Assessment Comments
Assessment remains based on results of a fish kill investigation in April of 2005.
Basis for Assessment
SUMMARY: The Class B(LW) (aquatic life) uses of this lake remain assessed (monitored) as “partially supported” due to a fish kill on April 14, 2005. A cause of this kill was not identified. According to the IDNR investigation, a kill that occurred just prior to the April 14th kill was apparently caused by a discharge to city (chlorinated) water to the lake. The party responsible for the April 14th kill was not identified. This impairment is appropriate for Category 5b of Iowa’s 2006 Integrated Report (=Section 303(d) list).
EXPLANATION: This kill occurred on or before April 14, 2005. The kill was attributed to “unknown/natural” causes. IDNR field staff investigated this kill. An estimated 80 fish were killed including largemouth bass (25), crappies (25), bluegill (20), and catfish (10). No estimate of the value of the fish killed was provided. According to staff from the city of Bondurant, an additional kill at this lake had occurred recently due to the discharge of city (drinking) water to the lake after a company had tested a tank for leaks. Chlorine present in city water is believed to have caused this kill. Some dead fish from this previous kill were still evident at the time of the April 14th kill. During the IDNR investigation, the water was clear and live fish were observed. Dead fish in various states of decomposition were present on the downwind side of the lake (north and east). A water sample from what appeared to be a field tile entering the lake from the west was analyzed by UHL for common Iowa agricultural chemicals and other water quality parameters. The results of this analysis did not suggest any causes of the kill.
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 during the most recent assessment period (2004-2007) 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. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.
