The URL can be used to link to this page

Home My WebLink AboutEisenbeis Block 243 - Geotechnical Report for Bluff Stability - 1998.06.00ENGINEERING LAND SURVEYING Sequim, WA 98382 P0. Box 2199 . 935 North Fifth AvenueIJ (360) 681-2161 . Fax (360) 683-5310 DEVELOPM ENT CONSU LTING Toll Free 68"1-216.1 WETLAND DELINEATION I "l I l I .Tune 1998 Geotechnical RePortforBluff stability Prepared for: Mr. MerrilL Conitz IJ I ,! j l I ,) rviPtRF_s B-- 25--,:Ji -rJ T 23747 013010 -ceonEPT- 061598 6"16 -qa -l I -t j l IIj I{ J I IJ 1lI I I "t I -l I zIlY GOLF COURSE -l -r--I DE FUCA WORDEN PARK FORT STATE : 4Sih :..,: I .... .'' ADMTRALTY tNLEr ' .--t ADMIRALTY oe 3' 1 _-J_ IERMIML ' : r ,.i..:,-.:'i.--.i,1 o PROJECT LOCATION VICINIW MAP NOT TO SCALE t . .. ..,. . fr" { R \'.:iffi19.:.1;1fiiffifr fi 1,;,,;i;:;i;:::;::i::;:;:t;llf::ii. \fiie..fl#ilfffilffi:::::i::::::::i:l ENGINEERING \:1:;l:;i:;l:;i:;fl-J[:;,fr:;iL:nl|it3l.U:i::riiiil:;1:;;:;;:;;:;;;l P.o. Box 21 LAND SURVEVNG \;.::"l.'.:.'l;.::4(.-::alWl Effi,:1i;;:;i.1:;:;1:;;:;;:;;:;1:;l 935 N 5th Ave. WETLAND DELINEAIION Sii:ii:r::ii:i::i:::::..::l?i ii.iZ$i::i::;::i:l sequlm' wA e8382 DeVelOplrtENT CONSULTINe &14:1:;;:;;:1;:;;:, .Wj.W,t&F[*ffili:;i:;;:;l:;:{ (360) 681-2181 f.,,,.,,,,..,,,..,,,,,,,,..,,.jg J Geotechnj.cal ReportforBluff Stability ABSTRACT This report reflects the results of a visual observation of sit.e condi- tions and review of available published data. It concludes that lhe soils and geologic conditions underlying Lhe site are stable and suit- able for residential development using conventional- construclion meth- ods. 1t addresses slope stability and erosion potential and provides recommendations for structural setback from top of sLope, foundaLion considerations, and control of water runoff for devel-opment of a home- site. [llhis report was originally cormnisEioned by Mr. conitz earJ.y in 1996. The field investigation waE perf,orrned on March 27' 1996. The first draf,t of this report was written shortly thereafter. f,he project waE put on hold after delivery of, the first draft and it wac agreed that the final draft 9f, this r€port could be conqrleted when convenient. For thes€ r€asQhsr production of thia f,ina1 draft report has been delayed until now. l :l J J J J J J .i 11 I 't I GeotechnicaL Report for Bluff Stabii-ity CONTENTS I. SCOPE AI{D PURPOSE...... II. PROPERTY DESCRIPTION III. REGIONAL GEOLOGY ... v. coNclusroNs . Homesite .... Water Runoff and Erosion Control VI. RECOMMENDATIONS General . Drainage and Erosion Control VII. ADDITIONAL RESOT'RCES VIII. REFERENCES FIGURE 1 1 1 L rv. LocAt coNDrrroNs .... ...... 2 A B A B . Grading and Foundations 2 2 2 2 a a 3 3 I I J 4 IOCATION !'AP FIGURE 2 . ... PLOT PI.^AN FIGURE 3 ... CROSS SECTION A - A' . . . . FOUNDATION LOCATIONFIGURE 4 ..... PHOTO 1 PHOTO 2 PHOTO 3 I .J I .,1 I J ' J 1] l_ Geotechnical Reportfor Bluff Stability I.SCOPE AI.ID PT RPOSE This investigation was reconnaissance in naLu and observing conditions on the subject parce areas and review of available publications' re and included traversingl- and immediately adjacentspecifically: Geology and Ground-Waler Resources of Eastern Jefferson Count Wash ton (Grimstad (McCreary1981 ) ,and So Surve of Jefferson Coun Are 1975) . In t oIIr shalfow subsurface exposures were made by hand, No precise measurements, scientific tests or englneering calculations were performed. The conclusions and recommendations are limit.ed to the normal standard of care of the industry for and investigation without benefit of scientific data and calcufations. The observaLions, interpretations, and concfusions herein are based on generally accepted professional engineer- ing and geologic principles and practice. The purpose of our study was Lo provide information concerning suitabil- ity of the subject parcel for residential development. This report ad- dresses slope stability, erosion potential, and control of water runoff, as well