HomeMy WebLinkAboutGEO2014-00048 for BLD2014-00939 - BLD Engineering / Geo-tech Reports - 12/4/2014 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
11910
(360)427-9670
Geotechnical ReportReview Acceptance Letter
December 04, 2014
JACK PECKENPAUGH
Case No.: GE02014-00048
Parcel No.: 322365000006
Project Description: RETAINING WALLALONG DRIVE.
The Geotechnical Report for JACK PECKENPAUGH has been received and reviewed by the
Planning Department. The report was prepared by S. Morta dated 9/28/2014.
Based on the certification provided by the licensed engineer/geologist, the referenced
Geotechnical Report was prepared in general accordance with the requirements in the Mason
County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.5. Mason County considers the
review valid until such time as scope of project, site conditions, and/or regulations change. Should
the scope of work, site conditions, and/or regulations change after the original review, then an
addendum from the original author of the report may be required to address these changes. The
report would only be re-reviewed if a permit for development were submitted after these changes
occur. Mason County does not certify the quality of the work done in this Geotechnical Report.
Please contact me at (360) 427-9670, ext. 365 if you have questions.
Sincerely,
Allan /orden
Land Use Planner
Mason County Planning Department
Comments:
12/4/2014 Page 1 of 1 GE02014-00048
Mason County Review Checklist
For a Geotechnical Report
• Instructions:
This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report
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 Report 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# r )A U Parcel#
Date(s) of the Document(s) reviewed: 0]&! 2 (0 t
(1) (a)A discus 'on of general geologic conditions in the vicinity of the proposed development,
OK? Comment:
(b) A disc ssion of specific soil types
OK? Comment:
(c) A discu sion of ground water conditions
OK?Comment:
(d) A disc ssion of the upslope geomorphology
OK? Comment:
(e) A disc ssion of the location of upland waterbodies and wetlands
OK? Comment:
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
refe enced maps and records
OK?V Comment:
(2) A site pla hich identifies the important development and geologic features.
OK?Comment:
(3) Locations 5pd logs of exploratory holes or probes.
OK? Comment:
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and
setbacks 7hall be delineated (top, both sides, and toe)on a geologic map of the site.
OK? Z Comment:
(5) A mini um of one cross section at a scale which adequately depicts the subsurface profile, and
which inc porates the details of proposed grade changes.
OK? Al Comment:
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions.Analysis should examine worst case failures. The analysis should include the
Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic syty factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
OK? t/ Comment:
(7) (a)Appro ate restrictions on placement of drainage features
OK?iZ Comment:
(b) Appro riate restrictions on placement of septic drain fields
OK? Comment:
(c) Appr riate restrictions on placement of compacted fills and footings
OK?j Comment:
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Pagel of 2 Form Effective June 2008
OK? Comment:
(e) Recom nded setbacks from the landslide hazard areas shoreline bluffs and the tops of
other opes on the property.
OK? Comment:
• (8) Recommendations for the preparation of a detailed clearing and grading plan which specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method q vegetation removal.
OK? Y Comment:
(9) Recommendations for the preparation of a detailed temporary erosion control plan which
identif.- I t e specific mitigating measures to be implemented during construction to protect the
Slope froi erosion, landslides and harmful construction methods.
OK? Comment:
(10) An analysis of both on-site and off-site impacts of the proposed development.
OK? Comment:
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion ntrol, and buffer widths.
OK? Comment:
(12) Recomm ndations for the preparation of structural mitigation or details of other proposed
mitigati .
OK? Comment:
(13) A site m drawn to scale showing the property boundaries, scale, north arrow, and the location
and n t re of existing and pr9ip o d dev lopment on the sit
OK? Comment: r_
Are the Documents signed and stamped?
Type and #of License: Z '
If not approved, what is the next action/recommendation for further action?
Reviewed by on
Time spent in review:
SECOND REVIEW/UPDATE:
Reviewed by on
Time spent in second review:
THIRD REVIEW/ UPDATE:
Reviewed by on
Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment
Page 2 of 2 Form Effective June 2008
�r
GEOTECHNICAL ENGINEERING REPORT FOR
10' x 60' PULLOUT ALONG EXISTING DRIVEWAY
9890 SR-106, UNION, WA (Parcel #: 32236-50-00006)
Prepared for: EI. Kristyn & Son Construction Inc.
