Laserfiche WebLink
DDRW is considering the construction of a percolation pond, which <br /> was mentioned at the public meeting for the OU-1 Proposed Plan <br /> held on January 14 , 1993 . DDRW said that it was also suggested <br /> by the State agencies . It is envisioned that the pond will be <br /> utilized to percolate and evaporate the treated water pumped from <br /> the aquifer. Mr. Robert Raspo, TRC member, asked why does DDRW <br /> require a pond? DDRW stated they plan to replace the water <br /> removed from the aquifer (e.g. , percolation and injection) . <br /> Attendees at the Proposed Plan public meeting suggested <br /> constructing the pond along with the State. DDRW said it would <br /> be cheaper than injection and maintenance would be less <br /> technical. The reinjection wells are subject to fouling. DDRW <br /> stated it would achieve the same results and it would be cheaper <br /> using percolation. The Regional Water Quality Control Board <br /> (RWQCB) stated facilities are required to look at alternative <br /> methods of disposal (e.g. , percolation, injection, alternate <br /> use, etc. ) . <br /> Ongoing Work• <br /> DDRW is currently monitoring TCE/PCE contaminated ground water at <br /> the Tracy Facility. The monitoring of OU-1 is being performed <br /> by Montgomery Watson. DDRW' s contractor, Montgomery-Watson, <br /> performs quarterly ground water sampling at the DDRW Tracy <br /> Facility and selected private residential wells . This <br /> information will be used during OU-1 design phase. <br /> Potential Source Areas : <br /> DDRW provided attendees with a map depicting the potential source <br /> areas of contamination. A risk assessment was performed which <br /> determined how much of a hazard via ground water pathway the <br /> PCE/TCE plumes pose to employees and the public. To make this <br /> determination they utilized geophysics, imaging technology, <br /> trenching, soil borings, and monitoring wells . This information <br /> along with new information gathered will be used to prepare a <br /> comprehensive risk assessment (all pathways : soil, water, air) <br /> for the Comprehensive Site Wide RI/FS . <br /> OU-1 Proposed Plan: <br /> The Proposed Plan reflects the preferred alternative selected by <br /> the lead and support agencies . DDRW selected air stripping as <br /> its method of cleanup. The air stripper will handle all volatile <br /> chemicals , not just TCE and PCE. It is speculated that it will <br /> take 30 years to clean up the ground water contamination at DDRW <br /> Tracy. <br /> 2 <br />