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HomeMy WebLinkAboutGeotechnical Report Review for VAR2008-00013 - GEO General - 8/28/2009 r MASON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT Planning Shelton(360)427-9670 Mason County Bldg.1 Belfair(360)275-4467 411 N 5th Street Elma(360)482-5269 PO Box 279 �xsa Shelton,WA 98584 HOME PAGE—www.co.mason.wa.us FINDINGS OF FACT Landslide Hazard Area Buffer Reduction Applicant: Michael McGraw Parcel No.: 32330-51-06007 Site Address: 183 N. Canal Hide-A-Way, Hoodsport Date: August 28, 2009 Per the Mason County Resource Ordinance (MCRO) 17.01.100 (D)(6) an application has been made to reduce the required 50-foot buffer to 49 feet and to allow for the reserve drainfield area at the top of the slope. Notice of the application for the buffer reduction was made as provided in Section 15.07.010 of the Mason County Development Code. Per MCRO(D)(6)(c) findings have been made that there are no impacts to anadromous fish or their habitat or to fish and wildlife habitat conservation areas. A Habitat Management Plan was submitted and adequately addresses mitigation for impacts to the shoreline buffer. The project was reviewed and approved by the Mason County Hearing Examiner. Findings have also been made that the approval is conditioned as necessary to be consistent with the recommendations contained within the Geotechnical Report and addenda that have been reviewed and approved by Vector Engineering, Inc. (see conditions attached to VAR2008-00013). This is a final administrative decision by the County. It is the appellant's responsibility to meet all legal requirements of any appeal process. If you have questions or require clarification on these issues please contact Tammi Wright, Land-Use Planner with Mason County at 360-427-9670 x295. Cc: Barbara Adkins, Planning Manager Mr. Bill McTurnal tZICEIVED ? r AUG 2 8 2Uuj E N 6 1 N E E R I N 6\N 309 WASHINGTON STREET NE M C C D - PLAN N I N G OLYMPIA WA 98501 TEL:360 352-2477• FAX: 360 352-0179 www.vectorengineeringinc.com August 26,2009 Tammi Wright Mason County Department of Community Development PO Box 279 Shelton,WA 98584 RE: McGraw Property Landslide Hazard Area Review Dear Ms. Wright, In our review letter dated July 29,2009 we requested that Mr. Cushman of Geotechnical Testing Laboratory provide a slope stability model representative of the slope with the a reserve drainfield constructed at the top. Mr. Cushman has provided a slope stability model and an explanation letter dated August 10, 2009 which appears to satisfy our request. Based on the above information provided to us by Mr. Cushman,we recommend that the 50-ft Landslide Hazard Area buffer be reduced to allow for the reserve drainfield at the top of the slope. Sincerely, *ye, . K\9000 Files\9027 MasonCo(McGraw)\Communication\Transmittal Letters\T1,02.doc Page I of I MASON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT Planning Shelton(360)427-9670 Mason County Bldg.I Belfair(360)275-4467 411 N 5th Street Elma(360)482-5269 PO Box 279 fxsa Shelton,WA 98584 HOME PAGE—www.co.mason.wa.us August 17, 2009 Ms. Kathy Maxwell Office Manager Vector Engineering, Inc. 301 Washington Stree, NE Olympia, WA 98501 Re: McGraw; VAR2008-00013 — Geotechnical Report Review Dear Kathy, I am enclosing the response from Curtis Cushman, Geotechnical Testing Laboratory, to a letter from Ryan L. Moore, P.E. dated July 29, 2009. Mr. Moore recommended that a reserve drainfield not be proposed within the 50-foot buffer at the tope of the Landslide Hazard area until Mr. Cushman provides a slope stability model representative of the slope with a reserve drainfield constructed at the top. I hope this meets your needs. Thank you for your assistance in this matter. If you have any questions feel free to call me at 360.427.9670 ext. 295. Sincerely, - G!�ri.�n.0 Tammi Wright, Planner Enclosure cc: Barbara Adkins Mike McGraw Bill McTurnal RECEIVED TAMMI WIGHT AUG 17 ZOOS PLANNER MASON COUNTY DCD P.O.Box 279 M C C D - PLANNING SHELTON,WASHINGTON 98584 RE: ADDENDUM ON SLOPE MODELS SITE INFORMATION: XXX NORTH CANAL HIDEAWAY LILLIWAUP,WASHINGTON GPS LOCATION: N47o 27' 19.11"W123o 06139.9311 PARCEL NUMBER: 323305106007 RESPONSE DATE: 08/10/2009 Dear Ms. Wright: I am sending you this note to try to explain the following cross-sections. These were sent in before within the note responding to Mr. David Strong, but there was considerable content in that letter and perhaps these points were not adequately covered. For these two cross-sections, we used the maximum slope angle that anyone considered valid, that is, 90%. There are no superposed weights as there is no structure except for the distribution pipes and associated plumbing. The models assume homogeneity, which is reasonable, as the site is the lobe of a landslide and any variation in lithology is likely to be chaotically incorporated in the general collapse. The water is the crucial ingredient. The slopes are modeled as if the entire hill is saturated with water. This adds considerable weight to the model. It is also unrealistic. To saturate the hill in such a manner would require far more water than can be expected from the reserve drainfield. We also saw no evidence of water in column along the hill slope, and none along the roads. The nearest wells indicate that static water levels are not near-surface. Water would also drain. In other words, these models are as about as worst-case as possible to the point of overstating any hazard. These models also indicate, strongly,that no slope remediation is needed. 0 a{ Wash; Respectfully Submitted, \�9f0�: GEOTECIiNICAL TESTING LABORATORY En eering Geologist 2439 Sed Gao�o� Curtis D Cushman LG, LEG �-- Senior Engineering Geologist ^JRTlS D ..,�I.. 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone#: (360)754-4612 Fax#: (360) 754-4848 G o cHNICAL TEsTi G UeoRAToRy SHEAR RESULTS(SAMPLE LOCATION AS SHOWN ON THE ATTACHED SITE PLAN) Peak Shear Stress vs. Normal Stress -- 2500 Shear=42* 2000 c C. tlM H 1500 `w m t 41 Y a m a 1000 �-1u ton 500 —�12 ton Cohesion =200 psf 0 0 500 1000 1500 2000 2500 3000 Normal Stress(psf) 10011 Blomberg Street SW, Olympia, WA 98512 2 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECRNICAL IUnNG ILAsoimToRy 10011 Blomberg Street SW,Olympia, WA 98512 3 Phone#: (360)754-4612 Fax#:(360)754-4848 GEoucKNI L Tmm no ToRy SLOPE MODELS(AN INCREASED GRADE ON THE HILL SIDE Static Mode! McGraw Slope Model • ' • Static Model • , • • , Fos 1.52 • • • • • • • • • • • 120 • ' • ' • 110 • , 1.52 P • • , � • 100 90 Name:Gravel with Sand Boo _ Unit Weight - = Phi:42 60 Phi-B:0 > 5o Piewmetric Line:I Proposed W 40 Building Location 30 Name:Sand ~�Uri We*123 ``— Bulk Head 20 Calxsbn:200 --'" 10 phu o 0 Pt Ix:1 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Distance (ft) 10011 Blomberg Street SW, Olympia, WA 98512 4 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEO T`ECHNI L USING ]LABORATORY Dynamic Model McGraw Slope Model • • • Dynamic Model • • • • • • Fos 1.20 • • • • • • • ' • • tt • • 120 • • • • • • 1206 • • 100 • 90 80 Name:Gravel'Nith San Vnit41'eight 133 -' --__ 70 Cohesion:200 C Phr 42 .