Silver Lake IA 06-LSR-1669

Assessment Comments

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

Basis for Assessment

Both fishable and swimmable uses were assessed as FST for the following reasons: (1) BPJ of DNR Fisheries, (2) results of monitoring in 1990 show that average levels of total-P, chl-a, and TSS are at or slightly better than overall average levels of the 116 SPOLs sampled in 1990 and 1992; level of secchi depth, however, was relatively low (0.4 m), but was within the overall average +/- 1 SD.   Assessment in 1992 states that uses are threatened by siltation and nutrients from agriculture and secondarily from unknown toxicity due to urban runoff.   Lake was monitored on March 2, 1993 at two locations for 7 ag herbicides in water and sediment.   No herbicides were detected in water; sediment sample from deep area contained low level of atrazine.   Lake water had lowest level of atrazine of the 15 reservoirs sampled; thus, assess DW uses as FS.