Loading...
HomeMy WebLinkAboutBLD2002-00367 Geotechnical Report r e _ NORTHWESTERN TERRITORIES, INC. . , /____ . -- Engineers IILand Surveyors f1 Planners Construction Coordination II Materials Testing • NTI • . , • . • • .• April 14, 1999 Dr. & Mrs. Sydney Schneidman 231 Porter Lane Port Townsend, WA 98368ZPI✓A Es 1740eW Fe pt..b Subject: Bluff Stability Report Update . PI Dear Dr, & Mrs. Schneidman: N Oo l 04, 3 o r 7�'- Background 2.-1 13103 In response to your request, I met with you at your home on March 3, 1999, to review the status of the marine bluff at the above address in Section 6, Township 30 North, Range 1 West, Jefferson County, Washington. The purpose of this review is to provide an update to NTI's "Bluff Stability/Building Site Evaluation" report dated February,1989, (revised May 5, 198s, copy attached for reference). This report update is directed to potential purchasers of your property to help them. understand the natural bluff recession process that is taking place. Discussion and Analysis The "Mechanics of Bluff Retreat" are described in the NTI report and further illustrated in the attached photocopy of Fig. 21 from Vol. 24 No. 1 , March, 1997, issue of "Washington Geology" published by the Washington State Dept. of Natural Resources (DNR). Figure 17 of the DNR report further illustrates and describes the slide activity resulting from the December 1996/January 1997 winter storms. The subject home is in the center of the Fig. 17 photograph. During the passage of the 10 years since the 1989 NTI report, the region has experienced record breaking weather conditions that have resulted in untold marine bluff landslides throughout Puget Sound, The I)NR report illustrates the extent and magnitude of some of these events. 717 SOUTH PEABODY, PORT ANGELES,WA 98362 (360)452.8491 1.800.654.5545 FAX 452.849E Dr. & Mrs. Sydney Schneidman • Bluff Stability Report Update April 14, 1999 Page 2.of 3 Findings My March 3, 1999, observations from the top of the bluff at the subject property are consistent with the photograph in Fig. 17 of the DNR report. Namely, the slide debris shown in Fig. 17 is currently at rest on the beach and is providing a temporary buttress that will protect the toe of the bluff for many years as described in the references cited above. On April 8, 1999, the horizontal distance from the top edge of the bluff to the foundation of the house was approximately 75 feet, The 1989 NTI report recommended a 75 foot setback, although the actual setback was closer to 80 feet. Therefore, the actual recession would have been about 5 feet. Although most, if not all, of this recession occurred in one event, this translates into 0.5 feet per year for the 10 year period. This is very consistent with the long term average of"six inches to one and one-half feet per year" cited in the NTI report. Conclusions The current condition of the bluff is consistent with the 1989 NTI report. As "predicted" a 5 foot deep slide has occurred during the past 10 year interval and the large debris pile on the beach will now provide toe protection for the base of the bluff for years to come. It must be noted, however, that regional changes in weather patterns, earthquakes and the like could reduce or increase the magnitude of a single event and/or long term average rate of bluff recession. Limitations This report is based on a visual inspection of the existing site conditions. No scientific measurements, tests or