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HomeMy WebLinkAboutGeoTech Assessment for BLD2007-00931 - BLD Engineering / Geo-tech Reports - 8/1/2007 07/31/2007 23: 29 3607053066 B & G PROPERTIES INC PAGE 02/04 06%01:07 11:16 FAX 1 360 867 9307 Bradier Group W_J V i Bradley-Noble Geotechnical Services A Division of The Bradley Group, Inc- Po Box 12267, Olympia WA 98508-2267 Phone 360-357-7883 • FAX 360-867-9307 1 August 2007 Mr. Brett Vandyke B & G Properties, Inc. p,p, Box 2856 Olympia, Washington 98507-2856 i SubjJect_ Response to comments of our report for 40 East Angus Cou f t presented from RH2. Dear Mr. Vanslyke: We have rovipwed the two comments presented in the review letter. As ted in the first full paragraph on page 2 of 2 of our 25 June 2007 report, subglacial till i for all of the sub glacial till is in excess 20 feet in es impermeable. Thickness g practical purposes p the general project area. In the G7msory of Geology and Related Sciences publl hed by the American Geological Institute a definition of impermeable is present We ql�lote "Impermeable = Impervious. (Hydrology) Having a texture that does not p rmit water to move through it perceptibly under the head differences ordinarily found i subsurface water. With the site being underlain at shallow depth by a soil unit that is f r all practical purposes impermeable, ground water, especially at the top of a sic a -where this building site is located, is obviously not an issue. In this paragraph,we o discuss the need to collect and control storm wafer flowing on the surface of the sl�bglacial till to ensure dry crawl spaces- This is the only ground water that will have an i1rifluence on the proposed construction. Preparation and sealing of reports prepared by our firm is governed by The Law Relating to Geologists, 18.220 RCW and 308-15 WAC. I have enclosed a copy of WAC 308-15-075 which addresses the requirements of dating, signing and sealing�f engineering geology reports. You will note on our 25 June 2007 report Tha the date is at the top of Page I of 1. My signature and title are at the bottom of Page i of 3. Next o to my signature is my professional scat. This is in conformance to our and r5td g the requirements. We are not required to sign or date across our seal, ihIugh some geologist do sign across their seals. In that our license exp►ries every year n our birthday, we do not need to note the date that our license expiries. Engle ring licenses are valid for two years, thus the need to show the date of expiration on the 07061502 Page I of 2 i . 07/31/2007 23: 29 3607053066 B & G PROPERTIES INC PAGE 03/04 wow.-44 11,16 PAR 1 360 807 9307 bradleT Group 07061502 Page 2 of 2 engineers seal. The reviewing parties have confused the requirements of li ensed engineers with those of licensed geologist A call to the Geologist Licensin Board e need for response to their Item 2. v reverted the P woul d have P If you have any additional questions, or If we ran help you with obtaining y ur permit please contact us at our Olympia office. Cordially, BRADLEY•NOBLE GEOTECHNICAL SERVICES o� wash � m� sfo David C. Strong, LE,G. �\cliZ9 �y Enclosure. Copy of WAC 308-15-075 A�sod Ge �o DAVIp C. SYR NG 0]/31/2007 23: 29 3607053066 B & G PROPERTIES INC PAGE 04/04 o8/o1./07 11:16 F.9j 1 360 88a6t779930j,tye _.__.un --.$rad1�39 Group gn�uccring g�logist stamA hcxe An gttswer key is not provided and you ; ansu+ered COO-Ctly- a eleaminaeon. o�W a s 1, - me not allowed to ke&P(r copy Yoti must submit a ro4uest e g �)Retake of ex2v" and the required fees to ! on a form provided by LhG board �I retake cattier pit of the examination 9-lsaso,oleo (Staauoq Autl+aity'. C7'W L8-ao 4tM.01,12-0L3, 30 j w5rol,etfecilve 625I0I.1 w do I obtain 9 9CM09 or sp2* WAC 308-L�'� R° eolo- o� Reci 'j'o obtain a license�a g ��0 10A cialt7llcenctb9redP ty. used GAO gist or specialty geologist Wltltout futh cxamrnat,on,You must meet all of the following criteria „�;fi�t;ans