HomeMy WebLinkAboutGEO2019-00009 for BLD2019-00133 GEO2019-00010 for BLD2019-00120 - GEO Geological Review - 1/24/2019 i' �EoZziq - WC09 - S I
C�E,6Zot9 - 000to - Try) VE
F&)--F)id
PLANNING
�1d 20 tq - 0 0 I2o � i r�
RECEIVED
FEB 19 2019
615 W. Alder Street
Geological Assessment
for
Zdilar Single Family Residential Property
581 E Bay Heights Drive
Parcel No. 12229-78-90053
Mason County, Washington
January 24, 2019
Project#1909
Prepared For:
Mike Zdilar CLYbr sT
PO Box 1394
Allyn, Washington 98524
Prepared By:
43045
Envirotech Engineering, PLLC f ss, NIA
PO Box 984 1/26/19
Belfair, Washington 98528
Phone: 360-275-9374
MASON COUNTY submittal Checkii5,
COMMUNITYSERVICES Building,Planning,Envitonment.il Health,Community Health 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 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 Mike Zdilar Parcel# 12229-78-90053
Site Address 581 E Bay Heights 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) 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) 5
(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) 10
(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 2018
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................................................................................................3
3.0 SUBSURFACE INVESTIGATION.....................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5
3.2 GEOLOGIC CONDITIONS.....................................................................................................................5
3.3 SPECIFIC SUBSURFACE CONDITIONS.................................................................................................6
3.3.1 Groundwater............................................................................................................................... 7
4.0 ENGINEERING CONCLUSIONS......................................................................................................8
4.1 LANDSLIDE HAZARDS.........................................................................................................................8
4.L] Landslides and Slope Stability Analysis................................................................................... 10
4.L2 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
rf
LCl.
laa
tir
l�1
ii
ff 1
l
® MASON COUNTY
COMMUNITY SERVICES
\ Building,Planning,Environmental Health,Community Health Geological Assessment
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 24, 2019, and entitled Zdilar Single Family Residence, 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 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
C LY bC ST
43045
GFf, f C/STT:.R�, ,fir
sS�UL 4L L 01126119
Rev. February 2018
Page 2 of 2
Disclaimer:Mason County does not certify the quality of the work done in this Geological Assessment.
1.0 INTRODUCTION
Envirotech Engineering, PLLC. (Envirotech) has completed this geological assessment for a
residential property located at 581 E Bay Heights Dr, identified as parcel number 12229-78-90053
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
January 17,2019.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 proponent of the property, and
observations from a field visit by Envirotech.The proposed development is expected to consist of
a new 24 x 36 pole building to complement the existing single family residence.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 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 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 Zdilar Geological Assessment
PO Box 984 page 1 Parcel 12229-78-90053
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019
(a",I
N
A
Project
Vicinity Map from Mason County Website
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 2 Parcel 12229-78-90053 LQ
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019
4.
1)
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on January
17, 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 property currently has an existing single family residence,a detached garage,and is surrounded
by residential development. E Bay Heights Drive extends along the west side of the property, and
Gills Cove Drive is located immediately to the North.Vegetation on and near the property consists
primarily of firs, maples, 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 on and beyond the property. Average slope grades
are approximately 30%with a vertical relief of approximately 40 feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the northwest of the planned development.This slope is
relatively minor within 300 feet of the Project,with an apparent slope grade of approximately 25%.
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.
2.4 Slope and Erosion Observations .,
The existing moderate slopes near the Project signal a potential landslide or erosion hazard area.
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 3 Parcel 12229-78-90053 y
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019 +
�r�
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_uot_nbserveo 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.
i
z T ,
Aerial Photo from Mason County Website
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 4 Parcel 12229-78-90053
Belfair,Washington 98528 Mason County,Washington 4
(360)275-9374 January 24,2019
ry,1
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 17,2019 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, 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 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 tilt--Un tratified 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 arc very angular,pebble-to boulder-size clasts are commonly striated and faceted.
having angular and(or)rounded edge.-%;boulders arc generally disseminated and relatively rare,
may contain interbeds ol'%and and gravel.The surface of this unit is characterized by streamlined
drumlins,striations,and flutes that are generally hundreds to thousands of tcet 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 wnd and ravel or unit O s. Vashon till local) crosscuts older
b Y 90 Y ,...�
sediments,forming angular unconfonnitics. thug folding and horizontal shearing may occur at
the base of the till or internally between layer%of till,especially in thick deposits.Unit Ogt ("
range%in thickness from 0 to at least 50 ft. :
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 5 Parcel 12229-78-90053 11!