calculations were performed. The findings of the report are limited to the normal standard of care of the industry for an investigation without benefit of scientific data and calculations. Dr. & Mrs. Sydney Schneidman Bluff Stability Report Update April 14, 1999 Page 3 of 3 The sole objective of this investigation has been to diagnose the bluff conditions at the. site. The report has been prepared for the exclusive use of Dr. & Mrs. Sydney Schneidman and designated potential purchasers. The report has not been prepared for use by others or other uses, The observations, interpretations and conclusions herein are based on generally accepted professional engineering and geologic principles and practice. This warranty is in lieu of all others, either expressed or implied. Sincerely, .QRRY N4, ' '''��of wask kr NORTHWESTERN TERRITORIES, INC. ~•y,,v ,; ' . / • • •Q.1�N53 0 t�j u ,A�SSIONAL gc1 R. Jer Newlin, P.E. Principal Engineer I EXPLRES (0u/0 o 1 JRN:eas Enclosures G:\G ENV erry1REPORTSCHS9901,rpt,wpd NORTHVicSTERN TERRITORIES, INC. � Engineers t Land Surveyors IIPlanners Construction Coordination t Materials Testing NTI CLM1 Af pC11H BLUFF STABILITY / BUILDING SITE EVALUATION In Section 6, Township 30 North, Range 1 West, W. M. Jefferson County, Washington Prepared For DERRICK REIJNEN Prepared By CLARK ASSOCIATES, A Division of NORTHWESTERN TERRITORIES, INC. February, 1989 • 717 SOUTH PEABODY, PORT ANGELES, WA 58362 (206) 452-8491 1-640-654.5545 . f BLUFF STABILITY / BUILDING SITE EVALUATION For DERRICK REIJNEN • GE'EN RAL On February 9, 1989, Timothy M. Reed, of Clark Associates, a Division of Northwestern Territories, Inc. , made a site evaluation of Lot FW in Govern- ment Lot 4 located in Section 6, Township 30 North, Range 1 West, W. M. , Jefferson County, Washington. Derrick Reijnen, the architect for the property owners,. Dr. and Mrs. Schneidman, was present for the inspection. CLIMATIC CONDITIONS It must be noted this investigation was performed after a period of exces- sive snowfall and unusually low temperatures. These conditions may have led to anomalies manifesting themselves during a visual inspection performed after uncharacteristic climatic events. SITE DESCRIPTION The property investigated is approximately 5 acres in size, more or less, with bluff frontage overlooking the Strait of Juan De Fuca. Topographic maps of the area indicate this bluff is approximately 100 feet high. The face of the escarpment has several trees and some low vegetative cover with some of the frontage bluff face having recently slumped. Angles of inclina- tion range from less than 60 degrees to near vertical. From the beach, it becomes apparent this is an actively eroding bluff. There were several noticeable areas of both recent slump and ongoing under- cutting, including erosional and fairly large bowl-shaped slumps (see photo- graphs). One area of recent slump encompasses a portion of the bluff on this property. Several hundred cubic yards of slumped material is piled up at the toe of this area. The material is still reasonably intact with small trees and. vegetation growing on the top. The poin .where this slump origi- nated is somewhat of a low point with severa unpaved roads nverging atvi this spot. j,belci °'"'• ! Access to the beach was gained from a path on a bench to the east of the 444, property. This bench probably represents a past area of slump approximate- ly eight to ten feet across. MECHANICS OF BLUFF