� 60 Phi-B:0 .f ' > so PiezonneUic Line:1 Proposed w ao Building 4 Location 30 Name:Sad Bulk Head 20 Uni Weigh 123 Cohesion:200 10 c,:34 ...B:O 0 = - 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Distance (ft) 10011 Blomberg Street SW Olympia, WA 98512 5 Phone#: (360) 754-4612 Fax#: (360) 754-4848 1 e c t o r f N G 1 N F F R I N G \N C 309 WASHINGTON STREET NE OLYMPIA WA 98501 RECEIVEDTEL:360 352-2477• FAX: 360 352-0179 www.vectorengineeringinc.com 2009 AUG 0 3 July 29,2009 MCC D - PLANNING Tammi Wright Mason County Department of Community Development PO Box 279 Shelton,WA 98584 RE: McGraw Property Landslide Hazard Area Review Dear Ms. Wright, Vector Engineering, Inc. (VEI)has reviewed the documents pertinent to the Landslide Hazard Area(LHA) located on the Michael McGraw property in Lilliwaup, Washington. The scope of our work focuses on the LHA and the potential effects of construction within the 50' buffer established by the Mason County Resource Ordinance (MCRO), Section 17.01.100.D.6.a. As requested by Mason County,this letter represents our findings upon review of the following documents: Geotechnical Report. Geotechnical Testing Laboratory, 12 December 2007. Michael McGraw Letter. Highland Excavation. 2 May 2009. Review and geotechnical comments on the Geotechnical Report prepared for Mr. Michael McGraw by Geotechnical Testing Laboratory under the seal of Curtis Dean Cushman and dated December 12, 2007. Bradley-Noble Geotechnical Services, 29 May 2009. Review Letter of David Strong. Geotechnical Testing Laboratory, 10 June 2009. The December 12, 2007 Geotechnical Report prepared by Mr. Curtis Cushman, L.E.G. identifies a LHA in the west portion of the site. The May 29, 2009 review of the Geotechnical Report prepared by Mr. David Strong, L.E.G. verifies the LHA. Section 17.01.100.D.6.a of the MCRO states that"a 50 foot buffer of undisturbed, natural vegetation is required around the Landslide Hazard Area." It is our understanding that an application has been or will be made to reduce the buffer as per section 15.07.010 of the Mason County Development Code. Proposed construction within the 50-ft buffer at the toe of the slope includes a single family residence and septic system with associated drainfield. There is an existing 20' right-of-way near the toe of the slope providing access to the adjacent lots. MCRO, Section 17.01.100.D.6.c states that"the Director shall approve such a reduction only on finding that the approval is conditioned as necessary to be consistent with the recommendations contained with the -1- X:\9000 Files\9027 MasonCo(McGraw)\Communication\Transmittal Letters\TL01.doc Geotechnical Report." Mr. Cushman makes the following conclusions on page 24 of the Geotechnical Report: We conclude the slope stability of the site will not be adversely impacted by the proposed septic drainfield and the proposed septic drainfield will not be adversely impacted by the landslide hazard area. We also conclude the proposed septic drainfield will not adversely impact the proposed structure. Based on our knowledge of the proposal,the recommendations made by Mr. Cushman and the assumption that a buffer reduction request will be made,Vector Engineer, Inc. recommends that the buffer reduction request be granted with the following provisions as shown on Figure 2, Site Plan of the Geotechnical Report: the proposed septic system and drainfield shall be setback 34-ft from the toe of the slope and the proposed building shall be setback 49-ft from the toe of the slope. The documents provided to us also indicate a proposed reserve drainfield at the top of the slope. Much of the concern exhibited by the neighboring property owners, Mason County and Mr. Strong centers on the reserve drainfield at the top of the slope. Mr. Strong has provided a technical review of Mr. Cushman's Geotechnical Report in which he questions various aspects of Mr. Cushman's slope stability analysis and makes the following recommendations on page 3 of his Review and Geotechnical Comments: To confirm the actual stability and slope profile, the following work needs to be completed. One, the slope profile should be established by a site specific survey by a licensed land surveyor. An additional boring at the top of slope must be performed to verify the actual subsurface soil profile. Undisturbed soil samples should be obtained for shear testing According to Mr. Cushman, "The steepest slope measured onsite was approximately 70 percent," while Mr. Strong"measured the slope using a Leitz Pocket Transit and found the slope angle to vary between 40 and 42 degrees(83 to 90%of slope)." In Mr. Cushman's June 10,2009 rebuttal letter he provides a new slope stability model with an increased slope of approximately 90%and "we STILL have acceptable Factors of Safety." In regards to Mr. Strong's recommendation for "an additional boring at the top of slope,"Mr. Cushman replied with: I admit to an important omission: I had sampled the hillside with a shovel near the north property line for the late Hal Park's lab work before I was fully involved with the report and before the drilling took place. This grab sample was subsequently tested for gradation and shear (sample 41674, 1110112007). This is the shear in the report. Its provenance was inadvertently not cited but is in our records. Mr. Strong need not be concerned. Regarding the reserve drainfield, William L. Russell, a licensed onsite wastewater treatment system designer for Highland Excavation, adds"From this designers viewpoint the only reason for a reserve drainfield in this case is that the State guide lines require a reserve area...I also predict that this reserve will never be constructed, because it would be far cheaper to rebuild the primary part." While there is no guarantee that the reserve area will never be utilized, Mr. Russell suggests that it would be more feasible to replace the primary drainfield rather than construct a drainfield in the reserve area. -2- XA9000 Files\9027 MasonCo(McGraw)\Communication\Transmittal Letters\TLOl.doc Furthermore, Mr. Strong's observations of the slope and the surrounding areas strongly suggest active surface erosion on the slope. In the Geotechnical Report,Mr. Cushman states that"no evidence of active surface erosion was