AECOM Report B&W - N - City of Guelph

City of Guelph2008 Annual ReportClosed Eastview Road Landfill SiteAlthough this has been the case, with the slight increase in water levels since the spring of 2007, three samplescould be obtained in 2008. The average boron concentration was 0.29 mg/L, which is slightly lower than thoseobserved before it went dry. This boron concentration has confirmed that concentrations continue to be wellbelow the Reasonable Use limit. As this is the case, it is expected that the RUG is still being met at thislocation.Location 65Similar to Location 63 above, the average concentration of boron in the outwash at this location continues tobe well below the Reasonable Use limit of 1.225 mg/L in 2008 at 0.51 mg/L. Therefore, the RUG will also bemet in the bedrock below this location regardless of whether or not the target elevation is met.Location 66-IAs with Locations 63 and 65 above, the average concentration of boron in the outwash at this location hasbeen well below the Reasonable Use limit of 1.225 mg/L since 1996. Therefore, the RUG would also be metin the bedrock below this location regardless of whether or not the target elevation is met. As with monitor63-I, samples have not been collected since late 1998 due to very low water levels. However, it was stillexpected that this location still meets the RUG due to the very low boron concentrations observed since itwas installed in 1995 (last boron concentration in Sept 1998 was 0.17 mg/L). This monitor was replaced inApril 2007 and is now designated 66-IR. One sample could be obtain form this location in June 2007 beforeit had insufficient volume to sample. The boron concentration observed was 0.55 mg/L, which still confirmslow levels exist and that they are well below the Reasonable Use limit. Although no samples could becollected in 2008, it still would be expected that boron will be below the RUP based on the 2007 results,which confirmed the results prior to 1998.Location 67Based on the initial boron concentration of 45.35 mg/L, the revised modelling in 1997 showed that thislocation could eventually (in about 300 years) exceed B7 limit in the bedrock. However, it was suspectedthat this initial boron concentration was not representative and there were already trends at that timesuggesting that it would quickly decrease to a point below about 14 mg/L where B7 limit would be achieved.In fact, that is what has happened. By 2000, the measured boron concentration at this location was 2.67mg/L. As with locations 63 and 66, this location has been essentially dry since 2001. During this period itwas reasonable to assume that there would still be similar boron concentrations in this area, and therefore,the RUG will be met. As with 63-I, the slight increase in water levels at location 67-I allowed sampling toresume in 2007. The average concentration of boron in 2008 was found to be 1.19 mg/L, which is lower tothose observed before it went dry. As well, this average concentration is also well below the 14 mg/L that isthe concentration level where B7 would be achieved.Not withstanding the above assessment, it is important to recognize that while the location-by-locationassessment of target elevations is a useful guide to the effectiveness of the PLCCS in different parts of thelandfill site, Reasonable Use compliance in the bedrock aquifer is applied at the site boundary, so there is amixing, or averaging, effect that will occur in the groundwater flow system. The revised modelling(111414_2ra_apr29-09_city_of_guelph.doc) - 32 -