Corydon Reservoir IA 05-CHA-1331

Assessment Comments

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses remained "not assessed."  The Class B(LW) aquatic life uses were changed from "partially supported" to "not assessed."   The Class C (drinking water) uses remain assessed as "not supported."  The fish consumption uses remained "not assessed."  EXPLANATION:  The Class A (primary contact recreation) uses were "not assessed" due to a lack of information on levels of indicator bacteria at this lake.   The level of support of the Class B(LW) uses was changed from "partially supported" to "not assessed" due to a lack of recent information on the status of the aquatic communities of this lake.   The previous assessment of support of the Class B(LW) aquatic life uses ("partially supported"; see above) was based on a 1992 "best professional judgement" review by the DNR Fisheries Bureau.   This assessment has not been updated since 1992 and is now considered too old (greater than five years) for characterizing current water quality conditions.   Thus, the assessment of the Class B(LW) aquatic life uses was changed to "not assessed."  The Class C (drinking water) uses remained assessed as "not supported." This assessment is based primarily on results of the 1995 UHL winter survey of Iowa water supply reservoirs (Miller and Kennedy 1995) that showed Corydon Reservoir had the highest levels of atrazine of the 19 reservoirs sampled (see assessment for the 1996 report above).   Fish consumption uses were "not assessed" due to the lack of fish contaminant monitoring at this lake.