must Your Name Here (I) Xot+r ed++raDtrG and eXpetienceQgaO atrJ,if nPP'y`ag meet the requirew—ts of WAC 309-15- for specialty geologist license.WAC 308-1-o�-090; tat or specialty A drogeologist stamp here (2)You cur*enre regismo-atration, hold a vicertificati n issued by a y geologist license,registration, °the board;and t N ash; o urlsdiction approved by ' anon O f! slate r� 'st exarcttrt ve assert 'he colcga ¢, 9. must ha p r m �. (3) You table to the board.If you are applying Io i adopted by or accep ou must also have passed a y a specialty geologist licensc�y to cpcciatry geologist examination adapted by or acceptableI tic board. o1-12.023.4 308.11-�,f"ca js+�uco-Adr�ry' (�'apt4r t822o RCw. Hydroscd09 525I01,ePf 6WID1'1 �O WAC 348-13.tY10 Do I peed a stamp?upon liccnstisa ed Ggo�e you must obtain a stamp beating your nrtrlleI litxnsc"umber. and the legend"State of Washington Liccased Geologi st"If Your Name Here o- you are licensed as an engineering gsolo giSt or hydro$colFacsimilcs of gist the specialty must be noted on the stamp. of-i2 0��.1! ln, filcd the stamps of the designs authorized by the director are j$xi.utory Autb-it); Chaptnt 18220 RCW- shown beiow. sn5mt.effccuve 625/[tt-) here r use my stamp Geologist stamp WAC 30 '15-a73 W Rtca do I 1a Q final eology • (1)You mace ctamD.sigort,rletterreport, orydvc;ument chat ji Wash, specialty geology rep l d anared under your sUpsiolt cc direr, p rj preps by you of PrepI�`r ♦� 9f end submitted to other parties• tt[es t•,ouAO within � f�� � uon +. a All figures, naps. p y ( do not need to be individually stamped reper�or documents c I maps and late signed arid dated. Unbound final fiuur0.. p r P �Q i ned and dated. t_. trust be individually s►amptd�s g colo� (b) preliminary eoly Or 'ally g or draft S but the finc.ttraents and all `tee coo �� work does not h9ve to be starnp�= N� b\0 associated figures,maps, and plates must be clearly marine Se d G e or draft. as rrliminary ^• p 2 You must stamp,sign,and sate �Y final geology your Name Here ( ) design and�i<"tc. 1 that is prepared ' - or specialty geology 1; ' �direction.�- by you or prepared under your supervis)T rIr I dncign and liminary or draft geology of specialty specification drawings do nut have to jT:s � bl�.h ; design and sPecification must be.clearly Irn as My or draft date wot'c��You Have oq y (3)If yw stamp.sign and you revicvvcd, you are responsible to the same extent as if ou prepared the repoR,design or specification �r75, jswjuloU AutbodtY: CbMer 1832n RCW.01-1"023,13OS' 50101.eircctiro(RS/ut.) �3l ice.3WIS wA tsrzwu rLA E R S E R S S T S New RH2 ENGINEERING,INC July 31,2007 HRp It~rh2-can Ms. Rebecca Hersha,County Planner maibox@rh2coin Mason County Department of Community Development Mason County Building 1 1 8W 720 8M2. 411 N 5d Street PO Box 279 Shelton,WA 98584 .Sent I ia: l:-mail to Robert fink WESTERN WASHINGTON Subject: B and G Properties Geotechnical Assessment Report Review 12100 NE 195e,St.Ste 100 Dear Ms.flersha: bott".WA Mill We have reviewed the following documents under our existing contract to provide Geotechnical Engineering review services to Mason County. (teq 425.951 5400 0 Geotechncal Assessment of the Slopes at 40 East Anus Court of the Iake Limerick Development, Mason County Tax Parcel Number 321275300158,dated June 25, 2007 and (tax)425.0 2774 signed by Mr.David Strong. The review was performed to ensure that the improvements are in concurrence with Mason County ordinances for geologic hazard areas. The engineer and/or engineering geologist and preparer of the documents remain responsible for all report and design issues. t Af,TCRN WASHINGTON We appreciate the thorough review of the geotechnical issues related to this site geological assessment. We only request that Mr.David Strong update the following. ,W Simon Sint SE,Suite 5 1. There is no mention of existing groundwater conditions under the site. While it is suspected that groundwater is well below the