3.4. SR 07-07-2008 - Laserfiche WebLink

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LI'e HYDROGEOLOGISTS ^ ENGINEERS ^ ENVIRONMENTAL SCIENTISTS June 23, 2008 Ms. Rebecca Haug City of Elk River Environmental Division 13065 Orono Parkway Elk River, MN 55330 RE: June 2008 Groundwater Monitoring Results Old City Dump, Elk River, Minnesota Dear Rebecca: Enclosed please find the 2008 annual water quality data for the Old Elk River Dump site located southeast of the City of Elk River (Figure 1). The groundwater sampling was completed on June 6, 2008 by Liesch Associates, Inc. (Liesch). Sample locations included monitoring wells MW-2 and MW-3 near the former City dump site (Figure 2). MW-1 formerly located north of the dump was sealed in 2002 when a parking lot for the city park was constructed in the area the well was located. Over ten-years of water quality monitoring at this upgradient well location evidenced no detections of VOC's so the well was not replaced. Laboratory results of the June 2008 sampling event (Table 1) indicate low level VOC detections of Tetrachloroethene (PCE) in MW-2 and Trichloroethene (TCE) in MW-3. PCE was detected in MW-2 at a level of 1.1 parts per billion (ppb) and TCE was detected in MW-3 at a level of 1.9 ppb. The VOCs detected during this recent sampling event are consistent with historic low concentrations found in groundwater samples collected from MW-2 and MW-3. Water level data indicates that the water table at the site remains consistent with water levels recorded over that last 7 years (attached Well Hydrograph). Groundwater flow direction could not be calculated as a minimum of three monitoring points are needed for this determination and MW-1 was sealed. Historic groundwater flow direction for the site has been southwesterly in direction towards the Mississippi River. Presumably this has not changed. The VOC concentrations at the monitoring well locations (MW-2 and MW-3) have been relatively stable over the last few monitoring events. TCE was not detected in MW-3 the previous year (2007) or in 2005 but it has been historically detected since 1989 at decreasing levels. PCE levels detected in MW-2 have remained relatively static since 1989. PCE .and TCE concentrations are currently below Minnesota Department of Health (MDH) Health Risk Limits (HRLs) for drinking water. MDH HRLs for PCE and TCE are currently set at 5 ppb. www.liesch.com LIESCH ASSOCIATES, INC. ^ 13400 15TH AVENUE NORTH ^ MINNEAPOLIS, MN 55441 ^ 763/489-3100 ^ FAX: 763/489-3101