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Home My WebLink AboutBLD1995-00057 Geo Tech Report FEE-1:1-199.7 OS 1 777 EDI3E1.11RTER HOMES 20640 T 0R6S F.02 SEWN NON I/ILSON, INC. 3 =A.nRANK� ��,EOTR�,HNIC•AL ANC E . �JNMGNIAL C:VN9' � �ANT$ H p Ay^;}•IC:RAGE 94,r.T LOOS February 2, 1995 Mr. Bob Cornelia Edgewater Homes Port Ludlow, Washington RE: LETTER OF. CONFIRMATION, GEOTECI3,NICAL SERVICES, RESIDENCE TIV LTJ77TX71 F'f.YT'N I' VTT.LA.GES. P0H1 LLIULUN`, WASH1 t—i1't7N Dear Mr. Cornelia This letter confirms your oral authorization on February 2, 1995 to provide geotechnical engineering services for the residence that you are constructing in the Ludlow Point Villages development, Port Ludlow, Washington. • The hill on which the, residence will he located is comprised of basalt rock. The foundation along the east side of the house is located on the crest of the hill that slopes down to the east at about 35 to 40 degrees. The basalt rock near the surface at this location is highly fra tuied with clay lining these fractures. There is some concern that the house footing located on this fractured, clay-lined rock at the crest of this steep slope may be unstable, Therefore, the scope of out work will be to observes routing excavA.tion5 along the east side of the phuu,ted sttu..L ie and Lu itifuine you when aJletivate healing e«cvulitet 1. We will provide you with a brief letter describing our observations and recommendations and our opinion regarding the foundation stability. We are prepared to perform these services for a lump sum fee of $350. If this proposal meets with our approval, please sign both copies in the spaces provided below and return can± slatted copy to us which alerts with the "Agreement for Professional Sets-ices," which will then serve as our agreement. To assist you and others in understanding the use and limitations of our proposal, Shannon & Wilson has prepared the attached, "Important Information About Your Geotechnical Engineering Proposal." rJ(_'!R"I- Tv- 57,4eET • su;TE 1.11 saArTLE WAsri!r,,0 LN yb' 3 Wp 655$ I 206.632.SC20 FAX 206.633•87'7 TDED 1. Q•933•f 5P 99F: TE EDGELLIPTER HOMES 2064770P!;9 . p • Mr. Bob Cornelia SHANNON MAiiLSON.INC. February 2, 1995 Page 2 While Shannon & Wilson can also provide environmental engineering services, we have limited our scope of services to those outlined above which does not include any assessment of any potentially contaminated soils er surface water/groundwater that may exist at the site. We look forward to working with you on this project. Sincerely, SHANNON & WILSON, INC. William J. Perkin Geologic Engineer Brian C. Dorwart, RE. Senior Associate WjP;BCD/wjp Enclosures: Agrccmcill Tut PlofeSsional SciNices, LS-95 (1195) Important Information About Your Geotechnical Engineering Proposal WP-6558-I FEB-1 1' '?F 12'F + ED��EJ i TER HOMES -G1 = SHANNON 6WIL ''" N, INC. �p� � L1 GEOTECHNir.A, AND EN. PONVENTA. CONSU,.TA'ti'.S FM'? NKS 1NCnDi,A;,E acs-TQN February 9, 1995. Edgewater Homes, Inc 53 Jackson Lane Port Ludlow, Washington 98365 Attu: Mr. Bob Comella RE: TRACT B, LOT 7, DIVISION 3, CAMBER LANE, LUDLOW POJ T VILLAGES, PORT LUDLOW, WASHINGTON This letter summarizes our field observations of the foundation excavation and engineering rtcommendatioris for the east footing of the proposed residence at the above site. This work has been conducted in accordance with our contract dated February 2, 1995. SITE AND PROJECT J)ESCRTFF ON The building site for the proposed residence is situated on a level site at the top of a rock hill. The rock consists of pillow basalt of the Crescent Formation. -The footing along the eastern edge of the proposed residence is located at the crest of the hill, which Mopes rtnwn to the east some 50 to 60 feet at about 30 to 35 degrees (see the attached slope profiles by Tillman Engineering). We understand that as the rock at the planned subecade elevation a1on8 the east forting a - exposed, you became concerned as to the competency of the rock, particularly with regard to its location at the crest of the slope. On January 13, 1995, Messrs. Brian Dorwart and Bill Perkins of Shannon & Wilson, Inc. met with you at the site to discuss these concerns, After briefly obwrvir,g the cundidon of the ruck exposed at that time, it was our opinion that the rock at the proposed foundation elevation may pose a significant, long-term, stabi}ity risk (e.g., when subjected to heavy rains, earthquake shaking, etc). On February 2, 1995, we observed overexcavation along this footing and indicated when suitable rock was ruched for supporting the footing. 