HomeMy WebLinkAboutGEO2022-00060 COM2022-00059 - GEO General - 12/10/2021 � E 0 2a 2Z • 60oce o
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MASON COUNTY Submittal Checklist
COMMUNITY SERVICES Geological Assessment
Building,Planning.tmuon mental Health,Community Health
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 Local Wrench Inc Local Wrench Parcel# 12329-43-90290
Site Address 100 NE Medical Center Rd
(1) A discussion of the 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 ground water conditions,
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) 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) 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.
Located on page(s) 10
(8) If the presence of a hazard is located within 300 feet of the proposed development,then the following are
delineated on a geologic map/site map:
(a) The area of 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 Geological Assessment
dated 12/10/2021 , and entitled Local Wrench Commercial Facility , 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.
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Disclaimer:Mason County does not certify the quality of
the work done in this Geological Assessment.
Page 2 of 2
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................................................................................................. 5
3.3.1 Groundwater............................................................................................................................... 6
4.0 ENGINEERING CONCLUSIONS &RECOMMENDATIONS......................................................7
4.1 LANDSLIDE HAZARDS.........................................................................................................................7
4.1.1 Landslides and Slope Stability Analysis.................................................................................... 8
4.1.2 Surface and Subsurface Drainage............................................................................................ 8
4.2 EROSION HAZARDS............................................................................................................................ 8
4.3 SEISMIC HAZARDS..............................................................................................................................9
4.4 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................10
4.4.1 Settlement..................................................................................................................................10
4.4.2 Concrete Slabs-on-Grade..........................................................................................................11
4.5 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................11
4.5.1 Excavation.................................................................................................................................11
4.5.2 Placement and Compaction of Native Soils and Engineered Fill...........................................11
4.6 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................12
4.6.2 Infiltration Rates.......................................................................................................................13
5.0 CLOSURE.............................................................................................................................................14
Appendix A-Site Plan
Appendix B -Soil Information
1.0 INTRODUCTION
Envirotech Engineering, PLLC. (Envirotech) has completed this geotechnical/ geological
assessment for a commercial property located at 100 NE Medical Center Rd, identified as parcel
number 12329-43-90290 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
November 19, 2021. 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). In
addition, this report conforms to the requirements outlined in the International Building Code
(IBC) Sections 1603.1.6 and 1803.6.
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 commercial structure, 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. Also, Envirotech addresses the reporting requirements
outlined in the IBC, and further evaluate the project as necessary with respect to geotechnical
constraints in order to provide recommendations that should be implemented during development.
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
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 1 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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.
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Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 2 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on
November 19, 2021 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 is currently vacant land that has been fully cleared and is surrounded by commercial
development. Land modification such as cuts and fills were also observed. NE Medical Center
Road extends along the west side of the property, and an unnamed access road is located
immediately to the south. Vegetation near the property consists primarily of cedars 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 19%with a vertical relief of approximately 25 feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the east of the planned development. This
slope is relatively moderate within 300 feet of the project, with natural slope grades of up
to 24%. Modified slopes of over 40% were observed for the road embankment on
Romance Hill. The upland area of the property is situated on a hillside. Landforms are
primarily of glacial origin with centuries of weathering overburden. Additional
geomorphology that is pertinent to both upslope and downslope areas are provided in the
Subsurface Investigation Section of this report.
2.3 Surface Drainage
The majority of the stormwater runoff originating upslope from the anticipated development is
expected to be moderate. Some scour and erosion was apparent near the project, and appears to be
mitigated.
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 Geotechnical/Geological Assessment
PO Box 984 page 3 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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.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 Geotechnical/Geological Assessment
PO Box 984 page 4 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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 November 19, 2021 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 Belfair 7.5-minute Quadrangle, Mason, Kitsap and Pierce Counties,
Washington" by Michael Polenz, Katelin Alldritt, Nicholas J. Heheman, Isablle Y. Sarikhan, and
Robert L.Logan,July 2009, provides the following caption(s)for the project area:
Alluvial fan -Silt,sand,paavel,and boulders,typically poorly sorted and
stratified. firms concentric lobes where streams emerge from confining
valleys and reduced gradients cause sediment load to be deposited.