101 S.E. Rosewood Court
Shelton, WA 98584
(360) 432-3147
Prepared by: Morta Engineering and Testing, PLLC
1018 E. Wishkah St.
Aberdeen, WA 98520
(360) 289-0958 cell
(360) 580-0648 cell
(800) 590-0958
(360) 861-8493 fax
Smorta e,aol.com
Contact: Steven P. Morta, P.E.
Px EC11I'VED
OCT 14 Mli
426 W, CEDAR ST.
September 28, 2014
Sep.28,2014
` Page l of 6
MET Engineering, PLLC
To: EI.Kristyn& Son Construction Inc.
101 S.E. Rosewood Court
Shelton, WA 98584
(360)432-3147
Subject: GEOTECHNICAL ENGINEERING REPORT for 10' x 60 PULLOUT Along
Existing Driveway Located at 9890 SR-106,Union,WA
(Parcel#:3170 9054 4001)
1.0 Introduction
On September 21, 2014 this geotechnical engineer registered as a professional civil engineer in
the State of Washington visited the above site to perform a soils exploratory investigation for the
proposed 10' wide by 60' long pullout along the existing driveway. The primary purpose of the
pullout is to provide additional parking for a pickup and a boat trailer.
The objective of this geotechnical engineering report is to determine feasibility of constructing a
10' x 60' pullout to be located on the uphill side of the existing 18% grade driveway. Due to
existing steep cut slopes, a retaining wall will be required to help stabilize the toe of this slope
and also provide long term stability of 10' x 60' pullout.
2.0 General Description of the Site
The proposed 10' x 60' pullout site is located on the uphill side of the existing +18% grade
driveway with very heavy trees and vegetation that have grown back after the driveway was
constructed. These existing fir trees are approximately 15 to 20 years old are growing near
vertical indication a relatively stable slope. It appears that to provide adequate width for the
driveway the uphill bank was excavated to form, in some places, a nearly vertical slope 10 to 1.5
feet high. A detailed slope stability analysis will be discussed later in this geotechnical
engineering report.
A single story residence is located at the top of the driveway with a shed located on the
downhill side of the residence. There were no signs of slope instability during this geotechnical
engineer's site and soil investigation such as new or old slides,ground fissures,or leaning trees.
This geotechnical engineer determined that there would be sufficient space between the existing
driveway and the steep bare cut slope on the uphill side to safely accommodate a 10' x 60'
pullout that would be used for parking for the owner's truck and boat trailer.
3.0 Geology
About 15,000 years ago, the Vashon glacier began to melt and recede from the lands that will
come to be known as the Puget Sound region and the Columbia Basin region. (Ref Derek B
Booth and Barry Goldstein, "Patterns and Processes of Landscape Development by the Puget
Sound Ice Sheet, "in Regional Geology of Washington State, edited by R. Lasmanis and E.S.
1018 E.Wishkah St.,Aberdeen,Washington 98520
(360)289-0958 Bus,(360)861-8493 Fax,(800)590-0958 Toll Free
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Sep. 28, 2014
Page 2 of 6
MET Engineering, PLLC
Cheney.) By 11,000 years ago,the glacier retreated to the border of present-day Canada. During
its advance, meltwater flowing under the ice sheet carved out Lake Washington, Lake Tapps,
Lake Sammamish, Puget Sound, and Hood Canal. The other major shaper of the land: the
pushing of the Juan de Fuca Plate underneath the North American plate, and the docking of
terranes(fragments of continents)had already occurred long ago.
The Vashon Stade was the last glacial advance and retreat to cover the region. It was the last of
at least seven glaciations during the Pleistocene Epoch, which lasted from two million years b.p.
(before present)to about 10,000 years ago.
Extending as far south as the Olympia area to the west and the Spokane area to the east, the ice
sheet, at its thickest, was 3,000 feet. In comparison, the Pacific Northwest's tallest skyscraper
(as of 2012), Seattle's Columbia Center, is about 997 feet tall.
