West Okoboji Lake - Main Basin South IA 06-LSR-1653

Assessment Comments

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

Basis for Assessment

Used assessments of support of the Class A (primary contact) uses (=FS) and Class B(LW) aquatic life uses (=FS) developed for the 1994 report.   To assess support of the Class C (drinking water) uses, used assessment developed for the 1994 report (=FS) in combination with results from the February 1995 sampling for eight common agricultural herbicides as summarized in Miller and Kennedy 1995.   Results show that three herbicides were detected at relatively low levels: atrazine (0.29 to 0.38 ug/l), cyanazine (0.12 to 0.17 ug/l), and simazine (0.2 to 0.23 ug/l).   Levels of atrazine and cyanazine were less than one-half the average reportable concentration for the 19 reservoirs sampled, and the levels of atrazine were less than one-half the MCL of 3.0 ug/l.  Thus, continued to assess support of the Class C uses as FS.   For 1995 RAFT levels of all contaminants in carp & yellow perch were < 1/2 FDA action levels (=FS).