HomeMy WebLinkAboutGEO 2024-00100 BLD2024-01177 SFR - BLD Engineering / Geo-tech Reports - 2/27/2021 PLANNING
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Geotechnical Report
Proposed Single Family Residence
200 E Smith Cove Way, Shelton
Parcel No. 12019-50-00018
Mason County, Washington
February 27, 2021
Project#20241
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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APPENDIX A
SITE PLAN
VERTICAL AND 10IIAATA SCALE-
SCALE, 1 INCH•60 FEET
7t 60
PRWOSED HOUSE
EXISTING GRACE
j%1
= CASE
INLET
POORLY GRADED SAND
WITH GRAVEL (SP)
SECTION A-A
FRIJECT/OWNER/ LOCATIO(-
SINSLE FAMILY RESIDENCE
&EOTECHNICAL REPORT
�Tt�Tii 9-SD-00018
NOTES, VASO6 CtWTY,VASHDKTON
I)MINOR GRADE CHANGES REWIRED IN ORDER TO ACHIEVE E114WC"cLH ENGINEERING
POSITIVE DRAINAGE xx 2)THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF jnp W,SHINGTON 98528
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. $* .'N76
LOVER DEPTHS ARC BASED ON SITE GEOLOGY,
YELL LOG(S),AND/OR E%PERICNCC IN THE GENERAL AREA SOIL PROFILE
SCALE, 1 INCH =80 FEET
0 20 46 ao
APPROXIMATE TOE OF
CRITICAL SLOPE EXCEEDING
40%
PROPERTY LINE �
CASE INLET A
9�
APPPUAIMTE TOP 1 0EMC'AL.
SLOPE EXCEEW" 4*%
50 FT VEGETA71Dd BUFFER FROM `ROOF DRAINAGE TO
TOP OF CRITICAL SLOPE 'o BE 7IGHTLINED
BYIIND SLOPE TOE
f IM
OUTLINE OF BUILDABLE AREA
11
TPIO 60 FT CONSTRUCTION SETBACK FROM
TOP OF CRITICAL SLOPE
A
A
39%±
h
CO � mo
L�
L
9y n
tmtk� polli r?16WdTaY LLMMIXb
1.Lim41-9 Wc.ir11.R&T AY Tawny a ra T`IM Lit W"AL I love..=;: 5g4r"f F. r lT:Y �E: T,rk9t
or.fif yw'r"t w N:"I?.xvr4a m gF 4,lymmm m r4w,Pp To no I GIMI EC"411MAL
&CIVIRTIUK b%I+E IMT FG102Ei"W'71 S<
CO4-GUM YEW Z%-W NJ17EL FROM A? I Z R 30JM NO 90 E'.YKM Ctrf";YAV
IIaWol-Imil tl VL'1.3 1lAZA*JffSn v;::YN.:Qit"4 X r+-*ul+.x7@itf:I, LIED PMpFiY.1AA':� ';ilkg
KFawl.
A ZMA&M 3r�NOT Yl is4:CL1iFLL 3-.R^fE'.'A:OCSTtO yIZy�, .• �
W L°TY_FA9YA£B THAT WE WWW Af5i., AC'9F OF ^LgPM 7LE +"f" Ll.V-JarMTSI izl4MG
Er tALLP='t Ws-Fs frATLW--F'rr-. WITH w3?'TI)m TU -HF pol"JTFT P]I=s"
LTIES MIST BE VEREM BY Tit DWNM OCCaMIC"AT:114 L'1 rtE ILAPE DGICATM MMFAOL MASAMTDY VM3
GEOTECIt.bB.AL REPORT PROYIOE orrw=.B;IFPERS,x7THL CTC..VITH 36*-RrJ- 874
RELATIMN TO GM R C FEATURES,YO. PROPERTY LM.6•THESE OEO MIlt 03411LAt
rrAritu NAY w Luca m. am nc Sister litre' y DR NrawwMB I nl 1tv SITE PLAN
?ems
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Crosser Geotechnical Report DATE OF LOG: 2/23/2020
PROJECT NO: 20241 LOGGED BY: RJM
CLIENT: Teresa Crosser EXCAVATOR: N/A
LOCATION: 200 E Smith Cove Way DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI DEPTH N CURVE
AND TEST DATA 10 30 50
0
5P Poorly graded SAND with GRAVEL.
1 -
2
i
3
4
5
6
Excavation terminated at approximately 6
feet
7
8
9
10
No Groundwater Encountered ENVIROTECH ENGINEERING
This rnformabon pertains oNy to this boring and should not be Geotechnical Engineering
interpreted as beng rndvNe of the entire srte
Map Unit Descnphon Indianola loamv sad.5 to 15 percent slopes---Mason County.
AashrNtw
Mason County, Washington
lb—Indianola loamy sand,5 to 15 percent slopes
Map Unit Setting
National map unit symbol 2t635
Elevation 0 to 980 feet
Clean annual precipitation 30 to 81 Inches
A1ean annual air temperature. 48 to 50 degrees F
Frost-free period 170 to 210 days
Farinland classification Prime farmland if Irrigated
Map Unit Composition
Indianola and sundar soils 85 percent
f.luioi components 15 percent
Estimates are based on observations.descriptions.and transects of
the nrapunit.
Description of Indianola
Setting
Landform Eskers,kames.terraces
Landlorm position(three-dimensional) Riser
Down-slope shape. Linear
Across-slope shape Linear
Parent material Sandy glacial outwash
Typical profile
Or-0 to i inches slightly decomposed plant material
A- 1 to 6 inches loamy sand
Bw l 6 to 17 inches loamy sand
Bw2- 17 to 27 inches sand
BC-27 to 37 inches. sand
C-37 to 60 inches sand
Properties and qualities
Slope 5 to 15 percent
Depth to restrictive feature.More than 80 inches
Drawage class Somewhat excessively drained
Capacity of the most limiting layer to transmit tvater(Ksat) High to
very high(5 95 to 99 90 inthr)
Depth to water table.More than 80 inches
Frequency of flooding None
Frequency of ponding None
Available water capacity Low(about 3.9 inches)
Interpretive groups
Land capability classification(irrigated) 4e
Land capability classification(nonirrigated) 4s
Hydrologic Soil Group A
Forage suitability group. Uroughty Soils(G002XN4U2WA),
Droughty Sods(G002XS401 WA)
'I:.\ Natural Resources web Soar Survey 221r2021
dg-M Conservation Service National Cooperative Sal Sur.ey Page i of 2
t �
Map Unit Description Indianola loamy sand 5 to 15 percent slopes---Mason County.
A'ash+ngton
Other VBgetatrvp classification Droughty Soils(G002XN402WA),
Droughty Soils(G002XS401 WA)
Hydric soil rating No
Minor Components
Alderwood
Percent of map unit 8 percent
Landform Ridges.hills
Landtorrn position(two-dimensional) Shoulder
Landform position(three-dimensional) Nose slope,tall
Down-slope shape Linear,convex
Across-slope shape Convex
Hydnc sod rating No
Everett
Percent of map unit 5 percent
l andforni Kames,eskers,moraines
Landform position(two-dimensional) Shoulder,footslope
Landform position(three-dimensional) Crest,base slope
Down-slope shape Convex
Arross-slope shape Convex
Hydnc soil rating No
Norma
Percent of map unit 2 percent
Landtorni Depressions,drainageways
Landform position(three-dimensional) Dip
Down-slope shape Concave,linear
Across-slope shape Concave
Hydnc soil rating Yes
Data Source Information
Soil Survey Area Mason County,Washington
Survey Area Data Version 16,Jun 4,2020
t W% Natural Resourcos Wab Sal Survay 2/21/2021
dd" Conservation Service National Cooperative Sal Survey Page 2 of 2
Map Unit Description Sinclair shotty loam.5 to 15 percent slopes--Mason County.
Washington
Mason County, Washington
So—Sinclair shotty loam. 5 to 15 percent slopes
Map Unit Setting
National map unit symbol 2hn7
Elevation 0 to 300 feet
Afean annual precipitation 25 to 50 inches
P.,fean annual air temperature 50 degrees F
Frost-free period. 200 days
Farniland classification Farmland of statewide importance
Map Unit Composition
Sinclair and simdar sals 100 percent
Estimates are based on observations,descriptions,and transects of
the mapunit
Description of Sinclair
Setting
i.wriform Till plains
Typical profile
H I-0 to l►inches gravelly loam
H2-I1 to 35 inches very gravelly loam
H3-35 to 60 inches gravelly sandy loam
Properties and qualities
Slope 5 to 15 percent
Depth to restrictive feature 28 to 42 inches to densic material
Drainage class Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat) Very low
to moderately low(0 00 to 0.06 imhr)
Depth to water table About 18 to 30 inches
Frequency of flooding. None
Frequency of ponding None
Available water capacity Low(about 3.7 inches)
Interpretive groups
Land capability classification(irrigated) None specified
Land capability classification(nonrrngated). 4s
Hydrologic Sod Group B
Forage suitability group Limited Depth Sods(G002XN302WA)
Other vegetative classification Limited Depth Sods
(G002XN302WA)
Hydnc soil rating No
Data Source Information
Sod Survey Area Mason County Washington
Survey Area Data Version 16,Jun 4,2020
i♦Uq Natural Resources Web Sort Surrey 222112021
i Conservation Service National Cooperative Sal Survey Page 1 of i
WATER WELL REPORT
Ongiaal i I•cM-Faoletgy,I"cM-otaoer,3"caps-drift. CURRENT
s't'u t#1t,t Notice of Iatent No.V421M
Construction/Decommission('s"in cock) �(�6
® Construction i3Unique Ecology Well ID Tag No.Ann 978
❑ Decommission 0MINAtINSTAIL 770N Water Right Permit No.
