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HomeMy WebLinkAboutBLD2004-01680 GEO-Tech Report - BLD Engineering / Geo-tech Reports - 12/21/2004 r STArFo� MASON COUNTY o ' N PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER sv _ � Shelton,Washington 98584 �0 DATE: December 21 S`, 2004 �s 4 INTER-DEPARTMENTAL COMMUNICATIONS TO: Tammi Clark, DCD—Planner FROM: Alan A. Tahja, P/W-Co. Hydr. Engr. WO#PLG-04 SUBJ: Geo-Report Review NAME: Blair Garage @ 8050 E Hwy 106 BLD2004-01680 Tammi, The geotechnical report prepared for the proposed Dallas Blair residential garage to be constructed at 8050 E Highway 106,Union, has been received and reviewed by Public Works. The report appears to satisfactorily address County requirements for geotechnical reporting. The report's author indicates that, in his opinion,the proposed development of the property will not cause stability problems for either the subject property or neighboring properties. From the contents of the report, I recommend accepting the report as satisfying the County's requirement(s) for stability investigation and geotechnical reporting. Recommendations contained in the report should be incorporated into the site's development 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 report identifies the site's soils as potentially erodible, so implementation of erosion and sediment measures as recommended in the report should be made conditions for permit issuance. 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. In summary,the geotechnical report appears acceptable, and the proposed residential development of the property should be allowed to proceed, subject to the engineer's recommendations. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Sincerely, TO BE KEPT IN THE A an A. Tahja PARCEL FILE File: H: \WP\GEO\Reviews\Blair.doc WORK ORDER - PUBLIC WORKS DEPT. J (A) Date: ' —014 (P Work Order PERMIT Number. ���� _ U pequested by: / aAuthorized by: Date: W nType of Work: 7n r C11- CM L1.1 �f RCHARGE TO: --c NAME C) v AGENCY/COMPANY BILLING ADDRESS - PHONE Pub. Works Person In Cha e: (o) Project Time Line: (from-to dat 2/ TO Pmled Stag dde: Z/ �J te: Estima ed Fin sh Da Apprw*we hours: ESTIMATED TOTAL='S: COST ESTIMATE (D) 1�3t4 Flrrployee tut Han mil- Frings% TOTAL= f l�IQ BAIJE< TOTAL:g EQUIPMENT USED: MATERIAL USED- (F) Actual Cost = BARS: PROD Al. DATE Employee Q Nance LBAl4 Hours Subtotal Ednae% TOTAL$ EQUIPMENT USED: pjg y� ! TOTAL t'S MATERIAL USED: TOTAL ALL (G) BILLED DATE INV/ PAID DATE REC.M CKN RECEIVED MARTIG ENGINEERING P.O. Box 11850 DEC o 9 2004 Olympia, WA 98508-1850 426 W. CEDAR ST! (360) 754-9687 Fax (360) 705-0789 December 8, 2004 Mason County To BE KEPT IN THE Department of Community Development PARCEL FILE 426 W. Cedar E P.O. Box 578 Shelton, WA 98584 Attn: Planning Department Re: Geo-Tech Report Compliance Report for- * Owner: Dallas Blair (360) 898-8100 8050 E. Hwy 106 Union, WA 98592 * Site Location: Approximately 1-Mile east of Alderbrook @ newer 8050- Residence on south side of Highway 106; * Tax Parcel No.: 32234-34-00060; * Mason County: Sec 34, Township 22 N, Range 03 W; * Proposal: Construct a new 12-foot wide by 24-foot long Garage behind (south of) the newer constructed Residence; Attn: Mason County Planner, I, Kenneth W. Martig, Jr., PE, of Martig Engineering have completed my engineering investigations regarding the Geotechnical Report requirements associated with the above referenced property, as required by the County. The proposed action at this site is to Construct a new 12' x 24' Garage behind the existing Residence at the above referenced property. As a result of our investigations, outlined within this Report, we can affirm that all potential Landslide Hazards can be overcome in such a manner as to prevent harm to property and that no significant Environmental Impacts will result if this project is permitted as outlined within this Report and its attachments. 