East Lake (Lenox) IA 05-PLA-1478

Assessment Comments

Monitored in 1993 for Survey of Water Supply Reservoirs (Miller & Kennedy 1993).

Basis for Assessment

Lake was monitored near dam and near north inlet on Feb 3, 1993 for 7 ag herbicides in water and sediment.   Relatively high levels of atrazine and cyanazine were detected in water near the dam and inlet:  dam: (atrazine 1.2 ug/l; 8.7 ug/kg; cyanazine 1.1 ug/l; 7.0 ug/kg); inlet: (atrazine 1.3 ug/l; 5.7 ug/kg; cyanazine: 1.2 ug/l; 4.5 ug/kg).   Although below the MCL, these relatively high levels during winter suggest the possibility of levels > MCL during summer.   Detailed study at Corydon Res.  (Kalkhoff 1993) showed that levels of atrazine were relatively low during ice cover of winter but increased to well above the MCL during summer.   Additional monitoring is needed to determine levels of herbicides in summer.   Although levels of atrazine in water are < 1/2 MCL, consistenly high levels in both samples suggest threat to DW use from ag pesticides; thus, assess as FST.