Fairfield Reservoir 1 IA 03-SKU-909

Assessment Comments

Assessment is based on results of the "Iowa Voluntary Atrazine Monitoring Program" for 2000 & 2001.

Basis for Assessment

SUMMARY:  The Class B(LW) aquatic life uses and the fish consumption uses remain "not assessed" due to the lack of water quality information upon which to base an assessment.   The Class C (drinking water) uses remain assessed (monitored) as "fully supported / threatened" (minor impacts) based on the results of the Iowa Voluntary Atrazine Monitoring Program conducted in 2000 and 2001 by Syngenta Crop Protection, Inc.  (formerly Novartis Crop Protection, Inc.).  

EXPLANATION:  The Class B(LW) uses remain not assessed due to a lack of information on the aquatic communities of this lake.  

The assessment of support of the Class C (drinking water) uses was based on the results of the Syngenta "Iowa Voluntary Atrazine Monitoring Program" in 2000 and 2001.   This monitoring showed that the time-weighted mean levels of atrazine in samples collected from this reservoir in these two calendar years were below the MCL of 3.0 ug/l.   The time-weighted mean of atrazine in 2000 (N=30) was 1.6 ug/l and in 2001 (N=31) was 1.2 ug/l.   Only one of the combined 60 samples collected from this reservoir in 2000 and 2001 exceeded the MCL of 3.0 ug/l with a value of 3.6 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, based on the single MCL violation in 2000, the Class C uses of Fairfield Reservoir No.  1 were assessed as "fully supported / threatened."  

Fish consumption uses were "not assessed" due to the lack of fish contaminant monitoring at this lake.