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LEEDSHILL•HERKENHOFF, INC. <br /> force necessary to move the contamination to the upper water <br /> ' bearing zone. <br /> Approximately 120 feet to the south, a very similar situation was <br /> occurring in the sewer line between MH#5 and MH#4, except that <br /> this situation was compounded by the sag and extremely flat slope <br /> ' of the existing sewer line. As shown on Figure 2.6, 16 sewer <br /> joints were found to be leaking excessively. The existence of the <br /> sag followed by the essentially horizontal sewer line (as one <br /> ' moves from MH#5 to MH#4) means that water within this 110-foot <br /> section of sewer line would tend to pond or puddle, instead of <br /> flowing through the system. With the water ponding in these <br /> ' areas, more leakage from the sewer line would occur. This fact <br /> plus the fact that both PCE and TICE are heavier than water and <br /> would tend to deposit and accumulate in these low spots indicates <br /> the method of contamination to the upper water bearing zone. <br /> ' 2. PCE/TCE contamination of LVMD well #1 was caused by a failure <br /> (fracture) in the existing well casing and/or the absence of a <br /> sufficient annular sanitary surface seal . <br /> ' As discussed in Section 2.4, a major casing separation was de- <br /> tected at a depth of 42 feet from the surface during a video <br /> ' inspection of the integrity of LVMD #1's casing. Water was seen <br /> to be entering the well through this fracture (@ 42 feet) and the <br /> ' static water level was measured to be 48 feet below grade. This <br /> difference in water level supports the data presented in Section <br /> 4.1, which discusses the separation of these two water bearing <br /> zones. Therefore, contamination of LVMD #1 was due to PCE/TCE <br /> contaminated water from the upper zone entering the well through <br /> the casing fracture, and not contamination of the lower zone. Two <br /> ' additional facts support the position that the lower aquifer is <br /> not contaminated. As discussed in Section 2.4.3, after remedial <br /> measures were taken to install an 80-foot liner and sanitary seal <br /> in LVMD #1, subsequent monthly and then quarterly sampling has <br /> showed no detectable contamination. LVMD #1 is now drawing water <br /> ' exclusively from the lower aquifer and not a blend of the upper <br /> and lower water zones. LVMD#2, located approximately 150 feet <br /> north of LVMD #1, has never tested positive for PCE or TICE contam- <br /> ination. This well has an 80-foot deep sanitary seal and is <br /> drawing water from only the deeper aquifer. <br /> ' 5-3 <br />