site within or below the till layer, please describe what was found on-site, including depth to groundwater via on-site reconnaissance or perhaps L1 wena wA98802 review of well lags in the.vicinity. If no groundwater was found on-site,state as such. 2. Professional Engineering Geologist Stamp: Per Washington Administrative Code, the (�05os.ea6.29�o I-E.G. Stamp shall be signed over top with a hand-written sign date and expiration date. Provide signature,hand-written sign date and hand-written expiration date. (tax)504 886.2313 This concludes our review of the Geotechnical Assessment Report. If you have any questions or comments,please contact me at(360)876-7960 ext.5342. KITSAP PENINSULA Sincerely, RH2 ENGINEERING,INC. 600 KltsM S(teet.Suite 101 + Pat orchad,WAN= 1, Dan Burwell,P. '. (tel)360 876.7M Project Engineer Dh/sphw 38303 - 1 (tax)360.876 7913E t a `' v e SIGNED' _ SIG 1 (Id)360 876.7960 07/11/07 gin W 1A13w\AfCAW-W1\112 it and t.Pn irrr es 07 W 10\1lr to Rebem HI .ha R RM;Pr—.t—G-xre u-A Rt w wd fit/1JU/100! 22: 1 ( Jbb lUnJUbb b & u Y KurLN 11t5 IINU r-Hut ULI u4 BP -Doo-7-0o931 Bradley-Noble Geotechnical Services A Division of The Bradley Group, Inc. PO Box 12267, Olympia WA 98508-2267 Phone 360-357-7883 • FAX 360-867-9307 25June 2007 Mr Vansl ke B AG-Properti P.O. Box 2856 Olympia, Washington 98507-2856 Subject; Geotechnical assessment of the slopes at 40 East Anus Court of the Lake Limerick Development, Mason County Tax Parcel Number 32f275300158. Dear Mr. Vanslyke: As requested, we visited the above property in order to observe site geology and slope conditions on this and adjacent lots. Our work consisted of a site visit, observation of soils exposed on this property and adjacent properties, review of proposed plans for the lot development, research into the area geology and slope stability history, and preparation of this letter. The project site is located in the Lake Limerick Development. This area is a gently undulating surface of the Vashon recessional outwash plain. At this site, we find the area adjacent to Angus Court to be of low relief. To the south of the area of Inw relief where the new residence will be constructed, we find moderate slopes down to the northeast and south. Slope angles as measured with a Leitz Pocket Transit varied between I 1 to 13 degrees (19% to 23% of slope). Slope angles are significantly less than the angle of internal friction of the soils mantling the slope and the underlying Vashon subglacial till. With slope angles less than the angle of internal friction of the material forming the slopes, slope stability is inferred. Examination of the soils exposed in road cuts and building pad cuts in this area, we find a thin layer of Vashon recessional outwash sands and gravels (Qvr). These soils are thin, typically less than four feet in thickness. Underlying the outwash soils is the Vashon subglacial till (Qvt). The outwash sands and grave-le wore fluvially deposited onto the Vashon outwash plain as the Puget Lobe of the Cordilleran glacier retreated to the north during the Fraser glaciation in late Wisconsinan time. These soils were deposited onto the subglacial till, Subglacial till is a mixture of silt, sand, and small gravel. It was deposited at the base of the advancing ice sheet and overridden by the ice which is thought to have been between one-half to one mile thick in this area. The grain size 07061501 Page I of 3 ,•a, 4 161111812061 22: 11 Jbb/UndObb t5 b u rKurtK i 1tZ) 1111� rHUEL L,-, 07061501 Page 2 of 3 distribution and loading by the ice sheet has created a soil unit chat has inaity engineering properties similar to those of lean concrete. It can stand steeply with only slow erosion occurring. Subglacial till is for all practical purposes impermeable. Site excavation for the building pad that exposes subglacial till will require special drainage considerations to ensure a dry crawl space. You should expect flows of water to develop on