Belfair,Washington 98528 Mason County,Washington ;ak
(360)275-9374 January 24,2019 � :
POO �
OIE y
JD
r r
f i U6 rL s'� Ogtoat
Ogcfs r _R Cylrysh
Oa b
1 r�''J,jJ��ary.] �•'A'e scarp -W;
Vdf pVf IACOA(q' FAUp Qb I
x
QD
oa...
.yy Oaf
QK
`1r t
�'.
rh, Ogt
Oat
i
Je
kY� MILE
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 3 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 Sinclair shotty loam, So,with 5%- '
15% slopes. See the soil map below, and the applicable SCS soil profile(s)in Appendix B of this
report. �f
{�1
Envirotech Engineering,PLLC Zdilar Geological Assessment t.r.
PO Box 984 page 6 Parcel 12229-78-90053 Ld
Belfair,Washington 98528 Mason County,Washington `=
(360)275-9374 January 24,2019
C,.r'j
A
t -
.
0 m 100 ab
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 at least
50 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 directly above the hardpan on occasion.
t:)
t.C"r
u6
„f
t.t•�
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 7 Parcel 12229-78-90053
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019 S
L
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.
t'1
')
U"i
C�1
)
f'1
Envirotech Engineering,PLLC Zdilar Geological Assessment CL
PO Box 984 page 8 Parcel 12229-78-90053 IIJ 7
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019 +=C
toms
/ aatn sr�r' ,
Ally n-U.Mn t orp or
pin .r KOtn
Project
florin Ba p
�21-.__�__�r
w2
f'
, l ltody Bay
h�Stable
vJ Intermediate r m
OW Modified I
V Unstable
y Unstable(old slide) •�•
y Unstable(recent slide)
bay
s' //-
0 0.5 imi S'''j/
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 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:
r•l
t+wi
ti 1
rµl
tW•
!w
Envirotech Engineering,PLLC Zdilar Geological Assessment
PO Box 984 page 9 Parcel 12229-78-90053 uJ
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019 ;
LO
4 . Project
l 1
f
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
reveal ring 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 st&bility assessment provided herein; and the Engineering
Conclusions provided later in this repot it is our opinion that the project is not within a landslide
hazard area,and that the proposed site alterations wt not encourage a an slide hazard.
4.1.2 Surface and Subsurface Drainage
This project does not appear to experience significant subsurface drainage or surface runoff. It is ?`
our opinion that groundwater or surface drainage is not a limiting factor for this Project.
4.2 Erosion Hazards
Based on the USCS description of the Project soils, the surface soils are considered moderately
erodible.According to the Resource Map from the Washington State DNR,as provided above,the
Project is not within terrain labeled `highly erodible.' This Project is not within an erosion hazard
area as defined by the MCRO. Erosion hazard areas are those with USDA SCS designations of
River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on slopes 15% or
eater Ac and Ad Clo uallum Silt Loam on slopes 15%or greater Cd Harstine Gravelly Sand 13t• ( )� Q Pe 13re ( )� Y Y
Loam on slopes 15%or greater(Hb),and Kitsap Silt Loam on slopes 15%or greater(Kc). r.j
Envirotech Engineering, PLLC Zdilar Geological Assessment
PO Box 984 page 10 Parcel 12229-78-90053
Belfair,Washington 98528 Mason County, Washington
(360)275-9374 January 24,2019
t
Temporary and/ or permanent erosion control measures may be required for any site when land
disturbance is involved. Erosion control will mostly depend on the timeliness of construction,
moisture content of the soil,and amount of rainfall during construction. Soil erosion typical to the
existing conditions and planned disturbance of this Project include wind-borne silts during dry
weather, and sediment transport during prolonged wet weather. Sediment transport of disturbed
soils could be from stormwater runoff or tracking off-site with construction equipment. Although
an engineered erosion control plan is not warranted for this project, Best Management Practices
(BMP's)should be employed during and after construction.Ordinary BMP's includes silt fencing,
protection of drainage outlets and vegetating denuded areas.
Erosion control information and specifications may be found in the applicable "Stormwater
Management Manual for Western Washington,"prepared by the Washington State Department of
Ecology Water Quality Program.
