Lake Lashane IA 05-GRA-1374

Assessment Comments

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

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses, Class B(LW) aquatic life uses, and the fish consumption uses remain "not assessed."  The Class C (drinking water) uses are assessed (monitored) as "fully supported."  The source of data for this assessment is the results of the Iowa Voluntary Atrazine Monitoring Program conducted in 2000 by Syngenta Crop Protection, Inc.  (formerly Novartis Crop Protection, Inc.).   EXPLANATION:  The Class A and Class B(LW) uses remain not assessed due to the lack of water quality information needed to assess these uses.   The assessment of support of the Class C (drinking water) uses was based on the results of the Syngenta "Iowa Voluntary Atrazine Monitoring Program" from March to October 2000.   This monitoring showed that the time-weighted mean level of atrazine in samples collected from this lake in 2000 was far below the MCL of 3.0 ug/l.   The time-weighted mean of atrazine in 2000 (N=20) was 0.87 ug/l; no sample values exceeded the MCL (maximum atrazine level = 0.3 ug/l).   Based on DNR's Section 305(b) assessment methodology, if the average contaminant level in source water is less than the MCL, and no sample values exceed the MCL, the Class C (drinking water) uses of the source water should be assessed as "fully supported."  Fish consumption uses were "not assessed due to the lack of fish contaminant monitoring at this lake.