ARCHIVED REPORTS_RESPONSE TO COMMENTS ON DRAFT REMEDIAL ACTION PLAN 2015

Home Browse Search

Page 6 6. As suggested in the attached comments from Jenifer Beatty, the Draft RAP does not consider the possibility that the current drought or future droughts may trigger the need to install additional supply wells on the south side of the Stanislaus River. If this occurs, these wells could shift the local groundwater gradient to the south, causing additional impacts to the property owners south of the river. Through proper implementation of the Water Management Plan (WMP), the Water Replacement Contingency Plan, and long-term groundwater monitoring,Nestle should be able to prevent human exposure to their groundwater contaminants by guiding the design/location of new wells in this area or taking other actions such as installing well head treatment. However, under drought conditions, requests to install new supply wells south of the river are unlikely to be denied. Furthermore, Central Valley Water Board staff is unlikely to require residents to install their new supply wells deeper than Nestle's groundwater contamination given the additional costs and the possibility that the deeper water-bearing zones may be unsuitable for their needs due to naturally-occurring metals or other inorganics. Given these probable limitations, the TCE plume may spread southward under drought conditions and significantly increase groundwater restoration time. Therefore, a groundwater remedy for the southern TCE plume that relies solely on MNA and institutional controls is not supported by Central Valley Water Board staff and management. Nestl6 Response: If additional supply wells are installed south of the River and become impacted by COCs from the former Nestl6 facility,Nestl6 will take appropriate action per the WRCP. This may include wellhead treatment rather than well replacement as an appropriate response under drought conditions. Pumping groundwater solely for remediation during drought conditions is not a viable solution unless there is a beneficial use of the extracted groundwater. 7. This letter requests submittal of 2 work plans and 1 design plan in the next 80 to 120 days. These documents have a much higher priority than the Interim RAP; therefore, the Interim RAP should be submitted after these documents. Please adjust the RAP schedule and your project resources to meet these new priorities. Nestl6 Response: Comment noted. Per our response to General Comment#5, Nestl6 requests an extension on the 31 May 2015 Work Plan for remediation near the lagoons. 8. The proposed remedial action objectives at the beginning of Section 2 are absolute objectives as defined by Integrated DNAPL Site Strategy(ITRC, November 2011) and do not describe all the necessary steps or activities (functional objectives) needed to achieve them. For example, if after completion of the on-going study, MNA is accepted as a remedy component for the southern TCE plume or portions of it,then one of the necessary objectives to trigger transition to this passive remedy would be construction of a groundwater monitoring network able to provide early detection of contaminants migrating southward beneath the river (per General Comments 2 and 3 above). A second objective to trigger the transition would be reduction of the contaminant mass to target concentrations that are expected to minimize the risk to nearby receptors. Central