1 PROPOSED PROJECT Dallas Blair proposes to construct a new 12-foot wide by 24-foot long Garage, behind (south of) his existing residence on the property at the south end of the Asphalt Driveway serving his property. The Site Plan Map, Attachment 3, shows the proposed location of the Garage on his property. He has met with Mason County Staff and is proceeding to process the necessary Permits. The Vicinity Map, Attachment 1, shows the location of the site and neighboring property by Tax Parcel numbers. HISTORY OF SITE During November & December of 1990, the small-unnamed stream (that now flows thru the 36-Inch Diameter CMP Culvert Pipe under the Blair Asphalt Driveway) flooded massively, due to the uncontrolled clearing and grading for a new resort (to be called the "Black Bear Resort"). Huge volumes of uncontrolled runoff and massive amounts of eroded soil flowed down the creek and down the prior existing driveway that served the prior existing Residence on this site, then over highway 106 and then into Hood Canal. I, Ken Martig Jr. PE, was engaged by Mason County to Design & Monitor Construction of a solution to this flooding problem. The solution consisted of the installation of the 36-Inch Culvert with an Earth-Fill Bermed entrance, to insure that all Creek-Flows enter the culvert. Even when the Creek carried these high flood flows during the 1990 heavy rains, the steep hillsides upon the subject property (as well as the proposed site for constructing a new 12' x 24' Garage) remained Stable, as confirmed by my inspections at the time. Now, in 2004, the Black Bear Site has revegetated, thus restoring runoff amounts to normal flow rates for the watershed. The Creek's remaining enlarged Flow-Channel and the installed 36-Inch Culvert both have flow capacities much greater than that now required. Therefore, the likelihood of future Creek flood conditions is quite remote, especially since Mason County now has Clearing, Grading, & Drainage Regulations that will prevent the reoccurrence of the conditions that led to the flooding in 1990, should development of the tributary property be attempted again. The following discussion summarizes our: Site Investigations; Research of Site Conditions; Analyses; and Conclusions, allowing this Geo-Technical Report to be completed for the above referenced site. 2 GEO-TECHNICAL REPORT 1. Geology, Soils, Groundwater, Landslides: This site was found to be stable. No structural landslides were found on or near the building site(s), only minor Soil-Sluffing at isolated locations along the 25 to 30 foot high steep bank. This Soil-Sluffing is the result of many decades of Freeze-Thaw type erosion of the underlying cemented Till and minor erosion of the upper loose granular soil due to interflow seepage along the top of the Till during the wetter portions of the Winter seasons. The USGS Union Quadrangle Map, Attachment 2, and the Elevation View (Measured Section A-A), Attachment 4, show the steep Bank on the site, as do the 6-Pages of 35-mm Photographs, Attachment 5. The Mason County Soils Survey shows the site to be Alderwood gravelly sandy loam with slopes from 30 to 45%. The property of concern here, is located along the south right-of-way of Hwy. 106. The property's building site(s) are situated on gently sloping (10% to 12%) ground. The 25 to 30 foot high steep bank runs generally along the Highway, approximately 120-feet south of the south-edge of pavement. This bank consists of Alderwood cemented till, standing near vertical to an average height of 25-feet. Typical freeze-thaw type erosion has created a small Soil-Sluff prd �5 wedge along the natural toe of the bank (see Section A-A on Attachment 4). h �cY�i�le On the subject property, this Soil-Sluff wedge is stable, since the sluffed soil has �;l reached its natural angle-of-repose ( a 1.0 to 1.0 slope). No further stuffing will 1�DL occur unless the stable wedge is disturbed. Only a 2-foot high exposed near vertical r bank exists above the top of the stable soil wedge. South of the 25-foot high top-of- bank, the Stable ground slope is 1.0-foot of rise to 1.75-feet of run. No encroachment into the stable Soil-Sluff wedge is necessary to construct the new Garage as proposed. Therefore, the long-term stability of the adjacent steep slope will be maintained. It should also be noted that the proposed location of the new Garage will not encroach into the Earth-Fill Berm at the entrance to the 36-Inch Culvert. No other signs of landslide activity were found. 