HomeMy WebLinkAboutSHX2016-00043 GEO - GEO General - 10/23/2016 TAHJA ENGINEERING, Inc.
.PO Box 235 1-loods _rt, WA 98548
l '
(360) 877-9512
Masan Co DC
Planning D vision
427 W Ced ar 5t o VA r
Shelton, A, 985114
Tacoma P iir
Wynnae ri t
3628 Sou 3 '�'S et 84
ma Taco , A 9$4*3192jox
Stelae& B nda C Igan
502 Sumni r ve,
Sumner, 983 173
.(253) 863 1 8
Geotechnical Report Addendum
Lake Cushman Div.3,Lot 36
I l0 N Discovery Dive,Hoodsport
Parcel No. 4231$-SQ-00036,DCP2012-00018
Mason Co. Case No.s, BL 2012-0460a&6062§W1132012-09 61
I U2016-UQ0021, SEPZ_01_"0054 S 2Q01§-QO043,
BLb2016-00546 Bulkhead
INTRODUCTION
I was infor nt d in entail from Mr. Steve Colgan(dated 1011 lll6)with a forwarded
message fr W ae Wright that Mason County could not issue a permit for the Colgan
r+ckery_h ead;
I read throe igh you geotechnical report and it did not address the justification requirements
required in iection A,Appendix g(pages 85-8)of the Shoreline Use Specifications and Permitting
Guidelines.. ... Base I on the information that was in the report it does not appear that Tacoma
Power shori kline fro Ting your leased your lot will qualify for a bulkhead,"
Ms Wright lir I her d rected Mr.Colgan's attention to Tacoma Power's Shoreline Use Specifications
Appendix E (I ages 5-8). l authored the Geotechnical Report to be used by Mr.Colgan for
permitting oses which I custom;arity write to address Masora County's Landslide Hazard Area
Critical Re c 0 dinance requirements. Prior to writing the report for Mr.Colgan I read through
the Biologii al Bval ion(BE)/Habitat Management Plan(HMP)prepared by Kimberly Schaumburg
of BioReso es, I 11C, t found the BE very thorough addressing habitat features at the project
location an i clu Erosion and Sediment Control recommendations which are expected to be
implement pro oted in the BE.This addendum to my original report is intended to supply
justificatior nkess for the sought activities and permits.
The follow- lans rs are offered for the requirements identified in Tacorna Power's Shoreline Use.
ee Spificati ns�Ap dix B;
File:r- Pr,�o VIVI. 'f-C' Igan Cis.R)pi:ddnd- 1 of 11 10126,12 16
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Section 4. $ s REL. E STABILIZATION MEASURES;
Pg B-5 1'ar ph 1.
Tacoma P r al Shoreline Stabilization Measures only where necessary too protect
existing t lipr ry structures',existing permitted structures, new water c3ependnt
develop tS, n non-water-dependent development,inclining single-family residences,
public i vNem unique natural resources; public health,safety or welfare;or the only
feasit�e a ess to rty. Tacoma Power may allow feline stabilization measures to
protect exi `+119 itted structures,Public improvements, unique natural resources, or Public
health,sa# or. are, Tacoma Power may consider shoreline stabilization measures if they
are nec to ure or protect the only feasible accessto a property..They are not allowed
for the pu of eating additional land area or securing temporary shoreline*uses.
The existir j, egal amps,pier& float have all been identified by Tacoma Power as permitted.
features. T a -xist ng features are deteriorating as a result of wind and boat wake erosion.
Every own r 've I cen in contact with at lake Cushman has complained about the loss of
their lake iorelin as a result of wind waves and boat wakes.The Colgan pier and float
shown bet w rev that the float landings have been undermined during their lives and
without ad 'tonal placement armoring the existing features will require substantial repairs
or replacen ei it. M , Colgan is undertaking the proposed rockery bulkhead to preserve the
shoreline i now exists.There is no intention of creating new upland or reclaiming
shoreline t t has ready been eroded away.
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Fare:[",-.r'rgje'i ls��P-C n Geoo Rpt Addndn, 2 of H 10,26/2016
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TAIIJA I:l`UNEFRING. Inc.
j PO Box 235, Floodsport, WA 98548
(360)877-95 t
Page 13-5 P raP 2;
Tacoma F' re q tires a shoreline stabilization project Applicant first consider non-structural
shorelines .liz�a' measures( i ngineenng)and to demonstrate that such alternatives are
not Ieasibl b4fore uesting a Permit to install structural shoreline stabilization measures.
Structural $su may be allowed only where erasion Presents an imminent danger`to
existing str res. The imminent threat must be n to potentially occur within three years
as demonsl ra bi a geotechnicail analysis urrtenting tidal actions, weaves, or erosion
PROVIDEE t thf following provisions are met
Non-struct4al shoo litre stabilization measures have not been successful along the bake
Cashman s tine, No natural areas of the shoreline have been able to withstand the
constant ercsion of e shoreline,and typically are eroding with little impediment. The
Geotechnict I Itepo prepared dated 9/30116 dues not elaborate on either the need for
protection t e so rce*of the erosion. As stated above,every waterfront owner at Lake
Cushman hi s co taint about the:erosion of their(Tacorna Povverf rP)property and has
expressed a n d to irotect the property they have. Every bulkhead or retaining wall installed
along the la a shoe line represents an owvner's feeling that their property is being;
unnecessad y rode I away and that their property needs protection. The erosion of the
shoreline is a.dilitat id by the annual lowering of the lake and exposure of the shoreline
between the 1 e's 720 and 738:k elevations to the elements. The summer recreational Kiat
waves and wir d dri e~n waves easily erode away the shallow layer of soil loosened by the
annual free - haw nvironment.This is an annual process with an accumulative impact.
Damagemailleco idere€i insignificant to a non-interested observer, but is an ongoing and
constant thr at tot property owner($).
I've been vi litina, U ike Cashman since the mid 195tils and have; witnessed a constant
deterioratioi o the ake shoreline due to erosion and undermining elf the shoreline along the
approximat 730 to 736 shoreline elevations. luring nay 20+ years of employment with
Mason Cou t .s Pu lie Works Department, I provided engineering support to the County's
Planning& ildirt Department. During that time I was alerted to an annual loss of the lake
shoreline by o er l ensed engineers who made a claim that they'd observed a fairly const"t
erosion rate at nt;tt e lake's shoreline of roughly an inch per year. I feel this erosion rate is
defendable I or the conditions of any features installed along the shoreline in the.past 20
to 30 years. teal y,footings and other features buried 2 to 3' below they existing beach
elevations a' ecor ink undermined clue to the Suss of the supporting wails. It is not
uncommon o ee a tl year old feature standing with a concave condition deveeloping.long
the bulkhe paralle with the shoreline.
