Red Haw Lake IA 04-LDM-1073

Assessment Comments

Assessment is based on (1) surveys of DNR Fisheries Bureau, (2) results of lake monitoring, and (3) results of fish tissue (RAFT) monitoring in 1997.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses were assessed as "fully supporting."  The Class B(LW) aquatic life uses remained assessed as "fully supported"; fish consumption remained assessed as "fully supported."  EXPLANATION:  Levels of indicator bacteria at Red Haw Lake beach were monitored approximately twice per week during summer 1999 by DNR Parks, Recreation and Preserves Division as part of a beach monitoring program at 11 state-owned lakes.   Results of the 34 samples collected at this beach showed that levels of indicator bacteria (fecal coliforms) were very low compared to other Iowa lakes, with the overall geometric mean (13 orgs/100 ml) well below the state WQ criterion of 200 orgs/100 ml.   The maximum level of fecal coliforms in the 34 samples was 120 orgs/100 ml on June 14, 1999; thus, no samples exceeded the state criterion of 200 orgs/100 ml.   According to U.S.  EPA guidelines for determining "full support" of primary contact uses (U.S.  EPA 1997b, page 3-35), the geometric mean of fecal coliform bacteria levels should not exceed 200 orgs/100ml based on at least five samples in a 30-day period.   In addition, not more than 10% of the total samples taken during any 30-day period should have a density that exceeds 400 orgs/100 ml.   None of the sixteen 30-day periods during summer 1999 had geometric means (N = from 6 to 10 samples per period) greater than 200 orgs/100ml.; the maximum 30-day geometric mean was 23 orgs/100ml.   No samples exceeded the EPA-recommended single sample maximum density for fecal coliform bacteria of 400 orgs/100ml.   Thus, the Class A (primary contact recreation) uses were assessed as "fully supported."  The Class B(LW) aquatic life uses remain assessed as "fully supported" based on review and approval of the previous (1998) assessments by the DNR Fisheries Bureau in 2000.   Fish consumption uses remained assessed as fully supported (=FS) based on results of EPA/DNR fish tissue (RAFT) monitoring in 1997 that showed levels of all contaminants < ½ of respective FDA action levels and DNR levels of concern (see above).