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Home My WebLink AboutGEO Assessment BLD2006-00654 - GEO Geological Review - 5/16/2006 STgTFO� MASON COUNTY o y PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER S T z Shelton, Washington 98584 r� N 7 OJ �O 1864 DATE: June 19, 2006 INTER-DEPARTMENTAL COMMUNICATIONS TO: Rebecca Hersha PARCEL # 12220-58-00008 FROM: John Sliva, Programs Engineer-PW BUILDING PERMIT NUMBER: BLD2006-00654 SUBJECT: Geo-Assessment Review NAME: Pioneer Builders Rebecca, The Geological Assessment prepared for the proposed new residence at 161 East Allynview Drive located in Allyn has been received and reviewed by Public Works. The geological assessment report appears to satisfactorily address County requirements for Geological Assessments. The proposed building location has a slope of 15%. Competent soil can be expected 6 to 12 inches below the existing ground surface. The lot averages a 26% slope with a 50% slope mentioned along the ditch line. The author notes that even though slopes approach 26%, the potential for landslide activity is not a concern for the single-family residences to go on the three lots. The author recommends site conditions for the proposed development do not warrant a more comprehensive Geotechnical Report. A visit was made to the site. The lot appeared to average the author's 26% slope and dropped to the ditch line at Allynview Drive at a 60% slope. There was an 8-foot vertical relief in the worst spot on this 60% slope going into the ditch line. Other spots were less in slope and vertical relief. This is the 50% slope mentioned by the author going into the ditch line. The report by Geotechnical Testing Laboratory appears to satisfactorily address County requirements for a geological assessment. A geotechnical report will not be required based on the author' s comments and recommendations. Recommendations contained in the report should be incorporated into the site development plans and made conditions for permit issuance. Adequate erosion and sediment control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts. The migration or release of silty water or mud from the applicant's property will be considered a violation of County and State water quality protection regulations. Please feel free to contact me at 724 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Sincerely, ohn Sliva 'Programs Engineer GEOLOGICAL ASSESSMENT 1419 1619 ; 171 EAST ALLYNVIEw DRIVE PREPARED O. PIONEER BUILDERS, INC. BY GEOTECHNIcAL TESTING LABORATORY OLYMPIA, MAY • 2006 � ; � '4 ._ � .)ter• ... - - �v�-; - � � „�� - } s; �" . ♦• 1� ��. �,��a � ��F. �i. 't �'r yf� 1 � .�gqS;yam A� GEOTECHNICAL TESTING LABORATORY CONTACT INFORMATION PREPARER INFORMATION GTL PROJECT NUMBER: 06-2521-05 ADDRESS: 10011 BLOMBERG STREET SOUTHWEST OLYMPIA,WASHINGTON 98512 TELEPHONE: (360) 754-4612 FACSIMILE: (360) 754-4848 EMAIL ADDRESS: GEOTESTLAB@COMCAST.NET CLIENT INFORMATION CLIENT: PIONEER BUILDERS,INC. CONTACT: Tim YHLER TELEPHONE: (360)340-3442 MAILING ADDRESS: P.O.Box 1094 PORT ORCHARD,WASHINGTON 98366 SITE ADDRESSES: 141,161,& 171 EAST ALLYNVIEW DRIVE ALLYN,WASHINGTON 98524 PARCEL NUMBERS: 122205800007, 122205800008,& 122205800009 GPS LOCATION: N470 23.136' W 1220 50.060' 10011 Blomberg Street SW,Olympia, WA 98512 2 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY SCOPE OF UNDERSTANDING PIONEER BUILDERS, INC. P.O. Box 1094 PORT ORCHARD, WASHINGTON 98366 RE: GEOLOGICAL ASSESSMENT SITE INFORMATION: 141, 161, & 171 EAST ALLYNVIEw DRIVE ALLYN, WASHINGTON 98524 GPS LOCATION: N470 23.1361 W1220 50.0601 PARCEL NUMBERS: 122205800007, 122205800008, & 122205800009 Mr. Yhler: As per your request, we have conducted a geological assessment and analysis for the above-mentioned parcels. The assessment was performed to satisfy the Mason County Critical Areas Ordinance 17.01.100.E4. A site reconnaissance was performed on May 8, 2006. The results of this investigation are to be found in the following assessment. We have provided three copies for your