seen." In his rebuttal letter to Mr. Strong, Mr. Cushman continues to say that"we stand by our observation that there is no evidence for deep-seated failure and the observation that no erosion was detected on Mr. McGraw's parcel." However, Mr. Strong provides examples such as: "a wood retaining wall constructed at the top of the slope that is failing due to soil movement,"or"trees growing on the slope that have bowed trunks...colluvium retained on the upslope side of the trees which suggest active downslope soil movement"among other observations. The physical evidence of surface erosion presented by Mr. Strong is too significant for Vector Engineering,Inc to overlook. Although Mr. Cushman has provided a revised slope stability analysis, it is unclear whether or not the model accounts for construction of the reserve drainfield at the top of the slope. Vector Engineering, Inc requests that Mr. Cushman provide further clarification of the most recent slope stability model and how construction of the reserve drainfield will affect the slope. Conclusions & Recommendations Mr. Curtis Cushman, L.E.G., of Geotechnical Testing Laboratory has satisfactorily met the recommendations made by Mr. David Strong, L.E.G. of Bradley-Noble Geotechnical Services. Vector Engineering, Inc. recommends that the 50-ft LHA buffer be reduced at the toe of the slope as shown on Figure 2, Site Plan included in the Geotechnical Report. This includes a 34-ft setback for the proposed septic system and drainfield and a 49-ft setback for the proposed building. Vector Engineering, Inc also recommends that the primary reserve drainfield not be proposed within the 50-ft buffer at the top of the LHA until Mr. Cushman provides a slope stability model representative of the slope with the a reserve drainfield constructed at the top. The findings of this letter are based on Vector Engineering, Inc's understanding of the project requirements and on documents prepared by Geotechnical Testing Laboratory, Bradley-Noble Geotechnical Services and Highland Excavation. Vector Engineering, Inc. staff did not conduct any field reconnaissance,but based all findings on the documents provided to us by Mason County. Vector Engineering, Inc. warrants that its services were performed with the level of care and skill ordinarily exercised by members of the same profession currently practicing in the same locality under similar conditions. No other warranty or representation, expressed or implied,is included or intended hereunder. Sincerely, l`t L Mop 4qP� was '', .0 4Pro" 4�Eineer re, P.E. 80 GIs �ti .r1 oNAL� ptPtAE3 OS/30'67 -3- X:\9000 Files\9027 MasonCo(McGraw)\Communication\Transmittal Letters\TLOl.doc . t o r Invoice f N 6 1 N E E A 1 N 6 \N C 309 WASHINGTON STREET NE OLYMPIA WA 98501 Bill To: Number: 9027-01 Mason County Dept of Community Development Date: 7/30/2009 PO Box 279 Shelton WA 98584 PO# VAR2008-00013 Project: 9027 MasonCo(McGraw) Terms: Due 20 days from date of invoice [Project Manager: Erick Mahugh Due Date: 8/20/2009 Serviced Description Quantity Rate Amount 7/30/2009 Project Administrator 1 60.00 60.00 7/9/2009 Supervising Engineer 1.5 140.00 210.00 7/28/2009 Project Engineer 3 115.00 345.00 7/29/2009 Engineer III 27 95.00 2,565.00 This billing is for work performed necessary to produce report dated July 29, 2009. Extensive issues or questions arising from the requested information may necessitate additional billing. Invoice Total: $3,180.00 [Billing Period: July 2009 We gladly accept Visa and MasterCard. Please call our office to make phone payments with your card. Thank You. TEL:360 352-2477 FAX: 360 352-0179 www.vectorengineeringine.com 0N Coop MASON COUNTY � aA Shelton (360) 427-9670 DEPARTMENT OF COMMUNITY DEVELOPMENT Belfair (360) 275-4467 Planning 482-5269 Mason County Bldg.1411 N.5th Elma (360) P.O.Box 279 Shelton,WA 98584 Sf June 30, 2009 Ms. Kathy Maxwell Office Manager Vector Engineering, Inc. 301 Washington Street, NE Olympia, Washington 98501 Re: McGraw; VAR2008-00013 Geotechnical Report Review Dear Kathy: I am enclosing a Geotechnical Report prepared by Geotechnical Testing Laboratory for Mike McGrow, applicant. Mr. Bill McTurnal has requested a third party review and we are providing you with a letter from him accepting responsibility for payment of your fees. Thank you so much for your assistance in this matter. If you have any questions, please feel free to call Tammi Wright at 360/427-9670 ext. 295., or me at ext. 286. Sincerely, Barbara A. Adkins, AICP Department Manager Enclosures c: Tammi Wright RKOWD June 28, 2009 JUN 2 9 2009 MASON CO. PLANNING DER Tammi Wright Mason County DCD PO Box 279 Shelton, WA 98584 Dear Ms. Wright: In response to your letter dated June 16, 2009,please consider this my formal request for a third party review in the case of Michael McGraw. Also please be advised that I will be responsible for the cost of the third party review. SincLumal l ) Yl PO Box 12048 Olympia, WA 98508-2048 G Eort Nic iL "T` "SING LABORATORY RECAZN2D TAMMI WIGHT Juh .F 5 `9 PLANNER MASON COUNTY DCD P.O.Box 279 MASON COUNTY SHELTON,WASHINGTON 98584 RE: REVIEW LETTER OF DAVID STRONG SITE INFORMATION: XXX NORTH CANAL HIDEAWAY LILLIWAUP,WASHINGTON GPS LOCATION: N47°27' 19.11"W123°06' 39.93" PARCEL NUMBER: 323305106007 RESPONSE DATE: 06/10/2009 Dear Ms. Wright: Thank you for the opportunity to respond to you concerning the letter sent to Mr. Bill McTurnal on May 29, 2009 by David Strong LEG, in reference to the above property owned by GTL's client, Mr. Mike McGraw. Mr. McGraw has requested that I contact you to insure as quick a resolution to this as possible. Mr. Strong brings up several points, some of which will require technical rebuttal. I do not wish to get esoteric, so if on review, a point has been "fogged over," I apologize for that and will clarify upon your request. To simplify matters, I will take his points in order followed by my response per point. In the description of the site (alongside which Mr. McGraw has written "Not Correct"), Mr. Strong has stated that the slope is between 83% and 90% instead of 70%. Locally, Mr. Strong may be correct, although when I review our pictures and sketches, I am not sure of these places. The 70%was derived by tape,traverse, Brunton, and use of the site map, which were modeled with the total difference in elevation to derive a reasonable overall slope. Please see below. In the following paragraph Mr. Strong takes issue with the statement"no evidence of active surface erosion was seen," citing several examples of nearby surface creep. Creep is indeed an erosional process and should have been mentioned. That said, "surface erosion" was meant as downcutting and visible erosion of materials. The