The erosion) 0 ough not occurring;at a fast rate, is perceived,by every oww7ter with a
bulkhead, oi desirin protection with a bulkhead, as an imminent threat their property as it
exists, and a 5 t e owners wish to keep it.
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fife:(`:'.Pr oject TJ'<C ol. n C e cwkid.E.Idndnj 3 of 1 1 10/26/2 f 16
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360)877-9512.
Required P-o� isio s;
I, Such sl Oli results in maintenance of fish habitat, hydrologic processes and
improved ter
lity and ensures no net loss of shoreline ecological functions as
docurnent.4ir iaHMP.
Theffiolo c Evg lcation prepared for the project reports that the proposed stabilization
measures m ill not i iterfere with fish habitat,hydrologic processes, will improve water quality
and Nvill no result n a net loss of shoreline ecological functions.
2. A Shore in-G technical Assessment is required to demonstrate whether naturally
occurring o ai b . � t such as shoreline erosion caused by tidal action, currents, or
waves are ca isi a threat within a three year timetrame, The assessment shall estimate
timefftrame., aid s of erosion and report on the urgency of the specific situation. The
erosion mi st con We an imminent or inevitable threat
a
con e1c
I authored g g-otec iical report for the Colgan property instead of a geotechnical assessment,
a report pro vii ling formation not required in a Mason County level assessment.Pictured
a t
below is a t at iral etch of the Lake Cushman shoreline, protected only by natural
e
vegetation. n V e. Cushman shoreline realizes only Mind driven lateral flow and.seasonal
t
wind wave! and t wakes causing erosion of the freeze-thaw weakened shoreline..
As indicated above an erosion rate of roughly an inch per year of shoreline is eroded away.,
with the be wh bet v reen the approximate 720 to 736 elevations dropping down at a rate of 1"
vertically p r Car. e Colgan residence location was measured during the topographic
survey oft ro y that I performed,and found to be approximately 47-feet east/landward
of the lake' 738 o reline location.The ground slope between the residence and the 7,38
shoreline me, I ed at an average 7,6376'slope. Below is an image showing that given
-v I 'an annual e sion, e of an inch per year,it will take roughly 75 years for the shoreline to
fty
reach the wj.soerly xtent of the primary residential features. I consider this imminent and
inevitable.
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�pwytw 5 1 TN7 -71 7 .2 yeam Wme amim mch"rarAmm
114 1311-7.4.vn
File:C.-Projec4 r TP-Colo in Ceti-RpiAddrida) 4 of 11 10126/2016
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TAHJA ENGINEERING, Inc.
PO Box 235,Hoodsport, WA 98548
(360)877-9512
Page l3-6, $1aragrajh 1;
Structural rneasu es that utilize natural materials such as rock are preferred over structural
measures tdt*t manufactured matenals,such as concrete or lumber.
The propos.-d an-nc ring is composed of natural riprap quarry rock. The filter fabric specified
to be instal ed betv ren the rockery backfil I and the natural earthen back is synthetic, but has
a useful li fi�n keas d in decades when protected from sunlight (UV Rays)and will not
produce any C[etfiry ental impacts to water quality or habitat.
Page B-6, 1 laragral h 2;
A shoreline�eot nital assessment conducted by a licensed geotechnical engineer must
demonstre-ti�that -structural measures(bioengineedng)are not feasible before Tacoma
Power witl c(ns' structural stabilization measures in the A and B Shoreline Classifications.
Generally, T Power does not allow either structural or non-structural shoreline
stabilizatic n nea res in the Resource Management Classification; however,non-structural
stabilizatkk rit i�eas ores(bioengineefing)may be considered under certain circumstances.
The Colgan propedy is located in an area of Lake Cushman identified in Mason County's
Environ,me it iDesi ations Map as"Residential". I am not aware of any location on Lake
Cushmamn �re s armoring or bioengineering have been successful. The photograph
below Of a portion of the Lake Cushman shoreline is an example of the inability of
natural Iveg e �tion stop or slow erosion and its inability to stop the advancement of the
shoreline h ndw
... ......
kve.�C. gan Geo-Rpr Addndnt 6of 11 10/26/2016
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360)877-9512
'Page B-6,F gra 3;
Regardles of the reline stabilization technique or shoreline classification, the Applicant is
required to n ate that wave action or fluvial force is the primary re for shoreline
erosion, or ca , such as drainage outside the Project Boundary or improper
vegetation' t,are not adequate reasons to gain approval for imple ruing s cline
stabiliza� rhea s.
Annually,v hen th lake is lowered from its summer seen high water elevation to its low
water cleva ioh,th shoreline. between the lake's 732±down to the approximate 720
elevation b c mes wash boarded"displaying the daily erosion down the shore. The
photograph or the revious page shows a section natural lylunprotected shoreline. The trees
and ve etat or alo the shoreline are constantly attacked and undermined, resulting in their
eventual de iv= ry it to the lake as the photograph demonstrated.
Page B-6, P grap 14 with subsections,
A ficensec e,Viner must design all shoreline stabilization measures(structural or non-
structural)a measures must:
I am Curren ly liceded as a Professional Civil Engineer, WA State.License 30784.My
license is ct rrimt.
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1. Be litri to minimum size necessary to protect the shoreline,
2, teO gfeen
ally parallel to the shoreline.
3. Be reed the'adjacent tot side lot l€nes, if extended onto the shoreline.
4. fie d edllow the shoreline.contours or s , of lands.b. Not i ude eation or dredging ether than that specifically required for installation of
the staotlizat4measure-
Not i e a discharge of dredge or fill material into the reservoir other than baclefill to
suppod sure' erasion control measures.
7, Not be,fot the I urpose of reclaiming of land that has been lost to erosion.
I, The profw 's th minimum size the owner feels he needs to protect his property.
2. The pro s d de 'g,n aligns the proposed rock installation parallel with the existing
shoreli
3. The propeseA art ioring is confined between adjacent properties.
4. The prop s d roc ry installation is located along the shoreline's 738 elevation.
5:No ex e us a)cavation is being promoted.
6.The BE F re tired for the proposed rockery installation contains specific Erosion and
Sedime t i 4on l me=asuros. See pages 16-17 of the BEIHMP.