Wake Indent Mrueba
PROPOSLDIIS6: ®Dolmewc 0 Idrtrw 0 tdmietr Property Owner Name Bonnie Reece
DMIMIS RAINIIIIIIII 'DfRR+M lift .....u.-,_.., WOSITMA1MM
TIMIGMp Oslft�w•rtolfrefwle>«nwf fl�l� � ! 5 y
- ltv 9tfdl >teaerwliart e6isi tlaff l
.48>oslvili 181if lNshg Le1d 1AI-Womgyc>t$-i;Vt�rpSJ@ SAo $its M I3e
1Mtt�0srh mwwmg t" 06VA'dftwit
paitell�ifettltar�. �
flN�IrTt�,)r'T90ntfMElAMi � T �
fietisg H W AIId r M us Am art A.we In R { is,t.r SO Lot ...�.__ Miz_.__.. t,-, ._._..._
( to UNW: ❑l ioer imtalkd_` Due.from_ft to _ft I IZQI MEM Lang Deg_ Min_ Sec
❑Inve ded Dts i From_ft to _0 CONSIRUCFION OR DECOMMISSION PROCED(W
rp,A%ntiom: M Yc C9 M, Ftamrsoo Desaihe by eahx,character,six of mresial a J unxnve,and the kind and
Type of ptrforrar used_ starare m�u%c r`mmerml(41SE1n timb mum ADDITU)NAL StIS I wvh fa le-t me F NECESSARY miry
for melt cMngc
��.. pit_
Yea GIs 7G#a zms.1I
.tYc+ rte�a56rar ( 1
s r>aa aeX3fie.l.i!Po. look brown.podery4a IQ1
lean 3Skw sera ZQ from ft Io in n brown afnd 3 yrrM loft 196
L Iham_Slot sam_fiom ft to ft water bearing
GmvWF inter paehd: ❑Yes ®No Ste of gm L—d
a,oc—lx pf—d fiom_A.to_fl
Satd.Sea:® Yes ❑No To whr dco?1p. --_—
Muenal used to seal Bentonfte
Dad any%traam co min unusahk water' 0 Yar ®No T
Type of wro'u I kqh of strata__
Method of eastmg sass off
N1MF.Manu(a+xurr's Neste `+
iype'.SUbmgrsable /t P 1
— W 7
WATER I.F�TI S:1-4—face tlevr.oa nhesve mean su level_ft
Stwc kvel fl below top of well
Artnm ptwtue!_Rs pa square inch Dee..��_.
5rkrcats.vfdrrs�tF9FWS.bR."•.��.'�'.+ay�-�, ....,»......m...R .��...�.,�.•... - —...�.�
a1'.R 1"f953e :`+sa+c}yz+s&sR'tw>r�<rtC+c klu�lptltblaarA0AIhf
Y.cW._gsl/min with_ft dmwdown after_hrs •~ ,^• t V' 0
Yrld_pl I—wmh_fl.dmvdown after_Itrs
Y.M dal/tmLL welh_R dmvdown fter ohm. % ^ _-
Rnu.rn Baru more oaken m sen�rfim prrp rormnl ogJ h+,arr lcw•1 a.enr.rdJn..wrll --
tnp
Trine Wren 1ave1 Time Wuer Ewen Tlme Wray level t Va-. 'nl•'r l•." 'hl
-4 aftr— slim Dal—
Temp.,l..ofwr_Wu&ebK.iWwAysit.rdrl ❑Yes ®No Tax Parce)No.1201&7S90053
WELL CONSTRII(T1ON(MRTIMATION:I a structed and/or accept resporsstbility for corWruaion of this well,and its compliance with all Washington well
cautruclias standards. Materials wcd aaa the information reported above arc true to my best Intowledge wA belief
®Driller❑"guiecr❑Trainee Driller or trainee License No.1706 Drilling Company Knapp Drilling Inc
4wre(rtis tar F-)Knapp.Dwarte Address 50 F Lc act drive
airier frralmea SiqgmsWnCity,State,Zip Shelton,W♦ 98594
IF TRAINEE.Driller's Uumse No.
------ (:anuaculr's
Milo's Si Rcg strubort No.KNAPPD195281 Ihtc-L-Q-a-7
rcY o50.1•lo tne.vo5i F I gy,.an Fyval oppe m my rmaptoyn
APPENDIX C
SLOPE STABILITY
1 O O
1 _ 1 O
1 _ O
1 . 3 O
1 40
1 5 O
1 c+O
1 . 7 O
1 . 80
1 . 90
. 00
7 4
Pr an
Deatat=ils Dynamic AnrLlyaia
Ane�1y�1� Siaho�
1 O U
11U
1 �O
1 3 O
1 4 O
1 . S O
1 . 60
1 . -7 0
1 . 80
. 90
-2 . O O
984
Pr���cct Cro.3acr Rcparc
DtgLa=11c Static Analysis
Analymim BiaYaop
APPENDIX D
EROSION CONTROL
GEOTEXTILE FABRIC
WRAP AROUND TRENCH
TO AT LEAST ENTIRE
BOTTOM OF TRENCH
BEFORE PLACING GRAVEL 2'x2'x5' WOOD POST OR
12' DEEP, 8' WIDE TRENCH EQUIVALENT OR BETTER
FILLED WITH 3/4' TO 1 1/2'
WASHED GRAVEL OR VEGETAT�N
14 FT
DWAXTlll�t OF -�----. EXISTINii
WATER FLCM -ten ND SURFACE
_ r�r'r
r
SILT FENCE - CROSS SECTION
N.T.S.
2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC
OR EQUIVALENT OR BETTED AND WIRE MESH
E 6 FT MAX. O.C.
EX=TI1MG
URUJND KWFACE
e r
12' DEEP, 8' VIDE
TRENCH FILLED WITH 'FT
3/4' TO 1 Me 67 rt
WASHED GRAVEL OR,VEG
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - CET:-IL
N.T.S.
PROVIDE FULL WIDTH
3/4 IN TO 1 1/�Np FTINGRESS/EGRESS
CRUSHED GRAVEL
PLACED AT 6 IN
MINIMUM DEPTH
WELL-DRAINED
SOILS
-0.02 IN/MIN F'_LL LENGTH
R=25 FT MIN
g —
&Errs% mail
STABILIZED CONSTRUCTION ENTRANCE
N.T.S.
�EfEn+M)FArt�:Iva(a1WILDW.71IrE�
,FhER;+L )DTE3,
SEE3tAIC F9if. P.A':d Sl.OT°EY
_H[)[ R THE TEk!W.49V ER[%Z"AEG AECD>'ENT 17BNTK0. W,;RIr= ON
K..'YA PAO:'E TO ME N AAM ATE U-oul—I:IIFiTM:A;.TZV4 I7B UMT04LTMC 1,IEFOGE 0E6 INSTALL MEMO SIN( A4;E Ae-'.OFF CUI TAC L
FW.L MITALL 416iT110ft EI<iIIEV NO SEMWAT CORTINiI FAMMIEL YCMMS BOOB Z WVAENT TOWUM IHTE7rKE.'TIIR I:ArE
ALL 61tUNDSM AHD SETT COLON FACILITIES A"SEH.=SHALL TE L'4TMLm LEVHL SPIEAIam MO DIEM AIDS Cw
EFUMED ONLY AM 110MATELY K41PTAIKED.TF Hff=NfT, IS THE 3W 30 01"Z F07H WITH FAWIN FOCI VARFrL.E.
.ALL FRMM ANN SEMM(r 9(TPML F4mjT7ES?MID IEVSZS VMU 7E LEFT M FILLCVM SUFA6C MORNIZIND C.PERFONie ALL WE?ArxW
N(.X UTIL THE EPSUIPE AREAS HAVE BEE);PEWV#*HiLY I(TAI]L22ED. OK III TO TE Xam
x%mm AS A111A4 ma-W.AND XH I ID ME
-FTaWV ' E.411'110NN(XLSTCOL,Wn21, ?bNV m AT TIE MYI:l)7 1Z Pam RA ADDS.
