Comment submitted by Stephen Spencer, Regional Environmental Officer, Office of Environmental Policy and Compliance, United States Department of the Interior

Following my request for comments on this proposed listing that was sent to appropriate Department of the Interior Bureaus and Offices, these comments were provided to this office by the USGS Texas Water Science Center in Austin, Texas. ____________________________________________________________________ Per your request for comments on the possible listing of the Donna Canal as an NPL Site, we wanted to pass along our thoughts. Our research team did a series of studies of PCBs in the Donna Canal to identify and isolate the source of PCBs, including all of the suspended-sediment chemistry sampling done there. We conducted 5 sampling campaigns between Feb 1999 and April 2001; the April 2001 suspended-sediment sampling mentioned in the EPA fact sheet for this site was done by us. We collected the samples and passed them to TCEQ colleagues who had them analyzed, I believe, at the EPA lab in Houston. Suspended sediment was the medium in which PCBs were detected. Our studies were published in a USGS Fact Sheet (http://pubs.usgs.gov/fs/fs01602/pdf/FS_016-02.pdf) and included as a case study in a journal article documenting our suspended-sediment sampling methods (http://tx.usgs.gov/coring/pubs/Arch%20Env%20LVSS.pdf). We wanted to summarize for you and others some of our findings and understanding of the site: Studies by EPA and TCEQ in the 1990s found extremely high PCB levels in some fish but they were unable to detect them in water or bottom sediments using traditional sampling approaches. We were asked by TCEQ to attempt to locate the source using what at the time were new methods we'd developed for isolating suspended sediment from large volumes of water (we call it large-volume suspended sediment (LVSS) sampling). From 1999 to 2001 we made five sampling trips to Donna and succeeded in narrowing the search radius down from 5 miles of canal to a short stretch of canal, probably a few hundred yards or less, just downstream from the siphon. It appears that PCBs in suspended sediment are much more bioavailable than PCBs in bottom sediment. Concentrations in suspended sediments in the Donna Canal are typical of concentrations in bottom sediments in many urban lakes we've sampled but are much higher in fish. On each trip, in spite of the fish-possession ban, we saw many people fishing in the canal (see cover photo on our Fact Sheet), thus, it's clear that the ban alone is not preventing human exposure. The combination of a relatively clearly defined source area and high fish concentrations with ongoing human exposure suggests to us a serious problem with a manageable solution. Our team is a part of the USGS National Water-Quality Assessment (NAWQA) Program's National Synthesis Team. Our primary research is national-scale trends in metals and organic contaminants using lake sediment cores (see: http://tx.usgs.gov/coring/index.html). In addition, we have done a number of sediment-chemistry studies including several PCB source investigations at military (Mountain Creek Lake and Lake Worth in Dallas and Fort Worth) and industrial (Devil's Swamp Lake in Baton Rouge) sites. Either Peter Van Metre or Barbara Mahler of the USGS Texas Water Science Center are willing to participate on a site team addressing remedial decisions for the Donna Canal.