thrust of the issue is the deep-seated failure. Creep is endemic for sloped surfaces in Western Washington. It is a fact of life every residence built on or near a slope must reckon with. We stand by our observation that there is no evidence for deep-seated failure and the observation that no erosion was detected on Mr. McGraw's parcel. If the presence of creep is a matter of concern,this concern should be toward the existing homes as well as this parcel. If creep can be remediated, as was done with these homes, it can also be done on the McGraw property. Mr. McGraw indicated the land swap has been"done and approved." In the following paragraph, despite the jejune editorial concerning professional standards, Mr. Strong brings up an interesting point concerning the location of the drill hole. Not having an unlimited budget, we felt that the primary object of the drilling was to verify the buildability of the site; hence the hole was located near the proposed residence,primarily to test likely fill and water table depth as well as soils. (Also: see below). 10011 Blomberg Street SW,Olympia, WA 98512 1 Phone#: (360) 754-4612 Fax#: (360)754-4848 GtOrEcaNicAL TESTING LABORATORY Now, for the next paragraph. I admit to an important omission: I had sampled the hillside with a shovel near the north property line for the late Hal Park's lab work before I was fully involved with the report and before the drilling took place. This grab sample was subsequently tested for gradation and shear (sample #1674, 11/01/2007). This is the shear in the report. Its provenance was inadvertently not cited but is in our records. Mr. Strong need not be concerned. (There is another reason: see below.) Additionally, in this paragraph, Mr. Strong makes an error. Apparently, he is unaware that the Direct Shear method of ASTM D 3080-04 specifically allows compacted specimens (Section 7.5.2 ff). This is the technique here employed. Disturbed samples are permitted. Mr. Strong's statement on wet/dry conditions is not only confusing; it does not appear to be relevant. Next paragraph: please see our models. We prefer the empirical to the anecdotal. As any slope not at its internal angle of friction is subject to instability; there would be few places on the coastland or in upland Mason County that would be buildable. Even soils reposing at their internal angle of friction are susceptible to erosion. And no one is using apparent cohesion. I thank Mr. Strong for his recommendations, but as most or all are not needed, they are not pertinent to this geotechnical discussion. Concerning retaining walls. Nowhere do we discuss "Construction of a standard cantilever retaining wall" as Mr. Strong accuses. We only provide geotechnical data, as we do in all reports, if such construction is envisioned. The construction details for short walls are... Mason County's. In addition, please note that on page 21, we state "Walls greater than 4 feet in height must be designed by a Professional Engineer." (Emphasis added.) This is our stated policy and apparently was overlooked by Mr. Strong... Finally, Mr. Strong is absolutely mistaken when he says we recommended an active soil pressure of 25 pcf. What was given was the active pressure coefficient (Ka) which not only doesn't have units of pcf; it is unitless and is used by engineers to calculate total active pressures. (As Pa=0.5Kayh2). This basic error is why we use engineers to design retaining walls, and not engineering geologists. The paragraph beginning "In summary"relates to points already answered above. The final paragraph introduces new points even though there was a "summary" paragraph above it. This involves the existing concrete bulkhead. Mr. Strong implies we should have evaluated the wall. That is not the purview of an engineering geologist, although the bulkhead looked pretty solid to me. I believe the nuts and bolts of installing the pump-up system is best left to the engineer of record and the contractor. We have evidence of the slope being disturbed by human activity with little consequence (beyond the obvious residences): e.g. the unsupported cut to the immediate south of Mr. McGraw's property. This cut, according to Mr. McGraw, reaches a height of 8 feet on the Herrmann property located behind the garage sitting across the right-of-way. These final paragraphs are those referenced by the notes ("See below") in various places in the text above. Please bear in mind, the opposition to Mr. McGraw appears to depend on a narrow sliver of upland that may be built with a secondary drainage field for the residence proposed for lower on the site. There are no structural elements of consequence, and the material is well drained. It is difficult to imagine a circumstance in which the amount of water injected into the system will damage the hillslope, especially when compared with torrential or 1001 1 Blomberg Street SW,Olympia, WA 98512 2 Phone#: (360) 754-4612 Fax#: (360)754-4848 Gr" ®mcnNi L TEsTING LABORATORY even normal rains. In any event, surficial drainage can be planned for, and, if needed, 2" pin-piles could be employed to secure the hillside. In fact, please find attached two new slope stability models. For these models, we used an increased slope of approximately 90%, we reduced the cohesion to 200 psf, consequently increasing the shear to 42 degrees (a better fit for the three test points on peak shear stress vs. normal stress curve), we put the water table near surface (adding weight and ignoring the fact that the water will readily drain), and we STILL have acceptable Factors of Safety. It is odd that this lot should cause such a problem for Mr. McGraw alone. The entire development, waterside as well as the view sites, is located on the "hummocky terrain" of an old and large landslide. The drillhole we advanced, the sample taken for shear, and observation of nearby outcrops show that any "layer-cake" model is not possible unless it is on a fairly small scale. We have therefore modeled it as homogeneous. If the load proposed by this drainfield design is not tolerable, then many of the houses, especially those built before the latest geotechnical rules were drawn up,may not be safely located, and I have not seen any claim that they are unsafe, despite the abovementioned creep. Respectfully Submitted, GEOTECHNICAL TESTING LABORATORY Wash; �o 6►.iy n du Curtis D Cushman LG, LEG ineering Geologist ,� Senior Engineering Geologist 2439 o�sed G eo�o ^JDTIS AN CUSHMAN 10011 Blomberg Street SW,Olympia, WA 98512 3 Phone#: (360)754-4612 Fax#: (360)754-4848 Bradley-Noble Geotechnical Services A Division of The Bradley Group, Inc. PO Box 12267, Olympia WA 98508-22.67 Phone 360-357-7883 • FAX 360-867- MAY 2 9 ZUUJ 