4.3 Seismic Hazards
Soils immediately below the expected foundation depth for this Project are generally Type D,
corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the
regional seismic zone is 3 for this Project. The estimated peak ground acceleration ranges from
0.50g to 0.60g. This estimation is based on the United States Geological Survey(USGS)National
Seismic Hazard Project in which there is an estimated 2%probability of exceedance within the next
50 years.
The nearest Class `A' or'B' fault to this property is the Tacoma Fault Zone. This fault is a Class
`A,` and is located in the immediate vicinity 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. i"d
Envirotech Engineering,PLLC Zdilar Geological Assessment (..
PO Box 984 page 11 Parcel 12229-78-90053 W
Belfair,Washington 98528 Mason County,Washington ;Z
(360)275-9374 January 24,2019 r_t
[;1
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
V.
Envirotech Engineering,PLLC Zdilar Geological Assessment G.x
PO Box 984 page 12 Parcel 12229-78-90053 �«
Belfair,Washington 98528 Mason County,Washington
(360)275-9374 January 24,2019
i
APPENDIX A
SITE PLAN
111
It 1
Lo
i
t.1,J
(;1
SCALE, I INCH 80 FEET
0 20 4
EXISTING
SINGLE FAMILY
RESIDENCE AND
GARAGE
i
PROPERTY LINE
APPROXIMATE LOCATION
OF TOE OF ASCENDING
SLOPE
l
PROPOSED 24X36 e
POLE BUILDING
• .• 33it
APPROXIMATE LOCATION OF
TOP OF DESCENDING
EXISTING DRIVEWAY SLOPE
PROJECT/ OWNER/ LOCATION-
SINGLE FAMILY PROPERTY
GEOLOGICAL ASSESSMENT
MIKE ZDILAR
NOTES, 581 E BAY HEIGHTS DRIVE
1. SLOPE INDICATORS VERE FIELD MEASURED BY ENVIROTECH, AND/ OR PARCEL 12229 78 90053
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 PO
VASHINGTON 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
Map Unit Description:Sinclair shotty loam,5 to 15 percent slopes—Mason County,
Washington
Mason County, Washington
So—Sinclair shotty loam, 5 to 15 percent slopes
Map Unit Setting
National map unit symbol: 2hn7
Elevation: 0 to 300 feet
Mean annual precipitation: 25 to 50 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 200 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Sinclair and similar soils: 100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Sinclair
Setting
Landform: Till plains
Typical profile
H1 -0 to 11 inches: gravelly loam
H2- 11 to 35 inches: very gravelly loam
H3-35 to 60 inches: gravelly sandy loam
Properties and qualities
Slope: 5 to 15 percent
Depth to restrictive feature: 28 to 42 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 30 inches
Frequency of flooding: None
Frequency of ponding: None
Available waterstorage in profile: Low(about 3.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification (nonirrigated): 4s
Hydrologic Soil Group: B
Forage suitability group: Limited Depth Soils(G002XN302WA)
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 14, Sep 10, 2018
i s[m Natural Resources Web Soil Survey 1/23/2619
Conservation Service National Cooperative Soil Survey Page 1 of 1
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Zdilar Geological Assessment DATE OF LOG: 01/17/2019
PROJECT NO: 1909 LOGGED BY: JEL
CLIENT: Mike Zdilar EXCAVATOR: N/A
LOCATION: Parcel 12229-78-90053 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
Light brown, low moisture, very dense
3 _;•_. : 'hardpan'
Excavation terminated at approximately
3.0 feet
4
5
6
7
8
3
10
`t
•i
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.
GEOZOjo - GYbo ,�
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#: 0 LI2 20 L n CO 13 5 Parcel#'s: /2 2Z47 - 78
Date(s)of the Document(s) reviewed: -f—
!O /a�-
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? P` Comment:
(d) A discussion of the upslope geomorphology,
OK?_��Comment:
(e) A discussion of location of upland waterbodies and wetlands.
OK? I// 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 express on of past slope instability(presence of hummocky ground or ground
cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating
downslope movement, etc.).
OK? ✓ Comment:
5. A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records.
OK?_ --� Comment:
6. An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or
setback and the potential for landslide activity at the site in light of the proposed development.
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:
,&/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? 7 Comment:
Are the Documents signed and stamped? By whom?
License#: A- 45 License type:_R5::�42
f✓
FIRST REVIEW Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by , on G' 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