box 984 page I Parcels 12220-58-00007,-00008,-00009
Belfair, Washington 98528 Mason County. Washington
(360)275-9374 January 14,2019
M17 st.
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Project
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Vicinity Map from Mason County Website
Envirotech Engineering,PLLC Pioneer Builders Geological Assessment
PO Box 984 page 2 Parcels 12220-58-00007,-00008,-00009
Belfair,Washington 98528 Mason County, Washington
(360)275-9374 January 14,2019
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on January
10, 2019 by a representative 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 properties are currently vacant land with no improvements, surrounded by residential
development. E Allynview Drive extends along the east side of the parcels. Vegetation on and near
the property consists primarily of firs, blackberries, 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
Plan in Appendix A for an illustration of the general slope indicators with respect to the planned
development
Descending slopes exceeding 15% are located beyond the property. Average slope grades are
approximately 25% with a vertical relief of approximately 60 feet. Isolated areas of slopes
exceeding 40% were present, however, the vertical relief appeared to be less than 10 feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the west 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 and crest. 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.PLLC Pioneer Builders Geological Assessment
PO Box 984 page 3 Parcels 12220-58-00007.-00008,-00009
Belfair,Washington 98528 Mason County. Washington
(360)275-9374V January 14,2019
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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Aerial Photo from Mason County Website
Envirotech Engineering,PLLC Pioneer Builders Geological Assessment
PO Box 984 page 4 Parcels 12220-58-00007,-00008,-00009
Belfair,Washington 98528 Mason County, Washington
(360)275-9374 January 14,2019
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was gathered during research and a
site reconnaissance. The site visit was accomplished on January 10, 2019 by a representative 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, QS. 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 Belfair 7.5-minute Quadrangle, Mason, Kitsap and Pierce Counties,
Washington"by Michael Polenz,Katelin Alldritt,Nicholas J. Hehemann,Isablle Y. Sarikhan, and
Robert L.Logan,July 2009,provides the following caption(s)for the project area:
Envirotech Engineering,PLLC Pioneer Builders Geological Assessment
PO Box 984 page 5 Parcels 12220-58-00007,-00008,-00009
Belfair, Washington 98528 Mason County, Washington
(360)275-9374 January 14,2019
Vinhan tit -Unsiomcd,unstratifncd ihut Iocaldy Wndedl mix of clay.silt
sand.and gra\ek typically supported by a sandy matrix:molly gray but
locally ranging to tan,light brow n.or orange.typically um}catherLd:
Wgnrcnt till compact,with fe cnrbling porn rctc.
lot near the.urtacc commonly hackly and lorI 1.va r and om ered by I to
t+It uflw>,e ablation till:dcT,tisited directly by glacial icc and commooniy
Includes clasts or clump,plucked hunt underlying louts_C'lasts are
coinntonly striatcd and faceted.%lily angular or rtwndcd edge.,.BuuklctN
arc gerwraldv spam-uodun the fill Nit largo:terraticI lxouklen otplutonic
OF tttctattwrphic conk arc ctiminon on till surfaces.Sonx exry+suns include
onterbands:mid tense,tN,and and gravel.Ittcalh w ith shears and looms.
Till limn,it ktcallg patchy and seemingly ranktmly distribuictl c+ncr up ro
A several urns of ket thick,wilh it thwkne.c of;to 20 It most einnown.It
typically domualc-�,but is also h.call}dtscontinutou,ton.fluted surtaee,,
with individual drumlin iticasunnh 0.1 to 0.3 mi wide by WN to 1.3 nit
long and the tong axis aligned a ith the dircclion of ice thou Till typically
is in sMrp.unconlhnttabdc camIAO\ugh underlying unit,-nttnt cumrnroh
JJ%ame out%a0%(wfil Ova and subunit►. Ltut(Igt lies stratigraphicaddy
behm unit Og o.It may inclutle unicOtgniicd expostaes of iddrr fill A
chap bt)ttndary nusnlatch lktuccn unit Quit fin the trap and unit Qlvn tin
the Vatiglnt quathmigic'to the mouth 41.(zan and Wakh.2(917)may have
resulted tront a nap-producttkon error in the ntmthwest ciorwr of the
laughs nutp!bosh d.t tan.Hash Do%11 aft Geolog\'and Varth Rce iurcc,.
