Lake Lashane IA 05-GRA-1374

Assessment Comments

Assessment is based on results of the "Iowa Voluntary Atrazine Monitoring Program" for 2000. S

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses, the Class B(LW) aquatic life uses, and the fish consumption uses remain "not assessed."  The Class C (drinking water) uses were assessed as "fully supported / threatened."  EXPLANATION:  The Class A (primary contact recreation) uses were "not assessed" due to a lack of information on levels of indicator bacteria at this lake.   The Class B(LW) uses were not assessed due to a lack of information on the aquatic communities of this lake.   The Class C (drinking water) uses were assessed as "fully supported / threatened" based on the 1998 results of the Novartis "Iowa Voluntary Atrazine Monitoring Program."  This monitoring showed that the time-weighted mean level of atrazine in samples collected from January to December 1998 (2.3 ug/l, N=13, maximum=5.9 ug/l) was below the MCL of 3.0 ug/l.   Based on DNR's Section 305(b) assessment methodology, if the average contaminant level in source water is less than the MCL, but a level in one or more samples is above the MCL, the Class C (drinking water) uses of the source water should be assessed as "fully supported / threatened."  Thus, the Class C uses of Lake LeShane were assessed as "fully supported / threatened."  Fish consumption uses were "not assessed due to the lack of fish contaminant monitoring at this lake.