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";a. ;a '^.rs,--5 -.c� -ate. .;"„P�r� E Ida Mr. Kyle Christie July 16, 1990 Page 7 Prior to purging, water-level measurements were taken at each well location (see Figure 1). Purging, pH, and specific conductivity measurements, sample collection, storage, and transportation procedures, as well as sample equipment decontamination procedures, were the same as those used in November and December 1989. All groundwater produced during purging and sampling was disposed of by Armour. Field and Analytical Results--January 1990 The average depth to groundwater beneath the site in January 1990 was 57.54 feet. The groundwater flow direction was to the southeast under a hydraulic gradient of about 0.002 (10 feet per mile). Dissolved BETX concentrations in groundwater samples collected during January 1990 are included in Table 1. January 1990 benzene concentrations are shown on Figure 1. Complete laboratory reports of the January 1990 groundwater sample analyses are enclosed as Exhibit A. January 1990 analytical results show benzene concentrations in groundwater in monitoring wells W-2, W-2A, W-213, W-3, W-4, W-5,W-6, and W-7 are greater than the California Department of Health Services (DHS) Maximum Contaminant Level (MCL). Xylene was also above the DHS MCL in monitoring wells W-2 and W-3 for the January 1990 quarterly sampling. Ethylbenzene concentration was below its respective MCL. DHS MCLS for benzene, ethylbenzene, and xylene are 1.0 ppb, 680 ppb, and 1,750 ppb, respectively. Toluene was identified in concentrations greater than the DHS drinking water action level (action, level) in monitoring wells W-2, W-2A, and W-3. The action level for toluene is 100 ppb. Dissolved hydrocarbons (C4 to C12), ranging from <50 ppb to I8,000 ppb, were present in monitoring wells W-2, W-2A, W-3, W-5, W-6, and W-7 in January I990. As the water table declined in elevation between July and October 1989, the BETX concentrations decreased. As the water level returned between October 1989 and January 1990 f to a higher elevation where the majority of the hydrocarbons are located in the soil, the BETX e concentrations increased. Conclusions a BETX concentrations in groundwater in on-site and off-site monitoring wells are greater than the j BETX concentrations identified during the last quarterly sampling in October I989. The approximate 2-foot increase in the water table since October 1989 has significantly affected BETX concentrations. The water� table has risen from 2.11 to 2.44 feet_in-the_majority-of the_---- ----------- - --- -- -- - groundwater-groundwaterwells. In well W-2B, the water table has risen only 0.69 feet. The increase in groundwater elevation may have enabled the hydrocarbons adsorbed onto soils in the capillary fringe zone to re-enter the groundwater. Brawn and Caldwell Consultants