HomeMy WebLinkAbout501044011 Geotech Assessment
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05/23/06 lS:3SFAl 1 ~60 647 3144
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s1'RA'l'UM GROUP
I~\ GrII1I s-.lIelI....... WA 9Wl
_ (360)714.9409
JUDIlI5. 2005
PetF\eel
13353314 AveIIUC South
ScaUIe, W A 98144
Re: 0e0IaI1 AII...I
Tax hrccls50104401I111d 501044012
lofICIoD CQunty. WesbiDetOO
Dear Mr. f\cel:
StratuIlI OJoIIP Is pleased to pteIellI the results of our geolo&Y BSSC8SJlent of the above
refonnced propcty, ~ putIlOSt of this geology asgessment was to I) lletl:I'IDiDe 1IIe IUIlabIIltr
of ~ property for the aitDls of a _eIIC8. 2) quall1BIively MIuate the risk of slOpe faII\JR5, DI
3) ptOVide __ site deve\opJIleIIt BDd mAint'-llAl\Cl! ""nmm_OOS for ~ orllE
~adi- to A ~ _ble bluff. Bast4 on my inaigalion of~ si1c aM
vicifttty. il it my I\PilIion th8t ~ site is suiIable for de\'CIQImClIlIll "residcnlial jJUpen)'
provided the ~)ltSellted in thiS reporIllll follo'l\l4. .
SCOPE or SEllVICES
The ~ of OUI' ItlYices included the following:
1)
Conducted a si~ ~~l to visually inspect the subject ~ and viciaity
incIudin; the bluff slope conditions, ~opc conditiODS on IIICl in tile vicinity of tile
properly 8IId sOOl'elitle conditiOll1,
oburved surface soil conditions on the sI10reline slope of tile p1'O\II\Y and . tbc
top of the blulfby excavating sbaIIow \!aDd duB test pits.
Prepared 1Iris \'ellCIl summariziDa our fiOOiDgs, includiDg III miuIIim ofdlc
few'bili!y ofbui1diDa a residlD:e 011 the subject 1IOIlCI1Y.. qualitlli1e M1uBIion
of the IImIB b\ulf Mlbi1it)'1 ~ tiJrsitodovc~ aud
~ fO!' further inMigation, ifllCCCSS8lY.
2)
3)
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GENtRAL GEOLOGY
NorIkw<JWll Waohl'\ll"11 has been ~ by coatiDeDtll allUlifn a.1Our ~-
the p\eistocelle Epoch (1.6 millioo to 10,000 yeatllgo). DuriPll\bQe aIacisllID4l1Qlg,lIj ,iDs
IJlll!qJlacW periods. the uIlderIyioa bedrock was eroded and I rcIetiveIy 1bIck layer of rJ->>l
...t_ aa4 interglacial fluvi81 sedimenlI were deposited over tbe IIIIdcrlyln& llcdnJo:k hi die:
viciDity of the subjcgt properlY.
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Th8 ~IQlic M., of!lurficial DeDosits in the ~ 30' ~ 60' OIl~n"ll!. W.......~ ~Qunt.
MinIrd md Dembrof. 1993) indicates the IIIbject JlIOl*tY IS IIIlderIain by V - glaciallIU.
The' J. C W' (~1976)~tbe
suh;eet property 8Dd the \IhJtf exposed on ~ subject IlfOIlefl'Y are _lain V. ~ till
UlIdifferentiatedpre..V- glaciation deposits, r- Vasbon glacial tin coMistsofvsy COIDJICl.
poorly sorted lIIix of .,.Iilt. SIIId lIIId aravel wilh occasiorW houlders. TheIe !IlIlIimeIIb were
~teddi!lllllly by g\JciaI ice4urina:thelutg1lCi8lperiodapproximl!dy II,OOO~ 1llU.
