Assessment Comments
Assessment based on results of (1) ambient monitoring by Illinois EPA near Lock and Dam 15 (station M 02) from 2000-02 and (2) fish contaminant monitoring conducted by ALCOA & U.S. EPA/IDNR in 1996, 1998, and 2001.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were not assessed due to lack of information upon which to base an assessment. The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from 2000-02. The Class C (drinking water) uses are assessed (monitored) as "not supported" due to violations of state water quality criteria for arsenic. Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 1996, 1998, and 2001. Sources of data for this assessment include (1) results of ambient water quality monitoring conducted from April 2000 through November 2002 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 sufficient data for indicator bacteria from Station M 02 of the Illinois EPA monitoring network. Only four samples were analyzed for indicator bacteria (fecal coliforms) during the 2000-02 period (geometric mean = 31 orgs/100 ml; maximum = 450 orgs/100 ml); this amount of data is not sufficient for developing an assessment of support of the Class A uses. The Class B(WW) aquatic life uses are assessed (monitored) as “fully supported” based on results of Illinois EPA monitoring at station M 02. This monitoring showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 11 samples collected between April 2000 and November 2002 and (2) no violations of the Class B(WW) chronic water quality criteria for toxic metals during this time period. Thus, based on results of chemical/physical water quality monitoring, the Class B(WW) aquatic life uses are assessed (monitored) as "fully supported." Class C (drinking water) uses, however, are assessed (monitored) as "not supported" due to violations of the human health water quality criterion for arsenic. Levels of nitrate (maximum value of 2.6 mg/l in the 11 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 nine of the 11 samples (82%) collected, with a maximum level of 2.0 ppb and mean level of 1.0 ppb (with the two 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 (1.0 ppb) is over five times the human health criterion of 0.18 ppb; thus, "nonsupport" of drinking water uses is indicated. Fish consumption uses remained assessed as "fully supported" based on (1) lifting of the fish consumption advisory in August 2000, (2) 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, 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 (see assessment for the 2000 and 2002 reports).