Subunit(hoaf identities relict late llolocene(or in at least one instance
prohahh V.1,hon rece,%ionall alluvial fans that resemble unit Qaf in cvcr\
3.3 Specific Subsurface Conditions
The following subsurface conditions are estimated descriptions of the project subgrade utilizing
information from the depth of penetration at all testing, sampling, observed and investigated
locations. Soils for this project were described utilizing the Unified Soil Classification System
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 5 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
(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, with indications of up to ten feet
of fill. Competent bearing soils were encountered at 12 inches below the existing native ground
surface in locations where the ground was probed. Fill areas were not tested. For engineering
purposes,these native soils consist of distinguishable layers,as presented below.
Soils within the upper 2 feet of natural ground were observed to be moist, brown silty sand with
gravel (SM). Soils below the upper SM layer were observed to be grey, low moisture, silty sand
with gravel (SM), locally known as 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 Everett very gravelly
sandy loam, Eh, with 8% - 15% 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 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.
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 6 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
4.0 ENGINEERING CONCLUSIONS & RECONMIENDATIONS
The following sections present engineering assessments and conclusions and recommendations
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 Department of Natural Resources (DNR) "LHZ — Final A-1 Map — Landslide
Inventory — Mason Watershed, by Sarikhan, et. al., May 2007," previous landslide activity is
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:
Envirotech Engineering GeotechnicaV Geological Assessment
PO Box 984 page 7 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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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 revealed during the project research. However, 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 `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 greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd),
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 994 page 8 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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 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.
43 Seismic Hazards
The nearest Class `A' or Class V fault to this property is over 5 miles to the south of the project.
This information is based on the USGS Quaternary Fault and Fold Database for the United States
with the following description:
Fault Name: Tacoma fault
Fault Source URL: https://www.usgs.gov/natural-hazards/earthquake-hazards/researchLink
Fault System: Tacoma fault zone
Fault System Code: 19
Fault Visiblilty: inferred fault trace
Geologic Age(Years): <15,000
Geologic Age Description:Holocene
Soils immediately below the expected foundation depth for this project may use the following
seismic parameters:
Category: Seismic design category D2
Category Code: D2
Category Description: 0.83 <S(DS)<= 1.17, where S(DS)is the 5 percent damped design
spectral response acceleration at short periods
The potential for liquefaction and other earthquake induced hazards are believed to be low for
this project. This is based on subsurface conditions such as soil characteristics and the lack of a
permanent and substantial shallow water table. Subgrade characteristics that particularly
contribute to problems caused by seismic events include submerged and confined, poorly-graded
granular soils. Although gravel- and silt-sized soil particles could be problematic, fine and
medium grained sands are typically subjected to these types of seismic hazards.
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 9 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
4.4 Building Foundation Recommendations
Recommendations provided in this section account for the site development of a typical
commercial facility. The recommended allowable bearing capacities and settlements as presented
below, consider the probable type of construction as well as the field investigation results by
implementing practical engineering judgment within published engineering standards.
Evaluations include classifying site soils based on observed field conditions and soil testing for
this project. After deriving conservative relative densities, unit weights and angles of internal
friction of the in-situ soils, the Terzhagi ultimate bearing capacity equation was utilized for
determining foundation width and depth. Foundation parameters provided herein account for
typical structural pressures due to the planned type of development. A structural analysis is
beyond the scope of a geotechnical report, and a structural engineer may be required to design
specific foundations and other structural elements based on the soil investigation.
Stepped foundations are acceptable, if warranted for this project. Continuous, isolated, or stepped
foundations shall be horizontally level between the bottom of the foundation and the top of the
bearing strata. The frost penetration depth is not expected to extend beyond 12 inches below the
ground surface for this project under normal circumstances and anticipated design features.
A modulus of subgrade reaction of no more than 150 pci should be used for the foundation
system. Friction between the bottom of the foundation and soil may be utilized to resist lateral
loads. A coefficient of friction of 0.5 may be used for this application, and should account for the
vertical dead loads only.