7. Mr. Cold; as pressed no intention of reclaiming land he has already test. His intent is
to prese his 11roperty without further loss of shoreline or waterfront features.
File:C':'Prgjee 1 -C ' nGet.-RptAdcfmIm 7 of 11 10/26/2016
TAHJA ENGINEERING, Inc.
PCB Box 235,floodsport, WA 99549
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(360)877-9512
Page 13-6 Para ph 5 with subsections;
The fol `ng r irernents apply specifically to structural shoreline stabilization measures:
Struct refs ma Je of tires, rubble, petroleum based products, railroad ties, filled barrels,
brick, It, solid waste:, or scrap machinery are not allowed.
No dis-ally od substances are proposed to be incorporated in any of the proposed work,
« Gabio ri baske ts are not allowed,
No gabion trpactu s are proposed as any part of the project..
• The b 1 of ffm structure must not be located more than are average of one horizontal
foot lali evMrd f the toe of the slope.
Plans prep ell for be proposed armoring specify the installation along the 735 lake elevation
where didsho line abruptly climbs approximately V/2 feet to the residence's yard
elevati n.'.
AdeqL at, bar toe protection must be provided to ensure stability without relying on
additic rAl ripr ip,
Plans dev o ed f r the proposers armoring are intended to comply with this requirement.
Strum m t to flush with exisfing adjacent shoreline*stabilization structures, except
when structures do not comply with the design or location requirements
descri he `n
The propo d arm ring extends from n-- 15' back from a non-fish bearing stream to the north,
to the herly extent of an existing pier, ramp& float. The proposed armoring will not
extend furt ier water-ward then any neighboring features.
ConstAic5on ct stabilization structures must be completed prior to any backfilling.
As indicatc J the BEJIMP,the construction is likely to proceed in small sections by the
owner, who ill Im ckfill the portions of the rockery, that he completes at any one time.The
total proje mph lion time is expected to Last approximately three weeks, Nvith most of the
work being rfo ed during week end stays at the residence. Mr. Colgan has also indicated
that he ma a nplo a contractor to perform the proposed work, Whoever performs the
proposed v ot c wil be required to comply with Erosion and Sediment Control Kest
Manageme t roc ces.
All cis tructi materials, including riprap and backfill, mast be obtained from an upland
sourc _
ltiprap quary rock is expected to be procured from either Little Creek Quarry,or front
the:Taylor romn Quarry located south of Shelton.
• tru r�s mt st be driven into the reservoir bend a depth sufficient to prevent
under Tiining used by erosion.
The propo ripe tumor is specified to be keyed into the beach substrate roughly
2-feet. The ri rap dace,by its rough facing/texture is expected to minimized scour
produced b y the I ping of wave water down the face of the bulkhead,
Fite;C:>Prgje s 1`P_Cf an(Y-Oo-kyl Addndni 8 of 11 10,+26/201
TAHJA ENGINEERING, Inc.
PO Box 235 11 -port, IWA 98548
(360) 877-9512
tru mtA I tae structurally tight to prevent seepge of backfill material.
Beach grave s wd i Ats excavated to install the proposed riprap armoring wvill be re-installed
as backfrll h nd rockery it is assembled. A Ater fabric layer is specified bet-wee n the
baackfill mat n the excavated trench dug to install the rockery.The filter fabric's
purpose is t Id native soil in place while allowing groundwater interflow.
• All nu ts, ils, cables,straps, etc, used to secure and support structures most tae
No corrosivt r0ted kls have been specified for installation in the proposed work.
• All t u must meet or exceed ds estabirshed in'Best Management
Practic s i or th P Use of Treated Wood in aquatic and other Sensitive Environments
Sectior 2. )-
No wood m, ti*ials iave been specified for installation in the proposed work.
Page B-7,P; r rap 1.
TacomaP r es that Shoreline Use Permit Applicants follow guidelines from the
lydegrade d am k Rotftvon Go ernes(WD 2)and Chapter 220 of the
Washingtor S ate reunistrative Code AC 220) designingwhen tithe stabilization
measures. ection must incorporatemitigation measures as necessary to
achieve no loss productive fish habitat. The following highlights key points of WAG 220;
however,t gu' lines may change over time App4icants proposing shoreline stabil,ization
projects, I I with Mason County and Tacoma Power staff to assure they are familiar
h cans
The BF/Ili 3repa ed for the proposed project has addressed project impacts and
appropriate: i dgati, tr measures.
Page B--7,P *rap ?, 3 &4,
Repair an ropta rn,e nt of existing shoreline stabli Lion structures
When an rig faead is being repaired, construction shad occur Nrther wat rd of
the existi balk than is necessary for construction of the footing
Remnants o `'eat "pile bulkhead are still in place near they southerly end of the,proposed
armoring, 'l e,arm ng proposed is landward of dose 11 old pilings which aTe'sche�dul;:d to
be removed desc 'bed in then BE/HMP.
An existan str uct may to replacedif there is a d str`ate�d need to protect principal uses
fromer ' tau by currents or waves arvd not caused by normal sloughing,vegetation
reffict, p0
The propost armoi'erg is not being promoted as a replacement for the"failed" piling
bulkhead. T kiphoti igraph on the next page of the remnants of the:original piling bulkhead: is
an indicatica i Of the erosion occurring at the Colgan property. Since,the installation of this
piling bulkt,00,rot hly 5 feet of shoreline has eroded away.
The propo pmo 'ng,is being promoted as a new structure.
Fite:t`; Proje l :W-Colli 2n G a-Rpt Actitauk 9 of H 10/26/2016
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360)877-9512
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Page B-8, I ar�agra 1,2& 3;
Replac l stnA ture shall be desr"gned, located,wed, and constructed to minimize effects on
shoreline w4cess and fish and wildlife habitat_
The propo� d armc ring is not being,promoted as a replacement. The BEAAMP has been
developed lens this requirement is met..
Replacern n of a led bulkhead shall be permitted in the same location and dimension as the
original bu d, such replacement is commenced within five years of failure. The burden of
proof of 101 AM the original bulkhead shall be on the applicant.
The proem -dl,arrnring is not being promoted as a replacement.
Existing1he
that are Ding replaced shall removed unless removing the structure
would cmor ecological disturbance than leaving it in place. Replacement bulkheads shall
not encrwat rtt of the ordinary high water rr�arc unless a geotect►nical assessment
conclS file ly feasible way to address overriding safety or environmental concerns. In
such re acernent shall abut the landward sick*of the existing structure.
