South Raccoon River IA 04-RAC-1183

The Class A1 uses remain assessed (evaluated) as "not supported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the four samples collected in May and June 2005 at the DNR/SHL TMDL Site 32 (6,734 orgs/100ml) far exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. All four samples (100%) exceed Iowa’s single-sample maximum criterion of 235 orgs/100 ml. The four sample dates in 2005 and the associated E. coli levels are as follows: May 26: 680 orgs/100 ml; June 12: 240,000; June 13: 30,000 orgs/100 ml; June 23: 420 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to DNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). The amount of data (four samples) does not meet DNR guidelines for Clean Water Act assessment and listing that require at least 10 samples be collected per site over a three-year period. This amount of data also fails to meet DNR guidelines for overwhelming evidence of impairment which requires at least five samples over a three-year period such that the geometric mean criterion would be exceeded even if the remaining five samples were all less than the level of detection (i.e., 10 orgs/100 ml). Assessments based on data that do not meet DNR assessment/listing guidelines are considered “evaluated” (i.e., of lower confidence); these assessments are not appropriate for adding waters to Iowa’s Section 303(d) list of impaired waters. Such assessments are, however, appropriate for addition of waters to IR subcategories 2b or 3b and to Iowa’s list of waters in need of further investigation.

The Class B(WW1) (aquatic life) uses are assessed (monitored) as "partially supported" due to the occurrence of a fish kill that occurred on or before April 11, 2014. Approximately 16,600 fish were killed over eight miles of stream. The value of the fish was reported as $1,846.22; the cost of the DNR investigation was set at $1240.42. The cause of the kill was identified as a spill of ammonia fertilizer. The following is from the report for this fish kill:

Anhydrous ammonia was released into Brushy Creek when the Oak Ave bridge collapsed, sending a tractor and anhydrous ammonia tanks into the stream. Kill extended from bridge 8 miles downstream, ending in South Raccoon River at Montieth Ave (T79N R31W Sec23).

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 will be placed in IR Category 4d (impaired but TMDL not required). At the time of this assessment (December 2016), there is no indication that DNR has sought or received restitution for this fish kill. Thus, this assessment segment is placed in Category 5b of Iowa’s 2016 Integrated Report (=303(d) list).

Results of biological sampling in 2005 and 2012, however, suggested that the Class B(WW1) aquatic life uses should be assessed (evaluated) as "fully supported.” A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were 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 2005 FIBI score was 59 (good) and the BMIBI score was 54 (good). The 2012 FIBI score was 53 (good) and the BMIBI score was 65 (good). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI and BMIBI BICs 2/2 times in the last 12 years.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 12 years; however, the multiple samples were not collected during a recent five-year period.