Assessment Comments
Assessment remains based on results of a fish kill investigation in June 2009.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life 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. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to a lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (monitored) as "partially supported" (IR 4d) based on results of a fish kill investigation in June 2009.
EXPLANATION: The kill occurred on or before June 8, 2009 and affected an unknown, but small number of fish. While the number of fish killed was small, the value of the fish was high, as many trout were killed. The kill occurred along a 4.5 mile stretch of Buck Creek one mile NNW of Garnavillo. The cause of the kill was suspected to be of human origin, as there was a recent pesticide spill to the stream and the potential from runoff from an open cattle feed lot. Updated information suggests the kill was related to runoff from the open cattle feed lot. IDNR sought and received restitution for this kill.
According to IDNR’s 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 during the most recent assessment period 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. Thus, this assessment segment was placed in Category 4d of Iowa’s 2012 Integrated Report and remains in IR 4d.