On the west side of the Cascade Mountains, two lobes covered the Puget Lowlands. Along the
north side of the Olympic Mountains the Juan de Fuca Lobe moved west, and between the
Olympics and the Cascades the Puget Lobe moved south. In the Puget Lowlands,the Puget Lobe
shaped much of the topography below 3,000 feet. As the Puget Lobe advanced, it deposited
hundreds of feet of Lawton Clay, Esperance Sand, and Vashon Till. Melt water flowing below
the ice carved out troughs that we know as valleys. Many of the area's water bodies filled these
troughs, including Puget Sound, Lake Washington, Lake Union, Lake Tapps, and Lake
Sammamish. Some of the meltwater moved across the direction of the ice flow, creating east-
west oriented valleys like the cleft through which the present-day Lake Washington Ship Canal
runs. The receding ice left moraines at its margins, outwash deposits left by meltwater streams,
and exposed drumlinoid ridges that largely run parallel to each other.
The upslope geomorphology consisted primarily gravelly loam soils resulting from the
deposition of the last Vashon recessional glacier. Furthermore, there were no signs of
groundwater in the form of seeps or wet areas along the face of the near vertical slopes located
on the uphill side of the existing driveway. In addition there were no indications of upland water
bodies or wetlands.
4.0 Soils
Two soil exploratory borings were completed as indicated on Engineering Sheet 1.0.
Essentially, both sites were very similar consisting primarily of very gravelly loam soils with an
allowable soil bearing capacity of at least 1500 psf. This was determined by using a sharp
pointed steel geoprobe which when pushed into the native soils only went down approximately 8
to 10"at both locations.
Reference is also made to Sheet 1.0 for a typical slope cross-section that indicates very gravelly
soil conditions. Due to the very heavy vegetative and the new fir tree growth, the 10 to 15' of
near vertical height appeared to be stable due to an extensive root system which acts as
reinforcement to hold the dense gravelly loam soils together. In addition, these extensive root
systems increase long term slope stabilization through the process of evapotranspiration whereby
1018 E.Wishkah St.,Aberdeen,Washington 98520
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Sep. 28 2014
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MET Engineering, PLLC
the roots absorb excess moisture from the native gravelly soils and re-evaporate this excess
moisture back into the atmosphere through the leaves and pine needles.
5.0 Slope Stability Analysis
A slope stability analysis was completed for the 10' to 15' high near vertical slopes located on
the uphill side of the proposed 10' x 60' pullout. For the static case, i.e., for the non-seismic
event, the resulting factor of safety was computed to be 0.970 and since this was less than the
normally accepted value of 1.500, this was considered unsatisfactory. Pertinent soil parameters
such as slope angle, cohesion, density, height of slope, and internal friction angle of the soil were
taken consideration.
Similarly, for the quasi-static, i.e., for the seismic case the resulting factor of safety was 0.845
and since this was less than the normally accepted value of 1.100, this was considered to be
unsatisfactory.
The Puget Sound Coastal Zone Slide Atlas indicates that the area around the proposed
construction site, i.e., 9890 E. SR-106, Union, WA, is"Stable"per the attached map. Also,there
were indications on the site that indicated any signs of slope instability such as slides, ground
fissures, or leaning trees.
6.0 Slope Stabilization Measures
6.1 Preserve All Trees and Vegetation on Uphill Side of Pullout and Near Vertical Slope
As mentioned earlier in this geotechnical engineering report that the trees' root system provide
reinforcement to the soil especially during heavy torrential downpours where saturated soils have
a tendency to slide if trees and vegetation have been removed. In addition, the extensive root
systems help to absorb excess moisture from the soils through the process of evapotranspiration
as explained earlier in this report. Another important contribution of the trees and vegetative
ground cover is that they protect the gravelly loam soils from the direct impact of rain drops
which otherwise could potentially cause soil erosion. The leaves and pine needles break the fall
of the raindrops first and then harmlessly seep into the insitu soils.
6.2 Construction of Concrete Retaining Wall
The 6' high concrete retaining wall along with the 2' thick concrete base acts as an anchor to
help hold the toe of the steep slope in place especially during periods of heavy rainfall or during
a seismic event.
Some maintenance by the owner may be required if there should be some sloughing of the steep
cut uphill slopes be removing any sloughed soils that may have come in contact with the concrete
retaining wall. Also, a 4" diameter PVC perforated drainpipe placed on the uphill side of the
retaining wall as shown on engineering Sheet 1.0 will help to collect any water that may flow off
the cut slope and direct the water down to the drainage ditch on SR-106.
