Mill Branch Creek IA 04-LDM-6387

Assessment Comments

Assessment is based on results of a fish kill investigation in August 2010.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are "not assessed" due to a lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" based on the results of a fish kill investigation in August 2010.

EXPLANATION: A fish kill occurred at this site on August 23, 2010.   The kill was a result of a leak from an anhydrous ammonia tank pipe.   The cloud was sprayed down with water by the fire department.   A road culvert and a tile intake/line allowed the ammonia to reach Mill Branch Creek.   Mill Branch Creek flows into Cotton Creek, which then flows into White Breast Creek.    Dead fish were observed in all three of these streams below the tile line.   The kill affected 10.5 miles of these streams.  Approximately 2784 fish were killed.   No information on the species of fish killed was provided.   The estimated value of these fish was $12,891.81.   IDNR sought and received restitution for this fish 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 (2009-2011) 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 will be placed in Category 4d of Iowa’s 2012 Integrated Report.