Assessment Comments
Assessment remains based on occurrence of a fish kill in May 2002.
Basis for Assessment
[NOTE: 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 (2012) 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" due to a lack of water quality information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" (IR Category 3b) due to occurrence of fish kills in September 1998 and May 2002; both kills affected Brown Creek and its confluent, the Des Moines River; both kills were caused by animal waste.
EXPLANATION: The 2000 and 2002 assessments of the aquatic life uses of this stream were based on the occurrence of a fish kill in September 1998 (see assessment for the 2000 and 2002 reports). According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates ongoing impairment of the aquatic life uses. Although three years had elapsed since the 1998 kill, an additional kill, also caused by an accidental release of animal waste (liquid manure), occurred on May 24, 2002. According to the fish kill report, an underground pipe broke resulting in the drainage of a holding lagoon. The liquid manure entered Brown Creek and traveled downstream to the Des Moines River; an estimated 33,400 fish were killed over an 18-mile stream/river reach. The party responsible for both the 1998 and 2002 kills was identified, and IDNR sought restitution for the value of the fish killed.
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 was placed in Category 4d of Iowa’s 2006 Integrated Report. IDNR considers IR 4d fish kill waters with no subsequent kills in at least the five years subsequent to the kill as appropriate for movement to IR categories 2b or 3b (i.e., Iowa’s list of waters in need of further investigation). Thus, this assessment segment was moved to Category 3b of Iowa’s 2010 Integrated Report and remains in IR Category 3b.