29 May 2009 M CC D - PLANNING Mr. Bill McTurnal P.O. Box 12048 Olympia, Washington 98509-2048 Subject: Review and geotechnical comments on the Geotechnical Report prepared for Mr. Michael McGraw by Geotechnical Testing Laboratory under the seal of Curtis Dean Cushman and dated December 12, 2007. Dear Mr. McTurnal: As requested, we have reviewed the above report prepared as part of the permit process for a new residence proposed by Mr. McGraw to the immediate south of your Mason County Tax Parcel 323305106004 on North Canal Hideaway, Lilliwaup area of Mason County. This letter will present our review comments on this report. We are familiar with this area. We have prepared a report for a proposed project at your beach cabin, our report date 27 July 2007 and for another residence to the south on Beach Drive. We met with you and other neighbors on 21 May 2009 to discuss the proposed construction and to allow for us to again observe site conditions on the McGraw and adjacent properties. Our work then has consisted of this site visit, a review of the report prepared under the seal of Mr. Cushman of Geotechnical Testing Laboratory, and preparation of this review and comment letter. The McGraw property is a "pie" shaped piece that has a frontage of about 68 feet at the bulkhead adjacent to Hood Canal. The apex of the property is in the upland area, in a area now used for driveway of the upslope property at 120 North Canal View. From the information provided for Figure 2, Site Plan of the report, we find one boring indicated. This boring was conducted at the northeast corner of the proposed residence footprint. No other subsurface exploration is indicated. Figure four of this report, titled cross section, shows the area of proposed construction to be of low relief. We are in agreement with this portion of the cross section. In the cross section, between 100 feet to 150 we find a steep slope indicated. From 150 to 09050701 Page I of 4 09050701 Page 2 of 4 200, we find represented again an area of low relief. This is consistent with our observations. In the cross section, the slope is indicated as being 70%. We disagree that this is the actual slope as it exists at this site. We measured the slope using a Leitz Pocket Transit and found the slope angle to vary between 40 and 42 degrees (83 to 90% of slope). On page 7 of the Geotechnical Testing Laboratory report, it is stated that no evidence of active surface erosion was observed. This is not a supportable statement based on physical evidence obvious to visual field observation. On this slope above the project area, we can observe a wood retaining wall constructed at the top of slope that is failing due to soil movement. On the slope of this property, the low-growing vegetation indicates that soil creep is active. To the north as you drive into the property along North Canal Hideaway you can observe that most of the trees growing on the slope have bowed trunks. Many of these trees have colluvium retained on the upslope side of the tree which suggest active downslope soil movement. At the top of the slope, which is easily accessed by Canal View Road we can observe a failing retaining wall system on the west side of the residence at 120 N. Canal View Road. At this site, the asphalt pavement for the driveway also shows distress due to lateral movement creating tension cracks in the pavement. This movement is to the east towards the top of slope. At the top of slope, there is a small segmented block planter. The eastern four blocks, those adjacent to the top of slope, show downslope deflection due to loss of soil support caused by movement of the soils forming the slope. From our field discussion, we understand that the property owner of 120 N. Canal View Road has agreed to a land swap where the apex of the McGraw property will be exchanged for a section of property adjacent to the slope. The actual location of this property must be located by survey as we understand that this will be proposed for the reserve drain field. With the obvious instability of the slope as indicated by the deflection of the planting bed segmented blocks and vegetation on the slope, we have concerns about placement of a drain field near or at the top of slope. With the steepness of the slope, we expect that the soil profile will be a thin layer of weathered soils over dense soils. The thickness of the weathered soils will determine if on site infiltration is possible. Also, the added water load to the weathered soils of the upland and the colluvium of the slope will be a destabilizing influence. The proposed drain field area must be evaluated by a competent design professional. We have reviewed the slope stability analysis prepared in this report. One boring away from the slope does not meet standards of the industry. Extrapolating data from a boring not conducted specifically to evaluate the soils forming the slope is not the standard of practice of our profession. The top of slope is easily accessed by standard truck mounted soil exploration equipment. 09050701 Page 3 of 4 Mr. Cushman has indicated a Peak Shear Stress vs. Normal Stress on page 31. The depth of this soil sample is not indicated. Our review of the soils in the boring log on page 30 and the gradation analysis of select soils indicates that the soils are cohesionless. In the laboratory test, a cohesion of 250 p.s.f. This is a false cohesion created by negative pore pressure (i.e. the soils are dry) . When the soil is saturated, no cohesion is present. We are also curious how a soil sample was obtained for laboratory testing. The boring log indicates that only the 2-inch outside diameter split-spoon sampler was used to developN-values. B definition, the 2-inch diameters lit spoon samples are Y P P P considered to be disturbed samples. To obtain a soil sample for shear testing a ring- lined sampler (Dames & Moore Sampler) or other larger diameter samplers would be required to obtained undisturbed soil samples for shear testing. The question then is how this shear test was actually performed and is the data valid. If we use the indicated shear angle of 38 degrees, this is the angle of internal friction of the soils. This angle was obtained from soils not cropping out or forming the slope, but are extrapolated from the one boring conducted away from the slope. With our measurement of the slope being in excess of 38 degrees, the slope then is obviously unstable. Stable slopes have slope angles less than the angle of internal friction of the soils forming the slope. Use of apparent cohesion for increased safety factor in cohesionless soils is not acceptable. To confirm the actual stability and slope profile, the following work needs to be