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9 N Canepa's Car Wash ( Pacific Avenue) Probleni Assessment Report and Corrective Action Plan Page 5 filled mud cracks and carbonate nodules are abundant in the silt sequence. The color of the silt ranges from reddish- to yellow- brown across most of the site, and olive gray to blue gray in some of the samples from beneath the former site of the USTs and piping. The silt sequence is present beneath much of the site; however, it thins to the northwest where sand becomes more abundant. Below approximately 60 feet, sands are more abundant and apparently more continuous . Interbedded lenses of clay and silt are present to the depth of drilling ( I 10 feet). The deeper sands likely were deposited by aggrading streams sweeping back and forth across the distal portion of the alluvial fan . Groundwater beneath the site is unconfined and the depth to the water table in June of 2002 was about 35 feet. The overall trend for the water table elevation was downward from 1950 to at least the middle of the sixties . From 1994 to second quarter 2000, the trend was upward with a rise of about 20 feet at the site. Since second quarter 2000 , the trend for the hydrograph has been relatively flat with a seasonal range of about 2 feet. A hydrograph of the available water level data from all monitor wells on site is presented in Figure 6 . The groundwater gradient is eastward at approximately 0 . 003 with an estimated flow velocity of 5 .5 cm/day. WHF carried out a 24-hour pump test in 1994 to estimate the hydraulic properties of the unconfined aquifer. MW- 1 was pumped and MW- 4, - 6, -7, and -8 were used as observation wells . Analysis of the results indicated an optimum pumping rate of 5 gpm with an effective radius of about 140 feet. Aquifer permeability was estimated at 126 gpd/ft2 . 5.0 DISTRIBUTION OF SOIL AND GROUNDWATER CONTAMINATION The twenty-foot rise of the elevation of the water table between 1994 and second quarter 2000 has resulted in saturation of most of the contaminated soil identified in the soil borings installed by WHF in 1994 (13- 1 , MW-2, NIW-6 , and MW-7) and in soil boring SB- 1 installed by Condor in 1998 - Since early 1995, the water table has been above the top of the well screens in monitor wells MW- 1 through MW-8 and, at present, the depth of water in the soil vapor extraction wells is approximately 20 feet. In 2001 , Condor installed three additional monitor wells (MW-9, MW-10, and MW- 11 ) screened at the water table, to assure more representative groundwater sample results . A deep monitor well (MW- 12d) was installed at the same time to investigate the potential vertical extent of the contamination. The distribution of soil contamination and soil remedial actions are summarized in Subsection 5 . 1 . Groundwater quality data are summarized in Section 5 .2. 5. 1 DIS'T'RIBUTION OF SOIL CONTAMINATION Analytical data for samples collected from soil borings and borings for monitor wells were used to investigate the distribution of soil contamination in the Subsurface resulting from the release of petroleum hydrocarbons. The soil boring and monitor well locations are shown in Figure 2 . Soil contamination resulting from the release was detected in sarnples collected from depths ranging from about 35 feet to 55 feet beneath the former location of the USTs and piping to the dispensers. The distribution of the contamination in plan view is shown on Figure 7. The distribution of soil contamination in cross section is shown in Figure 8 (originally Figure 7, WHF, 1994). In 1998 and 2001 , Condor installed soil borings to further investigate the extent of contaminated soil . Contaminated soil was found in samples from boring SB- 1 , located adjacent to the dispenser island (Figure 2), at depths extending from 25 feet to 70 feet. In soil boring SB-2, located on the opposite side of the dispenser island to the west, contamination was found in samples from depths of 26 feet to 70 feet. 1 ., n ILA CONDOR