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Geologic map from Washington D:\'R websire
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
Envirotech Engineering,PLLC Pioneer Builders Geological Assessment
PO Box 984 page 6 Parcels 12220-58-00007,-00008,-00009
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 14,2019
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 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 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 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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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
100 feet below the current ground surface. 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 direct]} above the hardpan on occasion.
Envirotech Engineering. PLLC Pioneer Builders Geological Assessment
PO Box 984 pa,,e _ Parcels 12220-58-00007,-00008.-00009
Belfair, Washington 98528 Mason County. Washington
(360)275-9374 January 14,2019
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 slopes are
generally not prone to landslides due to small grades and accommodating geology. 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. PLLC Pioneer Builders Geological Assessment
PO Box 984 page 8 Parcels 12220-58-00007. -00008,-00009
Belfair, Washington 98528 Mason County. Washington
(360)275-9374� January 14.2019
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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
ed record 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 has not labeled portions of this project
as medium to 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,PLLC Pioneer Builders Geological Assessment
PO Box 984 page 9 Parcels 12220-58-00007,-00008,-00009
Belfair, Washington 98528 Mason County, Washington
(360)275-9374 January 14.2019
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Map from Washington State Department of Natural Resources Website
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
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 'high1,. erodible.' This Project is within an erosion hazard area
Envirotech Engineering. PLLC Pioneer Builders Geological Assessment
PO Box 984 page 10 Parcels 12220-58-00007. -00008.-00009
Belfair, Washington 98528 Mason County. Washington
(360)275-9374 January 14.2019
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).
Temporary and/ or permanent erosion control measures may be required for any site when land
disturbance is involved. Erosion control will mostly depend on the timeliness of construction.
moisture content of the soil. and amount of rainfall during construction. Soil erosion typical to the
existing conditions and planned disturbance of this Project include "N ind-borne silts during dry
weather. and sediment transport during prolonged wet weather. Sediment transport of disturbed
soils could be from stormwater runoff or tracking off-site with construction equipment. Although
an engineered erosion control plan is not warranted for this project, Best Management Practices
(BMP's) should be employed during and after construction. Ordinary BMP's includes silt fencing,
protection of drainage outlets and vegetating denuded areas.
Erosion control information and specifications may be found in the applicable "Stormwater
Management Manual for Western V`'ashington,"prepared by the Washington State Department of
Ecology Water Quality Program.
4.3 Seismic Hazards
Soils immediately below the expected foundation depth for this Project are generally Type D.
corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the
regional seismic zone is 3 for this Project. The estimated peak ground acceleration ranges from
0.50g to 0.60g. This estimation is based on the United States Geological Survey(USGS)National
Seismic Hazard Project in which there is an estimated 2%probability of exceedance within the next
50 years,
There are no known faults beneath this project. The nearest Class 'A' or 'B' fault to this property
is the Tacoma Fault Zone.This fault is a Class 'A,' and is located approximately 1 mile 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. PLLC Pioneer Builders Geological Assessment
PO Box 984 page 1 1 Parcels 12220-58-00007,-00008,-00009
Belfair,Washington 98528 Mason County, Washington
(360)275-9374 January 14,2019
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 ak,,ays 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, PLLC Pioneer Builders Geological Assessment
PO Box 984 page 12 Parcels 12220-58-00007. -00008,-00009
Belfair, Washington 98528 Mason County. Washington
(360)275-9374 Januan, 14.2019
APPENDIX A
SITE PLAN
V
SCALE 1 INCH = 80 FEET
0 20 40 0
i
i
i
PROPERTY LINE
i
PROPOSED
SINGLE FAMILY
RESIDENCE
2S�
PROPOSED DRIVEWAY
BUILDABLE
AREA
r
eI 4,
O�
3
ti
>= APPROXIMATE
LOCATION OF
Q TOP OF SLOPE
18it 4, EXCEEDING 40%
v
43i*
PROPOSED
SINGLE FAMILY
RESIDENCE
PROPOSED DRIVEWAY
PROJECT/ OWNER/ LOCATION,
SINGLE FAMILY PROPERTY
GE❑L❑GICAL ASSESSMENT
PIONEER BUILDERS
NOTES 141, 161, 171 E ALLYNVIEW DRIVE
1. SLOPE INDICATORS WERE FIELD MEASURED BY ENVIROTECH, AND/ OR PARCEL 12220-58-00007, -00008, -00009
EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE WHERE APPROPRIATE. MASON COUNTY WASHINGTON
2. BOUNDARIES ON THIS SITE PLAN WERE NOT PREPARED BY A LICENSED LEGEND ENGINEER1
SURVEYOR, LOCATIONS OF SITE FEATURES AND GEOLOGICAL/ SUBSURFACE ENVIROTECH ENGINEERING
DESIGNATIONS AS SHOWN HERE, WITH RELATION TO THE PROPERTY LINES p0 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. TP1 TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Pioneer Geological Assessment DATE OF LOG: 01/10/2019
PROJECT NO: LOGGED BY: JEL
CLIENT: Pioneer Builders EXCAVATOR: N/A
LOCATION: Parcel 12220-58-00007,-00008,-00009 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 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
4
Light brown, low moisture, very dense
'hardpan'5
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.