4 C NCAT-, 34T, STFEET• S:Pi£ 1p4 PO aOK 3cc$N3 W-6943-01 :,,na.s32,83,C FAX 2GC• i3•87 7? TOL. 1•8;J•833,3388 FEE-13-1995 Eg EL-E1):11:TER HOMES 2C-164_7n81 , P.FE. Edgewater Homes, Inc. SHANNON&WILSON.,INC. Attn: Mr. Bob Comella February 9, 1995 Page 2 FOUNDATION SUBGRADE At ground surface, the halt at the site of the footing was moderately to severely weathered, with close jointsifractures (2 inches to 1 foot spacing). The fractures in the rock were filled with moist to wet clay/silt. This rack was easily excavated with a backhoe to an approximate depth of 9 feet and was extended on February 2 (1995) with an ca.cavator to approximately 17 feet. Ivry. F312! Perkins of Shannon i5. Wilaua'i, Tui . ut►oea'ved the eNc.avation of this rode with the excavator along the east footing, down to competent subgrade rock consisting of moderately weathered basalt with wide to very wide fracture spacing (3 or more feet between fractures). Little to no clay/silt was observed in fractures in the final subgrade rock at the base of the excavation. Based on these observations, it is our opinion that the subgrade rock exposed in the bottom of the excavation is adequate for bearing, and by constructing on this subgradc, the long-term stability of the tit footing is significantly improved. The depth to the competent stuhgrArle w'ck wag about 9 1/2 feet below planned footing grade in the southeast corner and 17 feet in the northeast corner of the east footing wall. The width of the footing excavation ranged from about 5 to 6 feet at the base to about 12 to 13 feet at the top. The surface of the more competent subgrade rock appeared to roughly parallel the overlying topography. At the base of the excavation, the rurfaee of the competent subgrade rock was cut so that the subgrade sloped down to the south at about 10 degrees, with one step of about 35 degrees, The competent rock continued to rise to the west, to the planned grade elevation, within about 7 to 9 feet of the west edge of the excavation (Le. toward the inside of the house). While some moisture was present on some of the fractures' surfams, the excavation was generally dry. We understand that to reduce the height of the foundation wall, you have selected to vise a t uutiolled density (in (CDF) to backfiit the excavation to within S fe4 t of the bottom of the footing elevabon. The footing anct an 5-foot high wan will be subsequently cvtiLtut:tt oil top of the CDF, We understand that this wall will be buried after completion. W-6943-01 rE2-'17-199E. 1:•20 EDCELIiiTER' HOMES R.417nAP,.; P.41 . Edgewater Homes, Inc. SHA1qNON 6\ LSON,INC. Attic: Mr. Bob Camella February 9, 1995 Page 3 CONSTRUCTION RECOMMENDATIONS We recommend that the east building foundation be constructed directly upon CLEF placed directly on the competent rock. We recommend that the CDF have an unconfined compressive strength of about 2,000 psi. All water, loose rock, and debris should be cleaned from the bottom of the excavation before placement of the CDF. We rc nmrnend that weep holes he provided a few inches above the wall footing or through the COP to allow for drainage of any water through the wall that may occur in the baclil 7ipslopc of the wall. We recommend the weep holes be er minimum 1 inch +disrrietwr Load be paced every 6 feet along the wall. Drainage should be 9 c'utexl to the bottom of the slope in, a tight line. The fractured rock excavated on the site will provide suitable backfill around the wall. We recommend that the cleanest rock be placed upslope of the wall to facilitate daa.inagc. We recommend that rock fill be compacted to a dense, unyielding state. The fill should be placed and compacted equally on both sides of the wall after the concrete has achieved sufficient strength to reduce construction forces, including any unequal lateral loads that may be placed on the wail by the fill placement. LIMITATIONS Oh wan eara .61� �*JiTa6 Lee I,rear MC t . atted.O .fd, °Iapea°Fwr s I,sfrerr»s�rie.% .41*gvIt Yo.sr Ge otechnicai Engineering Report," to assist you and others in understanding the use and limitations of our report. The analyses, conclusions and recommendations contained in this letter report are based upon the site conditions observed at the ground surface and in the excavation and assume the conditions observed are representative of the subsurface conditions beneath the site. W-6943.O1 PER--13-199F 09:01 EDGEWPTER HOMER. 2O . 17.70Pe P.1=17 • 1dgewater Homes, Inc. SHANNON bWILSON.INC. Attn: Mr. Bob Cornelia February 9, 1995 Page 4 Please note that the scope of our services did not include any environmental assessment or evaluation regarding the presence or absence of wetlands or hazardous or toxic material in the soil, surface water, groundwater or air, on or below or around the site. IF yuu have any questitrna rcgardi .e the oisser..-ations, ccnclu ioHd., o svc0ttiltiaitldatiOrit contained in this letter, plus,.sa c all us. We apprec:iate the opportunity to bC of service. Sincerely, SHANNON` & WLL SON, INC. e5T ON A,. William J. Perkins R Geologic Engineer ruL 50. avowsI T.rtIf '�a 00(3:2„.e.g. Brian C. Dorwart, P.E. Harvey W, Parker, P.E. Senior Accele ate Senior Vice President WJP:BCD:HWP/w3P Enclosures: Slope Profiles by Tillman Engineering Important Information About Your Geotecii. icat Report 'Wi54t�-41,L.'RJ'M'69e 3.3d�xt W-6943-01 FE2-17-1995 0 :1.7117.• E. 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