3505 SHORE AVE 2016-01-01 MF Import

GeotxhnicalEnginecring Leuer 3505 Shoro Avenue Deck Addition Evcrett,Weshington May 26,2010 NGA File No.827110 Page 11 excavate and romove wct soils in cases where drying to e compactable wndidon is not feasible. All compaMion should be eccomp6shed by equipment of a type and size suf6cicnt to attain the desucd dcgroe of compaction. Slab-on-Grade Slabs-on-grade sl�ould be supported on subgradc soils prepered es described in the Site PrepsraUoo�od Grading subsection of this letter. Where moisturz convo] is important, we recommcnd that all floor slabs be underlain by at least six inches of free-diaining sand or gravel for use az a capillary brcak. We recommend that the capillary break be hydraulically connccled w tha footing drain system to allow frce drainage from under the slab. A suitable vapor bamer, such aa heavy p�astic shxting (6-mi1 minimum), should be placed over the capillery break material. Site Drainage Snrface Drainege: Fina] site gradcs should allow for drainage away from the cop of the steep slope and away from t6e residence, We suggest d�at lhe finished �ound be sloped at a minimum gradient of duec percent for a distance of at leest 10 fce: away from the building. Runoff generated on this site should be collected and routed into a permenent discharge system. This should include all downspouu and runoff generated on all hard surfaces and yards areas. Under no circumstances should water be allowed to flow unconVolled ovcr the slope. Water should not be allowed to collect in any arca where footings, slabs,or pavcmen[s are to be consWcted. Subsurface Drainage: If groundwater is cncountered during conswction, we recommend that the contractor slope the bottom of lhe excavation and collect the water into ditches end small sump pits where tUe water can be pumped out of tbe excavation and routed into a peimanent storm drain. We recommend the use of fooring drains azound stiuctures. Footing drains should be installed at least one foot below planned 6nished Iloor elevation. The dreins should consist of a minimum four-inch�diemeur, rigid,slotteA or perforated,PVC pipe sucroundcd by free-dcaining matcrial wrapped in a filter fabric. We recommcnd that the free-draining materiel consist of an 18-inch•wide zone of clean (less than three- percent fines), granuler matcrial placed elong lhe back of walls. Washed rcek i^+ en accePtable drein metcrial or a dreinage composiu may be used. Thc freedraining mateiiel should eztend up the wall to NELSON GEOTECHNICAL ASSOCIA'IES, INC. �zl��