Clark Creek IA 01-UIA-6437

The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" due to a fish kill. The kill occurred approximately 6 mile southwest of New Albin in Allamakee County on or before October 12, 2015, and was attributed to runoff of land-applied animal waste from a hog confinement. The kill affected 0.75 miles of stream. Only two fish were reported as killed; the cost of the Iowa DNR investigation was $543.41. The following is from the Iowa DNR fish kill investigation report:

Cause of spill occurred when a manure booster pump had a cap blow off, causing manure to flow from the machine onto the creek bank. Estimated 1,000 gallons of manure was spilled. Most made it to Clark Creek. Very few dead fish were found either because they were land applied, the surge of water pushed them through when the berms broke and into the Upper Iowa River, or there just weren’t that many fish.

According to DNR’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. 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. 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 should be placed in IR Category 4d (impaired but TMDL not required). As of April 2016, there are no records of Iowa DNR having sought or received restitution for the value of the fish killed and cost of the Iowa DNR investigation. Thus, this assessment segment is placed in IR Category 5b of Iowa’s 2016 Integrated Report.

Results of biological monitoring in 2014 suggest that the presumptive Class B(WW1) aquatic life uses should be assessed (evaluated) as “partially supported”. This evaluated biological assessment was based on data collected in 2014 as part of the DNR/SHL headwater stream sampling project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2013 FIBI score was 27 (fair) and the BMIBI score was 58 (good). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61. Even though this site failed the FIBI BIC and passed the BMIBI BIC (using the BMIBI UAV (uncertainty adjustment value) of 8 points applied to single samples), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small presumed BWW1 (formally general use) stream and doesn’t fall in the calibrated watershed size.

This assessment is considered “evaluated” (of lower confidence) due to the lack of a biological assessment protocol for headwater streams. Prior to the changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this stream was classified only for general uses due to the inability of the stream to support a viable aquatic community at low-flow conditions. DNR’s existing biological assessment protocol, however, was calibrated to aquatic life reference conditions in larger wadeable streams with perennial flow. The aquatic environment of most headwater streams is one of extremes in water quality. Consequently, intermittent headwater streams tend to have biological diversity that is low relative to more stable aquatic environments of larger streams with perennial flow. Thus, the use of biological assessment methods developed for the ecologically more stable and diverse streams will likely overstate the existence of impairment in headwater streams. For these reasons, headwater stream reaches that show a failure to meet regional expectations for aquatic biota (fish or aquatic macroinvertebrates) will not be added to Iowa’s Section 303(d) list of impaired waters (Category 5 of the Integrated Report). The assessment type for these assessed waters will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to “monitored" (indicating an assessment with relatively high confidence). Such waters will be placed in either Category 2b or 3b of the IR and thus will be added to the state’s list of “waters in need of further investigation”.