the surface of the till during periods of heavy or prolonged rainfall. To aid in ensuring a dry crawl space and to protect the drain field that will be constructed down slope of the building site, we recommend that all roof rain leaders, catch basins, and trench drains be connected to a tightline disposal system. The collected water is to be conveyed below the drain field and infiltrated into the slope soils. To prevent localized saturation from developing, we recommend that the water be infiltrated by perforated pipes parallel with the slope contours. A footing drain system will also be required. Use of rigid plastic pipe for both system is recommended. Rigid pipe is more resistant to crushing and deflection during backfilling than flexible ADS type of pipe. The Tightline storm water collection system should incorporate glued water tight joints. Use of flexible ADS pipe is acceptable for the infiltration system. This pipe must be staked to the slope. The footing drain may be connected to the common discharge line at an elevation where backup into the footing zone cannot occur. Backfill against foundations must be placed in conformance with the International Building Code (IBC), Section 1803.2 Placement of Backfill. Site grading around the residence must be in conformance with the rpcluirements of Sprtion 1803.3 of the IBC to ensure positive drainage away from the structure and to prevent ponding against the foundation. We also recommend a minimum vertical separation between bottom of crawl space vents and top of landscape soils of three inches. This is to prevent the vents from becoming a conduit for water entry into the crawl space and to promote', good ventilation. Geologic Mup urthe Shelton I.100,000 Quadrangle, Washington by Robert L. Logan, 2003, and published by the Division of Geology and Earth Resources maps this area as Qn Till, late Wisconsinan. Plate I of Watcr-Supply Bulletin 29 Geology of Southeastern Mason County, Washing by John B. Noble and Dee Molenaar maps the project and genera areas as Qvt, Vashon subglacial till. This mapping is consistent with our field observations. With the slopes being underlain at shallow depth by subglacial till, deep rotational type of failures is not considered to be a risk at this site. Relative Slope Stability of the Southern Hood Canal Area, Washington by Mackey Smith and R. J. Carson and published by the Division of Geology and Earth Resources 1977 presents an opinion on area slope b 1/bti/2110! 22: 1 ! JbU/Undbbb is PSG U rKUrtK I lt5 irv­ r iur u� c t 07061501 Page 3 of 3 stability. In this mapping, which is at a scale that cannot be considered more than general, we find the project area mapped as a Class 1. Class I areas are believed to be stable. This opinion is supported by our field observations. We find the small diameter Douglas firs growing on the slope to be vertical with no evidence of surface soil movement rotating the root mass. No gPinmorphic expression of recent or past mass wasting events were observed on this and adjacent slopes. Based on our site observations and research, we have no objections to the placement of a new single-family residence at the location indicated based on geotechnical considerations. We do not consider that the project site or surrounding slopes are at risk of mass wasting events that would adversely affect soil foundation support. Good site grading practices and water management will be required to ensure a dry crawl space and to protect the slopes from concentrated flows of storm water. We do not consider the preparation of a Geotechnical Report is warranted at this site due to the site being underlain at shallow depth by highly overconsolidated soils. If you have any questions, or if we may be of additional service to you on this project, please contact us at our Olympia office. Cordially, oq W a s hr BRADLEY-NOBLE GEOTECHNICAL SERVICES David C. Strong, L.E.G. <. c � �C+ 1129 gay Posed GQo�o DAVID C. STRONG