3313 SMITH AVE 2018-01-01 MF Import

Marcli 3Q 2009 ' � HWA Projcct No. 2009-030-21 3.3.2 Footing ovcr I�.xcavation Considcrations All exisling fill matcrial encountcrcd in foundation cxcavations should be ovcr-cxcavated down until the native clny is cxposed. Thc cscavation should bc replaced wiili structural fill to the requircmcnts fbc sVuctural fill as described in Scclion 3.C.1. The horizontal limits of ovcr cxcnvation should cxtend 1 minimum distanoe from cdge of footing equal to thc dcplh of over excnv�tion. This will ensure tnat tho zonc of iniluence of the footing will be distributed completely in competent compactcd stn�cturul fi�l. Poundntion over- � excavation and replacement should be verified in the field by the,`gcotechnical cuginecr prior to constructing uny footing. lluc to the relntivcly wide spacing of thc existing gcotcchnical duta,vuriation in fill thickncss is difficult ta detcrminc at present;thc vuriations in fill thickpess will be more accuratcly defined during construction. Wc therefore recommend an obsc�ational approach during constraction to dcicrmine the depth uud lateral limits of over-cxoavntion. Por estimatiou purposes,an uvernge depth of ovcr-excavation and structural•fiil rcpl�cement of ahout 3 fcet may be ussumcd. We recommr�;l the ovcr-cxcavation and suvctural fill placcment be bid on a unit cost basis. 't 3.3.3 Sctticment Considcrations � Due to thc presence of approximatcly 25 feet ofbompres.sible cluy below the project site, bcnring cnpacily of shullow footings will be controlled tiy allowable settlemcnt rather th.u�ultimatc bcuring capaciry. 7'o dctennine that magnitude of anticipated footing settlemcnt,under varying Ucariug capncities and footing geometrics, compressibiliry indiccs for th;noimully consolidated clay wcrc ncedcd. 11WA(1999) periormed consolidation testing on day s�uuples from Uorings III[-2 and i3i-1-12. Thcsc boriugs DII-2 aud 13H-12 were drillcd approximatcly 1100 and 900 feet awny froin tlic IlR'C sitc respectively. 1lowevcr,based on thc relatively unifom� cousistency of tiic clny deposit across the transit stntion corridor(Yacific Avcnuc to the I3R7'sitc),we conchidcd tliut thcse samplcs urc represenmtivc of thc entire clpy deposit. Ow•consolidatiou tcsts o�i the clay sumples indicated a compression indcx (C�) ranging from 0.08 lo0 0.18. We took thc I�iglier vnluc, C�=0.18,for conscrvative foundation desigtt purposes. Using lUe abovc stftted compression indcx (C�),an ussumcd 2V:111 vcrtical slress distribution,and slandnrd one dimensional consolidntion theory,we computcd foundation setllcmcnis for vnrying.�pplicd Uearing pressures versus squnre footiu�width. The resulls of these calculations are prescnted in Pigure 3 of this report. It is our recotnmendalion that the sL uctural eng�-�ecr utilize the infonnntion presentcd in Pigure 3 zoo9-o�o z i o:,n��A S HWA GeoSc�eNcr•_s IHc /