Existing in-situ soils for this project indicates that the structure can be established on shallow,
continuous or isolated footings. Foundations shall be established on relatively undisturbed native
soil that is competent and unyielding. Alternatively, foundations may be constructed on selective
re-compacted native soil or compacted engineered fill as described in the Earthwork Construction
Recommendations Section of this report.
For a bearing capacity requirement of no more than 1750 psf, a minimum continuous footing
width of 18 inches shall be placed at a minimum of 18 inches below the existing ground surface
away from fill soils atop prepared subgrade and unyielding soils. For a columnar load of no more
than 3 tons, a circular or square isolated foundation diameter or width shall be at least 24 inches.
Foundation recommendations are made available based on adherence to the remaining
recommendations that are provided in this report. Alterations to the aforementioned foundation
recommendations may be completed upon a site inspection by a geotechnical engineer after the
foundation excavation is completed.
4.4.1 Settlement
Total and differential settlement that a structure will undergo depends primarily on the
subsurface conditions, type of structure, amount and duration of pressure exerted by the
structure, reduction of pore water pressure, and in some instances, the infiltration of free
moisture. Based on the expected native soil conditions, anticipated development, and
construction abides by the recommendations in this report, the assumed foundation
system may undergo a maximum of 1.0 inch total settlement, and a maximum differential
settlement of 0.75 inch.
Envirotech Engineering Geotechnicall Geological Assessment
PO Box 984 page 10 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
4.4.2 Concrete Slabs-on-Grade
Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted
coarse, granular material (Retained on U.S. Sieve #10 or greater) that is placed over
undisturbed, competent native subgrade or engineered fill per the Earthwork
Recommendations Section below.
The recommendations for interior concrete slabs-on-grade as presented herein are only
relevant for the geotechnical application of this project. Although beyond the scope of
this report, concrete slabs should also be designed for structural integrity and
environmental reliability. This includes vapor barriers or moisture control for mitigating
excessive moisture in the building.
4.5 Earthwork Construction Recommendations
Founding material for building foundations shall consist of undisturbed native soils to the
specified foundation depths. Compacted engineered fill, or selective re-compacted native soils
may be used to the extents provided in this Earthwork Construction Recommendations Section.
The following recommendations include excavations, subgrade preparation, type of fill, and
placement of fill for building foundations.
4.5.1 Excavation
Excavation is recommended to remove any excessive organic content or other deleterious
material, if present, beneath foundations and to achieve appropriate foundation depth.
Additional sub-excavation will be required for this project if the soils below the required
foundation depth are loose, saturated, not as described in this report, or otherwise
incompetent due to inappropriate land disturbing, or excessive water trapped within
foundation excavations prior to foundation construction. All soils below the bottom of the
excavation shall be competent, and relatively undisturbed or properly compacted fill. If
these soils are disturbed or deemed incompetent, re-compaction of these soils below the
anticipated footing depth is necessary. Excavations shall be completely dewatered,
compacted, and suitable before placement of additional native soil, engineered fill or
structural concrete. Subgrades shall be prepared for ensuing foundations and slabs by
proof rolling with a steel drum roller, hand-held jumping jack, or other heavy
construction equipment until the soils are firm and unyielding.
4.5.2 Placement and Compaction of Native Soils and Engineered Fill
For engineered fill or disturbed native soils that will be utilized as fill material directly
beneath foundations, observation and/ or geotechnical testing is required prior to
foundation construction. The following placement and compaction requirements are
necessary.
For disturbed native soils or engineered fill beneath foundations, limits of compacted or
re-compacted fill shall extend laterally from the bottom edge of the foundation at a rate of
one horizontal foot for each foot of compacted or re-compacted fill depth beneath the
foundation. See the illustration below.
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 1 1 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
FOOTING
COMPACTED
NATIVE SOILS
OR ENGINEERED I
FILL
I
I 1 UNDISTURBED SUBGRADEI
Both engineered fill and native soils used as compacted fill should be free of roots and
other organics, rocks over 6 inches in size, or any other deleterious matter. If import
material is utilized as structural fill material for placement in building pad areas, we
recommend that it meets the current Washington State Department of Transportation
Standard Specification for Road, Bridge and Municipal Construction (WSDOT), Section
9-03(14), for Gravel Borrow. The material should be placed per the recommendation in
section 2-06 of WSDOT for sub-grade. Material should be placed in 12 inch vertical lifts
and compacted with a vibratory smooth drum roller to achieve 95% of the (ASTM
D1557) modified proctor. Each lift surface should be adequately maintained during
construction in order to achieve acceptable compaction and inter-lift bonding. Alternative
materials may be imported for this project and used for foundation support per the
geotechnical engineer.
Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be
limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined
excavations exceeding 4 feet should conform to OSHA safety regulations. Permanent cut
and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an
engineer.
4.6 Surface and Subsurface Drainage
Positive drainage should be provided in the final design for all planned residential buildings.
Drainage shall include sloping the ground surface, driveways and sidewalks away from the
project structures. All constructed surface and subsurface drains should be adequately maintained
during the life of the structure. If drainage problems occur during or after construction, additional
engineered water mitigation will be required immediately. This may include a combination of
swales, berms, drain pipes,infiltration facilities, or outlet protection in order to divert water away
from the structures to an appropriate protected discharge area. Leakage of water pipes, both
drainage and supply lines, shall be prevented at all times.
Subsurface water intercepted in the footing perimeter drains, and stormwater collected from roof
drains shall be separately tight-lined to drainage facilities to a location at least 15 feet downslope
of the structure. Roof and foundation drains may share a tightline if an above ground drainage
outlet is allowable and a backflow preventer is installed within the pipe system in order to prevent
roof water from entering the foundation area.
Upslope drainage appears to be mitigated. However, if this drainage is not functioning properly,
engineered drainage plans may be required.
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 12 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
4.6.2 Infiltration Rates
Infiltration rates are based on the Soil Grain Size Analysis Method as outlined in the
2012 Stormwater Management Manual for Western Washington. Based on soil
characteristics and the aforesaid drainage manual, infiltration was determined to be the
following:
Loglo(Ksat)_-1.57+1.90D10+0.015D60—0.013D90—2.08f�
where,
Y—,t=saturated hydraulic conductivity,cm/sec
Dio=soil sample 10%finer by weight,mm
136o=soil sample 60%finer by weight,mm
D90= soil sample 90%finer by weight,mm
ffi.=soil fraction passing#200 seive,by weight,mm
Loglo(Ksat)_-1.57+1.90(0.12)+0.015(24.39)—0.013(52.63)—2.08(0.181)_-2.03682
• K,= 10-2_036s2=0.009187133cm/sec= 13.02 in/hr
Ksat dsign=Kt x CIFT
CFT=CFv*CFt*CF.
Kea,= 13.02 in/hr
CFv= 1.0 (0.33 to 1.0)site variability and number of test locations
CFt=0.4 (0.4)grain size test method
CFm=0.9 (0.9)degree of influent control
K.t agg.=4.7 in/hr
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 13 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
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
Jessica Smith,M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
Envirotech Engineering Geotechnical/Geological Assessment
PO Box 984 page 14 Parcel 12329-43-90290
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 22,2021
APPENDIX A
SITE PLAN
SCALE. 1 INCH 90 FEET
��c6 4D BO
OUTLINE OF ALLOWABLE
BUILDING AREA
. . _ . . . . , FILL OBSERVED ONSITE. SEE
F 'I REPORT F13R RESTRICTIONS
z :....................................14,1
....:
W
U
PROPERTY LINE
u
o '
TPI@
7`S .
