Silver Lake IA 06-LSR-1669

Assessment Comments

Monitored in 1990 by ISU as part of the Clean Lakes Classification study (1994); in 1993 & 1995 for surveys of Water Supply Reservoirs (Miller and Kennedy 1993 & 1995).

Basis for Assessment

Used assessments of support of the Class A (primary contact) uses (=FST) and Class B(LW) aquatic life uses (=FST) developed for the 1994 report.   Used assessment of the Class C (drinking water) uses developed for the 1994 report (=FS) in combination with results from the February 1995 sampling for eight agricultural herbicides as described by Miller and Kennedy (1995) to assess support of the Class C uses as FS due to (1) atrazine levels (0.3 and 0.4 ug/l deep water/ inlet) that are less than the average reportable concentration for the 19 reservoirs sampled (=0.84 ug/l), (2) cyanazine level (0.3 ug/l, deep water) much less than the average reportable concentration (1.04 ug/l), and (3) no violations of the atrazine MCL.