1018 E.Wishkah St.,Abcrdeen,Washington 98520
(360)289-0958 Bus,(360)861-8493 Fax,(800)590-0958 Toll Free
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Sep.28,2014
` Page 4 of 6
MET Engineering, PLLC
6.3 Maintain a Minimum 15' Setback/Buffer Measured back from Top of Slope
It is recommended that a minimum 15' setback buffer be established from the edge of the near
vertical slope on the uphill side. This will ensure that the natural trees and vegetation that are
already growing there will be preserved within this 15' buffer zone. This geotechnical engineer
inspected the top edge of this near vertical face and did not notice any signs of slope instability
such as slides, ground fissures, or leaning trees in the downward direction. However, it did
appear that some of the trees had been cut back and that some of the vegetation had been
disturbed within the recommended 15' buffer zone at the top edge of slope.
6.4 Provide Adequate Drainage for the Addition 10' x 60' Impervious Surface
It is important that the increased surface water runoff from the 1.0' x 60' impervious road
surface be directed into the drainage ditch along SR-106. Also, it is recommended that the
downspouts for the existing residence be inspected to verify that roof runoff is being directed
into a suitable drainage area that does not drain directly onto the driveway or over the steep
vegetative slope.
6.5 Siltation Fencing
Installation of siltation fencing needs to be placed on the uphill side of the 10' x 60' pullout
construction area to contain any soil or water that may come off the steep bank during
construction. Water runoff from the siltation fence can be directed toward the drainage ditch
located on the uphill side of SR-106.
7.0 Concrete Retaining Wall
A detailed engineering drawing on Sheet 1.0 shows the dimensions of the retaining and typical
cross-sections that provides the thickness of the retaining wall and the footing dimensions. It is
important that the footing subgrade is thoroughly compacted prior to any concrete pour to ensure
that the retaining wall does not settle over the long term.
A detailed engineering drawing on Sheet 1.0 shows the dimensions of the retaining and typical
cross-sections that provides the thickness of the retaining wall and the footing dimensions. It is
important that the footing subgrade is thoroughly compacted prior to any concrete pour to ensure
that the retaining wall does not settle over the long term.
8.0 Detailed Clearing and Grading Plan
The 10' x 60' pullout area will require clearing and grubbing along with the tapered ends at the
entrance and exit areas. It is anticipated that there will be little to no fill required since the
pullout area will follow the natural grade near the toe of the slope.
1018 E. Wishkah St.,Aberdeen,Washington 98520
(360)289-0958 Bus,(360)861-8493 Fax,(800)590-0958 Toll Free
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Sep. 28,2014 66(
Page 5 of 6
MET Engineering, PLLC
9.0 Analysis of Both On-site and Off-site Impacts of the Proposed 10' x 60' Pullout
There will be negligible onsite impacts as long as the recommendations of this geotechnical
engineering reports are followed. No offsite impacts are anticipated since the entire project is
located within the property boundaries.
10.0 Final Development Conditions
Drainage will be provided on the uphill side of the concrete retaining wall and surface water
runoff from the 10' x 60' pullout will be directed toward the drainage ditch along the uphill side
of SR-106.
11.0 Structural Mitigation
The proposed 10' x 60' pullout does not require any structural mitigation except for the
proposed 6' high concrete retaining walls that is constructed which will help to protect the
pullout from any material that may come from the uphill side of the site.
12.0 Conclusions and Recommendations
1. Work on the concrete retaining wall will need to be done during periods of good
weather conditions that usually occurs from June 1 to October 31. If work is done at
other times of the year, then any exposed soils during construction will need to be
protected with clear 6 mil visqueen at the end of the work day. This is incase of
rainfall that may occur at night.
2. Siltation fencing will be required on the downhill side of the work area to prevent
loose soils and surface water runoff from flowing onto the SR-106 pavement.
3. This geotechnical engineer shall be called on out to the jobsite by the contractor
during the construction of the concrete retaining wall to ensure that the
recommendations in this geotechnical engineering report are followed. A follow-on
engineering field report shall be prepared by this engineer with a copy given to the
contractor and another copy given to the Mason County Department of Community
Development for their records. Preferably, this engineer shall be called out just prior
to any concrete pour. It is to be noted that this engineering inspection does not take
the place of a Mason County Inspector that will be based on the engineer's retaining
wall drawings.
4. If the new 10' x 60' pullout surface is paved with concrete, the initial wet surface
can be brushed with a broom across the direction of travel to provide vehicular
traction and also to slow down the surface water runoff from the driveway surface.
