Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in August 2005.
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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2010) 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 the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses of this stream remain assessed (monitored) as “partially supported” due to a fish kill in August 2005. The kill was caused by hog manure. The party responsible for the kill was identified, and IDNR has sought restitution for the value of the fish killed and the costs incurred by IDNR during investigation of the kill. This impairment is appropriate for Category 4d of Iowa’s Integrated Report. This kill also affected a portion of Roberts Creek (waterbody IA 01-TRK-0360-3).
EXPLANATION: This kill occurred on or before August 1, 2005 and was caused by a release of hog manure from an over-full storage pit: According to the IDNR investigation, an outdoor storage pit lacked sufficient capacity to handle the amount of manure delivered to it from an indoor storage pit; thus, an overflow occurred. Approximately 2.25 miles of Roberts Creek were affected by the resulting kill. The kill began in Section 8 of T95N, R6W, Clayton County, and proceeded downstream through Section 9, 15, and 15 of T95N, R6W. An estimated 8,000 fish were killed; other than a notation that the kill affected “mostly non-game species, no detailed information on species killed is available. No estimate of the value of the fish kill was provided. The party responsible for the kill was identified.
According to the IDNR assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”. If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. 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 will be placed in IR Category 4d (impaired but TMDL not required). IDNR feels that (1) TMDLs should not be required for kills caused by a one-time illegal or unauthorized release of manure or other toxic substance where enforcement actions were taken and (2) enforcement action is more appropriate, efficient, and effective for addressing a spill-related impairment than is the TMDL process.