#.51m 11011?CANTO INETLPJZ MAN L AID wrUIOF 14 WILL
ALL A6.£e(S"k;H HAVE II='f'CN rr0 OF'.JE+aETATTOti OR FWWJ0I`JE%L:YO; NEMW 111113INTION M MM WArKWMZ At mcomIrl TO
T'Inw.AE'TEVrTLI',.AL&wan ID FT,IR*rs: �Alm --+LNTQ;,]PAmI FOE A F78TIII NO FVMT 7 TIME NW Vl§t"n=
-11130 E[E D M7 THE L7.7LTED CVC'1LRUVr BELOW,ALL I9XnClXM AIREAL HEST AE b.SIOO 3101%vLARM 11MMON NOVINNNR E NCR sV,,:L W.
IMCMMI ArNllrijll7''ZE7H WAXINNE.*fWLL'HI T.'HTV;Ok OTFFO WFiMV" AiVOOQ IF THE I=ES BILL IE Jffil=NHr, tc;;.
t O'R`4(L T;cEAi71CST A>b=Lf`'A+ELE TO THE'ltE W tEyR. ..xa._` ;EEi.F(Lf „EOT07Xn.JM NAT,0A W, 'NLAx=QOVMK1.7.
0E'.TILL UNV DE A LEFTAILE YXK)4j THE Y'OM;TH. OF +"411L T4UVi FVP-& E tl APE TO ME L%M Af.10tWIO TO :-T'LIEIi:Y'
E'TERUE01, FD'rAVsEl smam1 AKY rvoI.EEB'404CIV7. XT .Z lit 7FE ATENEaT IF NVa:NTE SOLD kE:11111M0113, EZmECIALLY
E OVNET'.(IWPACID?BUT .wST+LSO M A,404DITEk 4TH RuLQ-M NETTI , At4lAkM T M VATLk IO U%At! wETLM±Its.
.OTHER r7rFlTlEt rAEATIVL'ST,
LdE hE FOL.LQ.cPG r"ECOD91 'JWD ZED tl&Ar FE FUR ENOMF_
Y SEASON(MAY ' TMRr SEPTEMBER 33)— THE CLEARING OF LAND.rCLUEING THE MNTRa. OR A COJNTY APPROVEC ALTERNATE SEED MIXTURE.
MOVAL IF FXISIING VE(E'TATOI'i OR OTHER GROUND COVER.MUST BE LIMITED TO
WO AS MJCH LARD AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE PROPORTIONS PURITY GERMV'41`111
HERVISE START UZED, AFTER HAVING BEEN -LEAREB OR OTHERWISE DISTURBED SHAME BY VEIGHTc%) (%I
Y NO LATER THAN SE-TEMPER 30 IF A GIVEN YEAR.UNLESS IMMEDIATE
ABILIZATICN IS SPECIFZD IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL RE➢TOP (AGNOSTIS ALBA) L0 92 40
REAS CLEARED OR DrNERWISC DISTURBED MUST BE APPROPRIATELY STABILIZED ANNUAL RYE(LOLIUM MULTIFL.OIRUM) 40 98 90
OUGHF THE USE Or RULCHDRG, NETTING, PLASTIC SHEETING,EROsM BLANKETS. CHEWING FESO£ 40 97 80
REE DRAINING MATERIAL. ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED (FESTUCA RUBRA COMMUTATA)
ISRPHYSICALFURMED
HE N OF ACTION, UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, (JAMESTOVN, BANNER, SHADOW. KO(ET)
tILIZD46 AND MULCHING(IFCLEARED OR OTHERWISE DISTURBED AREAS SHALL BE WHITE DUTCH CLOVER 10 96 90
DURING,T FOLLOWING PERIODS,MARCH 1 M MAY 15, AND AUGUST 15 TO (rRIFOLIUM REPENS)
OPER L SEEDING AFTER WTOBCR I WILL BE DONE WHEN COMFIXTIDN
THE PROJECT Is D(MINEMT AND THE ENVD04)4TAL CONDITIONS ARE CONDUCIVE MULCHING
SATISFACTORY GROWTH DN THE EVENT THAT PERANENT STAIRMATION IS NOTHO
SIBLE, AN ALTERNATIVE METD OF GROUND COVER, SUCH AS MULCHING, NETTING,L MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
STIC SHEETING, EROSION BLANKETS, ETC., MUST 1E INSTALLED BY NOLATER THAN FILER CELLU HO OF
ASE, AND SULD BE APPLIED AT A RATE 1000
TEMBERR 30. POUNDS PER ACRE.Z.MULCH BE APPLZU IN ALL_
THE 6YCKT THAT C(IErTQUC.`TIOY Au^TTVTF=[AOTFFA SITE OLlAa OPIBIIGT 31EA7U Tk aC'E D(TALNEXiOIALT S WITH GXPQSEJO SLOPES
NITIE-4 PW}attZUWPKIEC F I:AT LEAST 4 'OKSECIM fi SAM THE 3.ARAM S"JLl BE US®)Md1iATELr ATTU SEEDM OR:V
RACTO9--.H1NLL EE 1E2PU/N.TgU FOR TILE DEP6fnTJQt ff ALL CRUMI AREAS WHICH Chl*m DE'IEET!ED!E"..N.RE OF THE SEASUK 4LL
t,' WE)Ff C'OITESL FAZILSTIEP 1141LOIATE0' W113 STUNK VOCKM"AT AREAS 1WV R M91 I SHALL BE.LIMEZD r hWEWWM L
..f Er"L4E91'tcNUC SHE:DWY7.1I/ ;;OFTI£A."TLV SHALL ME MESPOtf[i.E FTW
3£ HNI7TTEN4VX AKA rAY'= OF ALL EAGUM Pi4 XEfIIKEK'tlWWL FN»ILIfXl- Tu-'ul m
ET SIF.+'UN lO(:MlETR( TMRJ APRIL 3B)— OM%I='N))iRE UNITWEHI]*TEA L rUPML'4804;LD BE I.)54D FUR THIS F7))D..ECT,DIE TO HI3H.T
.l4T— INS PT ( 4CTIVM LS IN MWZS'3,THE CLEA!7i 0 Or LAND,VX UDIN6 THE WASE F:4NM' b 5111L.:.
;f#L IF E:Er'ST"'VE:£TA IO"'N4(F DT7(EIR k:RD"IT)VEII. ;,)HILL BE L 01M P. TOPSOIL U'WIrN BE PUIEYD am SLOINZ Nor EY,OEOIVG`ri
'a1X:H LANt AREA AS CAh BE IMVERD OR WARD.UES VCTMN 24 IOLWS IN D, 971d'-`I`1!6 W.STOCKPO.DAI O!4-/SITE 300.3 SHALL OLT SE
EVEAtT A)AJOR ST(]'.t/M F'f(EWTED A)ar OR VRUllM An SE224E7iT p'umfiEE IF TCN'imi.I-FNE.ALILE a;il:r LOAMY U.OAN.SAW Loh".
(OFF-SITE IS O&f'iERVM =I LDV V40TY Y.LAY L9fb 3A? LIME(',
L O.EAREP OR�TH7 ED SMALL IEGETYE*P1. ATE NUTECI'VE 4.)IcHGF'CI(U A'I'D i BE GEBFIXP'B 70 THE IMELIATC I774.?4 E;T7(g,'
OR BE OTNMWW 1TAT8LrJ=)49H AR 7F:I.17NWD.(IETTIM I TX. 1EMN a Fi>i'AriX 7TI E3' J'3;J fi`+TH Ent«lE'T71 Fr.'OMFY4,D7?
LL
TL'OCS. EH OiM ILA!/EM TORT MTM4..ETC..VrM 3*1T;Ff'TFR*LgyA"* °yr TRULr, .,THE T Nr>LT 1,,, . -
,V7M@ IM MEMIM O1(ITHEkW=ITS%*=IF Vr TEIAQ ACTIYEIY WINV EB, jT-k a EdHlVffF ':]MOBIL LT,1F.E$'a3iALL TE F+1'I.A'E BEFORE
'ICI HINLING, SLUIMLNI IKAPS, ',LDIMLWJ PILAUS.LTC.. VILL NUi U!VA:W!tl AS xl�:il;NOSL
IJEOUATE COVER IN AND OF THEMSELVES.IN THE EVENT THAT ANY LANE AREA NOT
NU ACTIVELY WORKED RLTIAINS UNPROTECTED 13R FAS N13T BEEN APPROPRIATELY
TABMUZED 5 DAYS AFTER HAVING BEEN CLEARED,ALL CONSTRUCTION ACTIVITY (N
SITE, EXCEPT FIR APPROVED EROSMN AND SEDIMENT CONTROL ACTIVITY, SHALL
MEDIATELY CEASE UNTIL SUCH A TIME AS AFOtEMENTIONEC LAND AREA HAS BEEN
APPROPRIATELY PRUrEC7EO OR STABILIZED.
