Laserfiche WebLink
Quarts Owundwa/rrMo <br /> dy nMoiing Rapprl-Fourth Quar4r <br /> 5U1 F Street,Banta,C21ftmia <br /> BACKGROUND <br /> Aegis has been conducting groundwater monitoring and sampling at the site since <br /> February 1, 1991. Work conducted at the site prior to February 1991 included <br /> investigations by Earth Treatment Systems, Inc., of Manteca, California, Delta <br /> Environmental Consultants, Inc.,of Rancho Cordova, California,and Nations Groundwater <br /> Associates of Sacramento, California. <br /> GROUNDWATER MONITORING <br /> Groundwater Levels <br /> On October 13, 1993, Aegis personnel collected measurements of the depths to <br /> groundwater in wells MW-1 through MW-6. Since the previous monitoring event in <br /> July 1993, groundwater levels have decreased in wells MW-2 through MW-6 (Table 1, <br /> Figure 3) an average of approximately 0.67 feet, and increased in MW-1 by 0.02 feet. <br /> Based on the current data, the groundwater flow direction is estimated to be to the <br /> northeast (Figure 4) at an average gradient of approximately 0.003 ft/ft. Figure 4 is a <br /> potentiometric surface map of the shallow water-bearing zone on October 13, 1993. <br /> Previous groundwater levels are summarized in Table 1. All depth-to-groundwater <br /> measurements were conducted according to the Aegis standard operating procedures <br /> (SOP) included in Attachment 1. <br /> Water Sampling and Analysis <br /> On October 13, 1993, Aegis personnel collected groundwater samples from monitoring <br /> wells MW-2 through MW-6. The samples were collected according to the Aegis SOP <br /> included in Attachment 1. All the samples were submitted under chain-of-custody to <br /> Pace, Inc., of Novato, California, a state-certified analytical laboratory. The samples were <br /> analyzed for concentrations of- <br /> Total petroleum hydrocarbons (TPH), as gasoline, by modified EPA Method <br /> 8015, <br /> benzene, toluene, ethylbenzene, and total xylenes (BTEX) by modified EPA <br /> Method 8020, <br /> TPH, as diesel, by GC-FID/EPA Methods 3510/8015. <br /> Well MW-1 was not sampled due to the presence of floating liquid hydrocarbons. The <br /> analytical results are summarized in Table 2. The analytical reports and chain-of-custody <br /> form are included in Attachment 2. Concentrations of TPH, as gasoline and diesel, and <br /> benzene reported in Table 2 are also shown on Figure 5. <br /> 90-099H.�MR -2- <br />