Corydon Reservoir IA 05-CHA-1331

Assessment Comments

Basis for Assessment

Continue to assess support of the Class C (drinking water) uses as NS due to high levels of atrazine reported by Kalkhoff (1993).   Results from sampling in January 1995 as reported by Miller and Kennedy (1995) showed that Corydon Reservoir had the highest concentration of atrazine (2.6 and 2.4 ug/l; inlet and dam, respectively) of the 19 reservoirs sampled; levels of cyanzine (2.1 and 2.3 ug/l at inlet and dam) were also among the highest of the study.  Levels of atrazine metabolites were also highest of the study.   The assessment of support of the Class C uses as NS remains despite (1) the fact that Corydon Reservoir is not used as a source of drinking water (city of Corydon receives drinking water from the Rathbun Rural Water Association and (2) that the MCL for atrazine was not exceeded during the study.   USGS monthly mon from 1990 thru Dec 94 shows spring/summer viols of atrazine MCL.