Cedar Lake IA 04-LDM-1101
Madison County S19T76NR27W near Winterset.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
- Trophic
- Unknown
- Trend
- Stable
- Created
- 6/11/2019 10:02:13 AM
- Updated
- 6/11/2019 11:06:28 AM
The Class B(LW) aquatic life uses and fish consumption uses remain “not assessed” (IR 3a) due to lack of water quality information upon which to base an assessment. The Class C (drinking water) uses are assessed (monitored) as "fully supporting" (IR 2a) due to low level of the monitored contaminants (nitrate and atrazine). The sources of data for this assessment include (1) information from the Iowa DNR's Water Supply Section on violations of MCLs in finished water as summarized in annual compliance reports of Iowa’s public drinking water program from 2010 through 2014
The Class B(LW) (aquatic life) uses and fish consumption uses remain not assessed due to the lack of water quality information needed to assess these uses. Fish consumption uses were “not assessed” due to a lack of recent fish contaminant monitoring at this lake. Note 1: A TMDL for nitrate at Cedar Lake was prepared by DNR and approved by EPA in 2005; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. This impairment remained in IR Category 4a through the 2012 IR cycle. Due to lack of subsequent nitrate MCL violations, this assessment is moved to IR Category 2a for the current (2014) IR cycle.
The assessment of support of the Class C (drinking water) uses are assessed as"fully supporting" (IR 2a) due to lack of nitrate MCL violations from the Winterset Municipal Waterworks during the period 2012 through 2016. As documented in subsequent Iowa DNR drinking water program compliance reports, no violations of the nitrate MCL occurred at this utility in calendar years 2010 through 2014 (covering IR 2016 cycle). Because the trend of lower nitrate levels and no nitrate advisories has continued through this IR cycle, the lake is assessed as“full support” of the Class C (drinking water) uses.
Regarding atrazine, the results of monitoring from 2012-16 are similar to those from previous IR monitoring periods and continue to show generally low levels of atrazine in this reservoir. There were no violations for samples collected from the Winterset Municipal Waterworks during the 2012-16 period that exceeded the Class C criterion for atrazine of 3 ug/l. Based on DNR’s assessment methodology, if none of the moving annual mean contaminant level in source water is greater than the MCL, the Class C uses of the source water should be assessed as “fully supported.”
Note 2: A TMDL for atrazine at Cedar Lake was prepared and approved by EPA in 2010; thus, this lake was placed in IR Category 4a (TMDL approved) for the 2010 assessment/listing cycle. Because atrazine data over the 2010 and 2012 Integrated Reporting cycles showed “full support” of the drinking water uses, this assessment was moved to IR Category 2a (fully supported) for the 2012 IR Cycle.