Storm Lake IA 04-RAC-1143

Assessment Comments

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation uses) were "not assessed."  Continued to assess support of the Class B(LW) aquatic life uses as "partially supported."  Other beneficial uses remain "not assessed."  EXPLANATION:  The Class A (primary contact recreation) uses were changed from "fully supported / threatened" to "not assessed" due to the lack of information on levels of indicator bacteria at this lake during the 1998-1999 biennial period.   The previous (1998) assessment of support of the Class B(LW) uses ("partially supported") was reviewed and approved by the DNR Fisheries Bureau in 2000.   This assessment identified turbidity from natural resuspension of sediment, organic enrichment from natural shallowness as the primary water quality impacts at this lake.   This assessment is consistent with conclusions of a lake restoration study (Hoyman et al.  1994) that noted that Storm Lake--similar to other large, shallow, unprotected lakes--has persistent problems with turbidity due to in-lake dynamics that include wind-related resuspension of bottom sediments.    Fish consumption uses were changed from "fully supported" to "not assessed" due to the lack of recent fish contaminant monitoring at this lake.   The last fish tissue sample from this lake was collected and analyzed by Iowa State University in June 1993 as part of the "Storm Lake Restoration Study" (Hoyman et al.  1994); the fish species sampled was not identified [the most recent EPA/DNR (RAFT) fish tissue monitoring at Storm Lake was conducted in 1988].   Of the 16 organochlorine pesticides analyzed, only one was detected:  the level of DDE (0.150 mg/kg) was well below the FDA action level for DDT+DDD+DDE of 5.0 mg/kg.   Of the 11 toxic metals analyzed, mercury was the only one detected (0.080 mg/kg).   The levels of both DDE and mercury were well below both U.S.  FDA action levels and DNR levels of concern for fish contaminants.   Thus, these results do not suggest a fish contaminant problem at Storm Lake.   The result of this monitoring, however, are more than five years old.   Thus, these data are considered too old to characterize current water quality conditions, and the level of support of fish consumptions uses was changed to "not assessed."