1718 ENGLAND AVE 2016-01-01 MF Import

IGcotcchnical Enginecring I:valuatiun England Avcnuc Lot � lunc 2, 2005 NGA File No.411305 Page 12 ( Permanent drainage systcros should be installed for retaining walls. Recommcndations for these systcros � are found in the Sul,surface Drainagc subscction of this rcport. �Ve recommend that we be retained to Ievaluate tlie proposed wall dmin backfill material and drainagc systems. � Site Drainagc S�rfacc Drainage: Final sitc grades should allow for dr.�inage away Gom the top of the slecp slope and � away from thc pl:mncd residence. Ne suggest that thc finished ground bc sloped at a minimum gradient of 3 percent for a distance of at Icast 10 feet away from the buildirg and top of slopc. RunoF(gencrated 1 on this site shotdd be collected and routed into a perm.men[ discharge system. This should include all downspouts and runoff gcncratcJ on all hard surf�accs and yards arcas. Undcr no circumstances should v.�atcr bc allowed to flow uncontrollcd ovcr thc slopc. �'V.ucr should not be allowcd to stand in any arca Iwhere foolings, slabs, rockeries.or pavenunts are to be constn�cted. ISubsurface Drainagr. If ground�eater is encountercd during constniction, we rccommend that the ( contractor slope the bottom of the excavation and collect the water into ditches and small swnp pits where thc w�ucr can bc pumpcd aut of thc cscavatiun and routcd into a pcnnanent stonn drain. IR�c rcconuncnd Ihc usc of laatin,dr.iins amund stnicturcs. I�aoting drains should bc installcd at Ic�st onc I foot bclow planncd finished floor cicvation. 'Phc drains should consist of a minimum four-inch-diamctcr, ! rigid, slottcd or perforatcd, ►�vc n�� ,��«o��„a�a �y frec-draining m;ucrial wrapped in a filter fabric. Wc rccummend that the free-draining material consist of an IS-inch-wide zone of cican Qess than three- � percent fines), granular material placed alono the back of walls. Pea gravel is an acceptable dnin material or drainagc composite may also be used insteaJ. The Gce• raining ma�erial should extcnd up the Iwall tu one foot below the Gnished surface. The lop foot of soil should consist of impemieable soil placcd over plastic sheeting or buildino paper [o minimize surface water or fines migration into tha Ifooting drain. Footing dnins should discharge into tightlines Icading to an appropriate collection anti Jischarge point with convenient cicanouts to prolong the useful life o(the dr.iins. Roof drains shoulJ na bu conncctcd to �vall or footine dr.iins. I I NELSON GEOTECHN/CAL ASSOCIATES, INC. I I