ARCHIVED REPORTS XR0009933 - Laserfiche WebLink

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EA �V L) Sampling Plan - 152 East 11th Street, Tracy, CA �� Page 8 ENVIRONMENTAL HEALTH NAV 2 PERMIT/SERVICES • The following wells on the perimeter of the affected area will be sampled to monitor any migration of the plume of contaminated groundwater and to check for any hydrocarbon fuels migrating into the area from upgradient or co-gradient sources On the East side of the plume NAV 5, NAV 7, ULT 5 and ULT 8 On the West side of the plume NAV 6 and NAV 8 The following wells are located at the furthest downgradient points and will be sampled to monitor conditions in that area (Note. No components of gasoline have been detected in Well ULT 3 since June of 1991 ) ULT 3 and ULT 4 Wells in the Interior of the Affected Area To monitor changes in groundwater quality in the interior of the affected area, where the existing data show some of the highest concentrations of dissolved components of gasoline the following wells will be sampled ULT 6 and ULT 9 Schedule Following a comprehensive sampling of all wells in the combined array, which is scheduled for June 1993, the selected plume-perimeter and interior wells identified above (i e NAV 2, NAV 5, NAV 6, NAV 7, NAV 8, ULT 3 ULT 4, ULT 5 and ULT 8, and ULT 6 and ULT 9) will be sampled twice per year, once in September and once in February The February and September schedule has been selected based on experience in evaluation of groundwater quality at other sites in the northern San Joaquin Valley where fuels have been lost into the ground That experience shows that groundwater elevations can be expected to be close to their seasonal maxima and minima, respectively, during those months If groundwater elevations and contaminant concentrations are measured at those times, the data permits the effects of seasonal variations in the direction of groundwater gradients and the effects of the water table moving up and down across any zones of the subsurface that are affected by fuel hydrocarbons to be evaluated