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— :r fY.:m, �T z.. i�cE - ,�.— �---6 r": itra 131r.s,..: aaigte AnI Am� .. tIM x 3--2 Site Geology Geology underlying ARCO Service Station 434 was determined from the well log of Municipal Well 12 and from the boring logs of the three monitoring wells installed at the site. The well log of Well 12 was obtained from Lodi and is included in Appendix C with their permission. Municipal Well 12 was drilled to 696 feet and completed at a total depth of 490 feat. Well 12 penetrated a sequence of interbedded sands and clays. . Depth from grade to the first perforation is about 210 feet. Data on file with Lodi indicates static water level is at approximately 50 feet below grade. The pumping capacity of Well 12 is 1,300 gallons per minute (gpm) with a total production in 1985 of 252 million gallons. Production from the well creates a drawdown from static water level of approximately 20 feet. With static water level at about 50 feet and a drawdown of ? � = about 20 feet, the pumping water level would be at about 70 feet . { below grade. The well log for Well 12 shows the annular space of the € f well has a sanitary seal from 0 to 108 feet. The boring logs of wells W-1 and W-3 were used to construct cross arx� section A-A' shown on Figure 3-1. Cross section A-B was constructed from the ing logs ls �i Immediately orunder underlying the station is as se ies-3 asshof on Figure kilt, Sand clay. There appears to be a fairly continuous 15- to 20-foot-thick layer of sand at approximately 35 feet below ground surface. Groundwater occurs at approximately 50 feet below groundwater surface within an interbedded series of sand, silt, and clay. This water level occurs at about the same depth as the static water level in Well 12 and a ppears to be related to the regional aquifer system. Based on data obtained for this investigation and from existing geologic literature, the groundwater body beneath the site is one i continuous aquifer with no distinct perched zones apparent. The locations of other nearby municipal wells are shown on Figure 1-1. Locations of water, sewer, storm, and traffic underground lines for the Kettleman Lane and Hutchins Street Y intersection are shown in Appendix E. These maps were obtained from '• II Lodi and are included with their permission. t Groundwater Gradient Groundwater elevations obtained by Brown and Caldwell on April 15,-19 8 7 - — -- -- -�- -- -- , are--Summar-rzedonFigure2-i.---These__a re_relative eleva=�-- -------- tions based on an assumed bench mark of 100.00 feet near the ' # southeast corner of the site. They are not absolute elevations. :.� These elevations were used to construct the direction of groundwater flow and the hydraulic gradient .using methods outlined in USGS F Water-Supply Paper 2220. The groundwater flow is generally south-