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Civil_&_Geo_Final_Report.pdfo�irrww voo o �wwmmArmxa w,ea�w.wwro ..........v�ww wux�mmmm�rmm�mm�mm �����u ww.0 iumw. vvuvwvrnruv,G;amuuuuuoom� v:m oru amu�M�v�awwuuasam�u� im^®wrvwimwwmw.r nm uuuvouuuo�snmmmm�mmiuwwmu�w!��,w,au ebmoowowuw�o�aivm�m Date: October 16, 2015 To: Jennifer Lambert City of Edmonds From: Andrew Reaves, P.E. Principal Subject: Wiskerchen Residence As -Built Utility Plan Dear Jennifer; Attached please find the second submittal as -built plans for the Wiskerchen Residence, located at 645 0 Avenue N. I have responded to all comments in your October 9, 2015 corrective Notice. I have also re -ran calculations for the as -built storm drainage infiltration trenches with the additional offsite driveway area accounted for, using the required PS 36 East precipitation time series All other corrections to the model as requested by Jerry Shuster have been made. All trenches infiltrated all flows 100% with the design infiltration rate provided by the project geotechnical engineer. See calculations for the trenches in appendix A. Julian Liu, the project geotechnical engineer, has provided an as -built memorandum per your request, it is attached in Appendix B. IPS/I IP", K omuru�u�uwuuu m®ouawruu�w�wmuwuww.w.w�mvwm e�m��.����JH r� H. an.:.uJu uuu �uuuowwomwnmm�mwarauwvui mo�wwwv�wwirmwiwmmrepmimr�mom�nnm. r n�r�Mrm.. v�w.�;rvwwmmuw�moomwmoi orca�ro�uwouuww�.wx��swn SDA 1724 W. Marine View Drive; Suite 140 P: 425.486.6533 Everett, WA 98201 F: 425.486.6593 1r ' 1r" 1w yrs �uvurw�;: �rmwas ,ommu a uvemm —n.WI u u u u u I. 'Ili 61. w. .11 . I ijia n>rrvouMora am 0� y1UoouU U U U U U UIIIIIu— U U U U U IouooU 000u U Uu-_nmrmuuwrt�momoummonio 001 a I,uowro000 m Appendix A - As -built infiltration calculations .................. w..". �� ��, eA . ....... _ _ SDA 1724 W. Marine View Drive; Suite 140 P: 425.486.6533 Everett, WA 98201 F: 425.486.6593 II IiMrydmped null sommo Deselect Ze'. R.si.T.W [aI5 - _1Am SRIRr-.1 Rv-F-- GO This is the basin to the infiltration trench, with the additional driveway area added, total area to trench is 0.15 ac, which includes all the offsite driveway areas and roof area. , 1724 W. Marine View Drive; Suite 140 P: 425.486.6533 SDA Everett, WA 98201 F: 425.486.6593 Subbasin Nani I— . ...... F DesignalemBypanImPOC, Sudac"S" Inteillow Groundwater Flows To: fm�� Area in Basin I- Show Or4-S*cmd• Available Pervious Avri Timparvious ..... ...... I tgf­ .. .. .. . . . APIS r Atat;gff I jib", LIM6 FIN1�� . . ........ I',t WW 61,'e M F 7f AA Ao�, JI'5 Jur A, . ........... . io, ............ iP ILwrn Md Arses Deselect Ze'. R.si.T.W [aI5 - _1Am SRIRr-.1 Rv-F-- GO This is the basin to the infiltration trench, with the additional driveway area added, total area to trench is 0.15 ac, which includes all the offsite driveway areas and roof area. , 1724 W. Marine View Drive; Suite 140 P: 425.486.6533 SDA Everett, WA 98201 F: 425.486.6593 T IJ FeeflWyNaikkke j Outlet'i Outlet oullell 3 Downstream Connection Facility Type i6kam 1 00"ChAird I– Precipitation Applied to Facilly C, Facility Bottom Elevation Facility Dimensions Trench Length Outlet Structure Trench Bottom Width Rim Height (o F4.5 Effective Total Depthrpr Rimi Diamseiiiin) Bottom slope of Trench ou t Riser Type FF—W--- Left Sid. Slope ,r— Notch Type Right Side Slope it Material Layers for Layer 1 Thickness (ft) Orifice DimmeterHeight GMax Layer 1 porosity Number (in) (Ft) We Lays 2 Thickness (It) 0 Layer 2 porosity 2 ro" 0 Layo:3Thickrmss(l1) .... .... . .... I Fo— �A ld------- Li 0 Lays 3 porosity infiltration R$ --.!A Trench Volume at Riser Head (acre -ft) WO Moas...d Infirstim Rake nrAvt r4 Porti Increment Infiltration Reduction, Fucker Sbow Pond Table Use Wetted SwlaceA— (sidewalls) rVE-§ Total Volume Infillialed(ave-11) 57.291 Total Volume Through F.drly[acre-ft) 57.291 TokalVolumeThrough linsei(acie-ft) 0 lua-m InWated ion This is the WVVHM3 model after it has routed all rainfall events thru the trench, as is shown in the bottom right hand corner, the events infiltrated 100%, using Julians 4 in/hr design infiltration rate. This is utilizing the Dot time series per city of Edmonds code supplement in chapter 5.7 (Puget sound 36 precipitation) 1724 W. Marine View Drive; Suite 140 P: 425.486.6533 SDA Everett, WA 98201 F: 425.486.6593 Appendix 'B" - Geotechnical Letter of Site Stability 1724 W. Marine View Drive; Suite 140 P: 425,486,6533 SDA Everett, WA 98201 F: 425.486.6593 I J U & ASSOCIATES, INC. Geotechnical Engineering Engineering Geology Earth Science October 15, 2015 Mr. John Wiskerchen 16531 Broadway Avenue Snoho2nish, WA 98296 Dear Mr. Wiskerchen: Subject: Certification of Onsite Stormwater Disposal System Wiskerchen Residence 645 — 9h Avenue North Edmonds, Washington L&A Job No. 12-069 Prior to its development the subject property had remained vacant for many years; and the property and the rockery lining its west side had remained stable for all those years. The total amount of stormwater falling on the property in its pre -developed condition was basically the same as it is under the current developed condition, except that stormwater now is collected and reintroduced into the ground through infiltration trenches and drywell. In order for the groundwater flow pattern under the current condition of the property to simulate the pattern of the pre -developed condition, we recommended that the infiltration facilities be spread out over the property to minimize potential concentrated groundwater flow and, therefore, minimizing potential of groundwater seepage. The stormwater infiltration system was completed in April 2014, and it has undergone one full winter cycle. Since then, there has had no signs of erosion or soil movement or groundwater seepage within the property, and the rockery and slope below it have 19213 Kenlake Place NE - Kenmore, Washington 98028 Phone (425) 483-9134 - Fax (425) 486-2746 October 15, 2015 Wiskerchen Residence L&A Job No. 12-069 Page 2 remained stable. Based on the above, it is our conclusion that the as -built onsite stormwater disposal system has performed and functioned as designed. Please feel free to contact us if you have questions. Yours very truly, LIU ' ASS(Cl( INC. J. S. (Julian) Liu, Ph.D., P.E. Consulting Geotechnical Engineer LIU & ASSOCIATES, INC.