completed. One, the slope profile should be established by a site specific survey by a licensed land surveyor. An additional boring at the top of slope must be performed to verify the actual subsurface soil profile. Undisturbed soil samples should be obtained for shear testing. This boring should extend to a depth of at least ten feet below the toe elevation or to bedrock, whichever occurs first. This work will also verify the actual depth to the near surface water table. The cross section presented showing the piezometric surface is an estimate and is not supported by exploration data. In the report on page 21, a discussion is presented on the use of a retaining wall to increase the available land area. On page 22 of this report, a prescriptive design prepared by Mason County Department of Community Development is presented. The prescriptive design would be appropriate where level backfill would be equal to the height of the wall. Also, this prescriptive design is limited to a maximum wall height of eight feet. An active soil pressure of 25 p.c.f. is recommended for design plus surcharge. The 2006 International Building Code (IBC) mandates that retaining walls be designed to a minimum active soil pressure of 30 p.c.f. Construction of a standard cantilever retaining wall as discussed in this report has the risk of inducing a mass wasting event by removal of toe support of the soils forming the slope. Also, we do not expect that this type of wall can be constructed even if the toe 09050701 Page 4 of 4 of slope was cut. Once forms or walls exceed four feet in height, the void between the wall and forms is considered to be a trench under the Department of Labor and Industries Standards. We do not consider that sloping of the cut to meet the requirements of Chapter 296-155 WAC, Construction Work, Part N, Excavation, Trenching and Shoring is possible. Use of shoring to provide stabilization of the slope during construction will require additional geotechnical evaluation and engineering design. If a new retaining wall were to be constructed, use of a soldier pile wall with either wood or concrete panel lagging would be appropriate. Again, this would require geotechnical and structural engineering services. In summary, the geotechnical report prepared for this proposed residential development by Geotechnical Testing Laboratory under the seal of Mr. Cushman, L.E.G. for the McGraw residence has addressed foundation design, but has not addressed slope stability to the accepted standards of practice of our industry. At a minimum, additional soil exploration and obtaining of undisturbed samples for laboratory testing is required to adequately address slope stability. Once the actual location of the reserve drain field is established by survey, this location must be evaluated by a competent professional to ensure that the reserve area will not create a hazard to the slope and downslope structures by either movement and failure of the drain field or by the introduction of additional water load on the slope. We have geotechnical concerns about this proposed development due to the very limited area available for the residence and primary drain field. The lack of evaluation of the present slope stability and the ignoring of the obvious active downslope movement of soils must be addressed. Also, the stability of the building site is controlled by the continuing functioning of the concrete bulkhead which also restrains soils that form the available building area. No evaluation of the condition of this wall or if it is structurally adequate to ensure long-term performance has been presented. No recommendations have been presented as to how effluent would be transported to the reserve field without disturbing the existing slope. Cordially, BRADLEY-NOBLE GEOTECHNCIAL SERVICES O Wash/' David C. Strong, L.E.G. cj 1129 �Sed Geo ..�. MICHAEL MCGRAw P.O.Box 429 ONALASKA,WASHINGTON 98570 RE: GEOTECHNICAL REPORT SITE INFORMATION: XXX NORTH CANAL HIDEAWAY LILLIWAUP,WASHINGTON GPS LOCATION: N470 27.3283 W123°06.6643 DATE: 10/13/2008 Mr. McGraw: This letter serves as a response to the letter dated October 09, 2008 by Tammi Wright of Mason County Department of Community Development. The missing items in the original geotechnical report will be addressed as follows. 1. A line representing 50 foot vegetation buffer has been added in the site plan. It is to be noted that the right of the way for the adjoining parcel and the proposed septic system will be included in this "buffer zone", if enforced. I would like to emphasize the fact that the area does not contain any vegetation. We request you to apply for a buffer reduction request to the county as per section 15.07.010 from Mason County Resource Ordinance. 2. Figure 4, cross section has been updated and attached along with this letter. 3. Please refer the following line as a correction to the original report on page 10. "This site does not meet the technical criteria of an erosion hazard area." We apologize for the typographical error on the original report. 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. e of Was h Respectfully Submitted, CO,��� fo j GEOTECHNICAL TESTING LABORATORY 3-4 << 2439 c+a�8ed Geo�o rU1TIS DEAN CUSHMAN Curtis D Cushman L.E.G. Senior Engineering Geologist 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone#: (360)754-4612 Fax#:(360)754-4848 CROSS - SECTION A ( EAST-WEST) 70 ............................................. ........................................................................................................................r........................................................................................................................ 70 60 . . . . . . . . . . . ALTERNATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 n 50 SLOPE u"i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIEGETAMD" . . . . . . ale. . . . . . . 50 WITH 40 _j . . . NATIVE . . . . . . . . . . . . . . . . . . . . . . . 40 S�_ipu QIs M Qls 30 . . . . . . . . . . . . . . z 30 0 cn PROPOSED QIS 20 10 PROPOSED 20 5� BUILDING SEPTIC DRAIN Q13 QIS LLJ TIO 16%SLOPE OCATION FIELD 10 . , - I . . I . . I . . . . I : . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 10 GRAVEL W/ 0 SAND I 0 0 i50 1100 1150 1200 250 Geotechnical Testing Laboratory Geotechnical Services I0011 Blomberg St.SW FIGURE 4 Olympia,WA 98512 SCALE QAIQC Services Phone:(360)754-4612 =30' CROSS-SECTIONS Testing Services Fax:(360)754-4848 DATUM FOR THE SITE PLAN INCORPORATED VARIOUS TECHNIQUES AND SOURCES FILTER FABRIC MATERIAL W WIDE ROLLS USE STAPLESWIRE RING TO ATTACH Geotechnical INCLUDING THE FOLLOWING: USE FABRIC TO N WRE RE TAPING AND PACING,SLOPE MEASUREMENTS WI AN INCLINOMETER ANGLES AND zx2 xl a GAUGE WARE BEARINGS USING A BRUNTONO GEO TRANSIT,SITE LOCATIONS USING A GARMINO HAND FABRIC OR EQUIVALENT HELD GPS UNIT,TOPOGRAPHIC MAPS FROM DELORME®,MASON COUNTY G.I.S.WEBSITE, Testing AND SURVEYS RECORDED AT THE MASON COUNTY ASSESSOR. GEOLOGIC SITE 2 RECONNAISSANCE OCCURRED ON MARCH 20,"7 AND JUNE 27,2007 By LEVINE. Sd .Q� THE PRESENT RECORDED SURVEY WAS CONDUCTED BY FOREST LAND SURVEYS:THE DEVELOPED Laboratory SURFACE SURVEY IS DATED NOVEMBER OF 1993. THE SURVEY IS BASED UP THE PREVIOUS SHORT PLATS#1981 AND#1962. AREA `wx 2'XP WOOD POSTS,STANDARD OR BURY BOTTOM OF FILTER BETTER OR EQUAL ALTERNATE'. MATERIAL IN M12'TRENCH STEEL FENCE POSTS \ \ FILTER FABRIC S' \ FABRIC OR GAUGE WIRELIE �Q FABRIC OR EOUNALEM 7d \ \ GROUND SURFACE 5'd O PROVIDE ACC 1?WASHED GRAVEL BOTH SIDES L IN TRENCH 17 AND ON BOTH SIDES OF FILTER \ O FENCE FABRIC ON THE SURfACE S 2'XP WOOD POSTS ZA11� '., to O 8L-1 ALT:STEEL FENCE POSTS Geotechnical Services . PGK ''� v•� FILTER FANUC FENCE NOTES: /^, QA/QC Services \ , 1.FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLLOUT TO Ate^ � ` THE LENGTH THE BARRIER TO AVOID USE JOINTS.WHEN JOINTS A ARE NECESSARY.FILTER CLOTH SHALL BE SPLICED TOGETHER ONLY AT Testing Services \ QI$ A QI$ A SUPPORT POST WITH A MINIMUM INCH OVERLAP AND SECURELY � � FASTENED AT BOTH ENDS TO THE � , ' 2.ROB TS SHALL BE SPACED A MAXIMUM OF 6 FEET APART AND DRIVEN � SECURELY INTO THE GROUND(MINIMUM OF 301NCHES). O/r^'�' O �y 7 3.A TRENCH SHALL BE EXCAVATED APPROXIMATELY 81NCHES WADE AND 12 10011 Blomberg St.SW O. Y \• ((� INCHES DEEP ALONG THE LINE OF POSTS AND UPSLOPE FROM THE BARRIER. Olympia,WA 98512 lTs Y� is CIS //J (O� \ ESH \ `0 + SSUPPORT EVINCE SHALL BE FASTENED N STANDARD STRENGTH FILTER SECCUREBRIC IS LY TO THE UPSED,A WIRE LOPE SIDE Phone:(360)754-4612 \ \Lf R,/,, / (/ V' OF THE POSTS USINGNEAVY-0UfYNARESTAPLESATLEASTIINCM Fax:(360)754-4848 1`1I• LONG,TIE WIRES OR HOG RINGS.THE WARE SHALL EXTEND INTO THE S �S�GK C`, O Q TRENCH A ABOVE THE OF A INCHES AND SHALL NOT EXTEND MORE THAN 35 _ 4 T� INCHES ABOVE THE ORIGINAL GROUND AND HALLSURFACE. s p9 sE P 2 SIL EN 5 THE STANDARD STRENGTH FILTER FABRIC SHALL BE STAPLED OR WIRED Date: 12/27/07 TO THE FENCE AND 20114CHES OF FABRIC SHALL BE EXTENDED VEGE D REA,I INTO THE TRENCH.THE FABRIC SWILL NOT EXTENO MORE THAN 36 Designed by:PL INCHES ABOVE THE ORIGINAL GROUND SURFACE.FILTER FABRIC SHALL Drawn by: PL NOT BE STAPLED TO THE EXISTING TREES. 16%$LOPE S.WHENEXTRASTRENGTH FILTER FABRIC ANDCLOSER POSTSPACING IS Checked by: CDC Z0 USED,THE WIRE MESH SUPPORT FENCE MAP BE EUMINATED,IN SUC QIS _ H M1 /� A CASE,THE FILTER FABRIC IS STAPLED OR WIRED DIRECTLY TO THE Dwg#: 12-26-07-104 POSTS WATH ALL OTHER PROVISIONS OR ABOVE NOTES APPLYING. 00, I 7 FILTER FABRIC FENCES SHALL NOT BE REMOVED BEFORE THE UPSLOPE AREA HAS BEEN PERMANENTLY STABILIZED. GE ATE PROPOSED S PTIC DRAIN SYSTEM S FILTER FABRIC FENCES SHALL BE INSPECTED IMMEDIATELY AFTER EACH RAINFALL AND AT LEAST DAILY DURING PROLONGED RAINFALL,ANY REQUIRED REPAIRS SHALL BE MADE IMMEDIATELY. 50'VEGETATION BUFFER? GENERAL FROSIOH COITRQ NOTES: Qi8 \�� ((REQUEST WAIVER) 1. EROSION CONTROL MEASURES SHALL BE IN PLACE PRIOR TO THE BEGINNING OF CONSTRUCTION.THE PROJECT ENGINEER AND THE COUNTY SHALL INSPECT AND APPROVE THE INSTALLATION OF EROSION CONTROL MEASURES PRIOR TO BEGINNING CONSTRUCTION, DEVELOPED AREA 2.EROSION CONTROL MEASURES ARE NOT LIMITED TO THE ITEMS ON THIS PLAN THE CONTRACTOR IS RESPONSIBLE FOR THE ALTERNATE INSTALLATION AND MAINTAINANCE OF ALL EROSION CONTROL MEASURES NO SILTATION OF EXISTING OR PROPOSED DRAINAGE FACILITIES LIMIT OF LANDSLIDE HAZARD AREA NORTH SHALL BE ALLOWED.CARE SHALL BE TAKEN TO PREVENT MIGRATION PROJECT NAME: SCALE 1"=30' OF SILTS TO OFF SITE PROPERTIES 3.THE CONTRACTOR SHALL MAKE DAILY SURVEILLANCE OF ALL EROSION McG RAW SITE C.I.=S Ft. TO THE EROSION CONTROL AND KE ANY ASURES NECESSARY REPAIRSOR SHADDIT PROVIDE X)()(NORTH CANAL HIDE A WA' TO THE EROSION CONTROL MEASURES.THE CONTRACTOR SHALLLSSARY BY THE COUNTY EROSION CONTROL MEASURER AS DETERMINED NECESSARY BY THECOUNTYINBL LOCAL AND OR THE PROTON CONTROL .FAILURE LILLIWAUP,WASHINGTON TO COMPLY WITH ALL LOCAL AND STATE EROSION CONTROL AGAINSTREQUIRE ENTSTHE MAY CONTRACTOR IN CAVIL PENALTIES BEING LEVIED PARCEL 323305106007 AGAINST THE CONTRACTOR AND/OR PROJECT OWNER. 1.DURING THE WET SEASON.OVEMBER TO MARCH)ALL DISTURBED SOILS 0 10 20 30 SHALL BE STABILIZED WITHIN N HOURS AFTER STOP OF WORK EROSION ��� CONTROL MEASURES SHALL INCLUDE,BUT NOT BE LIMITED TO. COVERING THE EFFECTED AREA INCLUDING SPOIL PILES YATM PLASTIC SHEETING,STRAW MATTING,JUTE MATTING,STRAW MULCH, OR V,OOD CHIPS.SEEDING OF THE DISTURBED AREAS SHALL TAKE PLACE AS WEATHER PEWTS. 5.ALL SEEDED OR SODDED AREAS SHALL BE CHECKED REGULARLY TO MAKE SURE VEGETATIVE COVERAGE IS COMLETE.AREAS SHALL BE REPAIRED.RESEEDED,AND FERTILIZED AS REQUIRED. S TRACKING OF SOL OFFSITE HALL NOT BE ALLOWED IF ANY SOIL IS TRACKED ONTO A COUNTY STREET.IT SHALL BE REMOVED BY THE END OF T/AT WORWNG DAY,ANY FURTHER TRACKING OF MUD WILL THEN BE PREVENTED BY SWEEPING OR WASHING OF THE VEHICLES TIRES BEFORE DRIVING ON A COUNTY STREET. 7.NO MORE THAN 5D0 LF OF TRENCH ON A DOWNSLOPE OF MORE THAN 5 PERCENT SHALL BE OPENED AT ONE TIME. S.EXCAVATED MATERIAL SHALL BE PLACED ON THE UPHILL SIDE OF TRENCHES. 0.TRENCH DEWRTEMNG DEVICES SHALL BE DISCHARGED IN A MANNER THAT WALL NOT ADVERSELY AFFECT FLOWING STREAMS.DRAINAGE SYSTEMS OR OFFSITE PROPERTIES. 10.ALL STORM SEWER INLETS RECEIVING RUNOFF FROM THE PROJECT DURING SCALE:1 inch=30 feet CONSTRUCTION SHALL BE PROTECTED SO THAT SEDWENTIADEN WATER WALL BE FILTERED BEFORE ENTERINGTHE CONVEYANCE SYSTEM. 11.ALL OFFSITE CATCH BASINS IMMEDIATELY ADJACENT TO THE SITE SHALL BE DISTURBED FROM SILTATION. FIGURE 2 12 ALL DISTURBED AREAS SHALL BE SEEDED OR SODDED UPON COMPLETION OF WORK.THE CONTRACTOR SHALL BE RESPONSIBLE TO ENSURE THAT COMPLETE COVERAGE OF THE DISTURBED AREAS IS PROVIDED S THAT GROWTH OF THE VEGETATION IS ESTABLISHED. 