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PRE-CONSTRUCTION MONITORING RESULTS WOODBRIDGE NEIGHBORHOOD POROUS PAVEMENT PROJECT, SHOREVIEW ® pH ® temperature ® conductivity ® dissolved oxygen The June sampling event took place when pavement installation was just beginning and MW-1 was not accessible. The laboratory analytical data from both events is attached to this letter. VOLATILE ORGANIC COMPOUND (VOC) DATA Pre-construction groundwater monitoring has detected the presence of chloroform in one monitoring well. VOC data from both sampling events show chloroform detections in the off-site, upgradient well, MW-4. These detections, in micrograms per liter (ug/L) are compared to the Minnesota Department of Health's Health Risk Limit (HRL) below: Monitoring well Date Compound Result u /L Reporting Level u /L IIRL u /L MW-4 June 25, 2009 Chloroform 0.5 0.1 30 MW-4 July 9, 2009 Chloroform 0.3 0.1 30 The MDH developed health-based rules and guidance to evaluate potential human health risks from exposures to chemicals in groundwater. Both of these chloroform detections are far below the HRL set to protect public health. The MDH's website states the following: "HRLs, HBVs and RAA are only one set of criteria that state groundwater and environmental protection programs use to evaluate contamination. MDH's Health Risk Assessment Unit does not enforce or regulate the use of HRLs, HBVs or RAA but provides recommended values for use by risk assessors and risk managers in making decisions and evaluating health risks. Because these groundwater values are based on the ingestion of contaminated water, the chemical evaluation process does not explicitly consider other forms of exposure, such as the inhalation of chemical vapors that come from contaminated water. The evaluation process does not consider the impact of contamination on non-human species or the environment. Therefore, using HRLs, HBVs or RAA to set upper limits for contaminants in groundwater is not appropriate." The chloroform detections were unexpected but our inquiries to the Minnesota Pollution Control Agency's (MPCA) Voluntary Investigation and Cleanup (VIC) program regarding the potential source indicates that the road salt (sodium chloride) pile at the former Ramsey County Public Works facility, north of the subject property, is known to have leached salt down to groundwater. In response to our inquiry, James Kelly, Research Scientist, Environmental Health Division, MDH, stated the following in a related email dated August 3, 2009: "If it was a public works facility, I would assume they had a road salt pile. That may explain the high chloride in the groundwater (?). Free chloride combined with natural organic matter in the well could in turn explain the chloroform.... it would be somewhat analogous to chloroform generation in public water supplies due to chlorine used for disinfection. In any event, the results are far below the HRL of 30 ug/L. " This explains the presence of chloroform to our satisfaction. 2