The"old"i 41 ng b lkhead's removal is described in the BEA IMP, including;removal method
and remedi 1 actioi s.
Page B-8 c ion .1 Excerpts from WAC 220!lank Stabilization Guidelines;
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Sank slopi lig mu be accomplished in a manner that avoids release of overburden material into
the water, 0 verb rden material resulting from bank stabilization must be deposited so as not to
reenter ter,
The shorell iie elev ition at the back of the proposed armoring location is fairly level and is
planned to the t mporary storage area for materials excavated from the rockery's keyway.
Soils exca at d fa the rockery keyway will be covered with visqueen during any unworked
period last'ig for r, ore then 2 days.
File!C'.Proj is P-( pan t n.-Rpi,4ddndn; 10 of 11 10/26/2016
'I'AHJA ENGINEFRING, Inc.
PO Box 23-5. Hoodsport, WA 98548
(360)877-9512
Alteration pr dist bante of the bank and bank vegetation must be limited to the minimum
amount n sa to construct the bank stabilization measures.
The owner:&Jor hi contractor will comply with this requirement,
All disturb d areas must be protected from erosion within seven calendar days of completion of
the projec using etation or other marts. The banks, including riprap areas, must be
revegetat( J within one year with native or other approved woody species,
The owner vill abi e by this requirement, and will install sill fencing as needed to ensure no
materials e�cape tJh p d within
work area between work sessions. Erosion and sediment
control me�st res ould be installethin two days of Work idling. The proposed rockery
installation is bop to be constructed between Labor Day and Memorial Day(Wet Season)
and Westeill Wash gton's Stonnwater Management Manual fior Western Washington BMPs
Will be imlietileritcd.
Fish habi c)m nis such as logs, stumps,and/or large boulders may be required as part,of
the bank Jpi�ction project to mitigate project impacts. These fish habitat components must be
installed a c ding �o an approved design to withstand 1 00-year peak flows.
The BUH . I H P pro n ofed the riprap as an acceptable habitat feature. Additional mitigation
11 v
measures h v" not en promoted in either my work or in the BEJ IMP.
When Or othq f hard materials are approved for bank protection, the following provisions
apply:
I, B*k pro tt ction material must be angular rock.
2. The instat+tion must be designed and the rock installed to withstand I 00-year peak
flOos-
3 River gra Is may not be used as exterior armor.. except as specificalty approved by
T cma ower
The armor igits spc hied in the prO Jectplansas o o cane and twee main broken angular quarry
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rock.The ri)ckery c esign is massive enough and the lakes flows are minimal enough, that a
100 year fl:wwill otbeanissue.
River grav4ls are n t specified as any part of the design.
Bank pro filter blanket material must be placed from the bank or a barge, Tacoma
Power will a) d iroping onto the bank face only if there is an established toe and the material
can be co i ifi tc the bank face.
The owner- -ontrac or has indicated his intention of using one and two man rock that he can
deliver tot e work area in a wheel borrow or a small excavator operated from the land
landward o die la k D's OHW-738.
Please feel froar to contact me if there are any questions or concerns regarding this report or
my finding'�. Sincerely,
an.A.�Tana,
File:C- Prooj v IP-C11 an Geto-Rpe Addmhn 11 of 11 10126/2016
i as n County Department of Community Development
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Submittal Checklist For a Geotechnical Report
Instructions:
This checklist u t be bmitted with a Geotechnical Report and completed, signed, and stamped by the
licensed prof i nal(s who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason Co t Res urce Ordinance. if an item found to be not applicable,the report should explain
the basis for th nclu ion.
Applicant/Own r Ste a& Brenda Colgan Parcel# 423I8-50-00036
Site Address 110 Discovery Dr.,Lake Cushman Div.3 Lot 36 Hoods port,Washin ton
(1) (a)A d scossior of general geologic conditions in the vicinity of the proposed development,
Locate I cn pa (s) Pages 1-3 TAHJA ENINEERING Inc.Geo-Rpt
(b) A c isdussio i of specific soil types
Locate I c n pag (s) Pages 2-3&4&5 .
(c) A(Iscussioi of groundwater conditions
Locate c n pag (s) Page 4
(d) A c is usslo i of the upslope geomorphology
Locate I c n pag (s) Page 2
(e) A isousslo i of the location of upland waterbodies and wetlands
Locate On pa (s) Page 3
(f) A isoussio i of history of landslide activity in the activity in the vicinity,as available in the
referenced aps and records
Locate I on pag (s) Page 2
(2) A site F la whi identifies the important development and geologic features.
Lo ;d on ap(s) Geo-Rpt Plan Sheets 2-7
(3) Locat sand I gs of exploratory holes or probes.
Lc aged on ap(s) Geo-Rut Plan Sheets 3-4
(4) The ar a of the proposed development, the boundaries of the hazard,and associated buffers and
setbac s shall t e delineated(top, both sides,and toe)on a geologic map of the site.
La atled onMap(s) Plan Sheets 3-5
(5) A mini um of c a cross section at a scale which adequately depicts the subsurface profile, and
which i cmrpor es the details of proposed grade changes.
Lo at6d onMap(s) Plan Sheets 6&7&GALENA Stability Analysis pages 1 & 3
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(6) A desc ip ion ai d results of slope stability analyses performed for both static and seismic loading
condition Ana ysis should examine worst case failures.The analysis should include the
Simplif ac Bish p's Method of Circles.The minimum static safety factor is 1.5, the minimum
selsmi s fety f ictor is 1.1.and the quasi-static analysis coefficients should be a value of 0.15.
Locate pag (s) Page 4&GALENA Stability Analysis Printout pages 2&4.
(7) (a)Ap ro riate estrictions on placement of drainage features
Locate c n pag (s) Page 5
(b) Ap rc priate restrictions on placement of septic drain fields
Locate c n pag (s) Page 1
(c) Ap)ropriatj restrictions on placement of compacted fills and footings
Locate i c n pa (s) None
Page 1 of 2 1 Form Effective June 2008
Disclaimer: 0 son Co'my does not certify the quality of the work done in this Geotechnical Report.
(d) R o me 44ed buffers from the landslide hazard areas shoreline bluffs and the tops of other
SIC 3 on a property.
Locaten pa (s) Page 5
(e) R o me ed setbacks from the landslide hazard areas shoreline bluffs and the tops of
of er slope on the property.