Map Unit Description:Alderwood gravelly sandy loam, 15 to 30 percent slopes—Mason
County.Washington
Mason County, Washington
Ac—Alderwood gravelly sandy loam, 15 to 30 percent slopes
Map Unit Setting
National map unit symbol., 2t627
Elevation: 0 to 1,000 feet
Mean annual precipitation: 25 to 60 inches
Mean annual air temperature: 46 to 52 degrees F
Frost-free period: 160 to 240 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Alderwood and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Alderwood
Setting
Landform: Ridges. hills
Landform position (two-dimensional). Backslope
Landform position (three-dimensional): Side slope, nose slope. tall
Down-slope shape: Linear. convex
Across-slope shape: Convex
Parent material: Glacial drift and/or glacial outwash over dense
giaciomarine deposits
Typical profile
A- 0 to 7 inches: gravelly sandy loam
Bw1 - 7 to 21 inches. very gravelly sandy loam
Bw2-21 to 30 inches: very gravelly sandy loam
Bg-30 to 35 inches. very gravelly sandy loam
2Cd1 -35 to 43 inches: very gravelly sandy loam
2Cd2-43 to 59 inches: very gravelly sandy loam
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 to moderately low (0.00 to 0.06 in/hr)
Depth to water table: About 18 to 37 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Very low (about 2.7 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: B
zD� Natural Resources Web Soil Survey 1/13/2019
r Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description:Alderwood gravelly sandy loam,15 to 30 percent slopes—Mason
County,Washington
Forage suitability group: Limited Depth Soils (G002XS301 WA),
Limited Depth Soils (G002XF303WA), Limited Depth Soils
(G002XN302WA)
Hydric soil rating: No
Minor Components
Everett
Percent of map unit. 5 percent
Landform: Kames, eskers. moraines
Landform position (two-dimensional). Backslope
Landform position (three-dimensional): Side slope
Down-slope shape: Convex
Across-slope shape: Convex
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
Shalcar
Percent of map unit: 3 percent
Landform: Depressions
Landform position (three-dimensional): Dip
Down-slope shape, Concave
Across-slope shape: Concave
Hydric soil rating: Yes
Norma
Percent of map unit: 2 percent
Landform: Depressions, drainageways
Landform position (three-dimensional): Dip
Down-slope shape: Concave, linear
Across-slope shape: Concave
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 14, Sep 10, 2018
sDA Natural Resources Web Soil Survey 1/13/2019
i" Conservation Service National Cooperative Soil Survey Page 2 of 2
GEO Zol q- ODDS.
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: P)�ne� 8Ut IkfS
Permit 0 Parcel#'s: Z Z bu - S 9'0 DObY
Date(s)of the Document(s) reviewed: Ta►^ Iq ) 1-01�
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.).
- 7
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.
OK? J 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 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 Documents 2signed and stamped? By whom? A"
License#: 'S License type: �-
FIRST REVIEW XApproved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by on 0 J Time spent in review: l� }✓L 1�-.
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