SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

REMEDIAL ALTERNATIVES - 4 - 4.3 4 -4.3 Toxicity and Health Risks Outdated water quality criteria are given for 1,2-DCP. (See comment #3 for the Executive Summary for the most recent criteria). I don't understand why 1,2-DCP is compared to 1,3-DCP, since 1,3-DCP isn't a breakdown product and hasn't been found at this site. 4.4 Establishment of Action Levels The Basin Plan describes the method the Board is to use in setting groundwater cleanup levels. Groundwater cleanup levels are "equal to background concentrations if background levels are technologically and economically feasible to achieve. If background levels are infeasible to achieve, cleanup levels are set between background concentrations and concentrations that" protect beneficial uses of the waterbody and do not pose a significant risk to human health or the environment. "Within this concentration range, cleanup levels must be set at the lowest concentrations that are technologically and economically achievable." Based on the above, if 1,2-DCP were the only chemical in the groundwater beneath the site, then the cleanup level would initially be set at background (non-detect) and if necessary, would rise to 0.5 µg1I (the human health protective level). However, 1,2-DCP is not the only chemical in the groundwater. A human health risk assessment is necessary to determine the concentration of the chemicals which will not pose a significant risk to human health. 5.0 Alternatives for Removal of 1,2-DCP from Groundwater The report contains a quote "...an aquifer receiving a continuous supply of contaminants is extremely difficult to renovate; decontamination of groundwaters is often uneconomical and in some cases technically infeasible." This quote is not germane to the discussion because State and Regional Board policies require a discharger to remove the source of contamination. 5.1 Pumping and Treating with Activated Carbon The document contains a quote about DNAPLs, and the failure of pump and treat systems when DNAPLs are present. 1,2-DCP will behave as a Dense Non-Aqueous Phase Liquid when it is present at such a high concentration that it is not dissolved throughout the water column, but instead is found as a liquid which has sunk to the bottom of the water-bearing zone. No evidence has been presented to suggest that the 1,2-DCP found at this site is behaving in such a manner. 5.2 Pumping and Air Stripping Depending on the Air Quality Management District, and the pounds of gas to be vented, it is still possible to vent air strippers directly to the atmosphere. 5.3 Hydraulic Containment Again, the report contains a quote about DNAPLs. However, 1,2-DCP is not behaving as a DNAPL, so this quote is unnecessary. 5.6.3 Vaporization The document states that 1,2-DCP "will continue to vaporize from groundwater until it can no longer be detected." Given the physical conditions at this site, how long will it take for 1,2-DCP to vaporize from the groundwater until it can no longer be detected?