Locaten pa (s) Page 5
(8) Reco m ndati ns for the preparation of a detailed clearing and grading plan which specifically
Identifies eget tion to be removed,a schedule for vegetation removal and replanting, and the
metho o veg ation removal.
Locateon pa (s) . Page 5
(9) Reco mondati ns for the preparation of a detailed temporary erosion control plan which
identifi s�he.s cific mitigating measures to be implemented during construction to protect the
slope om ero on, landslides and harmful construction methods.
Locaten pa (s) Paee 5
(10) An an 'ly4is of oth on-site and off-site impacts of the proposed development.
LocatqJ on pa (s) Page 5
(11) Specif a ions f final development conditions such as,vegetative management, drainage,
erosio c ntrol and buffer widths.
Locat n pa (s) Page 5
(12) Recory mendati ns for the preparation of structural mitigation or details of other proposed
mitigat on.
Locate on pa (s) Page 6
(13) A site i na p rai in to scale showing the property boundaries, scale, north arrow,and the location
and ne ure of isting and proposed development on the site.
Locate n Ma)(s) Plan Sheets 2-5
I, Alan A. ahia.PIE. hereby certify under penalty of perjury
that I am a civi et,gine r licensed in the State of Washington with specialized knowledge of
geotechnical/g o gica engineering or a geologist or engineering geologist licensed in the State of
Washington wi h peci I knowledge of the local conditions. I also certify that the Geotechnical
Reports, date 9/3a 016 and entitled Steve&Brenda Colgan Geotechnical Report meets all the
requirements c f the M on County Resource Ordinance, Landslide Hazard Section, are complete and
true, that the r p 'rts d onstrates conclusively that the risks posed by the landslide hazard can be
mitigated thro h�the i Iuded geotechnical design recommendations, and that all hazards are mitigated
in such a man er as to Drevent harm to property and public health and safety.(Signature and Stamp)
o, w`
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IS
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`SIGNAL F,1�
Page 2 of 2 Form Effective June 2008
Disclaimer: aspn CCI inty does not certify the quality of the work done in this Geotechnical Report.
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360)877-9512
Mason Con DC D
Planning iv1sion
427 W Ce ar St
Shelton, NTA, 9844
Steve&B nda C111gan
502 Su r Ave.'
Sumner, 983 01736
(253) 863�19118
Geotechnical Report
Lake Cushman Div.3,Lot 36
110 N Discovery Drive,Hoodsport
Parcel No. 42318-50-00036,DCP2012-00018
Mason Co. Case No.s; BLD2012-00605 & 606, SWG2012-00161
MEP2016-00021, SEP2016-00054 SHX2016-00043,
BLD2016-00546 Bulkhead
INTRODUCTION
I was cont ct in arly fall of this year by Mr.Steve Colgan who requested my participation
in developi ng a ge4 itechnical report for his property identified as Mason County Tax Parcel
No.: 4231 - 0-00 36,a residential Lake Cushman parcel located in the Plat of Lake
Cushman Dh'sion 3,Lot 36.Mr. Colgan wishes to install a riprap.rock erosion protection
rockery alc ng the 0HW elevation of his Lake Cushman property.
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I have visi d the s to numerous times in September of this year to collect topographic
informatio Bede to prepare this report and develop drawings to provide for the protection
of the prop rty froi a erosion occurring along the waterfront shoreline of the property.
Measurem nts we made using a Trimble T5415 total station,a 4-foot range pole, a Sokkia
model No.I, Q47-5 inclinometer, 100 foot and 300 foot long fiberglass surveyor's tapes and
other field q Apnii nt common to surveying. Software employed in creating a site plan and
writing thi report ricluded AutoCADTM 2006, a SoftreeTM Terrain 3-d contour modeling
program, ALEN TM Slope Stability Analysis software and MicrosoftTM Office Word 2003.
Currently t i&Colg n property is developed with a single family residence,driveway,parking
areas, an ej isting site septic system in working order.Power is provided by Mason County
PUD No.3 land the Lake Cushman Maintenance Company provides water service. The
property ecintains mmoderate slopes,which could require evaluation under geotechnical
assessment report i equirements, but the proposed erosion control rockery has triggered a
geotechnic l tepor level report as part of the building permit being sought for the shoreline
armoring.
The following
th' en elements are required by Mason County to be addressed in
geotechnic 1 repo prepared to comply with Mason County's Critical Resource Ordinance
(MCRO)S� ctions 117.01.100 through 17.01.104.
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File:C.Wroje�tsrolgar Ceo-Rpt I of 6 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
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1. Sit- ACI AND GEOLOGIC CONDITIONS:
The centrE I ortio of the property has been cleared in the past during development of the
property f r '•esid ntial purposes. The perimeter of the property contains second growth
timber an tive inderbrush vegetation. The average slope between the property's boundary
along Dis o ery I rive and the lake's shoreline(-738)was measured at approximately
14.3%wl ocal areas with 15 to—20%slopes but without enough elevation difference to
require a geotechr ical document.
Inspectionofthe4 ologic Map of Shelton 1:100,000 Quadrangle,Washington',finds the
property 1 cated ij i an area between Lake Cushman to the west,and the Olympic Mountain
foothills t the ea.,t.The upslope geomorphology of the area surrounding the Colgan property
can be ty fled as steep and mountainous.A portion of the Shelton Quadrangle map reveals
the site so is are c assified as Qad,Alpine Glacial Deposits further described as follows:
AL IN {� ACIAL DEPOSITS
EAlpine drift, late Wisconsivan (P leis(ocene)—Undiftcrentiated
dl 1 edium-gray till and ouhN'ash Sand and gravel with little to no weatli-
'ing apparent;clasts consist mostly of local sandstone trod basalt;
t iay contain alluvium,colltiviunl, landslide debris, and peat; gener-
tj ity restricted to tipper reaches of valleys in the Olympic Mountains.
As a porti n oft Geologic Map of Shelton 1:100,000 Quadrangle on the following page
reveals,t olga i property is located in the vicinity of several fault lines identified on the
following map as 1) the terminus of two faults emanating from the north and terminating
approximiftely 3. miles to the southeast of the Colgan property on the north side of Dow
Mountain(2')a fa ilt line runs southwest to northeast through Lake Cushman approximately
0.6 mile c s of t Colgan site,and(3)a fault line which follows Hood Canal is located
approxim t y 71A miles east of the Colgan site.The presence of these features does not
represent i Ln;unus ial hazard,and standard seismic analysis of the site is intended to anticipate
potential -,ctonic impacts.
