AECOM Report B&W - N - City of Guelph

City of Guelph2008 Annual ReportClosed Eastview Road Landfill SiteIn the southwest section of the south collection system, leachate elevations were similar to the pump stationelevations (Figure 4b). As discussed in the past, only direct pumping of the PLCCS controls this section of thecollection system. The pipe inverts along this section are flat at an elevation of 339.5 mASL, which alsocorresponds to the pump station invert. Therefore, it is expected that the leachate levels measured in thissection would be similar to the pump station levels.In 2008, leachate elevations exhibited increased levels. This occurred in early January and April. Theincreased levels in January were due to the blockage in the Main Tank (Section 2.6). At this time the systemwas shut down as no pumping off-site could be undertaken until repairs could be completed. During this periodof shut down, increased water level measurement frequency was initiated to ensure that the leachate levelsremained below the sheet pile wall. Once repairs were made and pumping was resumed, the levels in thesystem dropped immediately. The increase in levels in April was caused by significant rains/runoff asoccasionally observed historically. During this period, increased water level measurement frequency wasundertaken to ensure that levels remained below the sheet pile wall. Water levels dropped immediately afterthe rain event.The overall patterns of the leachate levels and the system response, especially in January and April,continue to indicate that the south collection system is working as designed to collect and control leachatefrom beneath the landfill.West Collection SystemLeachate elevations in the west collection system exhibited a general decreasing trend from MH 2W to thepump station and from MH 8W towards the pump station (Figure 5). However, in 2007 and to a lesser extentin 2006, the amount of change in levels between the manholes has decreased. Landfill staff were contactedto assess if this was a possible maintenance issue beginning to occur in the West System. Landfill staffinspected the system and pump station and determined that the system was working as expected (good flowwas entering the pump station). However, after closer inspection of the pump station it was noted that thepump start float level could be lowered further. Therefore, to better optimize the pumping of the westcollector, the pump float level was lowered by 60 cm in the late spring of 2008. Since this time water levelsin the system have decreased and are at similar levels prior to 2006.As observed in the south system, leachate levels in the west system also increased in January and April2008 for the reasons discussed earlier in the west system. Increased water level measurement frequencywas also undertaken in the west system during these periods. A similar response also occurred in the westsystem as observed in south system.The overall patterns of the leachate levels and the system response, especially is January and April, continueto indicate that the west collection system is working as designed to collect and control leachate from beneaththe landfill. With the lowering of the pump start float level in 2008 the pumping of the system water levels havealso decreased.(111414_2ra_apr29-09_city_of_guelph.doc) - 10 -