2408 RAVENNA ST 2016-01-01 MF Import

�. � . (ieotechnical Engineering Report � Lowell Short Plat ]une 2, 1999 NCA Pile No. 359499 Page 11 In5ltrxtiou Areas We have used ibc United States Departrnent of Agriculturo (U.S.D.A.) soil group classificadon (Figure III-3.]) as prcsenud in Uie "Storm Water Management Ma��ual for the Puget Sound Sasin" (&:olopy 1992), to classify t6e soil samples analyzed. Based on our visual evaluetion of ihe soils observe� the material is classified as s I�atny sand. Hased on this manual, an infi!tration reu of 2.41 iaches per hotv should be used for the desi�of the in6ltration system,as indicated on Table III-3.1 for soila classified ac a loatny sand. Silt was observed to a depth of 4 feet in Test Pit 4, near the plsnned infittration trench in Lot 4. Slight ground water seepage was ohsErved within this exploration at a depth of 8 feet. Silts whete encouatered, should be overoxcavated down to the underlying sanda end be teplaced with pea grevel or other 5ee draining material. The bottom of Lfie trench in Lot 4 should be above a depth of 5 fiet m maintein a 3- foot seperetion betweea seasonal high weter and the bottom c:'the trench. Infiltrarion should not be used in the east half of the site due to existing fill and shallow ground water seepage. The soils in the plwnned infiltraaon area� are ��atiable and eilt leyers may exist whioh Could affect . infiltrati�n rates and paths. "Ib�e soils at the planned infittration depths were generally sends suitable for infiltration, however the silt leyers could become close W the infilhatioa trenoh in some eraes. We recommend that overElows ba installed in the event thei actual infilhxtion rate ie not su$Icirnt due to silt layers which limit watrs flow. The overflows would be a precaudonary measme. Wo expect that tlroy could be routed to the nearby wetland. � Drainage Footing drain systems should be used aroend the perimeter of the planned buildiqgs due to the observed subsurface water and tha plenned infiltration systems. The drains should be eonstructed similer to svell drains as described in the Leterxl Pressurd subsection of this roport. The footing subdrain should be tighUined to discharge into an appropriate stotm water disposal azw. We ezpeet that they could be routed to the wetland erea. ' Appropriste moistwe control should be utilized in slab areas. Measures taken s6ould iuclude providing a suitable capillary break and vapor bazrier for slabs-on-grade and sloping crawl apaces to drain. Capillary breeks aod vapor barriers should be used for slabs in eny csse where moisture concrol is important M outlet drain should be imstalled to allow water that may accumulate in a crawl space to drain from the NELSON-CDUVRE'TTE &ASSOClATES, lNC. �