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HomeMy WebLinkAboutBLD2013-00135 Geotechnical Report R AS • WASHINGTON STATE DEPARTMENT OF DOU6 yc ��tfRLANO Natural Resources Commissioner of Public Lands MOW b.� r : August 29,2005 Allegro Bothell Windermere Real Estate 1220 Water Street Port Townsend, WA 98368 Dear Allegro, At your request I visited Jefferson County parcels 001301030 and 031 to verify the existence of a stream. Our hydrology map indicates a Type Ns(old Type 5)water flows east to west across these parcels. I visited the site on August 26,2005. While there is a swale or ravine present at the location shown on the map,I could find absolutely no evidence of a defined channel. In short there is no stream on these parcels. If you have any questions regarding my observations please contact me at(360)732- 7175. S' cerely, , Ross 'n Forest Practice Forester Olympic Region cc: Jefferson County DO) • correspondence file • • OLYMPIC REGION 1 411 TILL1CUM LN I FORKS,WA 98331-9271 TEL:(360)374-6131 I FAX(360)374-5446 I 1TY:(360)374-2819 •4110• Equal Opportunity/Affirmative Action Employer RECYCLED►A? 0 NORTHWESTERN TERRITORIES, INC. 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362 Engineers Land Surveyors Geologists Construction Inspection Materials Testing Port Angeles(360)452-8491 E-Mail:infonti4u.com NTI (1) July 24, 2015 Mr. Robert Heinith 2937 NE 47th Ave. Portland, OR 97213 -J Subject: Geotechnical Review and Inspection Of The Building Site At The Heinith Property Jefferson County Parcel#001301030 6602 Cape George Road, Port Townsend,Washington 97213 Dear Mr. Heinith and Others Concerned, In July of 2015, Northwestern Territories, Inc. (NTI) reviewed the garage/shop building site location of the subject parcel for conformance with the recommendations of the July 20, 2007 Geotechnical Report by NTI and the April 16, 2008,Geotechnical Report Addendum by NTI. Trent Adams, Geotechnical Engineer in Training completed a site inspection on July 21, 2015. A new, roughly 1,400 square foot garage/shop was observed at the property. The position of the garage/shop meets the building setback recommended by NTI. The as-built structural setback distance provided from the garage/shop to the top of the slope on the northwest was measured to be 30 feet. The garage/shop is also located approximately 41-feet southwest of the proposed drainfield and easement for parcel#001301031. A drywell has been constructed at the site for mitigation of stormwater runoff from the garage/shop. The constructed drywell meets the 2007 NTI Geotechnical Report recommendations for implementing a permanent stormwater management system at the site. In our opinion the new garage/shop and drywell construction meet the geotechnical recommendations provided by NTI. Please feel free to contact the undersigned Engineers if you have any questions or need additional assistance. i (17 ( 1 . FED vN.�o�p fcFF .RSON Co `-�' Thank you for asking us to complete this review. NTI Engineering and Land Surveying Sincerely yours, AS S. Lt4 ©FWAS/yf ?► #' 2 7/Zy /, c, AL Steve S. Luxton MSc, PE Trent T. Adams BSCE, EIT Senior Geotechnical Engineer Geotechnical Project Manager \)/ OCP FLSoN GpV 0' 2 etjor- --- NTI ENGINEERING & SURVEYING 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362 Engineers Land Surveyors" Geologists R Construction Inspection[' Materials Testing (360)452-8491 1-800-654-5545 FAX 452-8498 E-Mail:info(o)nti4u.corn NTI www.nti4u.corn April 16, 2008 Robert Heinith 2937 NE 47th Ave Portland, Or 97213 Subject: Addendum to Geotechnical Report for the Property Described as Tax # 001301031, Lane De Chantal located in Section 30, Township 30 North, Range 1 West, W.M., Jefferson County, WA Dear Mr. Heinith: At your request, NTI presents this addendum to the geotechnical report that was completed by this office for the above referenced property dated July 20, 2007. This addendum addresses all proposed development on the parcel including access easements, septic systems, buildable areas, driveways, etc. as illustrated on the two enclosed site plans