Iowa River IA 02-IOW-622

Assessment Comments

Assessment is based on results of (1) USGS/NAWQA monitoring at Wapello from Oct. 1998 to Sept. 2001 and (2) fish tissue (RAFT) monitoring in 1997, 1999 & 2001.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses are not assessed, and the Class B(WW) aquatic life uses are assessed as "fully supported."  Fish consumption uses remain assessed as "fully supported."  EXPLANATION:  Monitoring conducted on the Iowa River at Wapello from October 1998 through September 2001 by USGS (station 05465500) did not include analysis for fecal coliform bacteria (in summer 1997, USGS switched from fecal coliform bacteria to E.  coli as the bacterial indicator for NAWQA monitoring; the Iowa Water Quality Standards specify fecal coliform bacteria as water quality criterion to protect Class A (primary contact recreation) uses).   The assessment of Class A uses developed for the 2000 report ("partially supported," see above) was based on a geometric mean of fecal coliform bacteria from the recreational season of 1996.   These data, however, are now considered too old (greater than five years) for characterizing current water quality conditions.   Thus, the degree to which this river segment supports its Class A (primary contact recreation) uses is "not assessed."  Regarding support of the Class B(WW) uses, results of the USGS/NAWQA monitoring from October 1998 through September 2001 showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 35 samples collected, and (2) no violations of the Class B(WW) chronic water quality criteria for chlorpyrifos, DDE, or dieldrin in the 34 samples analyzed.   The assessment of aquatic life uses developed for the 2000 report ("partially supported," see above) was based on two violations of the Class B(WW) chronic WQ criterion for dieldrin in the 52 samples collected between March 1996 and August 1998.   Because no dieldrin was detected in the 34 samples collected between October 1998 and September 2001, this assessment was changed to "fully supported."  Fish consumption uses remained assessed as "fully supported" based on results of EPA/DNR fish tissue (RAFT) monitoring near Wapello in 2001 that showed levels of contaminants in the composite sample of whole-fish common carp remain below ½ of the respective FDA action levels and DNR levels of concern.