This geotechnical engineering report has been prepared per accepted engineering practice. It is
important to note that the geological field data obtained is a "snapshot" in time. In the future
1018 E. Wishkah St.,Aberdeen,Washington 98520
(360)289-0958 Bus,(360)861-8493 Fax,(800)590-0958 Toll Free
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Sep.28,2014
Page 6 of 6
MET Engineering, PLLC
geological conditions can change whether natural or man-made. Therefore, if there are any
changes (such as downed trees from a storm, e.g.) to the site between now and the start of
construction, this engineer needs to be contacted to verify that the results of this geotechnical
engineering report are still valid after another site visit. Any questions or comments can be
addressed by e-mail at Smortggaol.com or by calling(360)289-0958.
Sincerely,
Steven P. Morta, P.E.
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1018 E.Wishkah St.,Aberdeen,Washington 98520
(360)289-0958 Bus,(360)861-8493 Fax,(800)590-0958 Toll Free
Smorta@aol.com
9890 Washington 106
Union,WA 98592 pq Save
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Figure 1 The entrance to 9890 East SR-106, Union, WA can just been seen on
the uphill side across from the low wood railing on the water side of the road as
indicated in the photo above. The parcel number to the property is # 32236 50
00006. Trees and vegetation protect the uphill slopes from slides especially during
the fall, winter, and spring seasons when heavy rainfall can last for several days.
This geotechnical engineer did not observe any signs of slope instability such as
leaning trees, cracks or fissures in the driveway, or any recent signs of slides along
the uphill side of the driveway. Escarpments along the driveway which bare vertical
soil faces appear to result from the initial excavation for the driveway. Minimal
excavation for the 10' x 60' long pullout is anticipated per the attached geotechnical
engineering report.
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Figure 2 This an aerial view of the property located at 9890 E. SR-109, Union,
WA which is located just to the east of the orange colored roof above. The driveway
is in the shape of an "S" curve leading up the the residence.
The hill side is very heavily vegetated with 15 to 25 year old firs that provide
protective canopy cover over the dense gravelly silty loam soils especially during
extended periods of heavy rainfall.
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Figure 3 This is a topographical map of 9890 E. SR-106, Union, WA and shows
that the elevation at the top of the driveway is approximately 25 to 30' with a 17%
grade going up the driveway. Reference is made to the attached photograph of the
paved driveway.
Figure 4 The 10.3 degree ((18.2 % grade) shows little to no signs of cracking or
any signs of road settlement and appears to be stable. A 10' wide x 60' long parking
area is planned on the uphill side of this driveway. Escarpments 10' to 15' high were
observed on the uphill side which are bare soils with a near vertical cut embankment
that more than likely was excavated out during the construction of the driveway.
This escarpment appeared to be stable due to the firs and alders that are growing on
the sides of the face with their root system providing reinforcement to the dense
gravelly loam soils.
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Figure 5 New vegetation in the form of firs and Alders have re-established
themselves on the nearly vertical escarpment face on the uphill side of the existing
paved driveway. It is imperative that this vegetative tree cover be preserved to
increase the long term stability of the uphill slope once the 10' x 60' paved pullout
located on the uphill side of the driveway gets constructed.
Again it is very important that these existing new tree shoots are left intact since
their root systems reinforce the very dense gravelly silt soils. In addition, they help
to remove excess moisture in the ground through the process of evapotranspiration
whereby the extensive tree roots absorb moisture from the subsurface soils and
evaporate this moisture back into the atmosphere through their limbs consisting of
pine needles.
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Figure 6 A steel soil probe was used to check the allowable soil bearing capacity
of the insitu native soils and was determined to be at least 1500 psf. This
geotechnical engineer was only able to push the probe down approximately a foot
indicating fairly high soil resistance and, therefore, excellent soil bearing capacity.
This increases the long term stability of the nearly vertical slope.
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Figure 7 This is a parcel map for the property located at 9890 E. SR-106, Union,
WA and has a parcel number of 32236-50-00006. It is to be noted that the property
also includes waterfront as indicated above. In addition, approximate 20' contours
are shown as white topographical lines indicating that the top of the 10' x 60' pullout
paved new section is at an elevation of approximately 17 to 20'.
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, I 2' 8„ 4' PRESERVE ALL TREES AND PRESERVE ALL TREES AND
2 VEGETATION ON UPHILL SIDE o
VEGETATION ON UPHILL SIDE 4 8" - OF RETAINING WALL FOR MAX.
