AECOM Report B&W - N - City of Guelph

City of Guelph2008 Annual ReportClosed Eastview Road Landfill Siteillustrates the boron trends. As discussed in the past, during a laboratory change in mid-1993, boron trendsbecame scattered. In 1995, this scatter began to show a consistent but stable trend. This trend haspersisted into 2008. There is no indication of leachate impacts in the bedrock groundwater based on boronalone.Figure 18 illustrates the chloride trends. As discussed in the past, there was a slight scatter just after alaboratory change in mid-1993, however, the chloride trends have exhibited very little variation over time. Asstated in previous reports, Location 37 is still exhibiting an increasing trend in 2008, as was originallyobserved in 1994. However, location 50-I, which also had exhibited a slight increasing trend from 1994, hasnow been stable around 50 mg/L since 2003.In 1998, chemical analysis of these locations showed that there might be a slight shift in the chemistrytowards a road salt or brine water signature at 37-I. As well, to a lesser extent, 50-I was also indicating apossible change in chemistry that may be starting to trend to a road salt or brine water signature. In 2008,the data collected still showed that this trend was occurring in 37-I with a further shift towards a road salt orbrine water signature.To address the increasing chloride in the above wells, an assessment to determine the possible source ofthese increasing chloride concentrations was conducted (i.e., whether they were from a possible leachatesource or from another source). This assessment was discussed in the 2002 annual report.The conclusion of this assessment was as follows:“In conclusion, with the existing information collected to date it does not appear that the change inwater quality at monitors 37-I and 50-I is landfill related. The information suggests that the change ispossibly related to a high chloride/low iodide source upgradient of the landfill. Although notconclusive, the only potential source identified in the area beyond the landfill would be from road salt.If this were the case, a pathway would be required to allow chloride impacted waters to enter thebedrock to the west of the landfill. The above assessment did identify potential pathways in theoverburden (granular soils) west of the site, however, the actual presence and extent is not known.Therefore, to determine if the cause of the chloride increase is from an upgradient source, furtherdrilling to the west of the landfill would be required.As stated earlier, the MOE has recommended that further monitors be installed to better define bedrockgroundwater flow in the bedrock beneath the site. One of the recommended locations is off-property andwest of both locations 37-I and 50-I. This location is close to the area noted to have granular material, whichmay go to depth and therefore, will help determine if this is occurring. Further, this location will provide abetter definition of the direction of groundwater flow in the bedrock and water quality west of the landfill.Therefore, if flow from this area is confirmed to be towards the landfill, and elevated chloride is found, thesource would be from further upgradient and not from the landfill.”Based on the above, six additional bedrock monitors were installed around the site including one locationwest of location 37 (Figure 3, location 92). Groundwater levels collected from these locations haveconfirmed the interpreted groundwater flow in the bedrock, along Eastview Road.(111414_2ra_apr29-09_city_of_guelph.doc) - 27 -