Further in 3pectioiand soil analysis finds the soil to be classified under the Unified Soil
Classific ion Sy em(USCS)as a SM-SC soil division. The soils in the proposed rockery
location 91,ere fou rid to be composed of a silty clayey fine sand with a highly erodible
character, P obin in various areas of the property found firm soils from the surface down
which gr y I ecame firmer at depths between 3 to 3'/2 feet.
Investigal i0r. of ashington's interactive geological mapping and Washington State's Dept.
of Ecolof y, Coftal Atlas found no unstable areas in the Colgan property vicinity.
DNR OF] 03-15I Geologic Map of Shelton 1:100,000 Quadrangle,Washington
File:C:0 ec�Volg nlGeo-Rpt 2 of 6 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
360 877-9512
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2. S11 E PLA WITH IMPORTANT DEVELOPMENT AND GEOLOGIC
FE kTURE
An Onsite Septic 1k ystem(OSS)is located in the general area shown on the attached site
plans.The s tem was originally installed in the late 70s and a new septic tank and pump
vault were in talle on the property in 2012 (SWG2012-00161). The system is reported to be
functioning,s tisf torily needing no repairs or alterations.
A stream I s been identified and reported on in a biological evaluation prepared by Bio-
Resources im chaumburg.The general stream location is shown on the attached site
plans and nat from an area on the NE side of Potlatch drive which accommodates the
stream wit E 24" liameter corrugated metal pipe. A small hand dug drainage ditch is located
on the adj inng pr.operty parcel parallel with the Colgan property's westerly boundary.Lake
Cushman locate at the northwesterly boundary of the property. No wetlands or other
water body s were found in the Colgan property neighborhood.
3. LC CATIC NS OF LOGS OF EXPLORATORY HOLES OR PROBES:
Soils were e plorg in the soil probe locations labeled on the attached site plans. Typically,
the surfac s¢ils re found to be moderately dense with a small gravel content.The main
soil comp n ntsv are found to be clay,silt&sand with a more compacted-cemented
character e d th increases.
4. AlOF PROPOSED DEVELOPMENT&BOUNDARIES OF HAZARDS,
BI FI-ERS,AND SETBACKS:
Currently y pla as for installing an erosion protection riprap bulkhead along the shore's
736 to 73 sl toreli le elevation are being pursued. The attached project plans shown standard
File:C.Wroj fs�CQ1g4 Wea-Rpr 3 of 6 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
20' sidey of buil ng setbacks and a 25' front yard building setback.A 165' building setback
line from ho lakes 738 elevation is included in the attached site plans.
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A slope st ep eno gh to trigger a geotechnical report(>40%)was not found within 50-feet of
the propo o acts ity area.The stream located north of the Colgan property has developed
slopes tha could I rigger geotechnical concerns(might be steep&tall enough to trigger a
geotechni au,repo t requirement),but the stream elevation and slopes have little or no chance
of effecting any o the existing or proposed Colgan property improvements.
No slopes)w re f nd on the Colgan property that meet geological report requirement
threshold aid n recommended setback or vegetated buffer appears warranted.
5. Cl,,C SS S CTION WITH PROPOSED GRADE CHANGES:
Two Gros s ctio views are provided in the attached plan sheets. One cross section view
shows the pope 's profile from Discovery Drive to the Lake Cushman shoreline.A second
cross sect or vie is furnished which shows the cross section geometry and details of the
proposed h'reli r,armoring.
Stability ysismodels were developed from the AutoCAD cross section which indicates
acceptabl actorof Safety(static: 5.4, dynamic: 2.5).No grade changes are currently
proposed] the operty.
6. S OPE S ABILITY ANALYSIS:
The slope 3 On an near the Colgan property appear stabile and display no indications of slope
instabilit , ether I hen erosion of the shoreline along the approximate 737-738 shoreline
elevations
The exist ng leve ed building area in the central area of the property displays no discernable
irregulars ies,sett.ements,fissures,or evidence of consolidation problems. The stability
model an tlyzed rtrayed two soil layers, a shallow(<2') surface layer of weathered glacial
loamy till,and a deeper soil strata which differs from the surface soil only in exhibiting a
higher co esion slue.
Unified S i Clas sification System typing places the soils in a dual symbol category SM-SC,
compose f cla ,silt and fine sand.The soils are modeled as an SM-SC soil characterized
with the E hE Ilow oil layer having a soil unit weight of 120 lbs/ft3,the deeper loam layer
having a o 1 unil weight of 125 lbs/ft3. Both soil layers are modeled with a phi angle of 330.
The shadl v r soil s modeled with a cohesion value of 200 lbs1W, and the deeper layer is
modeled a hesion character of 3001bs/ftz. The Lake Cushman high water level at 738
is a reas a le e imate of the ground water elevation in the property's vicinity, and is used
as the ph eo tic w ter level in the stability analysis models.
Stability m,ilysi,.Jof the Colgan property generated a Factor of Safety(FoS)for the site in a
static Iy is o .4,and a dynamic analysis FoS of 2.5.Both values exceed the required
County f tclors o safety.
File:CAPr ,4,1Co1+ ,lGeo-Rpt 4 of 6 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
360 877-9512
7. RF)]OMM ENDED SETBACKS &DRAINAGE:
The slope tability analysis indicates that the shallow slopes present on the Colgan property
are stable 'i their i resent geometry and conditions and do not represent a landslide or
geological', alzard 1 o either the existing property improvement or the proposed property
improve m nts.No,setbacks from any slopes on or near the Colgan property appear
warranted.'
Drainage oiiri.the resent site sheet flows to its natural drainage direction generally to the
northwest owards e Lake Cushman shoreline.The majority of the Colgan property is
maintainec in a na ural vegetated condition which provides natural stormwater treatment and
attenuatio . The misting stormwater runoff regimes are proposed to be maintained as they
currently i t.
8. CL ,GRADING,AND VEGETATION MANAGEMENT:
The locati n ilonE the lake shoreline currently is vegetated with low grasses and native
vegetation E Kcavition for the rockery wall keyway will be performed with a small tractor
and hand t o s an will require very little disturbance of the rockery installation area.
Mitigation pl' ntin is promoted in the Biological Evaluation prepared by BioResources LLC
dated 7-29 2 16.
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9. ERD
r0N AND SEDIMENT CONTROL:
Inspection ll o the cries 1951,No. 9 Soil Survey of Mason County found the site to be
located in areavvith a Hoodsport Soil type(He). The Hoosport soils are typically not
identified i n the C unty's Critical Resource Ordinance as susceptible to severe erosion when
disturbed. k form ]site specific Erosion and Sediment Control(ESC Plan)is not required for
sites with ioi i-erodible soils,but my inspection of the site soils found a prominence of silt
and clay irli the so' matrix, and I feel the erodability of the soil is high.
