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LEEDSHILL•HERKENHOFF, INC. <br /> these results, SJCPW subcontracted a pipe survey company to video tape and <br /> ' document the physical condition of particular sewer and storm drain lines, <br /> to pressure air test each joint and to pressure grout joints that were <br /> determined to be leaking in the vicinity of LVMD well #1. By early April , <br /> this work had been completed on three sewer lines and one storm drain line <br /> within a 100-foot radius of LVMD well #1. A total of 30 out of 68 sewer <br /> ' joints required sealing. Figure 2.5 presents a schematic of the sewer lines <br /> which were inspected/repaired. It should be noted that the sewer line <br /> between manhole #5 and #4 was found to have a significant sag in it at a <br /> ' location which coincides with the middle of Benjamin Holt Drive. This sag <br /> causes water to back up approximately 20 feet back toward manhole #5. It <br /> should also be noted that from this low point in the line, the slope of the <br /> ' sewer toward manhole #4 is extremely flat, with little slope. Figures 2.6 <br /> and 2.7 illustrate the location of the leaking joints which required sealing <br /> ' between MH #5 and #4 and MH #4 to Gettysburg Place, respectively. <br /> After sealing the joints, water samples were collected and analyzed from <br /> ' manholes #1, #2 and #3 (April 1985) . Four months after the initial sam- <br /> pling (August 1985) , the same manholes were re-sampled and analyzed. The <br /> results of both samplings are shown in the tabulation below: <br /> ' SEWER SAMPLING <br /> ' Concentration of PCE, ppb <br /> Manhole Manhole Manhole Manhole <br /> ' Date #1 #2 #3 #4 <br /> 3/ 4/85 160,000 <br /> 4/ 4/85 580 1180 283 - <br /> 8/21/85 71.7 Non-detect 18.1 - <br /> During 1984 and 1985, the sewer was cleaned approximately every month using <br /> ' a power auger. The auger would physically break up accumulated grease and <br /> sediments which inhibited flow in the sewer lines, but would not provide <br /> ' additional water to "flush" the sediments out of the sewer, so they would <br /> eventually resettle out and accumulate in low spots. In 1986, Lincoln <br /> Properties, Ltd. switched to a "hydro" flushing system which uses high <br /> ' pressure water to both physically break up, dislodge, and transport trapped <br /> grease and sediments. This system cleans the sewer much more effectively, <br /> ' 2-15 <br />