as homesite devefoPment. II. PROPERTY DESCRIPTION The subject parcel is located on the south side of Sims Way (State High- way 20) and a short distance westerly of the marine industriaf area in the City of Port Townsend, Washington (See Figure 1). It is triangular in shape, about 0.4 acres in area, and slopes to the southeast. The up- per portion, on which the proposed house is to be construcled' has a moderate slope (Photo L); below this area the slope increases to about 65 percent down to level undeveloped property (Photos 2 and 3) . This latter steep portion is about 60 feet in height; total relief across the property is about 90 feet. The surface of the parcel is generally smooth without irregularit.ies. It is heavily brush-covered and supports several large fir trees (photos). Ground surfaces within the parcel and adjacent areas appear to be natural; no cuts or artificiat fill are apparent. Residences are present in the area short distances to the southwest and northeast of the subject parcel. No evidence of erosion, surface water, or water seepage was noted on the Parcel. III. REGIOI{AL GEOLOGY The parce] and adjacent areas appear to be underlain by dense si1t, sand and gravel alluvial strata that was deposited by glacia.l- outwash streams over 10,000 years aqo. These deposits are typically poorly bedded and variable in composition lateral1y; bedding is generally horizontal. The ground surface, lncluding the steeper slope, is mantled by 1 to 2 feet of granular soil. This, together with the heavy brush cover, has pro- vided effective protection of the underlying glacial sediments from ero- sion. The glacial deposits have not been susceptible to gross instabil- ity such as landsliding. The deposits are largely granular and appear to drain well. l_ IV. LOCAI" CONDITIONS Surface soifs in the proposed buildi-ng area will likely range from 1 to 2 feet in thickness. Underlying glacial deposits are anticipated to be dense and resistant to lateral- movements. These deposits are anticipated Lo be very erosive if exposed in slopes. Trees on the property do not show indications of being affected by sig- nificant downslope movement or creep of soils such as tilting or curved trunks. No slope failures or significant erosion of ground surfaces were noted. However, the top of a slope on adjacent property to the southwest has been undercut by a small slope failure possibly caused by disposal of vegetation and other debris over the slope edqe. As previously men- Lioned, no springs, seeps' or gullying were noted 1n the area. v. coNclusroNs Development of a homesite on the subject parcel appears to be feasible in regard to existing geotechnicat and geologic condltions. A. Homesite The parcel and proposed building area appear to be stable and should be able to be utilized wlthout the need for extensive grading. A split leveL or "stepped" design conforming to the relatively gentle natural ground slope above the edge of the bluff on the parcel would be suitable (Figures 2 and 3). It is understood that City sewers will be utilized. B. Water Runoff and Erosion Control In general, development should not require major face fl-ow. However, runoff will be increased by driveway areas. al-terations of sur- flows from roof and I IJ VI. RECOMMENDATIONS The following recommendatlons are provided for development design and treatment of potential concerns as discussed above. A. General Alf clearing, grading, drainage, and erosion conLro] witl- be subject to the City of Port Townsend requirements. B. Grading and Foundations The fotfowing recommendations are believed to be appropriate for nor- maf construction practices on this site. They may be overruled by the written report of an appropriately licensed professionaf who has re- viewed this report, inspected the site, and approved of specific de- sign features at variance with these recoilrnendations. 