1315 PACIFIC AVE 2018-01-01 MF Import

rccommend a vapor ba�cr u ith bonded scams ha��ing a minimum thickness oC 10 mil be placed over the capillary brcak laycr. Below Sla6 Drainape We expect the static groundwater level to be located below the slab-on-grade Ievel tor the proposed building; however, perchcd groundwater may be prcsrnt above the slab subgrade elevation. It may be appropriate to install an underslab drainage system to remove water from below the slab-on-grade. The soil unit at Ihc slab clevation consists of glacially consolidatcd sand with silt. Perched groundwarer sccpagc should bc anticipated above thc undetlying till. We recommend ihat a contingency be included in the budget for a full underslab drainage systcm as presented below. [f necded, we mommend that the underslab drainage systctn include an interior pe:imeter drain connectcd to an cast-west longitudinal drain running under the cenier of thc building. The drains should consist of a minimum 6•inch-diameter perforatcd Schedule 40 PVC pipes placed in a trcnch at Ieast 12-inches deep. Thc top oC the undcrslab drainage system trcnches should coincide with the base of thc capillary break layer. Thc underslab drainage system pipes should have adcquate slope to allow positivc drainage to thc sump/graviry drain. Thc drainagc pipc should bc cithcr machine slotted or perfuraled. The slots should be a maximum of 1/8-inch wide with 4 slo4c per inch and cxtend the lower 60-degrce perimeter of lhe pipe. Pcrforated pipe should havc two rows o( 1/2-inch holes spaced 120 dcgrecs apart and at 4inches on-centcr. The undcrslab drainagc systcm trcnches should be backfillcd wilh pca gravel, or WSDOT Specificat:on 9-03.12(4),Gravel E3ackfill for Drains,or altemativc approvcd by GeoEnginecrs. The underslab drainage _rystcm pipes should bc routcd to a sump or gravity drain. Appropriatc cican-outs for drain pipe maintcnance should be installed. A larger diametcr pipe will allow for easier maintrnance of drain systems. If no special watctproofing mcasures are taken, Ieaks/seepage may occur in localized arcas of the below-grade portion of the building, cven iC the rccommended wall drainagc and below slab drainage provisions arc constructcd. If Icaks/seepage is undesirablc, bclow-grade waterproofing should be s��r�a. SUBSURFACE WALLS Subsurfacc w�alls will bc coaswctcd arowid Ilic sitc perimctcr. Latcral carlh prcssurcs for subsurface walls dcpcnd on Ihc typc of backGll matcrial, groundwatcr Icecls, compactivc cffon on backfill and amount of wall yielding. Wc recommcnd Ihat subsudacc walls be dcsigncd for lateral prcssures based on a uniform lateral prcssurc of 26}1 where 11 is thc height of the wall. Additional lateral eanh pressure duc to scismic loading should also bc included in thc�csign. Wc rccommcnd a unifortn latcral pressurc of 8H bc uscd in seismic dcsign, whcrc H is the height of ihe wall. In addition,the caAh prcssurc values prcsented above do not include the etTecls of surchargcs (floor loads, tra�c loads, or uther sudace loads). Surchargc eflects should bc considcrcd at appropriatc as shown in Figurc 5. Wc recommcnd that, wlicrc uscd, fill placed against permancnt walls should be compacted Io bc[wecn 90 and 92 perecnt of maximum dry density detennined in accordanee with ASTM D 1557, with hand-operaled compactors within a 5•feo� zonc bchind thc walls. O��cr-compaction near the wall should bc avoidcd Io rcducc latcral pressures against thc back of thc walL Rccommcndations for selection and placemcnt of bacl:fill arc prescntcd in a follaµing scetion. I��tr�.�'o. 177L-onl-o0 Pagr 11 GEOEMGINEERS� Junr n.1011,v ��