AECOM Report B&W - N - City of Guelph

City of Guelph2008 Annual ReportClosed Eastview Road Landfill Sitec) Groundwater flow directions around the site are similar to previous years. Assessment of verticalgradients towards the bedrock is similar to previous years. They are on average very low andtherefore the estimated downward flow velocity is also very slow, in the order of only a fewcentimetres per year.d) The interpreted shallow bedrock groundwater flow regime continues to be confirmed using therecently installed bedrock monitors in 2003 and 2007.e) Landfill leachate effects are contained on-site in the shallow groundwater system as the PLCCSis working as designed. There was no exceedance of Guideline B7, the Reasonable UseGuideline in the shallow groundwater attributable to leachate release in 2008. Historical minorresidual leachate effects are still observed south of the landfill along Eastview Road, outside ofthe sheet pile wall at location 16. It is expected that the residual leachate contamination willdecrease naturally over time through dilution with clean infiltration and groundwater flow.f) If the PLCCS continues to work as designed to prevent any further off-site migration of leachate,no new exceedances of Guideline B7 related to the landfill are predicted in the shallowgroundwater.g) The bedrock groundwater quality is similar to previous years. Location 37 (upgradient of thelandfill) continues to exhibit slight increases in chloride, whereas location 50 has exhibited noincreasing trends over the past few years. An assessment on these increasing trends, completedin early 2003, concluded that with the existing information collected to date it does not appear thatthe change in water quality at monitors 37-I and 50-I is landfill related. The information suggeststhat the change is possibly related to a high chloride/low iodide source upgradient of the landfill.Although not conclusive, the only potential source identified in the area beyond the landfill wouldbe from road salt. To further address MOE concerns, additional monitors were completed inSeptember 2007 to provide data to better refine groundwater flow in this area. Preliminary datafrom these new monitors continue to suggest that flow is into the landfill (i.e., 37-I is upgradient).This was based on limited water level and analytical data collected since late 2007. As there isnow just over one year of data collected form these monitors, an Interim report will be preparedand forwarded to the MOE on the overall findings upon completion of the Annual Report.h) There is no indication of leachate in the bedrock groundwater, thus the Reasonable UseGuidelines are being met.i) Guideline B7, the Reasonable Use Guidelines, is predicted to be met in future bedrock groundwater.Target elevations are being met in most areas within the landfill through the operation of the PLCCS.Where target elevations are not being met, the criteria used in the modelling completed in early 1997,were compared to the 2008 results and found to be similar. Therefore, the locations where the targetelevations are not being met would not cause Guideline B7, Reasonable Use exceedances in thebedrock groundwater. In addition, the 2008 chemistry and vertical profile trends observed in the lowertill do not indicate any presence of leachate impacts, again suggesting that Guideline B7, ReasonableUse will not be exceeded in bedrock groundwater.j) The 2008 results show that the landfill has a negligible effect on downstream water quality. Thistrend has been seen each year since the leachate collector system was installed in 1991.k) The MOE conduction an inspection of the closed Eastview Road Landfill on February 14, 2008.No non-compliant issues were noted by the MOE during this inspection.(111414_2ra_apr29-09_city_of_guelph.doc) - 62 -