1) Grading at the homesite should be minimized as much as pos- sible. Cut or fill slopes should not exceed 2 z 1-(horizontal : vertical) nor 3 feet in height. Foundation, retaining wa11, and util-ity trench excavations are excepted. 2-l -.1 Geotechnical Report of Bluff Stability Prepared for Mr. Merrill Conitz l) (\- r \t:|\t:i::*\\W,W:%ie%;iIi ENGINEERING \:.:.:.:.:.:.:.:.:.:.::Y...tl:..v:.:.:.v .wMbt:::.::.::'.:.:::.::.::..':P.O. Box 2199 LAN SURVEYING 9J5 N 5th Ave. NEATION Sequim, WA 98382 DEVELOpMENT CONSULTINe (;1.::.::,:.i::r.:r,W:g#t%-,.%. 3&W..:.:...,..:,|.:(360) 681-2161 ) Unretained slopes should not be planned closer than 20 feet from property lines. 2) No unretained side hill or prism fills should be planned. This will prevent erosion and transport of soils downslope. Material from foundation excavations should be exported. 3) Back-drainage should be provided for any retaining walls or footings that are, singly or in combination, more than 3 feet in vertical- height. 4) The base of structural footings should be seL back a minj-mum of 20 feet from the face of the bluff, measured as shown on the drawing included as Figure 4, unless a special founda- tion is designed by an appropriately licensed professional. 5) Structural footings shoufd penetrate into dense glacial sediments a minimum of 2 feet and shoul-d be tied to prevent the potential of any lat.eral differential movements. C. Drainage and Erosion Control Drainage from roof and paved areas should be collected and conducted to the base of the btuff via rigid PVC, CMP or equivalent drain pipe. The downdrain should be anchored to the slope or cabl-e-stayed to pre- vent. separation. It should outlet into a velocity dissipater such as a rip-rap and concrete apron to prevent erosion. No stormwater infil-- tration (drywell) facilities should be planned on the parcel. AII graded or stripped areas shoufd be planted immediately with grass and deep-rooted ground cover to minimize erosion and sloughing. See the publications listed under OTHER RESOURCES below. VII. ADDITIONAL RESOURCES In addition to the specific recommendations listed above, general advice for the owner of bluff properties is contained in the following threepublications: 1 e Stabilization and Erosion Control Usin Ve ation: A Manual of Practice r Coasta Prop v Owners, Publication No. 93- Vegetation Management: A Guide for PJrget Sound Bluff Property Own- ers, Publication No. 93-31 Surface Water and Groundwater on Coastal Bluffs: A Guide for Pu So Pr Owners Publ UA L-on All of these are published by the Washington StaLe Department of Ecol- o9y, sponsor of the Shorelands and Water Resources Program. They are strongly recommended and available at no charge. They can be ordered by calling the Department of Ecology at (360) 407-6000 and requesting the Pubfications Office. 0 3 l 4 I I .J VITI. REFERENCES Grlmstad, Peder; Carson, Robert J., 1981, Geoloqy and Ground-WaLer Resources of Eastern Jefferson County, Washington: Washington McCreary, U.S F. R., 1975, SoiI Survey of Jefferson County {qe11 Washington: Soil- Conservati-on Service. 09t '_-.. 0z/ L] ' l');r - a l!' = /OO'\a\9-(tr X X o- \ $+ o+s{ x { \ \_ .-:\ \__\q Op og B O€] a a8 --la\lNI ) "flzetoo8oPaaee,aryLtate,,/\/ Sceee'PaoeaRrr ltue9ru s War€Eqz; a,rEtVTFteuBE 3tt,///6of/tilrorr/H"=ZO' OOJoI-rlc)+Io(ocolr-: --t--f-r'i- -: -r--i..'f.'---i-t--1-_ i_ _ t_i:l'i-'-:-..1..._f-i-1'ppt!oN@oz.mmnz.o@(!azo5!DrzIacnmz.cJaooc3;@oC{@l\)z_rrtIozuooo@INoomrrlro!=rrlz.--.1ooz.acr r-:f'-i,ItrliItr-ttt-I"*-t_>;-\\---/FtauRE 2\.oS1*?aa\s\<\<,rt\\S.Nsc\\N\q)\\")\NItL-1hIl.\alt}.lo//z aa>ra€67- &tvTHIS MAP WAS PREPAREDBY OTFMRS: INCLUDEDHERE FOR ILLUSTRATIVEPURPOSES ONLY.$$JILILNss-a'80\\8f'e*7;:;,,\-s.t_ : 3 ,1 ag CTNss N/^0I lAadl + A al6 r r't/5 J ttsawq H + T otoHd -lsuaHlro/V- rPnor o ZIirt-SorrHERST'fulnatug fNOvJTn)4( ,4 na.e., r'1'gf.*r'1'.),nrr,' _#,.ti:.:ii.l"""ii-!.ItS t-oc6 Beaorn, Pno PaJe D Hotve s / 7 E r'f'"trLItttJItI-tft"LPaor o 3* A/onrH -Honn Es /T EArlnnue-TuousTnr pLFnea