The pie- vashQa alacj,tion dellosib ere described IS ~ of hltlabedded oxidized blown.
red..browD. IIIld pay pavel. -. silt, 8Dd clay. Tbe Iayas an: moderate\y to well bedded and
I1Illllllit COil_11IM 8IIIOIIIIts of ice-c0ll\aCt ck1loIits IIId \lIIlWISh gravellllCllllld. Garllly
the UIlit ill nonaJtciallllld bas abundant peat and woody debris. Thallll !IllCti1Dllllb .... deposited
sometime prior 10 the \est elacial event and include dfclosits of the Wbidbcy IIld Olympia
o"'1llI"';'1 per\ods. The sediments have been overridden and cotOOidakd by gIacia\ ice.
My obIervIlioJla oa the bluff face IIId within road cuts 6ioDa 8Il cxisIiIlg roed CIl dle lite a teat
pits OIlb \IIPI' poJ1iOIl of tbe PfOIlCl'IY IIId 011 the bluff iIl:e in the viclllity ofdle property is
COIIIistent with the m~1Ii of Birdseys (1916) desl1ibed Iilovc.lhc uplaM .. of !be
pl~ lI8ldy to lIIld in &Orne loeatiOlli partially down the shoreline slope are UDderIain by
glacial till. Most of the ahorelilll1 slope is IlllderIain by coarse. well paded. rolllllled ameI wi1h .
s8Dd IIld tilt. ScYeNl dillCODtinuous one- to three-fcot thick sand layen and slit ~ were
obIerved on the bluff filee.
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V<<11\1rd. varved IlltJ are 1o\:aled nearllle base of tile bluff at &e\'lllIl JocatiODl. All oftbe silts
IIlIlI paveIs wore 'Iflt'J COIIIp8I't IIld dcme. No woody layers were observed on die bluff face on
the subject property; however, woody laycn an: pmentat neJlIby _ OIl the bluff ace. I
interpret the .Its to Lave b Jepo~leJ in a 1luVW.. tlft8ffB 1111 glfiw
advance as they are in a hiahly compact and dease CODdiliooa some orpnic material is
pmeDt.
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SPECIF1C 8m OBSER.V ADOl'lS
The subject property consists of an 1Itl\8nt1 n with velY iCIltlc slopes boIIIIIlcd 0II1bc SOIItll z.'\d
t!It ~ R Qteep sIlO* blu[ Tho 1000000n oflll _ iI ~ 911 fiam lad a silt
pIaD. WtclI with televallt iDfunnation for iII_ve )lUqIllSelI is JllOvided in r_ 2. The shore
of Hood Canal bouDds!be JOUth side of the )lOIleItY. FIIbrmnan Hatbor.1D inletfmm Hood
Canal. be_ the east tide of the )ll'Il1le11y. Most oflbe UIlIand llOltion of tile JIIQIleI11 is coven:d
primlrily with Ileccmd llfOwth Pollilas fit IIDli aIdel U. witl1lllllmderstory of IIIal e\Iel'IlI=I
hIIllkIaberry. aod fem!I and other brush, A ~ clearing i!llOC8llld in lhc ceim.J )IOltioa
oflbl west portion oftbe property ITax p~ SOlO44OlI), A tTIiIer and umllllllechre '---..0
at this cIeariDg Iocatlon. ouo;ouou
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I... 13.200$
PlJfel& 50104'l01' on<I 501044012. 10_ C-'l. WI.
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The .boIeIiDe Mull' 011 the south side of the property md east side of the proPCItY is
Ipfft~ 170feelbigh. TbcbluffSl~an....~=~~:A.~
and alder wit\I a thick UllderstoJy of a varietY of IlIIW1 inclllUlI'i \lIIIMIo'l 0 polson
IIfCI! on very steep sections 8Ill not vegetated,
An old rolld i,lOC8led 00 the Itcep blull' slope. This road IlIg\es clown the bluff slope from the
lop of the bIuft' __ the lOuthwest comer of the to the sboreIiIlo 011 the east Iide of the property 11
Fishcnnln HIrbor. The road is pimIriIy a full beIIch cut into !be II. alld provi4e8 eIII'/ ICI:eII
to the lower part of the popertY. No slope fajlures have imp8cIed !be IIlId &loDg !be so~ -
b\ul'l' ,lope. Near 1M lower part of the roed near FishcJmsn Hm. an old slo)lefail\lfe of the
road lOuttl bas _ place. AaotI1er old road that is mostly ll'ee cavm _lip the eutllope
of the pIOpel'ly to the upiaDd area south of the IUbjcct Jlropelty. Both of ta road ll)lIlIIIl1' to be
fllirly old hulcI on the IJeeII arowin8 on the s1opc11 and immediately adjacent to the roads. Neither
road bu been actively uaed for llIIIIY years. The roads were likely fonnerly used to -
Fisbemlaa Harbor lIIIdIor loaaiag roads.