13.CATCH BASINS SHALL TRAP SEGMENT FLIER FABRIC MUST BE SITE P LA.P PLACED UNDER GRATE UNTIL VEGETATION IS ESTABLISHED. Serving Clients inAGUA TIERRA NorthwestPacific • Provinces since 1993WATER SERVICES, March 11, 2008 Dear Mike, I have enclosed the Geotechnical Report and the other original documents you provided Agua Tierra for the completion of your HMP report. Additionally, I noticed during file archival that several attachments had been left out of the original reports you were provided. I have enclosed two updated `Attachments' cover sheets, and the additional attachments. Please replace/add in the sheets that are enclosed. I apologize for the inconvenience. Once again,thank you for selecting Agua Tierra to work with you on your project needs. We are ready to serve any future needs you may have. Sincerely, Jennifer Overton Restoration Specialist 506 Edison St SE, Suite 100 Olympia, WA 98501 P. 360.754.3755 F. 360.754.3434 jennifer@aguatierra.net AGUA TIERRA LAND&WATER SERVICES,INC. 506 Edison Street SE,Suite 100 • Olympia,WA 98501 • T(360)754-3755 • F:(360)754-3431 www.aguatierra.net Rivers,Wetlands,Lakes,Marine Shorelines,Surface Mines DATUM FOR THE SITE PLAN INCORPORATED VARIOUS TECHNIQUES AND SOURCES FILTER FABRIC MATERIAL 80'WIDE ROLLS USBRICTOSTAPLES OR WIRE RING TO ATTACH Geotechnlcal INCLUDING THE FOLLOWING: FABRIC ORE TAPING AND PACING,SLOPE MEASUREMENTS WITH AN INCLINOMETER,ANGLES AND 2'XTXI4GAUGEWARE BEARINGS USING A BRUNTON®GEO TRANSIT,SITE LOCATIONS USING A GARMIN®HAND FABRIC OR EOUNALENT HELD GPS UNIT,TOPOGRAPHIC MAPS FROM DELORME®,MASON COUNTY G.I.S.WEBSITE, Testing AND SURVEYS RECORDED AT THE MASON COUNTY ASSESSOR. GEOLOGIC SITE T RECONNAISSANCE OCCURRED ON MARCH 20,2007 AND JUNE 27,2007 BY LEVINE. 5-V AF �' Laboratory THE PRESENT RECORDED SURVEY WAS CONDUCTED BY FOREST LAND SURVEYS;THE DEVELOPED SURVEY IS DATED NOVEMBER OF 1993. THE SURVEY IS BASED UP THE PREVIOUS SHORT Tor PLATS#1981 AND#1962. AREA 27Ir WOOD POSTS,STANDARD OR BURY BOTTOM OF FILTER BETTER OR EQUAL ALTERNATE: MATERIAL IN MIT TRENCH eTEEL FENCE POSTS �s o• FILTER FABRICZXM1 S \ FABRIC R EQUIVALENT WIRE IO FABRIC OR UGE W EHT T GROUND SURFACE SR PROVIDE 34'-1 1/T WASHED O GRAVEL BACITILL IN TRENCH IT AND ON BOTH SIDES OF FILTER OFENCE FABRIC ON THE SURFACE 8'MI O 27Lr ROOD POSTS ALT:STEEL FENCE POSTS .rod AAA• z�1� � Geotechnic-�a�l Services �l��jt*10A ��SePGY. `SL-1 V'�J FLTER FABRIC FENCE NOTES: QA/QC Services CUT TO ool ��(SAS` 6FS I/ OI 1 THE LENGTH OF THE BARRIER TO AVOID USE OFJOINTS•WHENJOINTS Testing Services a G) A ARE NECESSARY,POST FILTER CLOTH TH A MINIMUM 6-INCHALL BE SPLICED TOGAND SECURELY UELY AT \ GT" QIS 7- A FASTENED AT B T H ENDS TO THE POST. OVERLAP AND 9ECURELV QIS FASTENED AT BOTH ENDS TO THE POST. ,\ 2.POSTS SHALL BE SPACED A MAXIMUM OF 8 FEET APART AND DRIVEN �Q V' a 0 , 0 G � ` SECURELY INTO THE GROUND(MINIMUM OF 30 INCHES), F� ^ �y 3.A TRENCH SHALL BE EXCAVATED APPROXIMATELY BIRCHES WIDE AND I2 10011 Blomberg St.SW INCHES DEEP ALONG THE LINE OF POSTS AND UPSLOPE FROM THE BARRIER. Olympia,WA 98512 Y \" 10 7 4.WHEN STANDARD STRENGTH FILTER FABRIC IS USED,A WIRE MESH Phone:(360)754-4612 \„ Q OOFFTHHE OSTSS USING HEAVY43UTY WIRE STAPLES AFENCE SHALL BE FASTENED SECURELY OT LEAST IINNCM THE UPSLOPE SI� Fax:(360)754-4848 LONG,TIE WARES OR HOG RINGS.THE WARE SHALL EXTEND INTO THE R W TRENCH A MINIMUM OF 41NCHES AND SHALL NOT EXTEND MORE THAN 38 VICE INCHES ABOVE THE ORIGINAL GROUNDSURFACE. 6 \ 3A gECBP Z SIFT FE 5 THE STANDARD STRENGTH FILTER FABRIC SHALL BE STAPLED OR WIRED Date: 12/27/07 QI \ �9 INTO THE TRENCTO THE FENCE H TH 20 INCHES FABRIC SHALL NOT EXTEND THAN 35 Designed b PL FABRIC SHALL BE EXTENDED VEGE `D REA1 g y: \ INOTBESCHES TA EDTOTHEEXISTINGTVE E ORIGINAL REEyRFACE.FILTER FABRIC SHALL Drawn by: PL \ 1\ 16%SLOPE 6.WHENEXTRASTRENGTH FILTER FABRICANDCLOSERPOSTSPACINGIS Checked by: CDC USED.THE WIRE MESH SUPPORT FENCE MAP BE ELIMINATED,IN SUCH QIS A CASE,THE FILTER FABRIC IS STAPLED OR WIRED DIRECTLY TO THE Dwg#: 12-26-07-104 POSTS NTH ALL OTHER PROVISIONS OR ABOVE NOTES APPLYING. �O \ 7.FILTER FABRIC FENCES SHALL NOT BE REMOVED BEFORE THE UPSLOPE \ AREA HAS BEEN PERMANENTLY STABILIZED. \ \ V GE ATE S.FILTER FABRIC FENCES SMALL BE INSPECTED IMMEDIATELY AFTER EACH PROPOSED S PTIC DRAIN SYSTEM RAINFALL AND AT LEAST DAILY DURING PROLONGED RAINFALL.ANY REQUIRED REPAIRS SHALL BE MADE IMMEDIATELY. \ 50'VEGETATION BUFF R? iI GENERAL EROSION CONTROL NOTES:QIS (REQUEST WAIVER) 1. EROSION CONTROL MEASURES SHALL BE IN PLACE PRIOR TO THE BEGINM NO OF CONSTRUCTION.THE PROJECT ENGINEER AND THE COUNTY SHALL INSPECT AND APPROVE THE INSTALLATION OF I DEVELOPED AREA EROSION CONTROL MEASURES PRIOR TO BEGINNING CONSTRUCTION. 2,EROSION CONTROL MEASURES ARE NOT LIMITED TO THE ITEMS ON THIS PLAN.THE CONTRACTOR IS RESPONSIBLE FOR THE ALTERNATE INSTALLATION AND MAINTAINANCE OF ALL EROSION CONTROL MEASURES. NO SILTATION OF EXISTING OR PROPOSED DRAINAGE FACILITIES LIMIT OF LANDSLIDE HAZARD AREA NORTH SHALL BE ALLOWED.CARE SHALL BE TAKEN TO PREVENT MIGRATION PROJECT NAME: SCALE 1"=30' OF SILTS TO OFF SITE PROPERTIES. 3.THE CONTRACTOR SHALL MAKE DAILY SURVEILLANCE OF ALL EROSION M cG RA W SITE C.I.=5Ft. CONTROL MEASURES AND MAKE ANY NECESSARY REPAIRS OR ADDITIONS XXX NORTH CANAL HIDE A WA TO THE EROSION CONTROL MEASURES.THE CONTRACTOR SHALL PROVIDE ADDITIONAL EROSION CONTROL MEASURES AS DETERMINED NECESSARY By THE COUNTY INSPECTOR AND/OR THE PROJECT ENGINEER.FAILURE L I L L I WA LI P, WA S H I N G TO N TO COMPLY WITH ALL LOCAL AND STATE EROSION CONTROL REQUIREMENTS MAY RESULT IN CIVIL PENALTIES BEING LEVIED PARCEL 323305106007 AGAINST THE CONTRACTOR AND/OR PROJECT OWNER. 4.DURING THE WET SEASON(NOVEMBER TO MARCH)ALL DISTURBED SOILS 0 10 20 30 SHALL BE STABILDE0 WITHIN 48 HOURS AFTER STOP OF WORK EROSION CONTROL MEASURES SHALL INCLUDE.BUT NOT BE LIMITED TO, 6,:rN 17N AI(I COVERING THE EFFECTED AREA INCLUDING SPOIL PILES NTH PLASTIC SHEETING,STRAW MATTING,JUTE MATTING,STRAW MULCH, OR WOOD CHIPS.SEEDING OF THE DISTURBED AREAS SHALL TAKE PLACE AS WEATHER PERMITS. 5.ALL SEEDED OR SODDED AREAS SHALL BE CHECKED REGULARLY TO MAKE SURE VEGETATIVE COVERAGE 18 COMLETE.AREAS SHALL BE REPAIRED,RESEEDED,AND FERTILIZED AS REQUIRED. S TRACK' NO OF SOIL OFFSITE WILL NOT BE ALLOWED.IF ANY SOIL IS TRACKED ONTO A COUNTY STREET,IT SHALL BE REMOVED BY THE END OF THAT WORKING DAY.ANY FURTHER TRACKING OF MUD WILL TIER BE PREVENTED BY SWEEPING OR WASHING OF THE VEHICLES TIRES BEFORE DRIVING ON A COUNTY STREET. 7,NO MORE THAN 500 LF OF TRENCH ON A DONNLOPE OF MORE THAN 5 PERCENT SHALL BE OPENED AT ONE TIME. 8,EXCAVATED MATERIAL SHALL BE PLACED ON THE UPHILL SIDE OF TRENCHES. 9.TRENCH DEWATERING DEVICES SHALL BE DISCHARGED IN MANNER THAT WILL NOT ADVERSELY AFFECT FLOWING STREAMS.DRAINAGE SYSTEMS OR OFFSITE PROPERTIES. 10.ALL STORM SEWER INLETS RECEIVING RUNOFF FROM THE PROJECT DURING SCALE:1 inch=30 feet CONSTRUCTION SHALL BE PROTECTED SO THAT SEDIMENT4ADEN WATER WILL BE FILTERED BEFORE ENTERING THE CONVEYANCE SYSTEM. 11.ALL OFFSITE CATCH BASINS IMMEDIATELY ADJACENT TO THE SITE PROTE FROM SHALL DISTURBED EA SHALL ESEED, FIGURE A 12.ALL DISTURBED AREAS STALL H SEEDED OR SODDED UPON COMPLETION L)OF WORK THE COVERAGE F THE STALL BE RESPONSIBLE TO ENSURE THAT COMPLETE COVE RAGE A THEDISTURBED AREAS I6 PROVIDED.THAT GROWTH OF THE VEGETATION IS ESTABLISHED. 13.CATCH BASINSSHALL TRAP SEDIMENT FILTER FABRIC MUST BE SITE PLAN PLACED UNDER GRATE UNTIL VEGETATION IS N IS ESTABLISHED.