Assessment Comments
Assessment is based on results of (1) a fish kill investigation in April 2002 and (2) IDNR/UHL ambient water quality monitoring in 2004.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" due to occurrence of a fish kill in April 2002. This kill was caused by a spill. Sources of data for this assessment include (1) results of the investigation of the April 2002 fish kill and (2) results of IDNR/UHL monitoring for dissolved oxygen from May to December 2004 at the County Road X16 crossing (station 15030011).
EXPLANATION: The fish kill occurred on April 29, 2002, and resulted from the discharge of 1,500 gallons of 10-34-0 starter fertilizer from a local dealer of agricultural chemicals. Approximately 6 miles of this stream was affected; approximately 5,800 fish were killed. 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. A fish kill also occurred on this stream in 1995; the kill was attributed to animal waste from a feedlot (see the assessment for the 1998 report for more information).
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 (2002-2005) 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. IDNR sought and received restitution for the value of the fish killed in the April 2002 kill from the responsible party.
The results of IDNR/UHL water quality monitoring in 2004 show no violations of the Class B(LR) criterion for dissolved oxygen (5.0 mg/l) in the 26 samples collected from May to December (minimum value = 6.1 mg/l).