OF RETAINING WALL FOR MAX. LONG TERM SLOPE f6
LONG TERM SLOPE �_
STABILIZATION STABILIZATION 7
o
5'6„ l 6 6„ -'
• 1 IrLI LI i I I _ Q �
6"ROAD SUBGRADE L�- 6" ROAD SUBGRAQE 1 NOTE: REFER TO ATTACHED SLOPE
I`III-i -T TF ITI I I
I�I-I ->Il-II FOR 10'x 60' PULLOUT �� 11-
FOR 10'x 60' PULLOUT - I _ II STABILITY ANALYSIS 4
6" -III=I I -� L-Tf=IT 6 �_ v
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— �III- I III f it I -LTI--I - - - -{I�I y•- m
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#4 REBAR, 18"O.C. �w ~
#4 REBAR, 18"O.C.
4"DIAMETER PERFORATED DRAIN PIPE WITH 1/2"DIA. EA. WAY(HORIZ.
EA. WAY(HORIZ. HOLES AT THE 5 AND 7 O'CLOCK POSITIONS @ AND VERTICAL) _8
AND VERTICAL) 12"O.C. ALSO, WRAP 3"MINUS DRAIN ROCK IN a
HEAVY DUTY FILTER FABRIC a
Slope Stability Calculations (Simplified Bishop's Method of Circles)
r Not f o scale�nRs�
Potential
15 ft �`� Failure
Plane
Alpha=65 deg
(214%slope)
1. Compute factor of safety(FS)against sliding-Static Case(Ref "Stability Charts for Uniform Slopes"by
Radoslaw L. Michalowski, F.ASCE) - "Journal of Geotechnical and Geoenvironmental Engineering",April 2002.
From Figure 3"Stability charts for uniform slopes"the following parameters are known for gravelly loam soils(GW-SM):
c(cohesion)= 150 psf, gamma(insitu unit density)= 134 pcf, H(height of slope)=15 ft,
phi(internal friction angle)29 deg, then
G[gamma x H x tan(phi)]=150/(134 x 15 x tan 29)=0.1346
Then for a 65 deg (214%)slope from Fig. 3:
FS/tan(phi)=FS/tan(29)=1.75 or, FS=Factor of Safety Against Sliding= 0.970<1.500 NOT OKAY
Construction of 4'high concrete retainin_q wall will at toe will help to provide long term slope stability.
2. Compute factor of safety(FS)against sliding-Quasi-Static(seismic)Case(Ref: "Stability Charts for Uniform Slopes"
by Radoslaw L. Michalowski, F.ASCE) - "Journal of Geotechnical and Geoenvironmental Engineering",April 2002.
From Figure 4"Stability charts for uniform slopes"the following parameters are known for Clay, Silty soils(CL-SM):
c(cohesion)= 150 psf, gamma(insitu unit density)= 134 pcf, H(height of slope)= 15 ft,
phi (internal friction angle)=29 deg, then
c/[gamma x H x tan(phi)]= 150/(134 x 15 x tan 29)=0.1346
Then for a 65 deg slope(214%slope)from Fig.4 for a quasi-static analysis coefficient of 0.1:
FS/tan(29)= 1.60 or FS=Factor of Safety=0.887
For a quasi-static analysis coefficient of 0.2:
FS/tan(29)=1.45 or FS=Factor of Safety=0.804
As a result, for a quasi static analysis coefficient of 0.15,the Factor of Safety,FS=(0.887+0.804)12=0.845<1.100 NOT OKAY
Construction of a'nigh concrete retaining wail wiii at toe wiii heip to provide iong term siope stability.
SLOPE STABILITY ANALYSIS for Residential
Site Located at 9890 SR-106, Union, WA Prepared by: MET Engineering,PLLC,1018 E.Wfshkah St,Aberdeen,WA 98520
(Parcel#: 32236-50-00006) (360)289-0958, (360)310-0270 bus,(360)861-8493 fax,Smorta@aol corn
Prepared for:Tim Bailey,(360)432-3147 cell,(360)432-3147 office Sep,27,2014 Site Visit on Sun.9-21-2014 SHEET 2.0
at Noon to 1 pm
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• Mason County Department of Community Development
Submittal Checklist For a Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain
the basis for the conclusion.
