Assessment Comments
Assessment based on results of (1) ambient monitoring by Illinois EPA near Lock and Dam 15 (station M 02) and (2) fish contaminant monitoring conducted by ALCOA & U.S. EPA/IDNR.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were not assessed. The Class B(WW) aquatic life uses were assessed as "fully supported." The Class C (drinking water) uses were assessed as "not supported." Fish consumption uses were assessed as "fully supported." Sources of data for this assessment include (1) results of monitoring conducted from January 1998 through July 2000 by the Illinois Environmental Protection Agency at station M 02 at Lock and Dam 15 at Arsenal Island at river mile 482.9 and (2) results of fish tissue monitoring in Pool 15 sponsored by ALCOA in 1996 and 1998 and from the U.S. EPA/IDNR (RAFT) fish tissue monitoring program in 2001.
EXPLANATION: Class A (primary contact recreation) uses were not assessed due to the lack of data for indicator bacteria. Class B(WW) aquatic life uses: Monitoring data from the Illinois EPA station showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 14 samples collected between January 1998 and July 2000, (2) no violations of the Class B(WW) chronic water quality criteria for toxic metals. Thus, based on results of chemical/physical water quality monitoring, the Class B(WW) aquatic life uses were assessed as "fully supported." Class C (drinking water) uses were assessed as "not supported" due to violations of the human health water quality criterion for arsenic. Levels of nitrate (maximum value of 2.5 mg/l in 14 samples) and Class C toxic metals were well below their respective MCLs and Class C human health criteria. Violations of the Class C human health criterion for arsenic (0.18 ppb), however, occurred in six of the 14 samples (43%) collected, with a maximum level of 3.0 ppb and mean level of 0.74 ppb (non-detects set equal to zero). According to IDNR guidelines for Section 305(b) assessments, if the mean level of a toxic metal or pesticide is greater than an MCL or human health criterion, "nonsupport" of the drinking water use is indicated. The mean level of arsenic during the biennial period (0.74 ppb) is approximately four times the human health criterion of 0.18 ppb; thus, "nonsupport" of drinking water uses is indicated.
Fish consumption uses were assessed as "fully supported" based on (1) lifting of the fish consumption advisory in August 2000, (2) results results of ALCOA-sponsored fish tissue monitoring in 1998 showing that average levels of total PCBs plus the upper 95% confidence limits were below ½ of the FDA action level for both target species (common carp and river carpsucker) at all four sample sites in Pool 15 (see assessment for the 2000 report above), and (3) results of EPA/DNR fish tissue (RAFT) monitoring in 2001 showing that levels of all contaminants were well-below FDA action levels in composite samples of fillets from common carp and channel catfish. Levels of total PCBs in the 2001 sample of common carp fillets was 0.467 mg/kg (Aroclors 1248 (<0.19 mg/kg); 1254 (0.26 mg/kg); and 1260 (0.026 mg/kg)); levels of total PCBs in the 2001 sample of channel catfish fillets was 0.544 mg/kg (Aroclors 1248 (<0.16 mg/kg); 1254 (0.32 mg/kg); and 1260 (0.064 mg/kg)).