STOCKPLE MANAGD(DNT
STWK(Z E DYLL BE STABILIZED(VTIN PLASTIC COVERING OR OTHER APPROVED DEVICE)DAILY BETWL'E'N NOVEMDER 1 AND MARCH
3L
2.IN ANY SEASON.SEEDfNT LEACHING FROM STOCK PILES MAST BE PREVENTED
3.TOPSOIL SHALL NOT BE PLACED WHILE IN A FROZEN OR MUDDY CONDITION,WHEN THE SLK.RACE IS EXCESSIVELY WET,OR WHEN
S r%IST THAT INS OTHERWISE BE DETRIMENTAL TO PROPER GRADING OR PROPOSED SOCMC. OR SEEDING.
i.PRE�`1U*A• [?TAfLI!*0 GIFADC'ON THE QW TO EH TO?Mill`.FALL TE RAWTAMtt A-r.M 3-TO THE Wfwg+KD ALA=-
DTABILIZED CONSTAXTIDN ENT!?AIKE
L KiI IAL SE44LL SE A TmrI4 TO 3 LN7H OJIW,Y :iALLA i4 To a Wfl FIX IIESIOFMTGYL SONDE FAX LT LDT'-' ,'.MG MAY IE
TOP-DPCSSED WITH :RCH TO 3 INCH MIX, (STATE�TAN%AIRR wE='ICArIDCN,�:xrrO7H 8-tl-0
S. THE RAY,'.*AD SHALL BE AT LEAST E7'INCHES 7H= AND:N FEET LWG QV FEET FUR SITE&W7H L.Ei. THAN I AVE 1F
DISTURBED SOIL). WMTH SHALL BE FULL WIDTH OF THE VEHICLE INGRESS AND E61tESS AREA. SMALLER PADS MAY BE APPROVED
FOR SINGLE-FAMILY RESIDENTIAL AND SMALL COMMERCIAL SITES.
3.ADDITIONAL ROCK SHALL BE ADDED PERIODICALLY TO MAINTAIN PROPER FUNCTION OF THE PAD,
4.IF THE PAD (IDES NOT AEECuATELY REMOVE THE MUD FROM THE VEMUZ WHEELS, THE WHEELS SHALL BE HOSED OFF BEFORE
THE VEHICLE ENTERS A PAVED STREET,THE WASHING SLIM BE DONE ON AN AREA COVERED WITH CRUSHEC ROCK AND WASH
WATER SHALL DRAIN TO A SEDIMENT RETENTOIN FACILITY OR THROUGH A SILT FENCE.
CLT PENCE
OEOTEXTILE FILTER FABRIC TYPE SHVl !>E PER SY'ECIFIEG IN THE 'STQRMY67F7R HAAA(1?iF71T MANUAL
Tim:YV.>ET SOUND BASIN, IN APM'-ICAILE CIR'Nr` :TAbVARDS
.Cif= (TOE FILTER FABRIC STALL BE RACHASEL fit A CAVTINNAU5 RO1 CUT TO THE LENGTH OF
H BARRIER TO AVOID USE OF .ANTS IF .HINTS ARE NECESSARY,F71-70 FABRIC SHALL ME SIP=
W-.tTHE7;:ONLT AT A SUPPORT POST WITH A 1%4MU'1 6-1401 OYE4LAP AND SECDOELT FASTMED AT
7fTT1 E(AD$ TO THE POST,
STANDARC FILTER FABRIC SMALL BE FASTLREB UM-F. I'STAPLES D6 TIE WIRES TRW RBA.})A 4 IN
D.
.Mrr- SHALL BE SPA:E'U AWL PLACE➢AT DEPTHS INDWATED IN THE DETAIL'; ON THIS SHEET, AND
RI!dEIL SECJRELY INTO THE ilVAIID.
WOOL MESH SMALL BL 2*X2•X14 UAULt UR GUUIVILENI. T L VIRL•" MLSH MAY HL LLLMINA1LO It
TRA-STRENGTH FILTER FABRIC (MONOF'LANENT>,AND CLOSER POST SPACING Is usED.
.A TRENCH SMALL BE CXCAVATFD ACCORDING To THE DETAILS ON THIS SHEET ALONC� THE LINE OF THE
OSTS AND UPSLOPE FROM THE MT FENCE
SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS Or THE PROJECT.
APPENDIX D
DRAINAGE DETAILS
FUSE
F DRAIN. SEE
ROOF DOWNSPOUT
CONNECTION
DETAIL SOLID
LID GROUND
SURFACE
2R MIN
tXmm
4' OIA MI, /
SOLID PVC FINE MESH ♦' DIA PIPE
SCREEN
I? CATCH BASIN ANCHOR
(YARD DRAIN) EXPOSED PIPE
PER TTGI(TLI
DETAILS r
O
ROOF DRAIT[E DETAILS
STFFI rl AMPS (TYP)
CORRUGATED TIGHTLIIE HD R MIN SPACING 1/2 INCH DIAMETER
4-INCH MIN. DIAMETER SECURELY FASTENED TO PIPE
LEVEL SECTION
XT DIFrUSCR TCE
TWO 6-FOOT
ANCMpPS(TYP), NOTES,
BA REBAR OR L IT IS STRONGLY SUGGESTED M
EQUIVALENT 1 FT MIM UTU.= A MEAT WELMD"UN DM WM Y
PmYrTNfLEW CHW-0 rM OI L9E1:]F
E�Mn3 MASTIC ARE.
E It R-4VIX PIP!Di UZU,MAGCUP I
14WMTIM Ot-MMNUI.ri,Arm
NFEFUMV iNTKFFB4AICF '.B.
Wil TLIW DETAILS Y MRF CrAW7FTF*W 1 PF i PCH-IN
N.T.S. 6-INCH TEES, AND 2 INCHES FOR 12-INCH
TEES.
4.HOLE SPACING SHALL BE EQUAL TO
(L5 X HOLE DIAMETER).
5.DIAMETER OF TEE SHALL EQUAL
DIAMETER OF TIGHTLINE PIPE.
NO HOLES OPPOSITE
PIPE
° o
DRILL HOLES
° IN OF FRONT
ONLY
3 FT
MASON COUNTY
COMMUNITY SERVICES 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 is found not applicable,the report should explain the basis for the conclusion.
Note: Unless specifically documented, this report does not provide compliance to the International Residential
Code Sections R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section
1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Teresa Parcel# 12019-50-00018
Site Address 200 E Smith Cove Way
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) 5
(b) A discussion of specific soil types,
Located on page(s) 6
(c) A discussion of ground water conditions,
Located on page(s) 7
(d) A discussion of the upslope geomorphology,
Located on page(s) 3
(e) A discussion of the location of upland waterbodies and wetlands,
Located on page(s) 3
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and
records.
Located on page(s) 8
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Site Plan—Appendix A
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Site Plan and Soil Logs (Appendix 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 Map(s) Site Plan
(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) Soil Profile(Appendix B)
(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 coefficients should be a value of 0.15.
Located on page(s) 9 Page 1 of 41
(7) (a) Appropriate restrictions on placement of drainage features,
Located on page(s) 18
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) 19
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 16
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 18
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 17
(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) 17
(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) 11
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) 13
(11) Specifications of final development conditions such as,vegetative management,drainage,erosion control,and
buffer widths.
Located on page(s) 18
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 19
(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) Site Plan
I, Michael Staten, hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington
with specialized knowledge of geotech nical/geo logical 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
(C of Report,dated February 27,2021.and entitled Single Family
Residence, meets all the requirements of the Mason County
2.. t.
Resource Ordinance,Geologically Hazardous Areas Section,
is complete and true,that the assessment demonstrates
`. 43045 j conclusively that the risks posed by the landslide hazard can
`s
s,� \%1 be mitigated through the included geotechnical design
2/27/2 recommendations, and that all hazards are mitigated in such a
Disclaimer:Mason County does not manner as to prevent harm to property and public health and
certify the quality of the work done in safety.
this Geotechnical Report.
Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION................................................................................................................................. 1
1.1 PROJECT INFORMATION.................................................................................................................... 1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK........................................................................ 1
2.0 SURFACE CONDITIONS....................................................................................................................3
2.1 GENERAL OBSERVATIONS..................................................................................................................3
2.2 TOPOGRAPHY.....................................................................................................................................3
2.2.1 Upslope Geomorphology............................................................................................................3
2.3 SURFACE DRAINAGE..........................................................................................................................3
2.3.1 Upslope Water Bodies................................................................................................................3
2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4
3.0 SUBSURFACE INVESTIGATION.....................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5
3.2 GENERAL GEOLOGIC CONDITIONS...................................................................................................5
3.3 SPECIFIC SUBSURFACE CONDITIONS.................................................................................................7
3.3.1 Groundwater...............................................................................................................................8
4.0 ENGINEERING ANALYSES AND CONCLUSIONS......................................................................9
4.1 SLOPE STABILITY...............................................................................................................................9
4.1.1 Slope Stability Analysis.............................................................................................................10
4.2 EROSION............................................................................................................................................11
4.2.1 Shoreline Recession..................................................................................................................11
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION..............................................................................12
4.3.1 Liquefaction..............................................................................................................................12
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS........................................................12
4.5 LATERAL EARTH PRESSURES...........................................................................................................12
4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................13
5.1 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................14
5.LI Bearing Capacity.......................................................................................................................14
5.1.2 Settlement............................................................................................................ ..................15
5.1.3 Concrete Slabs-on-Grade..........................................................................................................15
5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................15
5.2.1 Excavation.................................................................................................................................15
5.2.2 Placement and Compaction of Native Soils and Engineered Fill...........................................16
5.2.3 Retaining Wall Backfdl............................................................................................................17
5.2.4 Wet Weather Considerations....................................................................................................17
5.2.5 Building Pads............................................................................................................................17
5.3 BUILDING AND FOOTING SETBACKS.................................................................................................17
5.4 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................18
5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................18
5.6 TEMPORARY AND PERMANET-P EROSION CONTROI........................................................................19
5.7 SEPTIC DRAINFIELDS........................................................................................................................19
5.8 STRUCTURAL MITIGATION...............................................................................................................19
6.0 CLOSURE.............................................................................................................................................20
Appendix A-Site Plan
Appendix B-Soil Information
Appendix C-Slope Stability
Appendix D—Erosion Control
Appendix E—Drainage Details
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned
single family residence located at 200 E Smith Cove Way, identified as parcel number 12019-50-
00018, Mason County, Washington. See the vicinity map on the following page for a general
depiction of the site location.
An initial geotechnical evaluation of the project was conducted by Envirotech on December 23,
2020. It was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were
present within 300 feet of the planned development. Based on this site characteristic, the
proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of
Mason County Resource Ordinance (MCRO) 17.01.100. During the site visit by Envirotech,
surface and subsurface conditions were assessed. After completion of the field work and
applicable project research, Envirotech prepared this geotechnical report which, at a minimum,
conforms to the applicable MCRO.
As presented herein,this report includes information pertaining to the project in this Introduction
Section; observations of the property and surrounding terrain in the Surface Conditions Section;
field methods and soil descriptions in the Subsurface Investigation Section; supporting
documentation with relation to slope stability, erosion, seismic considerations, and lateral earth
pressures in the Engineering Analyses and Conclusions Section; and, recommendations for
foundation, settlement, earthwork constriction, retaining walls, erosion control, drainage, and
vegetation in the Engineering Recommendations Section.
1.1 Project Information
Information pertaining to the planned development of the project was provided by the proponent
of the property.The planned development consists of a I-or 2-story single family residence,new
on-site septic system, and other ancillary features typical of this type of development.
Approximate building footprint and other proposed features with relation to existing site
conditions are illustrated on the Site Map provided in Appendix A of this report.
1.2 Purpose of Investigation and Scope of Work
The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the
project in order to provide geotechnical recommendations that should be implemented during
development. The investigation included characterizing the general project surface and
subsurface conditions, and evaluating the suitability of the soils to support the planned site
activities.
In order to fulfill the purpose of investigation, the geotechnical program completed for the
proposed improvements of the project include:
• Review project information provided by the project owner and/ or owner's
representative;
• Conduct a site visit to document the site conditions that may influence the construction
and performance of the proposed improvements of the project;
• Define general subsurface conditions of the site by observing subsoils within test pits
Envirotech Engineering Geotechnical Report
PO Box 984 page I Parcel 12019-50-00018
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
and/ or cut banks, review geological maps for the general area, research published
references concerning slope stability, and review water well reports from existing wells
near the project;
• Collect bulk samples,as applicable,at various depths and locations;
• Perform soils testing to determine selected index and/or engineering properties of the site
soils;
• Complete an engineering analysis supported by the planned site alterations, and the
surface and subsurface conditions that were identified by the field investigation, soil
testing,and applicable project research;and,
• Establish conclusions based on findings, and make recommendations for foundations,
drainage, slope stability,erosion control, earthwork construction requirements, and other
considerations.
N ' �a
Y be
H.iR dS Tdbd
tfftAAD - Q K '� j
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Peale
Passage
Vicinity Map from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 2 Parcel 12019-50-"18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on
December 23, 2020 by a representative with Envirotech. During the site visit, the type of
geotechnical investigation was assessed, site features were documented that may influence
construction, and site features were examined that may be influenced by construction. This
Surface Conditions Section provides information on general observations, vegetation,
topography, drainage and observed slope/ erosion conditions for the project and surrounding
areas that may impact the project.
2.1 General Observations
Currently, the property is vacant. Vegetation on and near the project consists primarily of
secondary growth firs, cedars, madronas, and other trees and shrubbery common to this area of
the Pacific Northwest. An aerial photo of the project and immediate vicinity is provided on the
following page.
2.2 Topography
The topographic information provided in this section was extrapolated from a public lidar source,
and incorporated observations and field measurements. Where necessary, slope verification
included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site
Plan in Appendix A in this report for an illustration of general topography with respect to the
planned development.
Critical descending slopes, with grades exceeding 40% appear to be within 300 feet of the
planned development. The maximum critical slope is approximately 95% with a vertical relief of
about 55 feet.
Ascending grades are generally located to the west of the planned development.These slopes are
relatively minor within 300 feet of the project,with no apparent slope grades of at least 15%.
2.2.1 Upslope Geomorphology
The upland area of the property and beyond is generally situated on a hillside of glacial
origin.
23 Surface Drainage
Runoff originating upslope of the development is mostly diverted away from the property by
accommodating topography. Excessive scour, erosion or other indications of past drainage
problems were not observed within the immediate vicinity of the planned development.
23.1 Upslope Water Bodies
There are no apparent water bodies or wetlands located upslope from the planned
development that would significantly influence the project.
Envirotech Engineering Geotechnical Report
PO Box 984 page 3 Parcel 12019-50-OW18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
2.4 Slope and Erosion Observations
The slope gradients near the project signal a potential landslide or erosion hazard area. Some
indicators that may suggest past slope movements include:
• Outwash of sediments near the bottom of the slope,
• Fissures, tension cracks,hummocky ground or stepped land masses on the face or top of
the slope,and parallel to the slope,
• Fine,saturated subsurface soils,
• Old landslide debris,
• Significant bowing or leaning trees,or,
• Slope sloughing or calving.
Significant slope instability indicators on the property or within the general vicinity of the
property were observed and discovered during research, but are located away from the influence
of the planned home.
Aerial Photo from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 4 Parcel 12019-504M 18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on
December 23, 2020 by a representative with Envirotech. Applicable information on field
methods, sampling,field testing,general geologic conditions, specific subsurface conditions, and
results from soil testing are presented in this section of the report. Appendix B of this report
includes pertinent information on subsurface conditions for the project, such as subsoil cross-
section(s), test pit log(s), and applicable water well report(s). Water well reports were utilized to
estimate ground water levels,and if sufficient, were used in identifying subsoil types. Applicable
test pit locations are depicted on the Site Plan provided in the appendix of this report.
3.1 Field Methods,Sampling and Field Testing
Information on subsurface conditions for the project was accomplished by examining soils within
test pits and/ or nearby banks extending to depths of up to 6 feet below the natural ground
surface. Information on subsurface conditions also included reviewing geological maps
representing the general vicinity of the project, and water well reports originating from nearby
properties.
Soil samples were not obtained from this project. Envirotech measured the relative density of the
near-surface in-situ soils by gauging the resistance of hand tools. Within testing locations, field
testing results generally indicated loose to medium dense soils in the upper 48 inches, and very
dense soils from 48 inches to the depth of terminus.
3.2 General Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the "Geologic Map of Washington," compiled by J. Eric Schuster,
2002 indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated
deposits, and dominantly deposited from glacial drift,including alluvium deposits. This project is
located within the Puget Lowland. Typically, "lower tertiary sedimentary rocks unconformably
overlie the Crescent Formation"as revealed in the Geologic Map.Initial sedimentary rocks were
formed from shales, sandstones and coal deposits from rivers. During the Quaternary period, the
Puget Lowland was covered by numerous ice sheets,with the most recent being the Fraser glacier
with a peak of approximately 14,000 years ago. Upon the glacial retreat, the landscape was
formed by glacial erosion glacial drift deposits.