Applicant/Owner John $r oah Pecke�amA Parcel#
Site Address S-la-Ae 120 u fe /OC L/w/0"I V/A
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) •5_erJjLyd ..3 0 agt/ y D
(b) A discussion of specific soil types
Located on page(s) _%PG o�Oyi 'T4 D
(c) A discussion of ground water conditions
Located on page(s) .fec ftt," 3.0 (4.2-)
(d) A discussion of the upslope geomorphology
Located on page(s) reckl m 3-o ( P. 2)
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) 2 o 1P4 2)
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps and records
Located on page(s) fee ft oN S:0 (Pa 3)
(2) A site plan which identifies the important development and geologic features.
Located on Map(s)�&eeakf p Jheef /. p
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) dheei�,I, b
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and
setbacks shall be delineated (top, both sides, and toe)on a geologic map of the site.
Located on Maps) Pme__r J/rt�` /.o
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details of proposed grade changes.
Located on Map(s)_ �Yl�rrd!Z J11e
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions. Analysis should examine worst case failures. The analysis should include the
Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5,the minimum
seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
Located on page(s) .Iec7L1,W1 •51 d
s ;
(7) (a)Appropriate restrictions on placement of drainage features orT 14
Located on page(s) Sec h'on C.L/ j/��,(f)
(b) Appropriate restrictions on placement of septic drain fields 426
Located on page(s) N�p_(_/S[r� W. C E D�''� T.
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s)_, _+)w 7, O 0%. q)
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) �Il r/-/We�! �.o
(e) Recommended setbacks from landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
Located on page(s) Cha�i�eerM!!5 Anef/,0
(8) Recommendations for the preparation of a detailed clearing and grading plan which specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method of vegetation removal.
Located on page(s) Jec�r`o fa cP O
(9) Recommendations for the preparation of a detailed temporary erosion control plan which
identifies the specific mitigating measures to be implemented during construction to protect the
slope from erosion, landslides and harmful construction methods.
Located on page(s) _�ecfr wr a-Q CPg r 3-SF)
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) J'ee4y-w+ ,S-)
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer widths.
Located on page(s) se-c f r l D,c3
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s) Sec fib
(13) 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) S`Oefl. D
1, .J l e c9ek, R Itior fa- 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 -r_ �/�_Z�'� ZDI� , and entitled
PU/lnut meets all the requirements of the Mason
County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment
demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the
included geotechnical design recommendations, and that all hazards are mitigated in such a manner as
to prevent harm to property and public health and safety. (Signature and Stamp)
by •'�o
o�
Z
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
March 26,2015
Page I of 1
MET Engineering, PLLG
To: El.Kristya& Sons Construction Inc.
c% Tim 13ailiey,(honer
101 S.E.Rosewood Court
Shelton,WA 98584
(360)432-3147,ei bailev��?ntsn.Cotlt
Subject: ONSITE ENGINEERING INSPECTION for IO' x 60,PULLOUT at 9890 SR-106,
Union,WA (Parcel#32236-50-00006)
Ref: GEOTECHNICAL ENGINEERING REPORT for I0' x 60 PULLOUT ALONG
EXISTING
DRIVEWAY,
Y 9890 SR-106, Union, WA 98592, prepared by MET
Engineering,PLLC,dated September 28,2014
On Thursday March 26.2015 this geotechnical engineer, registered in the State of Washington
was called on out to the site by the contractor to verify that the excavation work met the retaining
wall design of prepared by this engineer on September 28,2015.
This engineer inspected the excavation work performed by the contractor and took detailed
measurements for the retaining wall footing widths and heights and determined that the
excavation work was completed per this engineer's design as documented on Sheet 1.0 per the
reference above.
The contractor only removed trees and vegetation that was necessary for the construction of the
retaining wall located on the uphill side of the proposed 10' x 60' pullout. Due to steep slope
considerations it was decided that the actual width of the pullout could be reduced from 10' to 8'
and still provide enough room for parking a trailer on the new 8' x 60' pullout area.
No other exceptions or deviations were noted during this engineer's onsite inspection and
determined that the excavated site is ready for forming and the installation of#4 rebar at IS"O.C.
in both the
vertical and horizontal directions within the footing and within the 8"thick concrete
retaining
wall.
Sincerely.
Steven P. Morta. P.1:..
1018 E.Wishkah St.,Aberdeen,Washington 98520
(360)289-0958 Bus,(360)861-9493 Fox.(800)590-0988 Toll Free
Smorta
I