ARCHIVED REPORTS_XR0004170 - Laserfiche WebLink

Home Browse Search

i ' Ms_ Margaret Lagorio September 24, 1996 • Page 3 well W-1 was abandoned, because it was difficult to purge and sample, and was replaced by W-1A. Well W-6 was destroyed by a subcontractor during construction of a Boston Chicken Restaurant in March or April 1995. The well was properly abandoned in--XL— 1995 by a contractor hired by Boston Chicken. -� Geology and Hydrogeology The geology underlying the Site and the general vicinity was determined from boring logs of wells installed at the Site and surrounding area by BC. Locations of geologic cross sections A-A' and B-B' are shown on Figure 3. The Site is underlain by interbeds of sand, silt, and clay (Figures 4 and 5). These interbedded deposits are probably stream channel and flood basin deposits associated with the Mokelumne River and its tributaries. In general, fine-grained sediments underlie the Site, including silt and clay. Clay beds range from 2 feet to as much as 22 feet in thickness. The geology north, east, south, and southwest of the Site consists of coarser-grained sediments including silts, sandy silts, and sands. On May 9, 1996, the general groundwater flow direction was to the south under a hydraulic gradient of 0.003 (Figure 6). Historical groundwater flow ranged from the southwest, south, and southeast, under hydraulic gradients ranging from 0.035 to 0.006. Table 1 presents • historical groundwater elevation data. Surface Water The Site is covered by asphalt. All surface water drains away from the Site into storm drains. Any infiltration of stormwater into surface soils is not likely. There are no surface water bodies (lakes, streams, creeks, etc.) within 112 mile of the Site. Water Use A well survey of municipal wells is discussed within BC's Addendum No. 3 to the May 21, 1987 Problem Assessment Report. In summary, there is one municipal well within 2,000 feet of the Site, Municipal Well 12 (Figure 2). Historically, groundwater flows in the direction of Municipal Well 12. Municipal Well 12 was shut down on the day of the reported hydrocarbon release. A pump test of Municipal Well 12 in 1987 determined a hydrologic connection between the screened interval (210 to 500 feet below ground surface (bgs)) of Municipal Well 12 and the shallower on-site wells at the Site. Municipal Well 12 was sampled on April 2, 1987 by BC. In addition, City of Lodi Public Works sampled Municipal Well 12 on May 17, 1993 and August 19, 1993. Petroleum hydrocarbons were not identified in the April 1987 sampling • Use or disclosure of data continued on this sheet is subject to the restriction specified at the beginning of this document. 3382TO RRE 5 MLO S URE.DOC