provided by you. This additional information was requested by Zoe Ann Lamp of Jefferson County in a letter to you dated February 25, 2008. Based upon the attached site plans provided to us, the locations of the proposed development features are consistent with the recommendations of the geotechnical report. If you have any questions regarding this matter, or need further assistance, please do not hesitate to contact this office. Sincerely, /�, o ,� / NTI ENGINEERING & SURVEYING ' fa i• :w • '. Bill Payton, L.E.G. 711$ 9aa`o Engineering Geologist William C. Payton Jr, B:\Reports\HEIN0701.30(30-1).addendum.doc N _ _ 2. - - CfPe „ - r1- 1 ^ 2 a — ei 400 i • = 4 1,,<\\ . ' T 41 • \ C / (o-i r 1 ! 9 " 'C, �i r i Z-- , A \\ '. .- \ ' \\ -.e . -- , - 1- u; rc . -- „. 1 4 \ ". tt C Y ' _ , _ -.. •- ' _• ' , tiN: I r \ ..,, k -. t , \... rf.13 /4. .,s• , . _.__ S i k, _la.""'i-..i"..........' 0 r fi iI 1 k m_ tj • $ `; ii - 1-1 X' . -0/- - �p f I R •-' x • € - ---- -- -- ---+ - -- p, A _ .- iv, 17 ' -.--- '----1--- \' el i ik,k f__ -1 1 '' .4 g I i 1 11 i ,1_ , „ , I : f i , I i 1_ 1 1 w A , - -- (--{,---46-----EL.,_ 10:i,._. A) �J'T t4 g 6 E c.. e a- en u. (ki ca — ao o ca. .E.' vs- -i-i 17, .0 0 Cif ..' •••. ! r - • --? • U1 ---;)\'-- 1 ca. 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' Island `r f �: g T"ownsendBay Qa 5 pOki Inn. ,s Townsend r State Park 4 Indian fed T4Y Yh' .: '� Dacavery Bayg. t W.Ad J ! < e 6 Laraine Beach Property j/ & a Vicinity " � r �` .1 t, l j°9i i�tSC, � d ; Four `'- •:i ts. ' Syl Rd Comers ■ �/ 101E 4 - Adelina Beach• GEOTECHNICAL REPORT Prepared For Robert Heinith July 20, 2007 For the Property Described As Tax # 001301031, Lane De Chantal Located In Section 30, Township 30 North, Range 1 West, W.M., Jefferson County, WA Prepared by Nil Engineering and Surveying 717 S. Peabody Street Port Angeles, Washington 98362 Phone 360-452-8491 Fax 360-452-8498 Web Site www.nti4u.com E-mail info@nti4u.corn NTI ENGINEERING & SURVEYING 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362 „al Land Surveyors Geologists Construction Inspection Materials Testing - (360)452-8491 1-800-654-5545 FAX 452-8498 E-Mail:info@nti4u.com NT! www.nti4u.corn July 20, 2007 Robert Heinith 2937 NE 47th Ave Portland, Or 97213 Subject: Geotechnical Report for the Property Described as Tax # 001301031, Lane De Chantal located in Section 30, Township 30 North, Range 1 West, W.M., Jefferson County, WA IDear Mr. Heinith: Background At your request, NTI Engineering & Surveying, Inc. (NTI) performed a geotechnical inspection of the above-mentioned property, which included office research and a site visit for visual observations conducted on July 6, 2007. No subsurface exploration was performed. The purpose of this inspection was to observe the subject property by visual means and make recommendations regarding the development of the property in accordance with the Jefferson County Unified Development Code (UDC). The property is currently undeveloped. It is our understanding that development plans include the construction of a house, small cottage, and a shop. Site Description The subject non-waterfront r p operty is located on Lane De Chantal, with a partial view of Discovery Bay to the west (Figure 1). The property is bounded on the north, west, and south by residential property with Lane De Chantal to the north, and on the east by Cape George Road (Figure 2). There is an existing driveway on the property that leads to the proposed home site. The majority of the property slopes gently towards the southwest at approximately 7°. The northern half of the property is bisected by a ravine that trends in a southwesterly direction and drains over the bluff on the adjacent property (Figure 3). The steepness of the ravine side slopes are variable but are generally in the mid 20° to mid 30° range. The ravine was dry at the time of the site visit. There is a trail that leads through the 54th :1 r 474 49th a to x t m' Irr ��il .c Sst . , '! a, ,�'v 1a ,.y. � L II� �_�� 3 wr 1 m �'lbltltii) k —)ii` 9th �t `n Port _ �--�-_ . -=�t ,� A, Townsend a, n _+ .y, J`.