2. Site Plan and Important Geologic Features: The Site Plan Map, Attachment 3, shows the location of the Alderwood cemented till near vertical bank. Attachment 4 shows the Elevation View (Section A-A) of the bank, and Attachment 5 shows 6-Pages of 35mm Photographs supporting the text 3 discussions within this report. No overland flow of water exists upon the property, except within the Creek. A portion of the USGS Union Quadrangle Topographic Map (1" = 200'), Attachment 2, shows the site and its surrounds. Given the good infiltration characteristics of undisturbed Alderwood soils, and since the southerly land upgradient from the top-of-bank is and will remain undisturbed, no measurable surface water runoff is tributary to the building site. 3. Location of Soil Exploration Holes/Probes: The above-described Alderwood soil formation that exists at and near the site is confirmed by the exposed bank soils both onsite (Photo Page 5 of 6) and along the unnamed Creek. Given these exposed soil banks, no additional soils test borings or test pits were required to confirm the conditions and type of the site soils. 4. Cross Sections Showing Slope Disturbances: Attachment 4 shows the measured Elevation View, located as shown on the Site Plan, Attachment 3. This Section A-A shows the southeasterly elevation of the property. Photo Pages 3 of 6 thru 6 of 6 show the features associated with this section. The existing/proposed building site is located on gently sloping ground northerly from the stable steep bank and its accompanying stable Soil-Sluff wedge. Neither the near vertical upper bank nor the accompanying lower stable Soil-Sluff wedge will be disturbed when the new Garage is constructed. 5. Slope Stability Discussions: The existing Residence and proposed Garage site are located on ground that slopes 10% to 12% toward Highway 106 & Hood Canal. No expansion of this existing site is necessary, and the Asphalt Driveway already extends to the proposed location of the new Garage Southerly from this building site is the 25-foot high Alderwood cemented till steep bank and its accompanying Soil-Sluff wedge. The stable upper 2 to 4 feet of bank is near vertical. The accompanying stable Soil-Sluff wedge slopes 1-foot horizontal to 1-foot vertical. Southerly from the bank's top-of-slope, for a reasonable distance (30 plus feet), the ground slope is no more than 1.75-feet horizontal to 1.0-foot of vertical rise. All of this ground is stable and will remain stable since it will not be disturbed (I have personally observed this stability since 1990). As discussed within this report, the proposed new Garage construction will not 4 create significant environmental impacts and no landslide hazard will be induced. 6. Drainage, Septics, Water, Placement: Drainage at this site is not a problem due to the ability of the Alderwood soils to infiltrate precipitation rapidly. No signs of overland flow are visible and no drainage ditches exist on the property. An existing drainage system will be used to dispose of the garage roof runoff. The existing residence is served by a Well and an On-Site Septic System. These utilities will not be disturbed or modified during the construction of the proposed new Garage. 7. Clearing & Grading Plan: No new clearing or grading is necessary. The new Garage will be constructed on land presently cleared and graded in such a manner as to easily accommodate the proposed construction. In no case will any new clearing or grading occur within the Soil-Sluff wedge (or south of its northerly toe) or within the Earth-Fill Berm at the 36- Inch Culvert entrance.. 8. Erosion Control Plan: Since no runoff currently exists at the proposed Garage site, no special erosion control plan is necessary. A row of staked straw bales will be placed along the existing toe of the Soil-Sluff wedge to inhibit disturbance of the wedge. The building site soil that becomes exposed, outside of the new Garage building footprint and driveway area, shall be smoothed and planted with grass or covered with a minimum of 4-inches of loose straw. The short driveway section between the new Garage and the existing Asphalt Driveway shall be covered with several inches of crushed rock top-course, or Paved. 9. On-Site & Off-Site Impacts: In summary, no adverse environmental impacts or landslide triggers will result either on-site or off-site if this proposed development is permitted as presented within this Geo-Technical Report. 10. Final development Conditions: a. No clearing or grading of lands southerly of the wedge's toe-of-slope shall occur. b. The Garage roof downspouts shall be connected to the existing storm drain. 11. Discussion of Attachment 5, the 35mm Photographs (Pages 1 thru 6); These Photos show the Stable existing site where the new Garage is proposed. 