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Grading Ext Request BLD2014-0317 Saunders 15911 74th Pl W.pdfGeotechnical Engineers, Geologists Group Northwest, Inc. & Environmental Scientists GEO December 31, 2015 Mr. Leif l3jorback City of Edmonds 121 - 5h Avenue North New SFR at 15911 - 74' Place West, Edmonds, WA BLD2014-0317 MM39fiLmam On behalf of the client, Mr. Leroy Saunders, a new grading extension is requested. The contractor was not able to finish all the site earthwork within the allotted time period of the previous grading extension. The following earthwork items need to be completed: 1. Placement of rock and fabric in the seepage zone area east of the catchment wall; 2. Construction of the swale on the east side of the catchment wall and house; 3. Installation of the two stormwater CBs at the end of the swale east of the house; 4. Connection of street utilities to the house (power, gas, phone and cable); 5. Reshaping the slope between the driveway and west side of house. 6. Normal erosion control, including cleanup and rocking the driveway entrance. Completion Date With weather and reduced light considerations, the anticipated completion date for the above items is January 31, 2015. On January 31st, the site will be winterized in accordance with our previous submittal. Any remaining earthwork will be stayed until after May I't, 2016, unless the site is reevaluated by the geotechnical engineer of record to confirm that the site conditions are stable and work may start without creating erosion issues or affecting site stability and the site evaluation is submitted for approval by the City prior to re -commencing work. Site Stability Evaluation The site is currently stable and it is our professional opinion that the remaining earthwork will not negatively impact the stability of the site and the earthwork may continue through the end of January from a site stability and geotechnical perspective. 13240 NE 20th Street, Suite 12 Bellevue, Washington 98005 Phone 425/649-8757 FAX 425/649=8758 December 31, 2015 Grading Extension Request Page 2 New SFR, 1591174' Place W (BLD2014-0317) Temporary Erosion and Sedimentation Control (TESC) It is our opinion that the TESC methods used at the site up to this point have been satisfactory. No offsite erosion control issues have been observed. We plan to continue monitoring the effectiveness of the site's TESC, making modifications and replacing the TESC as needed. The principal TESC measures being used include: 9 Silt fencing. • Covering exposed soils with visqueen plastic and stabilizing the plastic with sand bags. • Covering other areas of exposed soil with straw mulch. • Maintaining the rock construction entrance. • Maintaining the erosion control measures in a good condition. Zn • Halting all earthwork activities during storm events and protecting exposed soils with visqueen plastic. The geotechnical engineer is monitoring the site weekly, or after storm events, and the reports are being submitted to the City. It is our opinion that the erosion control measures being used are sufficient to mitigate offsite impacts. From an erosion control perspective, it is our opinion that completing the remaining earthwork as soon as possible is better than waiting until next spring when the site soils will be more saturated, be more difficult to work with, and have a greater erosion potential. Sincerely GEO GROUP NORTHWEST, INC. Wade J. Lassey, LEG Engineering Geologist William Chang, P.E. Principal \-\P,M C of WASp, 1441 2i}114 NAL GEO Group Northwest, Inc. A,_