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Langston Is Alarket, i T615 Onth'
<br /> .Vtreet,Lathrop, California December 12, 1995
<br /> Phave rlLatLral& 1"ertical Ettent ofSecond Page• 3
<br /> Grounthpater Aquifer Work Plan
<br /> The water table via., measured at app;oxiwatwly 161,2 fw. t uclk),Y ,;iciiind levet The four existing
<br /> groundwater mon�toririg wells were then aband med, under permit, to avoid the possibility of
<br /> cross-contamination Excavanc-i of uncontaminated soil continued down to approximately 15'/2
<br /> feet below grou rid level Excavation of contaminated soil continued down to an a-v erage depth of
<br /> 25 feet, with the aide of a de-watering well Contaminated scil was tnicked directly to Forward
<br /> Landfill, Stockton, Califorwa and storkpiled for char act er izat�on and di3posal Pumped water
<br /> was treated ano discharged to Vh,_ City of Lathrop sewer system and City of Manteca treatment
<br /> plant After the excavation had Yrogrme-1 to its maximum limit due to roads and utilities,
<br /> compacted backfilling began Replacement of the groundwater monitoring wells was conducted
<br /> between Septembe, 21 and 23 1995
<br /> The interim renvcdial e,cca-at,cia ienioVed the secondary source of soil contamination in the area
<br /> of the former undeig,ou„d Stnrdge tank The de-watering of the excavation significantly reduced
<br /> the groundwater contamination plume Coptamiraticn was detected below the "Stockton Bliie"
<br /> clay in boring EWA 'No contama-wion was deteAed at this interval in any of the other borings
<br /> I
<br /> 30 Work Plait
<br /> This work plan has been developed for the purpose of conducting three (3) soil bonngs through the
<br /> second aquifer and completing each as a monitoring well These wells will be d-scretely screened for
<br /> rthe purpose of defining the gractient and direction of the second aquifer ,gi oundwater, and to determine
<br /> both vertical and lateral extent of .lie contamination i ed nti�e rc�n the well replacement phase of the
<br /> interim remediation The locations of the three (3) wells are proposed as shows, oa Figure 2
<br /> 31 DnIling
<br /> Permits will be obtain, 0 a,, x�c.cssai,j fv: all wells {ii,clw ung bu.ings) before drilling begins
<br /> The soil borings will be accomplished using a mobile mounted drilling rig employing the use of
<br /> a hollow stem flight auger no less than 3 1,14" i d and 8" o d
<br /> All drilling equiprnera will be tharoughly steari-cleaned before ,drilling begins to prevent the
<br /> introduction of cont unination. from off site, and bei ween borings to prevent cross
<br />' contamindtion
<br /> The borings will be loggel undtir the direct suvet-,iskon of a registered piofestiional using the
<br />' Unified Soil (:lassificat or. Fystem l l-igui e :) The c,-)isx, temure, rr.,nsiui c plasticity (if
<br /> applicable), consisteiiLy of the wa► maletials, perrinent zuil of bediock charac.rcristics and any
<br /> evidence ofcojitamAnation•witf be nntcd Adl wuti,i b; a:insy zcgn�,� a o the deniti-, at %vhtcli they
<br /> were enc ounterod will bti: rioted or, dic,,e lags
<br /> All borinAs will he dil',ILf Eli ScicL d niannei as to prevcr L c,cmta;:matioii between strata
<br /> Exploratory soil borino<< `,airbus the urr;atwateil zine ",ill be ba.,kfillyd with a cement and three
<br /> percent (3%) �;ntontte nv Ytm e
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