• 2*y
`Y PQ
PO
d3
�yY '
ACCESS kUF+i�
PROJECT/ OWNER/ LOCATION-
COMMERCIAL PROPERTY
GEOLOGICAL ASSESSMENT
LOCAL NOTES 0 NE MEDIAL CH INC
RD
1. SLOPE INDICATORS WERE FIELD MEASURED BY ENVIROTECH• AND/OR PARCEL 12329-43-90290
EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE WHERE APPROPRIATE, HAS13N C13UNTY WASHINGTON
2.BOUNDARIES ON THIS SITE PLAN WERE NOT PREPARED BY A LICENSED LEGEND ENGINEER-
SURVEYORNA .LOCATIONS OF SITE FEATURES AND GEOLOGICAL/ SUBSURFACE ENV[ROT ENGINEERING
DESIGTIONS AS SHOWN HERE,WITH RELATION TO THE PRO ECH PROPERTY LINES PO BOX ECH
MUST BE VERIFIED BY THE OWNER. THE CONCLUSIONS AND > SLOPE INDICATOtt BELFAIR. VASHINGTpJ 9852H
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(INTHIS SITE PLAN. TPI TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geological Assessment DATE OF LOG: 11/19/2021
PROJECT NO: 21322 LOGGED BY: RJM
CLIENT: Local Wrench EXCAVATOR: N/A
LOCATION: Parcel 1232943-90290 DRILL RIG: None
Mason County.Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
STANDARD PENETRATION TEST
SOIL STRATA.
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
SM Bro..n.moist.medium dens*SILTY
SAND• ith GRAVEL.Gravel Istfneand
subrounded.Sand is primarily coarse.
1 Non plastic.
C Light brown.low moisture.very dense
2 - 'hard an'
Excavation terminated at approximately
2.0 feet
i-
t= 4
L 10
No Groundwater Encountered ENVIROTECH ENGINEERING
Tnrs rnronnanon pertains only to tnis bong and snould not be Geotechnical Engineering
Itetpreted as berrg lnd=Ve of the enure sie
Map Unit Descnpbon:Everett very gravelly sandy loam.8 to 15 percent slopes---Mason
County.Washington
Mason County, Washington
Eh—Everett very gravelly sandy loam.8 to 15 percent slopes
Map Unit Setting
National map unit symbol: 2t62b
Elevation: 30 to 900 feet
Mean annual precipitation: 35 to 91 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 180 to 240 days
Farmland classification.- Farmland of statewide importance
Map Unit Composition
Everett and similar soils:80 percent
Minor components:20 percent
Estimates are based on observations.descriptions.and transects of
the mapunit.
Description of Everett
Setting
Landform:Eskers,kames.moraines
Landform position(two-dimensional):Shoulder.footslope
Landform position(three-dimensional):Base slope.crest
Down-slope shape:Convex
Across-slope shape:Convex
Parent material:Sandy and gravelly glacial outvash
Typical profile
Oi-0 to 1 inches: slightly decomposed plant material
A- 1 to 3 inches: very gravelly sandy loam
Bw-3 to 24 inches: very gravelly sandy loam
C 1-24 to 35 inches: very gravelly loamy sand
C2-35 to 60 inches: extremely cobbly coarse sand
Properties and qualities
Slope:8 to 15 percent
Depth to restrictive feature:More than 80 inches
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 water supply.0 to 60 inches: Low(about 3.2 inches)
Interpretive groups
Land capability classification(irrigated): None specked
Land capability classification(nonirrigated): 4s
Hydrologic Soil Group: A
Ecological site: F002XA004WA-Puget Lowlands Forest
Natural Resources Web Sod Survey 128=1
conservation service National Cooperative Sod Survey Page 1 of 2
Map Unit Description Everett very gravelly sandy loam.8 to 15 percent slopes---Mason
County.Washington
Forage suitability group: Droughty Soils(G002XN402WA).
Droughty Soils(G002XS401 WA).Droughty Soils
(G002XF403WA)
Other vegetative classification: Droughty Soils(G002XN402WA).
Droughty Soils(G002XS401 WA).Droughty Soils
(G002XF403WA)
Hydric soil rating: No
Minor Components
Alderwood
Percent of map unit:10 percent
Landform:Hills,ridges
Landform position(two-dimensional):Shoulder
Landform position(three-dimensional):Nose slope.tall
Down-slope shape:Convex.linear
Across-slope shape:Convex
Hydric soil rating: No
Indianola
Percent of map unit.10 percent
Landform:Eskers.kames.terraces
Landform position(three-dimensional):Riser
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 17.Aug 31.2021
t,q)A Natural Resources Web Soil Survey 12/92021
i Conservation service National Cooperative Sal Survey Page 2 of 2
Fee ana.N *FIFO"r c•or,ah WATER WELL REPORTS
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