5 This completes this Geotechnical Report of the above reference property. I, Kenneth W. Martig, Jr., PE, of Martig Engineering have completed the required Geo- Technical Report as documented within this letter Report and its attachments. I am familiar with this site, having frequently driven past it since 1961, having engineered a solution to a Creek-Flooding problem at this property in 1990, and having recently visited and inspected the site and its surrounds. As documented, potential landslide hazards have been overcome and no significant environmental impacts to the public or property will result if this proposal is permitted as discussed above. Ce ified b aeth artig, J . Attachments: 1- V'cini & Tax Parcel Map; 2- US Union Topography Map (1" = 200'), 3- Site Plan Map; 4- Elevation View, Section A-A; & 5- Six pages of 35mm Photographs. �. Asy� Q z -v q- O,`, G� TONAL EN FEXP1RES 1-9- 0 6 w 6 ..K I , 1 t t SISTERS POINT FOOD ChMA .. I I , , I i -----T--------------------------- - t Y TM t 33 I �C-i�t : � m.rvaxc,oi cr. .44 oy�. 1 x :36 I � 1� o p l oti ZO I I 1 100 I I 1 1 )40 1 1 I I 13400 1 1 i 1 1 I0)0 T To Belf+ o r. 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Box 11850 Olympia, WA 98508-1850 TT Fax ) 60) 754-97 05-0789 �CEIV D ( CEP 2 5 2006 September 25, 2006 MASON CO uNrY Mason County Department of Community Development 426 W. Cedar P.O. Box 578 Shelton, WA 98584 Attn: Debbra Coker, Lead Planner Re: Geo-Tech Report (SLOPE TOE PROTECTION WALUPLANTER) Compliance Report for: " Owner: Dallas Blair (360) 898-8100 8060 E. Hwy 106 Union, WA 98592 * - k newer 8050- Site Location: Approximately 1-Mile east of Alderbroo Residence on south side of Highway 106; * Tax Parcel No.: 32234-34-00060; * Mason County: Sec 34, Township 22 N. Range 03 W: * Proposal: Construct a new Slope Toe Protection, Wall & Planter; * PROPOSAL CLARIFICATIONS Dear Ms. Coker, I, Kenneth W. Martig, Jr., PE, of Martig Engineering, completed the Geotechnical Report (dated 12/8/04) for the above referenced property, and the August 14, 2006 "Slope Toe Protection Wall/Planter" compliance report. 1 am hereby submitting additional clarifications to recent concerns, passed on to me by Dallas Blair, regarding his proposal to construct a new garage: 1. Proposed new garage width: Instead of 12-feet wide, the requested width of the new garage is now 14-feet wide. We have reviewed this requested width increase to 14'. Our conclusion is that a 14-foot wide garage can fit as easily as the originally requested 12-foot 1 Monday, September 25, 2006 7.27 AM Kenneth W. Martig Jr 360 705 0789 p.03 wide width, with no adverse impact, and can be allowed; 2. Slope Toe Protection: The height of the existing wedge of sluffed soil, located at the base of the near vertical Till layer, is only about 5-feet to 8-feet. As discussed within the original 12/8/04 Geotechnical Report, the primary stability of the higher steep slope south of the proposed new garage is due to the structural strength of the Till soil mass forming the higher near vertical slope (which is very stable at a near vertical slope). The soil wedge in question is very small. It has been formed over a long period of time due to freeze-thaw deterioration of the face of the near vertical Till bank. This wedge is stable, having reached its angle of repose with a healthy natural vegetation ground cover on it. The only reason for any wall along its toe is to form a visual bumper, to stop inadvertent encroachment into the wedge. A 20' to 28"' high curbing (forming a level planter area for natural vegetation behind it) will have no structural load or surcharge load against it. It is purely a landscaping type fixture, creating a visual barrier that will arrest encroachment into the stable soil wedge at the base of the Till bank. Therefore, we have coordinated the installation of this curb/planter, by a Landscaper. It is completed and will arrest any inadvertent encroachment into the soil wedge during garage construction. Now that the soil wedge is protected by the completed new landscaping, and since a 14-foot wide garage is consistent with our recommendations within the original 12/8/04 Geotechnical Report, we concur that permits can be issued. We recommend that construction of the footings and floor be completed before the end of October, when the rainy season begins. 9/eAified eth artig, J o� .o o , 4 Ta�� ���NAu Eta 11-a 2