The sborcliDeanthe east side of the property consists of tidal cstuaIy ofFjsllermaq Hlrbor.
Fi.sberman H.bor is . natar8l harbor formed itI drowocd valley, The shorcIinc is very protected
from wave _II by . ameI bar tbIl extenda IICtOSS the harbor 1lIIlrBIu:c.
The lIhore1ine ClI1 the lIOIIIh side of1he 1ll'OPllrlY COIIIiIt8 of. gnMIllllld cobble beaI:h 011 the shore
of Hood CeuI. Erosion at !be toe of the shore\iDe bluff takes pip dmiDg very hiah tides
combined wl.th wind pncdIed waves. ExJloted lXIil Bt1be base oftbulope coosiSlS ofvay
camped SIIld and "vel with silt ~ Vtl'J compllCt silt .00 clay Iaycrs tha1 aD 8flI'I8I" 10 be
ero&iOll ~ A few Bid landslide deposits arc located at the base of tile s\ope at sevcral
loea!ioos. NINrII ahore\iIIa processes IlIe lakiDa place at this scctiOll of shoreline. No sboreIine
annoriDg _ obeerved along this sectiOIl of sbore1i11e.
The b1uff'is eroded by a combiaation of wave 8Clion that undermines the bue ofUlc bIIIff.
rallellina olmtterill off the exposed soils on the unvqctate<\ portiOllS oftbc bluff, alld periodic
sbalJowtopsoil W1-. The roatcriaI CJOded flom the blulTfacc is removed from tbI bB&c oftbc
blulJ IInIi traIIIpOrIeli aIona the shore towards the cast by wave 1Illlion. VfflY little Ilodslidr. debris
has MlIIlIlu!llcd at the base of the bluff.
I did 1lIII obaervc II\)' evidm;c (tension crllllb or trees lOIaled iDwmd ~ from tbI top of the
bIuft) lDdicatin~ In iDclpient Jloba1-1ype or dc:qMIeated tiiluR: on the subject property. The
plU_ oflllnishl ma\\lre Douglas. t'iri OIl the blufffacc indicatc$lhat!be eroaioII. on the
steep slope must be rehllively slow. A few smal1 WIUr seeps III'C presenlllll the lower JllIll oftba
slope. The _ of..,.,ptng water d1<1 not appeI1' to be crodina at . faster nde thin the Ill)'Illl
...... 0.00.
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65/27/2666 68:43 3664523383 JSF ENGINEERING
05/31/06 07:35 FA! 1 360 647 3744 STRATUM GROUP
S/JllOl> ""'.: \10). V~ "~~ \tt....lc "6-tob J
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PAGE 61
liiIos
1P 3~ ~ 311-qC(l}. J>k4d)
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J_ 15. 20llS
Parcels SOI044OIII111d SOI4Ml12.Jefferson County, WA
GeoIocr · .1It
abo"" or below the seeps. Soil at the seeps consisted of very compact sand and gravel underlain
by very hard silts. .
CONCLUSIONS AND RECOMMENDATIONS
Baged on my visual inspection of the subject property ancI vicinity, a residence can be located on
the upland portion of the property such that bluff erosion or landa1iding would not tbralItc:n the
stnJcture withi" the expected life of the structure (75 years). The residence should be set back 40
feet &om the top of the of the steep shorellile slope. It is my opinion from an engineering geology
llfandpoint that this setback distance wm be adequate tel allow for expeded bluff face faiJunls that
will result from the continued erosion of the base of the blufFby wave aOlllllld ravelling of tile
exposed soils on the bluff slope. For purposes of this repOrt, the telp of the steep slope is t1..nnM
as the location where the slope begins to exceed 20 degrees.