The "Geologic Map of the Longbranch 7.5-minute Quadrangle, Thurston, Pierce, and Mason
Counties, Washington" by Robert Logan, et al, 2003, provides the following caption(s) for the
project area:
Envirotech Engineering Gcotechnical Report
PO Box 984 page 5 Parcel 12019-50-OW18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
Ols LandOsde deposits Rock.wit,and organic matter
tkpouted by niass w a.tng.depending tat degree of
acti%stN,kkation%within the%late mass.ty-pc of shdc,
cohc%i%cncss,and tortspctawc tot flutcruk.may be
un%tratif ed,broken,chaotic,and pow ly wncd tic may
retain primary balding siructurc.may he cut by cla►tic
dtkcs or wrinal of reverse+hear planes;strtace is
conu ionly hununotky in lower reaches of deep-seated
iandslydc►or-stctrpetl ttith torMard-tit back-%shed
blocks in hcadssard arras,deep-seated dale►tend to he
relauvety large Slow-nwvtng slumps(Varn es. 19711)
comrsumly,trtuuftxm into slump earth Iltm s,can
conuusnly he recognvsrJ by hoAcd it mulomiy tilted
trees.And mist comnuml•ttcuf a1 the interface
hctvtccn poorly compacted,poorly cohcstse,permeable
%inds awerlying relatively impermeahk silt or clay
Iaym.shallow,more rapid dchrts f1tnw s cootntarlly
occur at the interface between tmpermeablc whoraic,
sukh 41.1111,and shalltrw.larsc.Pcmxable sails%tut arc
rich in organic nutter.Rack topples and furl tall,this
are too small to he shown a1 the snap oak tx%;ur
sshercvcr ncar,verucal btuf%xc prc%cnt.hpscalty
ttecauwe soh-or clay-rich layers such at units Opaf in
Ops fail along Mutts Unit Ols is ttxmn only ti here
landthdcs arc larkc or ob%o uic the urxhcrly 1ng geology
Vasllw ON I nsoncd and highly compacted mixture
of clay.sdt,sand,mW grascl dcpu►sted directly by
gtocrcr rcc.gray where fresh and Iight yelltmL%h brotsn
t0we oxtdvatl.very krA pcnnxahihty.mtrt tonsnumk
tnatrsx-suppnrtcd but may be class-wppurtcd,matrix
generally feel%nxorc finny than otitaash vtxls ahcn
%inbox Adsance outwasa laisd and gr"avrl utJ
09a IA%:ustnnc clad,,I It.ind and of mt than wmtcc.
Jctx>sitcd during gLictal advance:ccmuins wmc
Fog---] nongLrcial"mcnts..uth at cobhk,and np-up%of%tit
or peat as Lug akmg channel side,and hottonu.>;tay
~here fresh.light%citoutstt graN Nhere.Utncil.is,Lucd
expostires of lacustnnc alit and LUN%unit 09af,
resembk okkr glactolatmuine units,+atxls i unit Ogas)
totally IIXI ti thick,well weed.tint-grained yr nth lcnsc,
of cwrscr►aril and gavel,generally pernx*Nc air!
porous with krw 4:44k-M%tty retatiw too overlying and
undcrlt ing scdimcntx,and suhicct tit deep-scattd
l.,nd,htling
Prr-Vadwa gravel Gra%cl anJ%uxi of northcrn
prosenm c.witagraphkalk utderlsev the\'astxtn Otitt.
most corninonly c%ptncd underneath unit Opa.grasclly
pone orb arc relatively rhostanl to eftnkist,comnttrily
tinted orange yr nth moat-otxlc►tatning.moderately to
poorly wned,t.muntmly crtns bcdJcd but flay lark
prilnan sedttncntan ►nxtuttes,inferred to be of glacial
Orugin ho-low interglacial ctmdttton%do not appear
ttatJucttc to wren%%ith►uilkscnt ttrnrvtcmv to
deposit csiJcytrraJ gnvris rn nxtst of the l'ugea
fou land,and hcwause the ma)orlty tit the e%"Ures
intitk ntrthcrn•uturcc ctavt%
Envirotech Engineering Geotechnical Report
PO Box 984 page 6 Parcel 1 20 1 9-50-000 1 8
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
N
A Project
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QS IMF
Geological Map Department of Natural Resources Washington State
3.3 Specific Subsurface Conditions
The following subsurface conditions are estimated descriptions of the project subgrade utilizing
information from the depth of penetration at all testing, sampling, observed and investigated
locations. Soils for this project were primarily described utilizing the Unified Soil Classification
System(USCS)and the Soil Conservation Service(SCS)descriptions.
The project is currently composed of native soils without indications of fill. Within test pit
locations, soils within the upper 6 feet of natural ground were generally observed to be poorly
graded sand with gravel(SP).
The relative densities of the soil within selected test pits are provided above in Section 3.1.
Expanded and specific subsurface descriptions, other than what is provided in this section, are
provided in the soil logs located in Appendix B of this report.
According to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Conservation Service, the site soils are described as Sinclair Shotty Loam, So,
with 5% - 10% slopes, Indianola Loamy Sand, lb, with 5% - 15% slopes. The soil designations
Envirotech Engineering Geotechnical Report
PO Box 984 page 7 Parcel 12019-50-"18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
are depicted in the aerial photograph below, and descriptions are provided in Appendix B of this
report.
A
A
f,
0 O m 7A
Soil Survey From USDA Natural Resources Conservation Service
3.3.1 Groundwater
From the water well report(s)and knowledge of the general area, permanent groundwater
is at least 70 feet directly below the property at the building pad location. Surface seepage
or perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports.
Envirotech Engineering Geotechnical Report
PO Box 984 page 8 Parcel 12019-50-"18
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 27,2021
4.0 ENGINEERING ANALYSES AND CONCLUSIONS
The following section includes slope stability, erosion, seismic considerations, and impacts to
both on-site and off-site properties.
4.1 Slope Stability
Landslides are natural geologic processes, and structures near slopes possess an inherent risk of
adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering
cannot eliminate these risks for any site with sloping grades because gravity is constantly
inducing strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will
exacerbate these strains. Geotechnical engineering considers excessive wet weather and `design'
earthquakes in order to provide an acceptable factor of safety for developing on or near sloping
terrain with relation to current engineering protocol. These factors of safeties are based on
engineering standards such as defining engineering properties of the soil, topography, water
conditions, seismic acceleration and surcharges. Surface sloughing or other types of surficial
slope movements usually do not affect the deep-seated structural capability of the slope.
However, repeated surficial slope movements, if not repaired, may present a threat to the
structural integrity of the slope. If any slope movement arises,the slope should be inspected by an
engineer. Subsequently,maintenance may be required in order to prevent the possibility of further
surficial or deep seated slope movements that may be damaging to life and property.
According to the Coastal Zone Atlas of Mason County, Washington, the project is within and
near terrain labeled `Stable', `Intermediate', and `Unstable' regarding potential landslide activity.
Descriptions of these mapping units may be found in the aforesaid Atlas. A Stability Map from
the Coastal Zone Atlas for the general area of this project is provided below:
Flit-9
Squaw,let
Project
l
� Sou .'.rgSP i
Map from Washington State Department of Ecology Website
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According to the Resource Map from the Washington State Department of Natural Resources
(DNR), the project is not within terrain labeled `highly unstable' relating to soils. DNR labeled
portions of this project as medium and high slope instability with relation to slopes. A Resource
Map from the DNR Forest Practices Application Review System is provided below:
i
Project
w
mica
Soils-Hydric Soils
Soils-Highly Unstable Soils
- C Soils-Highly Erodible Soils
N is Westside Slope Stability Model(FP)
hlodeiate Slope Instability
p® - ■ High Slope Instabtl;ty
1:4,514 tee.
Resource Map from Washington State Department of Natural Resources Website
4.1.1 Slope Stability Analysis
The Simplified Bishop Method, utilizing `STABLE' software, was used to analyze the
static stability of the site slopes. Seismic conditions were estimated utilizing worst case
scenario values from the static analysis,a quasi-static analysis coefficient of at least 0.15,
and applying the applicable values to STABLE software. Various radii's and center
points of the circle were automatically selected, and produced factor of safeties in a
graphical and tabular format. Worst case scenario values were used in the slope stability
analysis in regards to topography, surcharges, water content, internal friction and
cohesion of the site soils. STABLE software has been repeatedly checked with manual
calculations, and consistently proved to be a very conservative program. The following
soil properties were used in the analysis, and are based on observed conditions, known
geology,and/or published parameters:
Upper 6 feet soil depth
Soil unit weight: 100 pcf
Angle of internal friction: 34 degrees
Cohesion: 0 psf
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Based on the slope stability analysis, unacceptable factors of safety could be present on
and near the critical slope,but do not reflect conditions where development is expected to
occur. For this project, at the location of the proposed development, minimum factor of
safeties for static and dynamic conditions were estimated to be at least 1.5 and 1.1,
respectively. See the slope stability information in Appendix C for a depiction of
minimum factors of safety away from the project.
4.2 Erosion
Based on the USCS description of the project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,
the project is not within terrain labeled `highly erodible.' This project is not within an erosion
hazard area as defined by the MCRO. Erosion hazard areas are those with USDA SCS
designations of River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on
slopes 15% or greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd),
Harstine Gravelly Sandy Loam on slopes 15% or greater (Hb), and Kitsap Silt Loam on slopes
15%or greater(Kc).
It is our opinion that minor erosion control recommendations provided in this report is sufficient
for the development of this project, and additional engineered erosion control plans are not
required. Temporary and permanent erosion control measures are required for site development.
Extents of temporary erosion control will mostly depend on the timeliness of construction,
moisture content of the soil,and amount of rainfall during construction. Soil erosion typical to the
existing site conditions and planned disturbance of the project include wind-borne silts during dry
weather, and sediment transport during prolonged wet weather. Sediment transport could be from
stormwater runoff or tracking off-site with construction equipment.