review and distribution. Often, because of design and construction details that occur on a project, questions arise concerning soil conditions. We would be pleased to continue our role as geotechnical consultants during the project implementation. We appreciate this opportunity to be of service to you and we look forward to working with you in the future. If you have any questions concerning the above items, the procedures used, or if we can be of any further assistance please call us at the phone number listed below. Respectfully Submitted, GEOTECHNICAL TESTING LABORATORY W88hl� r Harold Parks, L.G., L.E.G. Senior Engineering Geologist tom. EnplrqV OeoftIst p 827 P_Kp -31-0 a'Sed G eo�o HAR L W _ ,�*�.a„-wt dF, •, A. '{ ,Ptf .4 10011 Blomberg Street SW,Olympia, WA 98512 3 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY TABLE OF CONTENTS CONTACTINFORMATION ............................................................................................................................... 2 SCOPEOF UNDERSTANDING.......................................................................................................................... 3 TABLEOF CONTENTS.....................................................................................................................................4 PURPOSE....................................................................................................................................................... 5 SITECONDITIONS.......................................................................................................................................... 5 GEOLOGICCONDITIONS................................................................................................................................. 6 GROUNDWATERCONDITIONS........................................................................................................................ 7 DEPTHTO COMPETENT SOIL.......................................................................................................................... 7 PASTSLOPE INSTABILITY.............................................................................................................................. 8 HISTORY OF LANDSLIDE ACTIVITY................................................................................................................ 9 POTENTIAL FOR LANDSLIDE ACTIVITY........................................................................................................ 10 RECOMMENDATIONS................................................................................................................................... 10 VICINITYMAP............................................................................................................................................. 11 10011 Blomberg Street SW, Olympia, WA 98512 4 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY PURPOSE The objective of the geological assessment is to assess the surface and subsurface conditions prevalent at the subject site according to Mason County Critical Areas Ordinance 17.01.100.E4. The parcels are to be developed with three single-family residences. The residences will be constructed in the western portion of the site where the slope is less than 10 percent. Se _ - -��f9 f I � •a �f1fF� i/'its ... SITE CONDITIONS LiWieAlll W The subject site is of located approximately 0.5 miles west of Allyn, Washington. The lot is located in the moderately dev ped Lakeland Village subdivision, see the following vicinity map. Slope angles on this site range from 50 percent along the roadside ditch to 15 percent at the proposed building locations. The lot -,. gently slopes (averaging 26 percent) with eastern exposure. The site is bounded by undeveloped forestland on 'X the north, and residential lots on the ±� west and south. Allynview Drive borders the site parcel on the east. The lot is mostly vegetated with the Scot's ; broom,blackberry, bracken ferns, sword ferns, Oregon grape, huckleberry, lupine, salal, as well as