It is my understaDdina that the preferred buIJding site is located in the existina cleared area on the
upland portion of the JlIt>~ty. Some fill soils may have been pushed towards the south portion
of the cleared area at the lime of clearing and grading. However, I do not anticipate that the fill
soils are vet}'!hi" and it is unlikely that fill sons will be encountered if the home is setback 40-
feet fmm the top of the steep slope. The home should be founded on native undisturbed soil. The
native soil COM;sts on the upland area collSists ofvllfy compact sand and gravel or ghll:ial till and
will provide adequate foundation bearing.
1 do not anti~vate that the development of the subject property will cause any negative impacts
on the stability of the slope to the east of the subject property as 10Dg as the foJ Jowing
m;onm>"~ons arc followed.
Soils on the upland portion of the property appear to be relatively well drained. Roof dtainage
and any stonn water should be discharged dispelsed onto the forest floor of1he upland area of the
property.
Site ...ading soils Of debris, landscape debris, or any other material should not be disposed of
over the bluff face or placed at the lop of bluft: Over time debris will break doWn and form an
unstable mass that will slide damaging the slopes below.
Native vegetation. partiCularly tress and low native brush within 30 feet oftbe top of the bluff
should be disturbed as little as possible. Trees may be limbed for view purposes. IftIec$ are
thiJmed or limbed for view pmposcs on the bluff tiu:t; all debris from limbing should be removed
from the bluff faco. Some thinning of small DouglllS fir trees growing between the tope of the
bluff fiIc.e iUld the proposed home site should not cause any problems as long as the native brush
understory is left in pIace.
SbEIIn o~
PiIIl:S.16.05
4
OS/23/06 13:38 PAX 1 aau D~' ~I~.
_ 15.lOO5
~. '0104401l1hd SOI440I2.Jet\inOIICo\Jnll'. W/o.
CeoIeIr .UI ~-
A septic drain field sbouId not baVc any have any advcnc affects on 1he stability of tile bId as
long as the _ field is located at \east SO feet from BDY dopes steelJSI'than 40 degrees.
.
Bleil'''' the bluff is III elOCIia& blufl; slope fai1\1f81 !hould be expecte4 to occur 011 a periodic
basiL TbIl aaly way tn Pftlveat coatlnued erosion of the bile oflhe bluft'ia to consttUCt bard
Il'mOI'in& It 1M ,hclreline at lhcbllScofthe bluff. H~. die eroclIqbJllffacll as a feeder
blufl' (erosion III the b1uB' provK1cs "",Ii_) for the beII:bcs east of the subject ~,1Dd any
~ ~ will have II neptivc ~ on plOllIrtics down dtift from the bluff. The
COllJlrUelion of sbotelille annorin8 on other ptOPerties may cause an iDcrca3e of erosIoa oflbtl
..,bject ~. '!'be owner of the subject properly should ~ J6son C_ ofllclals
~ IllY JlICIlOMcI shoteliM protection prajects along the bluff or any 8bore1ine prollIClioo
conlltruellon. Thm life current1y 110 sborelTnc-armorcd IICU along this mctdt of cout\lne.
Pleuc note th8I. d1art life iDherent risks asmllled wi1h buildiDg on \otI near or alijll:Olll to -
tlopes. 1'IIllIe.. risks that the building owner sbou1d ~ IIIId be willing to IICCqll If
conditiCIIIS appar difl'ereltl than those destribed in thisl\!flOd, or albct conooms _ we reqIIllIt
that we be DOtffied SO we can revieW those areas and modify our recomJ1lI"'~ as requiTe4.
Stratum Cboup sppIOCiala the opportunity to be of service to yolL Should you hIIvc lIlY
quMi01l.l rquding our ~ please coatact our office at (360) 714-9409.
Sincc.rely yolll'S,
Z!v--
Du M\lSh_. M.Sc., 1.&G.
LiceD:JCd Enaineerina Geologist
S-Oloop
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06/01/08 11'31 FAX 1 380 647 3744
JSF ENGINEERING
STRATVIl GROUP
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JSF ENGll'oEERING
S'I'RATllK GROW
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