The Temporary and Permanent Erosion Control Section (Section 5.6) of this report consist of
specific erosion controls to be implemented. Additional erosion control information and
specifications may be found in the latest addition of the "Stormwater Management Manual for
Western Washington,"prepared by the Washington State Department of Ecology Water Quality
Program.
4.2.1 Shoreline Recession
Due to the close proximity of a shoreline,an evaluation of the shoreline recession rate for
this project was completed. This was accomplished by interviewing property owners
within the vicinity of the project, and/ or carefully reviewing and comparing historical
aerial photographs of the project. Historical aerial photograph sources may be found in
the 1951 aerial for the Soil Survey of Mason County, aerials from the Washington State
Department of Ecology,and from the Washington State Department of Natural Resources
website.Based on available information,we conclude that the past shoreline recession for
this project is less than 10 feet in 50 years.
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4.3 Seismic Considerations and Liquefaction
There are no known faults beneath this project. The nearest Class `A' or Class `B' fault to this
property is the Olympia Structure,which is approximately 8 miles to the southeast of this project.
This information is based on the USGS Quaternary Fault and Fold Database for the United States.
Potential landslides due to seismic hazards have been considered, and are addressed in the Slope
Stability Analysis Section provided earlier in this report.
Soils immediately below the expected foundation depth for this project are generally Type D,
corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the
regional seismic zone is 3 for this project. The estimated peak ground acceleration ranges from
0.50g to 0.60g.This estimation is based on the United States Geological Survey (USGS)National
Seismic Hazard project in which there is an estimated 2% probability of exceedance within the
next 50 years.
4.3.1 Liquefaction
The potential for liquefaction is believed to be low for this project.This is based, in part,
on the subsurface conditions such as soil characteristics and the lack of a permanent
shallow water table. Subgrade characteristics that particularly contribute to problems
caused from liquefaction include submerged, confined, poorly-graded granular soils (i.e.
gravel, sand,silt).Although gravel-and silt-sized soil particles could be problematic,fine
and medium grained sands are typically subjected to these types of seismic hazards. No
significant saturated sand stratifications are anticipated to be within the upper 50 feet of
the subsoil for this project.
4.4 Landslide,Erosion and Seismic Hazards Conclusions
DNR indicated historic landslide activity near the project. Mapped slope conditions, as delineated
by the Departments of Ecology and/or Natural Resources, were considered in our slope stability
assessment. Based on the proximity and severity of mapped delineations with respect to the
proposed development, results of the aforesaid slope stability analysis, observed surface
conditions, and other pertinent information, it is our opinion that the proposed development may
occur in accordance with the recommendations in this geotechnical report.
4.5 Lateral Earth Pressures
Retaining walls may be utilized for this project. The lateral earth pressures exerted through the
backfill of a retaining wall are dependent upon several factors including height of retained soil
behind the wall, type of soil that is retained, degree of backfill compaction, slope of backfill,
surcharges,hydrostatic pressures,earthquake pressures,and the direction and distance that the top
of the wall moves. A structural or geotechnical professional should design retaining walls based
on specific conditions.
Soil parameters for the structural design of retaining walls may be estimated as 134 pounds per
cubic foot (pcf) and 118 pcf for engineered fill and native soils, respectively. The angle of
internal friction may be estimated as 36 degrees and 32 degrees for engineered fill and native
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soils,respectively. These soil parameters are based on soil type and placement conforming to the
Earthwork Construction Recommendations Section in this report.
4.6 On-Site and Off-Site Impacts
From a geotechnical position, it is Envirotech's opinion that the subject property and adjacent
properties to the proposed development should not be significantly impacted if all
recommendations in this report are followed. This opinion is based on the expected site
development, existing topography, existing nearby development, land cover, and adhering to the
recommendations presented in this report. Future development or land disturbing activities on
neighboring properties or properties beyond adjacent parcels that are upslope and/or downslope
from the subject property could cause problems to the subject property. For this reason, future
development or land disturbance near the subject property should be evaluated by a geotechnical
engineer.
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5.0 ENGINEERING RECOMMENDATIONS
The following sections present engineering recommendations for the proposed improvements of
the project. These recommendations have been made available based on the planned
improvements as outlined in the Introduction Section of this report; general observations
including drainage and topography as recapitulated in the Surface Conditions Section; soil/
geologic conditions that were identified from the geotechnical investigation that is summarized in
the Subsurface Investigation Section; and, project research, analyses and conclusions as
determined in the Engineering Analysis and Conclusions Section. Recommendations for the
project that is provided herein, includes pertinent information for building foundations,earthwork
construction, building and/or footing setbacks, drainage, vegetation considerations, and erosion
control.
5.1 Building Foundation Recommendations
Recommendations provided in this section account for the site development of a typical one- or
two-story, single family residential structure. The recommended allowable bearing capacities and
settlements as presented below, consider the probable type of construction as well as the field
investigation results by implementing practical engineering judgment within published
engineering standards. Evaluations include classifying site soils based on observed field
conditions and soil testing for this project. After deriving conservative relative densities, unit
weights and angles of internal friction of the in-situ soils, the Terzhagi ultimate bearing capacity
equation was utilized for determining foundation width and depth. Foundation parameters
provided herein account for typical structural pressures due to the planned type of development.
A structural analysis is beyond the scope of a geotechnical report, and a structural engineer may
be required to design specific foundations and other structural elements based on the soil
investigation. Stepped foundations are acceptable, if warranted for this project. Continuous,
isolated, or stepped foundations shall be horizontally level between the bottom of the foundation
and the top of the bearing strata.The frost penetration depth is not expected to extend beyond 12
inches below the ground surface for this project under normal circumstances and anticipated
design features.
5.1.1 Bearing Capacity
Existing in-situ soils for this project indicates that the structure can be established on
shallow, continuous or isolated footings. Foundations shall be established on relatively
undisturbed native soil that is competent and unyielding. Alternatively, foundations may
be constructed on selective re-compacted native soil or compacted engineered fill as
described in the Earthwork Construction Recommendations Section of this report.
For a bearing capacity requirement of no more than 1500 psf, a minimum continuous
footing width of 15 inches shall be placed at a minimum of 18 inches below the existing
ground surface atop unyielding soils. For a columnar load of no more than 3 tons, a
circular or square isolated foundation diameter or width shall be at least 24 inches.
Foundation recommendations are made available based on adherence to the remaining
recommendations that are provided in this report. Alterations to the aforementioned
foundation recommendations may be completed upon a site inspection by a geotechnical
engineer after the foundation excavation is completed.
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5.1.2 Settlement
Total and differential settlement that a structure will undergo depends primarily on the
subsurface conditions, type of structure, amount and duration of pressure exerted by the
structure, reduction of pore water pressure, and in some instances, the infiltration of free
moisture. Based on the expected native soil conditions, anticipated development, and
construction abides by the recommendations in this report, the assumed foundation
system may undergo a maximum of 1.0 inch total settlement, and a maximum differential
settlement of 0.75 inch.
5.1.3 Concrete Slabs-on-Grade
Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted
coarse, granular material (Retained on U.S. Sieve #10 or greater) that is placed over
undisturbed, competent native subgrade or engineered fill per the Earthwork
Recommendations Section below.
The recommendations for interior concrete slabs-on-grade as presented herein are only
relevant for the geotechnical application of this project. Although beyond the scope of
this report, concrete slabs should also be designed for structural integrity and
environmental reliability. This includes vapor barriers or moisture control for mitigating
excessive moisture in the building.
5.2 Earthwork Construction Recommendations
Founding material for building foundations shall consist of undisturbed native soils to the
specified foundation depths. Compacted engineered fill, or selective re-compacted native soils
may be used to the extents provided in this Earthwork Construction Recommendations Section.
The following recommendations include excavations, subgrade preparation, type of fill, and
placement of fill for building foundations.
5.2.1 Excavation
Excavation is recommended to remove any excessive organic content or other deleterious
material, if present, beneath foundations and to achieve appropriate foundation depth.
Additional sub-excavation will be required for this project if the soils below the required
foundation depth are loose, saturated, not as described in this report, or otherwise
incompetent due to inappropriate land disturbing, or excessive water trapped within
foundation excavations prior to foundation construction. All soils below the bottom of the
excavation shall be competent, and relatively undisturbed or properly compacted fill. If
these soils are disturbed or deemed incompetent, re-compaction of these soils below the
anticipated footing depth is necessary. Excavations shall be completely dewatered,
compacted, and suitable before placement of additional native soil, engineered fill or
structural concrete.
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5.2.2 Placement and Compaction of Native Soils and Engineered Fill
For engineered fill or disturbed native soils that will be utilized as fill material directly
beneath foundations, observation and/ or geotechnical testing is required prior to
foundation construction. The following placement and compaction requirements are
necessary.
