Loch Ayr IA 05-GRA-1381

Assessment Comments

Basis for Assessment

Used results of sampling for eight common agricultural herbicides in January 1995 as reported in Miller and Kennedy (1995) to assess support of the Class C (drinking water) uses as FST due to levels of atrazine below the MCL.  Levels of four herbicides (atrazine, cyanazine, metolachlor and simazine) and two atrazine metabolites were detected.   Levels of atrazine in water were approx twice the average level of 1.03 ug/l for all 19 lakes, with levels in Loch Ayr ranging from 1.9 to 2.1 ug/l.   Levels of cyanazine (0.44 to 0.56 ug/l (dam and inlet)) were approx 1/2 the average concentration for all lakes.  Levels in finished water were lower than lake levels probably due to use of powdered activated carbon in the treatment process.