� _ l.�ia`S -. I �� ,4th St ,2 " ' Z Y i ' • <itt St 71h S1 ,, — �.� <,z"` 1st St�i Mill Ru f,. I*- — ', Y c i ,s" } xz- °Glen Cove da x _ --, a • 20 Port bi ,YO.,:to a, Lt;1,d V a -. , [ >_ 2' 0 ' T wnsendBay r'r •'. �r di Old Fort • Cepe a Townsend re) State Park / ' 'i 11Js.c -very Bay ° TP! _ `k i' ' Gardiner Beach Property b r:. -,'-� �� w Vicinity + -T-- m,�'' - Far pprt 4. tt�1 1lN g� �cbNg, :lfi oCaners -L—L M1 ` ,,o Adekna eeact T i �A Figure 1 ravine and down the bluff to the beach. The existing driveway passes around the head of the ravine and along the south side of it to the house site. There are also steep cut and fill slopes along the driveway. The property is well vegetated with young to mature trees, shrubs and brush. Site Geology The Washington State Department of Ecology's Coastal Zone Atlas maps the soil in the area of the subject property as Vashon advance outwash (Qva), with Vashon lodgement till (Qvt1) on the eastern edge of the property. The advance outwash is described as well stratified, well sorted sandy pebble to cobble sized gravel. In some places, sand predominates. This soil is good for seismic stability and good to excellent for foundation stability, but may be poor on slopes that approach the angle of repose of the material. This soil is generally stable in slopes up to the angle of repose, and may stand in steeper slopes for short periods. The till is described as a compact mixture of boulders, cobbles, pebbles, sand, silt and clay, generally overlain by 1-5 feet of ablation till. The I • IAtlas also describes this soil as bein excellent for foundation stability and good for seismic stability. The Atlas maps the stability of the property as Unstable. IThe Washington State Department of Ecology's "Geology and Ground-Water Resources of Eastern Jefferson County, Washington", April, 1981 gives essentially the I same description of the soils in the area of the subject property. 110, ,. ri 0 , ,..0,1,, i; ..,...iia.:. ,i,. 0, -,, .,, , , it. -: i Ad* r s. ak Ir r,. . .., ,14.1 A.,- vir 1 i;r1.• ' - iscilv 2 _It 1 Y y 4.4...1 - ....4.-wr_ ,-:-- . 4, . .. .te , 4 .,1 t.. ii:„.,. i. , ,,,, i:-.444_ .-, ,,,Ni.--41.v., - „, I-- ,,,,,%-:-.4.' ._ . .,. Napa va.+dai by xlfa�on carry Cary Sbrca G6 + , ., i ., .y X ~ ' �Y I 0 � Figure 2 I The Soil Survey of Jefferson County Area, Washington (United States Department of IAgriculture, 1975), classifies the soil in the area of the property as being predominantly Cassolary sandy loam (CfD) over the majority of the property, with Tukey gravelly loam (TuD) on the east side of the property. The Cassolary soil formed in reworked glacial Iand marine sediments and consists predominantly of silty sand, with areas of clay. Runoff is listed as medium, and the hazard of water erosion as moderate. The Tukey soil formed in glacial till on terraces and consists predominantly of silty or clayey sand Iand gravel. Runoff is listed as medium, and the hazard of water erosion as moderate. Visual observations made in the area were consistent with the above soil descriptions. I I I I ' w q / Approximate Driveway 1 Arr Location • a : i : cr•l xmanscn Canty Cetera NNYr Figure 3 Conclusions and Recommendations The property appears grossly stable at present, and the proposal seems feasible from a geotechnical perspective. It is our understanding that all construction will be east of the existing driveway and thus avoid the steep ravine slopes. Setbacks will also be needed for the steep driveway cut slopes. We recommend that no construction take place on slopes steeper than 30°, and that a 15' building setback line be established from where the slope becomes steeper than 30°. Further, the foundation requirements of the International Building Code (IBC) will need to be followed (See Appendix). Also, the driveway may need to be improved in order to provide year round vehicular access (slope armoring, rock, vegetation, etc.). The following recommendations should also be considered with regards to the proposal: 1. It will be necessary to maintain ground cover to reduce erosion from surface runoff. Any bare areas that develop should be revegetated. Native deep-rooted vegetation that requires little or no irrigation would be the most beneficial. 