For disturbed native soils or engineered fill beneath foundations, limits of compacted or
re-compacted fill shall extend laterally from the bottom edge of the foundation at a rate of
one horizontal foot for each foot of compacted or re-compacted fill depth beneath the
foundation. See the illustration below.
FOOTING
COMPACTED
NATIVE SOILS
OR ENGINEERED 1
'ILL
tt ISTUOIE 1D
Both engineered fill and native soils used as compacted fill should be free of roots and
other organics, rocks over 6 inches in size, or any other deleterious matter. Because of
moisture sensitivity, importing and compacting engineered fill may be more economical
than compacting disturbed native soils. Engineered fill shall include having the soils
retained on the No. 4 sieve crushed (angular), and should consist of the following
gradation:
U.S.Standard Sieve %Finer(by weight)
6" 100
3" 60— 100
No.4 20—60
No.200 0-8
Table 1
Particle Size Distribution of Engineered Fill
Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native
soils and engineered fill,respectively. Each lift should be uniformly compacted to at least
95% of the modified Proctor maximum dry density (ASTM D 1557) and within 3% of
optimum moisture content. Each lift surface should be adequately maintained during
construction in order to achieve acceptable compaction and inter-lift bonding.
Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be
limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined
excavations exceeding 4 feet should conform to OSHA safety regulations. Permanent cut
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and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an
engineer.
5.2.3 Retaining Wall Backfill
Native soils may be used as retaining wall backfill for this project if the total wall height
is 4 feet or less and the recommendations below are followed. Native soils for retaining
walls exceeding 4 feet in height must be approved by the local authority or evaluated by
an engineer.Backfll may consist of engineered fill, as presented in this report, or borrow
material approved by a geotechnical engineer. Compaction of these materials shall be
achieved in compacted lifts of about 12 inches. Each lift should be uniformly compacted
to at least 85%, and no more than 90% of the modified Proctor maximum dry density
(ASTM D 1557). If pavement or building loads are planned to be located within retaining
wall backfill, then 90% compaction is required. In addition, heavy construction
equipment should be at a distance of at least %2 the wall height. Over-compaction and
limiting heavy construction equipment should be prevented to minimize the risk of excess
lateral earth pressure on the retaining structure. Envirotech recommends that retaining
wall backfill is compacted with light equipment such as a hand-held power tamper. If
clean, coarse gravel soils are utilized as engineered fill, and surcharges will not influence
the retaining wall, compaction may be achieved by reasonably densifying granular soils
with construction equipment.
5.2.4 Wet Weather Considerations
Due to the types of subsurface soils, additional provisions may be required during
prolonged wet weather. Every precaution should be made in order to prevent free
moisture from saturating the soils within excavations. If the bottom of excavations used
for footing placement changes from a moist and dense/hard characteristic as presented in
this report to muck or soft, saturated conditions, then these soils become unsuitable for
foundation bearing material. If this situation occurs, a geotechnical engineer should be
notified, and these soils should be completely removed and replaced with compacted
engineered fill or suitable native material as presented in this section.
5.25 Building Pads
Except for minor 6 inches or less of fill, building pads for this project that consists of
built-up fill should be avoided.
5.3 Building and Footing Setbacks
Provided that assumptions relating to construction occur and recommendations are followed as
presented in this report, the factor of safety for slope stability is sufficient for a 60 feet footing
setback from the face of the nearby descending slopes exceeding 40%. See the figure below and
the Site Plan in Appendix A for an illustration of the setbacks.
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STRUCTURE
TOP OF
SLOPE SLOPE
FACE
�- SETBACK F❑❑TING
From the illustration above, structures may be located closer to the top of slope by extending the
foundation deep enough to maintain the recommended setback. In addition, the required setback
may be reduced by mitigation, and subsequently would require additional geotechnical studies.
5.4 Surface and Subsurface Drainage
Positive drainage should be provided in the final design for all planned residential buildings.
Drainage shall include sloping the ground surface, driveways and sidewalks away from the
project structures. All constructed surface and subsurface drains should be adequately maintained
during the life of the structure. If drainage problems occur during or after construction, additional
engineered water mitigation will be required immediately. This may include a combination of
swales,berms, drain pipes, infiltration facilities, or outlet protection in order to divert water away
from the structures to an appropriate protected discharge area. Leakage of water pipes, both
drainage and supply lines,shall be prevented at all times.
If impervious thresholds are exceeded per the prevailing agency code, then engineered
stormwater management plans are required for this project. The drainage engineer must
coordinate with a geotechnical engineer for input with relation to slope stability prior to
submitting drainage plans.If stormwater management plans are not required for this project, then
the following recommendations should be followed.
For this project, we recommend that infiltration is avoided in order to maintain slope stability,
and that roof runoff should be tightlined beyond the slope toe. Recommended drainage details are
provided in Appendix E of this report.
5.5 Vegetation Buffer and Considerations
For this project, we believe that a detailed clearing and grading plan is not warranted unless the
prevailing agency thresholds are exceeded, and basic vegetation management practices should be
adhered to.
Vegetation Buffer—Vegetation shall not be removed from the face of the critical slope or within
a distance of 50 feet beyond the top of the slope. However, any tree deemed hazardous to life or
property shall be removed. If tree removal is necessary, then stumps and roots shall remain in
place, and the underbrush and soil shall remain undisturbed as much as possible. Any disturbed
soil shall be graded and re-compacted in order to restore the terrain similar to preexisting
conditions and drainage patterns. See the Site Plan in Appendix A of this report for a depiction of
the vegetation buffer.
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5.6 Temporary and Permanent Erosion Control
Erosion control during construction should include minimizing the removal of vegetation to the
least extent possible. Erosion control measures during construction may include stockpiling
cleared vegetation, silt fencing, intercepting swales, berms, straw bales, plastic cover or other
standard controls. Although other controls may be used, if adequate, silt fencing is presented in
this report as the first choice for temporary erosion control. Any erosion control should be located
down-slope and beyond the limits of construction and clearing of vegetation where surface water
is expected to flow. If the loss of sediments appears to be greater than expected, or erosion
control measures are not functioning as needed, additional measures must be implemented
immediately. See Appendix D for sketches and general notes regarding selected erosion control
measures. The Site Plan in Appendix A depicts the recommended locations for erosion control
facilities to be installed as necessary.
Permanent erosion control is necessary if substantial vegetation has not been established within
disturbed areas upon completion of the project.Temporary erosion control should remain in place
until permanent erosion control has been established. Permanent erosion control may include
promoting the growth of vegetation within the exposed areas by mulching, seeding or an
equivalent measure. Selected recommendations for permanent erosion control are provided in
Appendix D. Additional erosion control measures that should be performed include routine
maintenance and replacement, when necessary, of permanent erosion control, vegetation,
drainage structures and/or features.
5.7 Septic Drainfields
Septic drainfields were considered in our geotechnical evaluation.This includes septic drainfields
with relation to the observed soil conditions, expected vegetation removal, and existing and
proposed topography. Based on the aforesaid parameters, the septic drainfields are not expected
to adversely influence critical slopes.This is also based on compliance with all recommendations
in this report.
5.8 Structural Mitigation
With respect to landslide alleviation or slope improvements,structural mitigation is not necessary
for this project. This determination is based on the anticipated improvements of the project,
engineering conclusions,and compliance with all recommendations provided in this report.
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6.0 CLOSURE
Based on the project information provided by the owner, the proposed development, and site
conditions as presented in this report, it is Envirotech's opinion that additional geotechnicat
studies are not required to further evaluate this project.
Due to the inherent natural variations of the soil stratification and the nature of the geotechnical
subsurface exploration, there is always a possibility that soil conditions encountered during
construction are different than those described in this report. It is not recommended that a
qualified engineer performs a site inspection during earthwork construction unless fill soils will
influence the impending foundation. However, if native,undisturbed subsurface conditions found
on-site are not as presented in this report,then a geotechnical engineer should be consulted.
This report presents geotechnical design guidelines, and is intended only for the owner, or
owners' representative, and location of project described herein.This report should not be used to
dictate construction procedures or relieve the contractor of his responsibility.
Any and all content of this geotechnical report is only valid in conjunction with the compliance of
all recommendations provided in this report. Semantics throughout this report such as `shall,'
`should' and `recommended' imply that the correlating design and/or specifications must be
adhered to in order to potentially protect life and/ or property. Semantics such as `suggested' or
`optional' refer that the associated design or specification may or may not be performed, but is
provided for optimal performance. The recommendations provided in this report are valid for the
proposed development at the issuance date of this report. Changes to the site other than the
expected development, changes to neighboring properties, changes to ordinances or regulatory
codes, or broadening of accepted geotechnical standards may affect the long-term conclusions
and recommendations of this report.
The services described in this report were prepared under the responsible charge of Michael
Staten, a professional engineer with Envirotech. Michael Staten has appropriate education and
experience in the field of geotechnical engineering in order to assess landslide hazards,
earthquake hazards,and general soil mechanics.
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or require
additional information.
Sincerely,
Envirotech Engineering
-31
Jessica Smith,M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
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