Nearly all j 3tgrmw, ter runoff will exit the Colgan property over the northwest boundary of
the properj y into I ake Cushman.Runoff from the proposed property improvements will have
little if an i pad on the Colgan property,neighboring properties or Lake Cushman. Access
to the site ]ready xists off of Discovery Drive(a private Lake Cushman Development
Road)andl is stabl in its present condition.
10. 01�-SITE ND OFF-SITE IMPACTS:
The comp ted im rovements to the Colgan property will not resulted in any adverse on-site
or off sitepact
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11. SPECIFIC kTIONS OF FINAL DEVELOPMENT:
No specifi riequi meats appear needed for the property's conjectural improvements,other
then pro t4d in e biological evaluation prepared for the proposed property improvements.
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9/30/2016
Fare:c:iPtQf crtcoga'lceo-Rpr 5 of 6 I
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360)877-9512
12. Cp NDATIONS FOR THE PREPARATION OF STRUCTURAL
TIGA ON OR DETAILS OF OTHER PROPOSED MITIGATION:
Modeling ofthe rthwesterly descending slope indicates that the location of proposed
property i nprove.nents will be safe.The installation of a riprap rockery as proposed by Mr.
Colgan ar d as de,,cribed in the attached AutoCAD drawings is a recommended structural
feature ini ended t impede the advancement of the lake toward the upland areas of the
Colgan p perty.
13. SI, �PL WITH THE LOCATION OF EXISTING AND PROPOSED
D ELO 11MENT ON THE SITE:
A site plaji is atta hed as an appendix to this report and is hereby made a part of this report
along witl,i the cross section view of the property and the stability analysis printout.
Summary&�'Con4 fusions:
The Colg ro rty is stabile in its current condition and mass sliding or slope failures do
not appe t�thr ten the existing or proposed property improvements. Without the proposed
armoring�along e Cushman's 737-738 shoreline elevation,the Colgan property can be
expected o loose ground at a slow but constant rate. The proposed improvements are
intended o Imp le the advancing erosion and protect the existing Colgan property
improve eats.
Please fe I free t contact me if there are any questions or concerns regarding this report or
my find' s. Si cerely,
of
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�S�IONAL E��'ti
Alan A. Tahja,P.E.
Attached G otechnical Report Checklist
1 real view,4 Plan Views&2 Cross Section View
G kLENATm Stability Analysis Printout
File:C:Wr'je*slCot n1Geo-Rpt 6 of 6 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360)877-9512
Colgan X-Section A-A Static Stability Analysis
GALENA vmmnaoz
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Diacavary Drive
600 C
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750 LaY.n NsT:sr. onA __
do Sarface Qake 738 E1.1
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700 Analysis: 1
Multiple Stability Analysis
650
j Mettlod: Bishop simplified
surface: Circular
600 Results
ci ical(minimum)
550 ' Factor of Safety, 5.41
0 100 300, 400 500 600 700 800
Wred:30eay2018 P-d.908ep2018
Proier,L Colgan Lk Cushma, D-8 Lot 38
Stauc
EdE CADocumentifd sett gs%ownerft ocumentslGalena FileslModelslColgan 1.gmi Tahja Engln0BPing,InC.
Galena 5.02 Analysis I Lesults Licensee: Tahja Engineering, Inc.
DATA: Analysis 1 - S atic
Material Proper; iies ( materials) -------------------
Material: I (M hr-Co lomb Isotropic) - Shallow Surface Soil SM--SC
Cohesion Plfi U itWeight Ru
200.00 33 0 120.00 1.10
Material: 2 (I hr-Co lomb Cu increases with depth) - Subgrade Soil SM-SC Firm
Cohesion PI, i' I UnitWeight Ru
300.00 33.0 � 0 125.00 1.10
Water Properties ---- ---------
Unit weight of a^ter:j62.40 Unit weight of water/medium above ground: 62.40
Material Profit sly (2 rofiles) -----------------
Profile: 1 (2 points1l Material beneath: 1 Shallow Surface Soil SM-SC
0.00 9 0'.00 800.00 950.00
Profile: 2 (10 point Material beneath: 2 - Subgrade Soil SM-SC Firm
0.00 7j 9.50 152.80 735.50 227.00 735.80
248.50 737.0 249.00 738.50
260.00 740.00' 320.00 747.00 468.00 767.00
587.00 777.00 663.00 787.00
Slope Surface (110 poi' ts) --------------
0.00 130.00 152.80 736.00 227.00 736.00
248.50 738.00 249.00 740.00
260.00 742.00 320.00 750.00 468.00 770.00
587.00 780.00 663.00 790.00
Fite:C:1Projecfs1Co1ga'IS1i7bflity nalysis 1 of 4 9/30/2016
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TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Phreatic Surface (� poi ts) --- 0.00 738.00 650.00 738.00
Failure Surface -- -------
Initial circular'surfa for critical search defined by: XL,XR,R
Intersects: XI : 1 .00 YL: 735.89 XR: 400.00 YR. 760.81
Centre: X : 262.21 YC: 876.63 Radius: R: 180.00
Variable Restrai R
t� ---� -----------------
Parameter descri tor: XL XR
Range of variati n, 220.00 250.00 65.00
Trial positions ithini ange: 12 12 12
RESULTS: Analysi 1 - Static
Bishop Simplifie Meth s of Analysis - Circular Failure Surface -----------
-------
Critical Failure'CjrClE Search using Multiple Circle Generation Techniques
Factor of Safety' fbr i itial failure circle approximation: 6.26
There were: 1399'' slzcce sful analyses from a total of 1729 trial circles
330 ns-lysrzs terminated due to unacceptable geometry
Critical (minima ) Factor of Safety: 5.41
Circle and Resul s Su ary (Lowest 17 Factor of Safety circles) ------------------
Circle X-Centr* Y ,Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 320.0 ,911.36 200.00 736.00 479.55 770.97
212.50 5.41
2 307.2 919.45 200.00 736.00 456.82 768.49
212.50 5.42
3 308.2 1911.99 200.00 736.00 456.82 768.49
206.59 5.42
4 - 309.1' 1904.40 200.00 736.00 456.82 768.49
200.68 5.43
5 321.0 903.44 200.00 736.00 479.55 770.97
206.59 5.43
6 310.1# 896.64 200.00 736.00 456.82 768.49
194.77 5.40
7 322.63 895.32 200.00 736.00 479.55 770.97
200.68 5.46:
8 311.1j 888.69 200.00 736.00 456.82 768.49
188.86 5.461
9 327.4!, ' 919.35 220.00 736.00 479.55 770.97
212.50 5.47!