RETREAT Bluff erosion is initiated at beach level where a combination of high tides, waves and long shore currents remove sand and gravel from the toe of the bluff, thereby causing undermining and over steepening of the entire bluff. This in turn, eventually precipitates slides from the top of the slope which form a slide debris pile near the slope base at beach level. This debris pile at the toe of the slope will act as a temporary buttress to prevent or reduce further sliding. However, once this debris pile is removed by waves and tidal current action, the cycle of undermining and induced sliding again continues which results in an inexorable retreat of the escarpment face over a period of time. Estimates of the rate of such escarpment retreat vary from place to place, but can average from six inches to one-and-one-half feet per year. Actual slide outs may be ten feet or more in depth, but may not take place except at eight- or ten-year intervals. CONCLUSIONS AND RECOMMENDATIONS 1. This property has a spectacular sea view, but also has an actively eroding 100-foot high bluff. The erosional patterns indicate a combination of beach and runoff effects which can pose a definite threat to any building constructed within the recommended setback from this bluff edge. 2. Considering the height and active nature of this bluff, it is recommended that a setback of 75 feet from the top edge of the bluff be -Imposed. 3. If a closer location to the bluff edge is desired for view considerations, an alternative might be a specially designed residence which could be moved relatively easily should future conditions dictate. 4 . A third alternative of erecting a protective sea wall at the toe of the bluff might be a solution, but might not be cost effective considering permitting problems and beach accessibil- ity. 5. In addition to minimum setback requirements, steps must be taken to alter runoff patterns. Landscaping must be engineered to divert rainfall runoff, provide effective moisture reduction and provide as much soil stability as possible. All structures should have gathering systems for rainfall runoff and provi- sions for diverting this water to some natural drainage away from the building site or immediate bluff area. All trees outside of the immediate building site should be maintained. Revised May, 5, 1989 v STANDARD DISCLOSURE STATEMENT This report is based on a limited budget investigation. Only visual inspec- tion of the existing site conditions and/or facility was conducted. No scientific measurements, tests or calculations were performed. The findings and report are limited to the normal standard of care of the industry for a limited budget investigation without benefit of scientific data and calcula- tions. Unless foundation plans are reviewed and the construction work is inspected by the Engineer, no warranty is made by the Engineer concerning conformity of the construction to the conclusions and recocmmendations of this report. • R Y •`� DER Neck % • r• was i 14 tic . / • o Timothy M. Reed •• Geologist ;0111,\ /i34/ • i �FSsIOHAI ECG: J. R. Jerry Newlin, PE • %.%%%%% Principal Engineer 4- 141- fc: Reijnen.Rpt Dir: TMR/Rpt - . ( ' . . . • ". ' -oar:-,:.•:••••. ---11!) .•,--- i • - " :-7'' ''-*'''' '.".o'' *' - :"• - .7. . .a,. . .A.„..••• -.--;...-. : _. . • ,...-......:.-r.z.. '. 17 1• •". tr , ....i.:".•',„,40....7 ... i-•'!:.... ..:•-•-,*.:- -2. ---zr-q.'-.-;;;.::*"...7.-..,, .'