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� l <br /> r <br /> Mr.H.C.Winsor <br /> February 23, 1988 <br /> Page 2 <br /> The City of Lodi (City) has continued to hold Municipal Well 12 out of service. In order <br /> — to properly maintain pumping equipment, the City has pumped Well 12 into the storm sewer <br /> about 10 minutes per week since the fall 1987. Well 12 is pumped at full flow (1,600 <br /> gallons per minute(gpm)). <br /> November 1987 Investigation <br /> j Two monitoring wells on Mervyn's property (W-7 and W-8) were installed, developed and <br /> sampled during the week of November 13, 1987. Borehole logs are shown in Exhibit B. <br /> Well construction diagrams are shown in Exhibit 2. With the exception of well <br /> i development, field methods used by BC in the November 1987 work are the same methods <br /> used in the April 1987 investigation. These methods are discussed in Chapter 3 of the <br /> May 21, 1987, Problem Assessment Report (Appendix 1). The three wells installed in <br /> November 1987 were developed by Armour Petroleum Service and Equipment Corporation <br /> (Armour Petroleum)of Vacaville,California,by pumping. <br /> Site Geology,Groundwater Occurrence,Flow and Groundwater Gradient <br /> ]Figure 2 shows the geology at the area as determined from the borehole logs. The <br /> sediments appear to be predominantly silt from ground surface to approximately 25 feet <br /> below ground surface under the ARCO station, and to approximately 45 feet below ground <br /> surface under the American Savings facility and the Mervyn parking lot. Beneath the silt <br /> layer, the sediments are predominantly sand with interbedded clays. Groundwater occurs at <br /> approximately 52 fee:below ground surface in a predominantly sand layer. <br /> t <br /> Figure 1 shows the uppermost groundwater elevztion contour based on measurements by BC <br /> -� on November 18, 1987. Figure 3 shows the uppermost groundwater elevation contours based <br /> on measurements by BC on February 2, 1988. cloth the November and February data show <br /> grondwater flow direction is to the south-southwest under a gradient of approximately 10.5 <br /> feet per mile(0.002). <br /> With the City's permission, BC has monitored the depth to static groundwater level in City <br /> i Well 12 since September 30, 1987. Table I compares static groundwater levels in Well 12 <br /> to static groundwater levels in the adjacent monitoring well, W-4, which is about 10 feet <br /> x from Well 12. <br /> r� <br /> 3 <br /> x <br /> E1 J <br /> t BROWN AND CALDWELL <br /> - 723SSTREET SACRAMENTO.CA 95814•(916)444.0123 ' <br /> r ; <br /> J. <br /> , , <br />