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I Y M1805 Harbor, Stocktoi-i ' ('Al'-A Approval Page 2 ' concentratioa of the B2 soil sample (f32 was located about 20 feet soutlleast of MW 2 and near the lateral txtLnt of the excavation proposed in altex7jadVL Al) was 4,100 jng/Icg at 15 feet bgg Acwrtling to Region Two Water QUAhty Control Board estftbhshed r,nvirunmcntal SctLcii levels (ESI.),wlltcuh CVRWQCR has begun using,and which was also refetenced in the discusbion of Al of ' the CAP-A, 500 ins/kg of Total PLtrpICUM Hydrocarbons (mtddle distillates)is thL aSI, for clap soil(>3 inCtLr-i b-,F) for both residential land use its wen as cominereial/industrial land use, and where groundwslrer is not a curt crit or potential SourCL of drinking water. Based on the soil data and ' HSL,CVR\VQGB and MTD agreed that the excavation should exrend w 25 feet bsg ut the source arca in order ro enhance the potenu.jl reduction of the contarninatioll to a most acceptable lcYvel of risk Cnr'1111I-d ' LI ll) reconjou nds evaluating dinner treatment altemattves for the excavated soil to reduce casts, such as land farthing instead of tr;uibporring and thgpo%ing the impacted soil to ail orf-site facility, H&II estimated $22K to$26K for uff-sire disposal of tillpactLd gntl This cost can be significantly rLducvd if the soil Lould be land-farined on site, and may irnprove the cost-effectiveness of option Al H&H tnfoicnally inlet with EHD on Apel 11,2005 at the Conti Group fatuity at 9504 IIarlan Road ;tstd dlbeasged the possibility and bcncfits of over-cxcitvatingwvitholit slionng. 11f4() agrLL5 wt(lt I f&1 i thac excavaling without shoting,has the flextbility to Adjust the extent of the excavation b ised ' . nit Geld obsLrvattatl W iethLl or not shoring is einploycd, }:IID requires that the:excavation to reach at least 25 feet ling in the source area I)unng quarterly monitoijttg evi-ntg,pujnl)tlig o 5 tcj 10 gallon/nitnute,.educes the water level in pumptoig wtll by 0 2 fret to 2 4 feet,so dewilenng may be prollleillatic E D encotitages you to evaluate the option of securing froin City of Srockton a pctinit to discharge the ti cared groundwater to publicly owned treatment works (PO'1%Xo to order to furthcL tednc.e tha cast of nlition Al I'lem submit the excuvarlon d,-sign and a veilficatintl of the ' lust Gstimate IIrLparLd and signed by an appropriate California-ltcetibcd pmfessronal engineer or erippic•ciing geologist All rcl)orts submitted to this agency that contain caginecting or geological interpretation must be prepared under rile superviston and bigned by the appropriately Caltfointa- 1iCLnst d ptnfessional(s) having responsible charge of the work preltiTrLd or reported ' R1 ID requires arty wells that might be impacted or damaged be properly destroyed bcfole ittll�l(-rnLntaiiolt of thL excavatlort Tliese wells should be replaced after the complctlotl of the work ' for post romediation monitoung Submit a worts plan to EIID that includes bath thL above- t tlri1t1o11Ld c%covation design, and destruction and rf placement of any Impacted wells to P-111) by Juste 20,2005. The work flail should also,address downtcsrmg issue, cumber of wells,putrilaittg tate, ' Ireatimcrit and disposal Proposal!"a,; well as hkc hhood of City of Stockton granling pt rmisston to dischArge post-trcaUnclat extracted groundwater to 110TW If you have any questions,please feel free to contact Jeffrey Wong at(209) 468-0335 Donna l fern,RE)IS,Directut Ilcwtrcl nttxuiall flctilill Department t ,VIJq effrLy Wong,Sensor RIiHS Nuel Hendersoii,jr,P(G LOIS/Site Mitigation Unit 1V LOP/Site Mitigation Unit IV C AWQGI3,Ccrltcal VallLy Region--James J. J.. Barton ' C t 11(f&Huff, Inc —Linda I tuff,PE,512 W Burlington AvLnue,Suite 100, 1 iGrtingc,IL 60525