. s': I... li.. • s ...:.....""7 " ."'0' .. :.:-S ---""•-•""' -'--"":;;.-...1;11:21.1f4 ..‘" "' 4: T-”, " / • ......-rt ..:,r4.:p•• 4 •...••414-:....7. ,,..:! .-:-.......-1 -' .-.-* •.! -i .1- --4/.7.:....i...;i5,-4, -.1%-e:...4,-,•:.e..,-Y-4:•••,---7;.--7'•-:-- ! ' \ .• .61,............61.417-.7.!-is•--....4zetaa•--Ft.C.4.---t:..:;.-.,,,•-•-•-_-----1-••••••--A.:,- I.,. •:-._Pr:' Ir-::•-...1..'"&i:•;-7,•-"P'.ifP.,;1.u...----.1--'''*:--.....' `-'*.*:. '7.; :.' ki - 11:11..0,1‘..;;;....",,-,iatira.lie it.'"-i.-.,".. .,....•.•••...74... .... • - -.-4",,., . / ::;4i.C.r..:-.--It"*-"'it..:40•.4-t.:::•-:• --- -. •".'" : 1-..-..;% ...-: - ..-..t.:.'!•!....."'"4":3'-'-•.47.-:••_:,'ISAt.ii.:4,...-.7P1.F-,...' '- ' • '--:.'7.--C.i..".: .,'"-:,.-,....,•,....:c••,--0.--:.......14.-..„."!...7:4-:„..•--2.7,7--.::,• ••:!-.....,, -'• .... . i!..: •,."..4-AT, r.:-.....1.--..-_--;..?;:.5--"c--i-,z-•-•-,.. . . ::.. ..0"..- -.• . •-•1.,,,,!.• :...Ast.. ....-....:,.!--;.;•!,;;;;V:•!,.411'.!.•,..,•..._ .,.. ••.. ...... ez-:._.•. ;,.,...... •II,C0 11:-.',-....,:: :••:!•:-.:it..1,111.f.',../!•••te:"±:--- ...':••tp... . •!i ‘..• '...I.-4 . . ::.:NE:t.".r., -,-. ..,-:.--- ••• ! r• •k::1•Z's"----•r e.z.1, A-.41-.11-;':-:-_,-.;''':'..•' : -'' '•.: --. ! -.1 . ..\. v.' "1 s....e.4.• -- .-..-. --- ....1--•:::''r -1 -,..-. . i ..:...1.,-;:ic..,....11., 4.....,-. 7.. , '2, -4 :to .,,, ....:. ...... -: ...... . - i.' :•••Iii--"..1-.....-44....f.T.SAI..4•4,c..•-t.-..;--:- .-,-.......“:::..lif..1.0.r.;•_,Y-7,1---...-. ;,,,..41,-.-..,..........;:.1.1.1.-F....;:-- T-'. ‘! - - - "' . ..•.-0,1 -..1"---0.. 0,---:- ..-:-•''.7 •-..*.' ...---.)-4e!!st-'20-:?•ii. i -.:".1"?..%.4?-•',:-.•%;ii:-*. -.•... _.---_,,. :.'......%:* :Leg .•.47.7.--:" 1.,..".- •2_- -A e••••-r ,-,..-....•-•.,..••:',ii;ie-s1 .... -. .."-:,, - ,_.•1-" :t s-.. . .-• •::... ;.--:. -. •-:2.0:1:%4. •I• _-•,4:.! -- '-•:::elt 4 ,. • : t-.......'. ......r-. L.... ..'.••Ii.11".. ir.'' 'I.- HI •__ ,- 7:"i7.t:•-.:,,tf, - -: : -.. . .-I-•:. -."-,41-.! • -,.....1.--. . - 4.1..t:-..:- . •• ••• •4.-44.--t-,.1, '.........--- VII . 7..•••.t..i•••••;.• • - s...::"...•..!3.;X..c.`:I -;:...:=:.. .t;i:14 i•••••........-:-...:-.:'-!:.7.2'..-%‘:•,-.....„,...:*...;....... ..Y,!..W.;:..7.:1• avip, If;.‘''.: .....".''''••:-....-'% ... .'7'.T••••••-.........•.-..;•;.ar.- •\..;:.1, ,....."1,• ' , 4 ill......S..,.F.!VriN7',.2.•::::•..,..... .• - •,-;".::e:.7._4 1,N.'..e.";r•li.e,4 1.1n11.1_%z,!.2.,:.•2.,.?j,:,4.2.1......h,...-...-.."..1...,-„..3b--N..:•.e4-.r...,.:."... ...,... ...,,12•"..•.*.-.1'„.'1............!...5...:4.r2.:1'!...Pi f1 .: r,. 1 4 ,..,,, .':......-,......LV.4 4 • - •...:-.........4"." ' • -: •'i . ''- •-•••• .., -,-% .4_,:'.. 1151,2t.''.4.0" ..-..;. -.117.,:t.:,' t..*- '''' .' • - ••• • ‘/.."'".. '11117 • '';;;:;et--, '• -- ---t-'''.•; 0.. Fr 3 r - --....•.‘eit •••` '•- 4 .....••.... --.-...-S-::.-- -.7.7:-'-- " .-. --.- -ru ti.i4."1 s---lz-= 4:--- -,*- .a, • - .4,-ge.:4,0_;V,,, -':_::!;:f;i:,,2;.4--.,,3.-.1,7,x .•Y! .!'t.-...,• • • • :.. •-'!''''.1.i .- 4:1:1:•...,.Zei.::-. ;`-;- " ' -1••,-.• . r.A...-:"*:•.y-•-•""--.- v .• . •• • . •••-. ---.:".---- -s: * -.•,411'.-2!.!.•igt.,? #,„ .7.1.../....- - .--._ . .., .... , . . •p•. --• . • -. .. - .1 .........•P A., •• •• • • ••"----4,-"- . -- • l'h :I.---- • - .••4-. ' 4. •. ....-.• .". .':. $•.--., '' ..: , ._ ... • * , , 1,.;;; :... . ' Il• it 3 ... ..1r.. '- 4..••• f. i`A' Bluff face with debris pile at toe of bluff. . • -. -,.... -...........g- :::-.. live, .