Handout 1_RAO-Pages from 111918_FS_workplan_D1712508-final-clean-forFAAST_upload Feasibility Study Workplan RAO Objectives Table Line No General EPA Remedial Action Objectives South Y Specific Remedial Action Objectives Comments Source: Per EPA Document 540/R‐96/023: Objectives applicable for all sites with contaminated groundwater include the following: 1 Prevent exposure to contaminated ground water, above acceptable risk levels. Allow additional groundwater production without treatment 2 Prevent or minimize further migration of the contaminant plume (plume containment). Design and implement remedies without increasing existing volume of groundwater impacted by HVOCs ( C ) (plume containment) 3 Prevent or minimize further migration of contaminants from source materials to ground water (source control). Concentration reduction to < 50 ppb at drinking water wells, mass removal for proposed remedial measure To avoid 97‐005 permitting requirements 4 Return ground waters to their expected beneficial uses wherever practicable (aquifer restoration). Not applicable for South Y study Source: Per EPA Document 540/G‐88/003: Remedial Action Objectives for contaminated groundwater sites should address the following: 5 Cleanup Level Assist in overall objective of supplying water without detectable HVOCs( C) to customers Comply with regulatory agency requirements and directives regarding HVOCs (C ) in groundwater Proposition 1 Metrics of Success: Estimated mass of contaminant removed over the projected life of the project RAO that aims to reduce contaminant mass to reduce the cleanup burden (e.g., reduce well head treatment duration) for downgradient receptors required to cleanup pumped water to MCLs for distribution and consumption – maybe this amounts to some level of concentration reduction, but still greater than MCLs in in‐situ groundwater. 6 Area of Attainment Address groundwater in mid‐plume area including groundwater < 100’ below ground surface with high concentrations of PCE in mid‐plume and/or replacement wells in deeper aquifer outside of the plume This is addressed above and likely to include the area of the plume between the source zone and the downgradient extent of the plume 7 Restoration Time Frame Anticipated remediation time frame is 30 years or less to remove the majority of PCE mass in groundwater in the mid‐plume area cost effectively RAO that acknowledge STPUD’s/Water Agency’s efforts as interim and will be maintained until such time that source control has been implemented by the RPs and groundwater concentrations have declined to influent levels that are equal to or less than the proposed cleanup level above) Other South Y Specific Objectives Preserve ability to recover HVOC( C) response costs from responsible parties and/or state grant funding in the future Preference for beneficial use of any extracted groundwater resource (i.e. not disposal to sanitary sewer or storm drain) Reduce costs (capital or long‐term O&M) for groundwater remedial wellhead treatment to retail customers Perform community outreach and information activities regarding HVOCs( C) in groundwater Notes: (a) STPUD is responsible for management of the groundwater basin. Other water supply entities are the water retailers. (b) Other parties have been named as responding parties to a Cleanup and Abatement Order issued by the Water Board. (c) HVOCs = halogenated volatile organic compounds including tetrachloroethene (PCE) and its degradation products.