Assessment Comments
Assessment is based on results of an IDNR fish kill investigation in August 2012.
Basis for Assessment
[NOTE 1: The original segment of IA 02-WIN-0025_0 was split into two waterbodies in July 2004, at the gravel pits located within Mason City. Downstream of Black Pit and Blue Pit, Cheslea Creek remains IA 02-WIN-0025_0. Upstream of these pits, this stream has been renamed as IA 02-WIN-0026_0. Assessment information for the 2004 reporting cycle and before refer to these two waterbodies together.]
[Note 2: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain “not assessed” (IR 3a) due to the lack of water quality information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" (IR 4d) due to the occurrence of a fish kill in August 2012.
EXPLANATION: The Class B(WW1) (aquatic life) uses are assessed (evaluated) as "partially supporting" based on results of a fish kill investigation in August 2012. The kill occurred on or before August 9, 2012 and was attributed to a discharge of iron-laden cooling water. An estimated 3,200 fish were killed with a value of $305 and an investigation cost of $345. IDNR sought and received restitution for this fish kill.
According to DNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill during an assessment period indicates "partial support" of the aquatic life uses. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody should be placed in IR Category 4d (impaired but TMDL not required). Thus, this assessment segment is placed into Category 4d of Iowa's 2014 Integrated Report.
