Fairfield Reservoir 1 IA 03-SKU-909

Assessment Comments

Assessment remains based on results of the "Iowa Voluntary Atrazine Monitoring Program" for 2000 & 2001. This reservoir has not been sampled as part of the Iowa VMP since 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 are assessed (monitored) as "fully supported" 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.).   Due only to a change in IDNR's assessment/listing methodology, the assessment of the the Class C uses of this lake were changed from "fully supporting / threatened" (minor impacts) to "fully supporting".   This assessment is the same as that developed for the previous (2004) assessment/listing cycle.    

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 remains 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 levels in source water are less than the MCL, the Class C (drinking water) uses of the source water should be assessed as "fully supported."  At the recommendation of U.S.  EPA Region 7, IDNR's 2006 assessment/listing methodology was changed to eliminate use of the "fully supported/threatened" (not impaired) category.   Thus, previous assessments identified as "fully supported/threatened" (minor impacts) were changed to "fully supported" for the 2006 assessment/listing cycle.   This change does not alter the 2004 assessment for Fairfield Municipal Reservoir 1:  this waterbody remains in IR Category 2a.


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