madrone, fir, n alder, and dogwood trees. No surface li water was observed at the site during �'' ,A the site reconnaissance. p ' ai sance. Rapid stream incision was not discerned at the site. , ( No slope instability was observed at or around the site. v 10011 Blomberg Street SW,Olympia, WA 98512 5 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY GEOLOGIC CONDITIONS The Soil Survey of Mason County, USDA Soil Conservation Service (1960) has mapped the site soils as an Alderwood gravelly sandy loam, 5 to 15 percent slopes(Ab). The survey reads: This is the most extensive, soil of the Alderwood series. It occupies undulating to rolling moraines. In undisturbed areas a 1- to 2-inch mat of very dark brown, acid organic matter is on the surface. This grades to a thin, dark grayish-brown, highly organic mineral soil. The surface soil consists of a friable, brown, medium acid gravelly sandy loam 8 to 13 inches deep. It has a �1 weak granular structure and contains numerous rounded shot. 1 Below the surface soil, to depths ran in g�om 18 to 24 inches, is a pale-brown gravelly sandy P g loam that is very friable, is single grained; and contains small to moderate amounts of shot . Between this layer and the cemented till is a 3- to 10-inch layer of very pale brown gravelly sandy loam. It contains no shot and is firmer but has the same texture as the layer above. However, it is faintly to distinctly spotted and horizontally streaked with brown and yellow. The cemented till consists of light-gray, gravelly sandy loam, and it normally occurs at depths ranging from 24 to 32 inches. It is impermeable to roots and very slowly permeable to water. The first few inches is usually laminated and streaked with reddish brown and yellow. Below this, to a depth of many feet, the till is uniformly cemented,fairly uniform light gray, and medium to strongly acid. A thin mat of roots often lies over the till. The cemented substratum tends to restrict the rapid downward movement of moisture. Use and suitability.-Not more than about 5 percent of this soil has been cleared and is used for crops or pasture. Most of the cultivated acreage is near the inlets of Puget Sound in the vicinities of Arcadia and Allyn. In this area the Alderwood soils are associated with the better agricultural soils of the Cloquallum, Sinclair and Kitsap series. Alder-wood soils need barnyard manure, green manure, nitrogen, or legumes to maintain a fertility for crop production. Phosphate fertilizers and green manure or barnyard manure greatly improve fertility. Nitrogen fertilizer is often applied with barnyard manure or when cover crops are plowed under. The fertilizer furnishes additional nitrogen needed to hasten decay of the organic matter. AK y: 't tr r, r 10011 Blomberg Street SW, Olympia, WA 98512 6 Phone#: (360) 754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY The Geologic Map of Washington — Northwest Quadrant (2002) has mapped the site geology as glacial till deposits(Qgt)of continental glacial origin. The report reads: Till— Unsorted, unstratified, highly compacted mixture of clay, silt, sand, gravel, and boulders deposited by glacial ice; may contain interbedded stratified sand, silt, and gravel. Includes part of the yashon Drift undivided. The Geologic Map of Southeastern Mason County, Washington, USGS Water-Supply Bulletin 29 by Noble and Molenaar(1970)describes the site as till. The till(Qvt) is described as: Cobbles and coarse gravel in matrix of fine sand, silt, and clay. Generally a compact, unsorted mixture. Extensively underlies drift plains in thicknesses of a few feet to more than 50 feet. Poorly pervious, but has sand and gravel streaks that may yield small quantities of perched groundwater. Serves as confining aquiclude to artesian groundwater at some localities near sea level. s f .. S- GROUNDWATER CONDITIONS Groundwater seepage was not observed at or near the proposed building location. Wetland vegetation was not observed onsite. Research of the local wells indicates that depth to static groundwater is approximately 60 feet below the ground surface and is,therefore,beyond the scope of this report. ANqr {Yr r I .y 10011 Blomberg Street SW, Olympia, WA 98512 7 Phone#: (360)754-4612 Fax#: (360)754-4848 s {�� ,� ��. i F ,S' r r f .1'ia ij �v+ .. + tis _ �`s►d i il' it . € r .,,z� n t� ,.