Assessment Comments
Assessment is based on results of an IDNR investigation of a fish kill in August 1999.
Basis for Assessment
SUMMARY: The general aquatic life uses remain assessed (evaluated) as "partially supported" due a fish kill in August 1999.
EXPLANATION: The previous (2000) assessment of the aquatic life uses was based on the occurrence of a fish kill near Ainsworth in August 1999. The kill was attributed to sewage from the Ainsworth municipal wastewater lagoon. An estimated 4,500 fish were killed (see assessment for the 2000 reporting cycle for more information). The party responsible for the kill was identified, and restitution was sought. 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 (2000-2002) indicates ongoing impairment of the aquatic life uses. The absence of a fish kill in the three-year period following a fish kill, however, suggests that impacts from the kill have likely dissipated. Because the most recent pollution-caused fish kill occurred on this stream segment prior to the most recent three-year period, but occurred no more than six years ago, the aquatic life uses can remain assessed as "partially supported." Due to the age of the kill (more than three years old), however, the confidence level for this assessment should be considered relatively low and the assessment type should thus be considered "evaluated."