10 328.41, 911.85 220.00 736.00 479.55 770.97
206.59 5.971
11 298.66 897.05 200.00 736.00 434.09 765.42
188.86 5.4115
12 297.1 904.48 200.00 736.00 434.09 765.42
194.77 5.476
13 299.01 889.46 200.00 736.00 434.09 765.92
182.95 5.400
14 296.010 911.79 200.00 736.00 434 .09 765.42
200.68 5.4814
15 299.71 911.57 180.00 736.00 456.82 768.49
212.50 5.4 6
16 329.0 904.20 220.00 736.00 479.55 770.97
200.68 5.4 7
17 295. 0 918.98 200.00 736.00 434.09 765.42
206.59 5.4 5
i
i
File:C:WivjeclslColgan4 ia6ilityA alysis 2 Of 4 9/30/2016
i
TAH.IA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
olgan X-Section A-A Dynamic Stability Analysis
GAL
ENA ve w s.o7
it6o
I I
1051)
o.l
I
950
90D
Aa
850 �"a
6is<mrex7 Dxiva
m o�
La". WEE^aR ;r _ - - n al sc Surface tLate 138 EL)
7s0 _...-
il'iV
700 ss✓�'Jl nal sis 1
MultipleStaldilityAnalysis
Malhod: Bishop Simplified
650 surface: Circular
esul
600
cdlfcal(minimum}
Factor of Safety: 2.48
550
D
300 400 500 6DD 700 800
LOD F.dted:306ep 2818 P.owssed:366eR p18
f ec: coigan Lk Cushma D-$Lot 36
Dynamio Tahja Engineering,Inc,
Fe: CADowments and Sell 5%(P ACAMy owmentslGalenaFileswiodemoolganDyn.gmf Licensee: Tahja
Galena 5.02 Ana y�is esults
Engineering, Inj
DATA: Analysis 1, - D namic Material Properties ( _materials) Shallow Surface Soil SM-SC
Material: 1 ( h,r-Co lomb Isotropic)
Cohesion phi U itweight Ru
200.00 3 .0 1120.00 1.10 rade Soil SM-SC Firm
Material: 2 (Mlohr-Co lomb Cu increases with depth) _ Sub grade g
Cohesion phi P1 UnitWeight Ru
300.00 3 .0 0 125.00 1.10
Water Properti 's --- -T
-- Unit weight of water/medium above ground: 62.40
Unit weight of w ter: 62.40
Material profile (2profiles) ----------------
Profile: 1 (2',point ) Material beneath: 1 - Shallow Surface Soil SM-SC
0.00 50.00 800.00 950.00
profile: 2 {1 points) Material beneath: 2 - Subgrade Soil SM-SC Firm
0.00 25.50 � 152.80 735.50 227.00 735.80
248.50 737. 0 249.00 738.50
260.00 14o.001320.00 747.00 468.00 767.00
587.00 777.00 663.00 787.00
Slope Surface k10 po nts) -------- 736.00 227.00 736.00
0.00 130.00 152.80
248.50 738.00 249.00 740.00
File:C.O-gjectslColg n1$tabifi Analysis
3 of 4 •9/30/2016
TAHJA ENGINEERING Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
260.00 7 .00 320.00 750.00 468.00 770.00
587.00 780.00 663.00 790.00
Phreatic Surfad (2 p)ints) ---- 0.00 738.00 650.00 738.00
Failure Surface --- ---------
Initial circular surf ice for critical search defined by: XL,XR,R
Intersects: 50.00 YL: 735.89 XR: 400.00 YR: 760.81
Centre: 62.21 YC: 876.63 Radius: R: 180.00
Earthquake Forc 1---- -----------
Pseudo-static e rthqu ke (seismic) coefficient: C.150
Variable Restraints - -----------------
Parameter descri'prtor:; XL XR R
Range of variation: I 220.00 250.00 65.00
Trial positions, wlLthi range: 12 12 12
----------------' _----_ _ ----------------------------
RESULTS: Analyst,Ls' 1 Dynamic
Bishop SimplifilDdiMetiod of Analysis - Circular Failure Surface --------------
Critical Failur ICirc e Search using Multiple Circle Generation Techniques
Factor of Safet for nitial failure circle approximation: 2.58
There were: 139 psucc ssful analyses from a total of 1729 trial circles
330' a aly es terminated due to unacceptable geometry
Critical (minim m Fa for of Safety: 2.5
Circle and Resu t Sutmary (Lowest 99 Factor of Safety circles) -----------------
Circle X-Cent el -Centre X-Left Y-Left X-Right Y-Right
Radius Fo
1 299. 1 1 911.57 180.00 736.00 456.82 768.49
212.50 2.4 5' i
2 300. 3 1 903.71 180.00 736.00 456.82 768.49
206.59 2.4 4
3 279, 9 911.52 160.00 736.00 434.09 765.42
212.50 2.4 6
4 288. 9 1 911.88 180.00 736.00 434.09 765.42
206.59 2.4 2
5 291.$6 902.57 160.00 736.00 456.82 768.49
212.50 2.4 2
6 287. 3 919.29 180.00 736.00 434.09 765.42
212.50 2.4 3'
7 289. 6 904.33 180.00 736.00 434.09 765.42
200.68 2.4 4
8 280. 2 903.72 160.00 736.00 434.09 765.42
206.59 2.4 4
i
9 312. 1 902.20 180.00 736.00 479.55 770.97
212.50 2.4 4
10 301. 8 895.66 180.00 736.00 456.82 768.49
200.68 2.9 7
11 290. 5 896.63 180.00 736.00 434.09 765.42
194.77 2.409
12 320,02 911.36 200.00 736.00 479.55 770.97
212.50 2.409
13 307. 6 ! 919.45 200.00 736.00 456.82 768.49
212.50 2.5 6
14 308. 0' 911.99 200.00 736.00 456.82 768.49
206.59 2.5 6'
15 281. 8 895.74 160.00 736.00 434.09 765.42
200.68 2.5( 7'
I
File:C:WrojectslColgan tabllity lalysis 4 of 4 9/30/2016