��stiff � � �j"�r;s, F r. 1� + -y v- r• s � � ,M,awi'� � .e'�� 5iti`-a!• J +"°"*'1.*et'��.. ✓r�"`r .931�� .�'c.3: L:: . •„F � � Y �� ;+�+\r �I�'•,_M'� �:��Z=fit. � t m Aa • 1 •1• "1 • 1 • • 1 • 1"1• • 1- • 1 1• -• MI • • 1" lot 'J • 1 A .' ,n ;iall 1, � 4 r,y.,e 3.�,. '-"'+!•` d.Z ?'`' a'.e,1f1 `�a.'7`„"+s,�y 'd+fi�18's.,� S S �'`.a aur• a �� i s' :c � '�t� ut,t , a '-a A �t. 1 •' !.'' {, oft ".eye' .�F.•< ryG -� a 1. ' .�.. �•..� ldg Aw. ;: t 3*:•as ia'�^ R- d, V .. / ,ia �S�ki£:? eta..F,Fjow MP t /i7 1 -1 1 ••• • 1 1 • • • • -from sty. /• .r - \T Y �� - F +'^yf�I� Syr �,� .; � ,S+k .� �. � � • . k'wa'�'�+*•,a r+•��.*t+�`.5. N,,,a' �'l '��a... ;j `�'J..:,��,i t >3 -. 11 i • 1- � — • 1 ` ; GEOTECHNICAL TESTING LABORATORY ft� 55 v' c r HISTORY OF LANDSLIDE ACTIVITY Slumping or sliding was not observed throughout the site. At the proposed building location,the slope is compact and dense with no indication of previous landsliding. The Coastal Zone Atlas, Volume 9, Mason County(MA-12)maps the site as having Vashon Till (Q,n) in the north portion of the site. The till is a tough, dense material of low permeability. It provides excellent foundation support. The site slope stability is described as"stable." The Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977)describes the site area as Class 2. Class 2 is described as: Areas believed to be stable under normal conditions, but may become unstable if disturbed by man's activities, if slope is oversteepened by erosion, or if subjected to strong seismic shaking. Slopes generally steeper than 15 percent, but may be less in some areas of weak geologic materials. Includes areas underlain by: well-drained sand and gravel, mostly on valley sides that lack known slope failures;glacial till with steep slopes; and bedrock. POW 10011 Blomberg Street SW,Olympia,WA 98512 9 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY POTENTIAL FOR LANDSLIDE ACTIVITY Even though slopes approach 26 percent, the potential for landslide activity is not a concern for the single-family residences. The Liquefaction Susce Susceptibility Ma o Mason County, Washington b Ma sino, Poelstr Bilderback, P tY P .f ty, g Y Palmer, g � Folger, and Niggemann(September 2004)maps the site area as having a very low liquefaction potential. The Site Class Map of Mason County, Washington by Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggemann(September 2004)maps the site area as site class C. Site class C is a very stiff soil or soft. r late 3 X 3"r [ x-rRIP a a a RECOMMENDATIONS n There is no evidence of soil erosion or deposition onsite to suggest that the site should be included in the Erosion 1 Hazard Area designation. Site conditions for the proposed development do not warrant a more comprehensive Geotechnical Report. We recommend no further action is needed unless areas of concern are unearthed during construction or damage ensues from vegetation clearing. To minimize erosion and sedimentation, we recommend that vegetation remain or be cultivated in areas outside the building location. If there are any changes in the loads, grades, locations, configurations, or types of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate. 10011 Blomberg Street SW, Olympia, WA 98512 10 Phone#: (360)754-4612 Fax#: (360) 754-4848 � 4 ' rr 7 �$Iy e• �•sy r. +� .��`! � -Ali!/fii^�---.�.��- - Fri AM IN -•i ;� , 61,MINIM �T S �� a �'- 3� �o �j- � — /(.�, � ss�s' ��"� � n —�j� ,� UPI�c� l2"'-� �-t �v� �l� i i -- - - � - = _ - - _- - _l_-�- -- - -- - -- --�- _ _ --- _ -- - -- - _ - -�_ I _ ---i--� —�— — a— — -- '- -- � �--- --- -__ -- - -- __ -- I -- -- �- - - � - _, - - - � - - - - �- - - -- -- - f - - -- - - - I - --- ---- - - - - _ _ _l_ - -- - ---- - _ � i - ,- - -