2. Vegetation on the ravine slopes provides stabilization to the soils. Existing established vegetation should be left in as natural a state as possible. If a better view is desired, selective tree removal, thinning and pruning should be done in such a way that minimizes disturbance to the soil and root zone and that insures the continued health of the vegetation. Damaged trees or trees that are in danger of falling, due to undermining of the roots for example, should be evaluated for removal because of the damage potential to the slope caused by the root mass of a large tree being pulled out of the ground, and also due to the risk of a tree falling on the house. If trees are removed, the trunks should be left in place so that the root mass can continue to provide stabilization to the soil. A tree expert could provide valuable consultation in this matter should the need arise. 3. Heavy irrigation or other activities that would contribute large quantities of water to the soil should be avoided. 4. Surface water should not be allowed to flow over the face of slopes as an uncontrolled or concentrated flow and cause erosion of the slope face. This can be controlled with vegetation and using berms or swales to direct runoff to a drainage system. Please see the attached DOE publications for more information on this subject. 5. Surface runoff from hard surfaces such as roofs, driveways, walkways and patios should be controlled and routed to a drainage control system such that surface water discharge to adjacent properties does not exceed predevelopment conditions. 6. Silt fences or other sediment control devices may be needed during construction such that sedimentation to adjacent properties does not significantly exceed predevelopment conditions. 7. All drainage control devices should be maintained in good working order and inspected at least once a year. For further information please review the three attached copies of booklets published by the Washington State Department of Ecology (DOE) entitled: "Slope Stabilization and Erosion Control Using Vegetation", "Vegetation Management: A Guide for Puget Sound Bluff Property Owners" and "Surface Water and Groundwater on Coastal Bluffs". These publications are now out of print but can be reviewed at the DOE website at: http://www.ecy.wa.gov/biblio/sea.html under the 1993 and 1994 year heading. The DOE website also contains more useful information regarding slope stability and site development and is highly recommended. Limitations This report has been prepared exclusively for you and your agents in conjunction with the above referenced project. The report has not been prepared for use by others or for other locations. Others may use it only with the expressed written permission of the Engineer. I Within the limits of scope, schedule and budget, this report was prepared in general I accordance with accepted professional engineering and geological principles and practices in this or similar localities at the time the report was prepared. No other warranty, expressed or implied, is made as to the conclusions and professional advice Iincluded in this report. The observations, conclusions and recommendations presented in this report were based on our visual observations of the subject property at the time of our site visit; no Ilaboratory tests were performed. Soil and geologic conditions can vary significantly between test holes and/or surface outcrops. If there is a substantial lapse of time, I conditions at the site have changed or appear different than those described in this report, we should be contacted and retained to evaluate the changed conditions and make modifications to our report if necessary. ISincerely, II NTI ENGINEERING & SURVEYING Ci) o "asi., 40 III Robert A. Leach, P.E., MBA y, •PF 13772 .O k� Principal Engineer ��Fss CIS EN �� 7 L3—p7 IIIEXPIRES 12/30/2008 I Bill Payton, L.E.G. Sa,s Engineering Geologist �- . 