REMOVAL_1985 - Laserfiche WebLink

Home Browse Search

GROUND WATER REMEDY TTON The RWQCB feels the InteriM.Sits Characterization Report (29 July 1987) is incomplete since the vertical extent (i.e. , deeper zones) of contamination and offsite contamination have not been assessed. Unocal is interested in moving forward with onsite interim ground water remediation to remove the bulk of contamination before further offsite migration occurs. Unocal wishes to prioritize ground water remediation efforts at this site by implementing onsite remediation first, followed by offsite remediation, if necessary. Offsite contamination may be reduced by the proposed onsite pumping. Agreement was reached to proceed with deep zone detection monitoring prior to finalization of the interim onsite ground water remediation plan. Based on the water quality found in the deep zone, the plan will be modified or finalized for implementation. Plates 1 and 2 provide in a flow diagram format the direction and steps required to implement the interim onsite ground water remediation plan. In addition there was discussion concerning the water quality of a nearby irrigation well located at the southwest corner of Pacific Avenue and Robinhood Drive and operated by Delta College. This well is located down gradient from the Unocal property. Ground water samples were collected on 22 October 1987. Low concentrations of toluene (1.16 ppb), ethyl benzene (0.15 ppb) , and total xylene (0.52 ppb) were detected from collected water samples. Benzene was not detected. Total petroleum hydrocarbons using EPA method 8015M were not detected. A concrete pit located near the irrigation well was observed to contain water and what appeared to be lubrication oils. A sample of the liquids from this pit detected the following concentrations: benzene (33.4 ppb) , toluene (7.49 ppb), ethyl benzene (ND) , total xylene (0.85 ppb) , and TPH (ND) . A copy of these results is provided for your convenience. Construction details or a lithology log for this well is not available. After brief discussion of the water quality from this well along wit4 the presence of lubrication oil in the vicinity of the well, it was concluded that the source of low contamination could occur from pump lubrication, oils, the Unocal gasoline plume, or a combination. Unocal wishes to move forward with completing site characterization and site remediation. The required tasks will be phased. At this time, Unocal intends to proceed with installation of the deep zone monitoring well and with the final design of the VES, in accordance with the logic on Plate 1. K0 FINFFI nFR 07QG A,,6--, P.4 n.;,.,,