Sam Ziemann From - Region of Waterloo

July 23, 2010Lisa Lachuta, P.Eng.Page 5 of 7Reference: Technical Memorandum A1 –Strange Street Well Field Water Quality AssessmentSULPHATEWithin the Strange Street production wells, sulphate has historically been well below theODWS AO of 500 mg/L (Figure 2), with all production wells except K17 consistentlymeasuring below 250 mg/L.Within monitoring wells sampled as part of the 2010 monitoring program, sulphateconcentrations in the aquifer did not exceed 100 mg/L, with the exception of SS13-99,where sulphate was measured at 177 mg/L. This is consistent with the 1999 monitoringevent, where sulphate was not observed to be above the ODWS AO in any of themonitoring wells (Stantec, 2000).NITRATEConcentrations for nitrate in the production wells have remained well below the ODWSMaximum Acceptable Concentration (MAC) of 10 mg/L (Figure 23), with the exceptionof one occurrence at Production Well K11 in June of 1987 where nitrate concentrationsreached 9.25 mg/L. Since 2000, levels for nitrate at all active Production Wells haveremained below 1 mg/L. This is consistent with findings during the 1999 and 2010monitoring well sampling programs, where nitrate was consistently either not detectedor was found to be well below the ODWS MAC of 10 mg/L.ORGANIC PARAMETERSNo VOCs were detected in any of the water quality samples collected during the 2010sampling event. Upon examining the 1999 water quality data for the select monitoringwells, the following detections for volatile organic compounds (VOCs) were noted forwells screened within the municipal supply aquifer:• At OW4B-46, near K11A and K13, detections were observed for benzene,ethylbenzene, toluene, m- & p-Xylene and σ-Xylene;• At SS08-99, north of the Westmount Golf and Country Club, benzene and toluenewere detected;• At SS09-99, west of the Strange Street Well Field, benzene, toluene and m- & p-Xylene were detected in the groundwater sample; and• At SS11-99, south of K18 and K19, acetone, benzene, toluene and m- & p-Xylenewere detected in the groundwater sample.Upon reviewing historical organic water quality data for the production wells, thefollowing parameters were observed on more than one occasion in the indicatedproduction well:• 1,4 dioxane was detected twice between 2004 and 2007 in Production Well K10;• Tetrachloroethylene was detected twice in 2004 and 2005 at Production Well K10and seven (7) times at Production Well K12 between 1992 and 1999;