1111 G:\Gen\Bill\Reports\HEIN0701.slope stability.30(30-1).Discovery Bay.doc v. I,g r•� .rrAtfir'- ?... 4rso '91/e ' $,./ °d c a4 [William C. Payton Jr. J 1111 II I I I 35' Qvtl 2°' _ Qvtl ,' -'1 /..--/,‘ •-,y-•••;Y‘I' 1 .';'2C,3 , . .,, • i •.0 , ' ,S c_reology :- . '6/ *31frr'r— I 60' Qo ti 45' - o i`t ,-. ,•// i i/' 11 4+ . ' ." • /30' Qpd 30' _. r \ 1 fl • • , • • ..60 I 45' Ow ''. - ...... ..--, - ,' - . 40' Qrlb -':..._-;44....- ---"--.-.:f: „, 7 . , 'Ur / I , . , • .. ,„ .. Qt5f e• .- ' I - + . , I ' ',‘Al, '-- ,' ' .: .• ' .Uos . -' x'• • TART tn.'. .-- , •.. . .__ . , . I G.t--:--.•g e . _;.••-,,-. _. ....._:":- -...-)..--,.-... ._.:4,4-k -:-, .,- , . .... • . . .,..., ...,.. .--, • '''N'As.,:tr•e••.- - ,-, , --....... - Cape George .•. 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Ursj" ., --/- I I "1-5vri , '''''t i Property Vicinity . ,. - Washington State Department of Urs Ecology's Coastal Zone Atlas . ... __. i SOILS AND FOUNDATIONS 1805.3 Footings on or adjacent to slopes.The placement of (2134 mm)from the top of the slope shall be capable of sup- buildings and structures on or adjacent to slopes steeper than porting the water in the pool without soil support. one unit vertical in three units horizontal(33.3-percent slope) 1805.3.4 Foundation elevation.On graded sites,the top of shall conform to Sections 1805.3.1 through 1805.3.5. any exterior foundation shall extend above the elevation of 1805.3.1 Building clearance from ascending slopes.In the street gutter at point of discharge or the inlet of an general,buildings below slopes shall be set a sufficient dis- approved drainage device a minimum of 12 inches (305 tance from the slope to provide protection from slope drain- mm)plus 2 percent.Alternate elevations are permitted sub- age,erosion and shallow failures.Except as provided for in ject to the approval of the building official,provided it can Section 1805.3.5 and Figure 1805.3.1,the following criteria be demonstrated that required drainage to the point of dis- will be assumed to provide this protection.Where the exist- charge and away from the structure is provided at all loca- ing slope is steeper than one unit vertical in one unit hori- tions on the site. zontal (100-percent slope), the toe of the slope shall be 1805.3.5 Alternate setback and clearance.Alternate set- assumed to be at the intersection of a horizontal plane drawn backs and clearances are permitted,subject to the approval of from the top of the foundation and a plane drawn tangent to the building official. The building official is permitted to the slope at an angle of 45 degrees(0.79 rad)to the horizon- require an investigation and recommendation of a registered tal.Where a retaining wall is constructed at the roe of the design professional to demonstrate that the intent of this sec- slope,the height of the slope shall be measured from the top tion has been satisfied.Such an investigation shall include of the wall to the top of the slope. consideration of material, height of slop e,pe, slope gradient, 1805.3.2 Footing setback from descending slope sur- load intensity and erosion characteristics of slope material. face.Footings on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lat- eral support for the footing without detrimental settlement. Except as provided for in Section 1805.3.5 and Figure 1805.3.1, the following setback is deemed adequate to meet the criteria.Where the slope is steeper than 1 unit ver- tical in 1 unit horizontal(100-percent slope),the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope. 1805.3.3 Pools.The setback between pools regulated by this code and slopes shall be equal to one-half the building footing setback distance required by this section.That por- tion of the pool wall within a horizontal distance of 7 feet FACE OF FOOTING TOPF SLOPEE SLOPE STRUCTURE ME OF 1.I!3 BUT NEED NOT ..,F..v... SLOPE EXCEED 40 FT MAX . YIII' H2 BUT NEED NOT EXCEED 15 FT.MAX. For SI. I foot=304.8 mm. FIGURE 1805.3.1 FOUNDATION CLEARANCES FROM SLOPES 2006 INTERNATIONAL BUILDING CODE® 347