-...•.-: •-,.....,s„,..,...• •,. ...-..--,,.....- - • -_, •,-.:-,. ._ ,-..t...,..:4„...:-,;:.*A.:....,.,„. ...4# , et rn, y. •,;::.. . -- •-,...• • -- • _ -- -. .•, - •_.•:*.-4.--_,..-.-.0#3•.•.---,-••-va..r.-a. •••-: .`"za• - •,---••.-.V‘r. #.v.'-----:-,7-.7.civr--#1.4 rot.r-- I. ,..- - - ..,,- - f.-;,... •!;•_,-*'• ‘,‘ -- ),Ji.i-- . 14 ••14•;Velii :,•••1-: .-- - ':.•-_- :.-:e--... -. -, • - .-.-:-- - :.. -i -i•--.4•-z-. :T1-"*.-ii7f •_;;;-'.," ,..-i'-: . . - ..,-. - : -..-_„ :- ...,. .. -,v.A0,--:.%1!.. .:„ yt,.0...- tri,.....e.e.1:.1.. 1. .;-.i.. . - . '.... %.2 ,.;..-"..•••1..,,,.... I.....N I,-4 4,....17..;.“. -1-...-174"-:!- ••"-•;••••;"-i "_•-• -.: "..._;/-••:;..-:- ••-..,..'_':' -...-- i. .- • .7 V. . .•A-••••.:1•,......!.;•:„.•„,,,.-•N•1..-1,7 i• --jr..s . ,.- %-:.---... 11.tx;•.:.:-.7.1- 1,_„'•••• •:-,..t.y....• •. • -..-....,,:-'•:•----4,• .1-.---.-„,..;%-:- 77-- #. .s•-z...• ,si!,•;1!;•••:.,- f 1..i.4A-..-2----...1/4,-,11.-F-,./:.\-.:;•.izz:,.% ,f..4::::..,-.•-• "..t... _ ; ..• . .-:-.-_-.•4,.•••••••_ •i':-.4-'•-•''re--Ut ,-..•-•••,-?-••----;!--.S.let-ist . ------e , .4A!'vl".•• • --:7•-•Lbs_: .-t ...... •k ) ....,:•:••••%•%„,:._, - - .-t-,k_...111-:,-,.../-. -1:3- ,,i.----- iiiip- .....-4;-...- - • " --.:_ .. -...„,.. ,. -„,-,.._.-...1-,.t•..-...7,,-.7.-- •-•t-s.-., .„„i.se1450.,..!......,::::..1...... .3.,- -et 4. -- - -k- "'•••• 1-i..''''.;,iti...,:-.."..-.I..,,I. • . .". .'.........'*-4". I'.r."" -.' -'-•.S•:%7•-t.e,A-:le2. ' ... :4,:ivt"::27.. .4::„......1,e 7 0 ',-.*:;:-.-...- t 's•V--s.. •,N,;,•t'• C- °-!- .•'- ,-I...!.." -,:i• . s f-79r.,-, :•si..A...-.-:-IVTit..- ,;._- - A-,. :- .-..;.- . -,.....-Ar.4 .• ,..7. V.. lh __ y4,...4 I2 ''''..-.t.: ... .•- 447;.2.:-4..... ..: -.L:#--1...AC.i."...1't.<1.,..ite Vej.4 ;. Vb. W4141b 1.1..Siitr70.... ! ..,:j.,., . '. .• .., -;4.4.--:•: -*- .4001. -9.... ,,,,4'.:..Xj....%41....55..4; .....4'..t.. ..ef.61,1:1.. ".'?:... .-4-:.''::.'A-.3%-iji.:ferk --....;.• ''. :...ct-t10:;•;:.1::4;-.'' ..._,-.--.t-.`,,•-,.-,.v.---.,7,:'•...:-.'1o•--.•.-._.,_:-"_..j.2.(..'‘ % .N4 _ ..;.t4c.;i;: t.674' ivi_fyi•-f.51'•.2"4,"''''11115.11..;:,`-"1:..,.1p".-'^:.:,..-.-.6•.-',;•,.•.••.:•-•w4.-1 1? 1g,f 11 tfr•-_.,:T-'•::.f.,....' -.444""-"P•44.4 ir • ••:'.7 ....___241.1,,,,..".'4.'„1,...41:•• • -. •• . ' ,' '% ...: ::,:...*-....:3....:4_, ..:-.. :::17....•_.....,;, ,•, .. ....s. -,,..-.t,...r•-:. .•.:;•.. . _--- -....,_ t ...,..1-i."' - 4 .'-:.-1.--3..*- $•r•.,i-• -.7--‘=•%-k; --•',---•.:-1%11'1---- ..;-* ' " a •b- ';1-'.., 1-81"'"•..-'... ..--7 -:- -:..", . .sir...„...........t.„ ., .......... ,..d. %. I.5.,-...ior . • • .. • 000.... 4 ...,,... :.•.,._.e.„..._ ,... „.....,,,_• _ ....:Inorire. •,......-- -...- .4- .. ,,,...,..... .-....._.".IP •..:* /1P.F.0 .4, . s.V../It..„,.. .r• , 44,, .' '' iiii..., - ..nt - 4 /- -1,- • -q-1:-.0--.: - . der , -. 0.6*-g- W •In.' • • .4-4... • 14 - • 4-, w . '.•.P : 4 k ,,.. .4:41'• . -.• ,,,' . .-' , 1 • .. , .p, - - . ,-, • , .. - A •-i-!' . •-..-,: (-4i, • . '......* • ;.:-.; . A.- 0 .• - - - 1-•- ., si -. ;1 ....., A!..11..2. . • ,.• • 411 ,... -,r ... ... • .. ii.- ' - •. ••.- --- • ''` .." • ' r Debris pile at toe of blufl. . , - •••1474 V 4...... .• EFSI. :!".r--f. 7, kt s. -1- • {-; III a . A. t F f•W. 21...- " �pY' 4.•�+�..4- '• t t 4.•' l—iY': Jr_lcMt`�f -/ .4)..,: ,.. ..•.• . ,. ... ........ .........,_ . .,.... _,.:.,..,. ....:•, . . 0. • .. • !_ ..,sue — r• •. Yv s .wsr i..- i Road and property back from edge of bluff.