EPA has received many questions about implementing the final CCR disposal rule. The Agency is developing responses to these questions and will be posting them to this Web page periodically.

The questions and responses below fall under the category of groundwater monitoring and corrective action:

• The final rule requires that if a constituent of concern is detected above a statistically significant level, that the groundwater protection standard must be set at either the Maximum Contaminant Level (MCL) or at the background concentration. Whereas, the proposed rule, like the municipal solid waste program, would have allowed the owner or opera tor to establish an alternative groundwater protection standard based on site­ specific conditions. Has EPA considered whether this will impact future and on-going corrective action at coal ash disposal units in states that utilize risk-based decision making?

  If the Safe Drinking Water Act MCL or background-based cleanup levels are lower than a risk-based level the state has used, the federal regulations would require that the corrective action include treating the groundwater in the uppermost aquifer to a level lower than the risk-based level. If, however, the MCL or background-based cleanup levels in the federal rules are higher than a risk-based level the state has used, the state regulations would require that the corrective action achieve a level lower than the federal levels. In some cases, it is possible that the corrective action provisions in the final rule would require a more rigorous treatment than required under state law, and in other cases, less rigorous treatment than required under state law. The potential number of these scenarios occurring at corrective actions related to coal ash disposal units is unknown.

• If a state decides that there is no human receptor for the groundwater and that a cleanup standard above the MCL or background is appropriate, would that meet the minimum requirements of the rule?

  The rule requires that the groundwater protection standard (either the MCL or the background level, whichever is higher) must be met by the chosen corrective action remedy, in order to preserve the groundwater as a natural resource and for its potential future use as a source of drinking water.

When new implementation questions are posted, the Agency will identify them with an icon located next to the question. The complete list of questions and responses will also be updated each time new questions are posted.