Assessment Comments
Assessment is based on results of (1) IDNR investigations of fish kills in September 2001, September 2002, and August 2006; and (2) 1999 & 2002 IDNR/UHL biological monitoring data: FIBI = 30 (fair), 5 (poor); BMIBI = 47 (fair), 30 (poor). FIBI BIC = 43, BMIBI BIC = 54.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to a lack of water quality information upon which to base an assessment. The Class B(WW-2) aquatic life uses are assessed (monitored) as “not supporting” based on results of IDNR/UHL REMAP biological monitoring for fish and aquatic macroinvertebrates conducted in 1999 and 2002. “Impairment” of the Class B(WW-2) uses is also indicated by the occurrence of pollutant-caused fish kills in 2001, 2002, and 2006. The sources of data for this assessment include (1) results of biological monitoring conducted in 1999 and 2002 as part of the IDNR/UHL biocriteria and REMAP projects and (2) results of IDNR investigations of fish kills in 2001, 2002, and 2006.
EXPLANATION: The Class B(WW-2) aquatic life uses are assessed (monitored) as "partially supported" based on results of fish kill investigations in 2001, 2002 and 2006. The most recent of these fish kills occurred on August 1, 2006 and was attributed to animal waste. Multiple fish kills occurred in this area after heavy rains. Very low dissolved oxygen levels, high ammonia levels (15 ppm), and the odor of manure were noted during the investigation. Approximately 21,834 fish including bullheads, chubs, and minnows were killed within a five mile stretch of this stream near Royal. The estimated value of these fish was $4777.06. At the time of this assessment there are no records that IDNR has sought/received restitution for this fish kill.
A fish kill also occurred on this stream segment south of Royal on September 19, 2001. The kill was caused by the discharge of cattle manure from an open feedlot; an estimated 8,900 fish were killed. No estimate of the length of stream affected is available. Water quality monitoring conducted with a field kit during the fish kill investigation showed a dissolved oxygen concentration of zero and an ammonia-nitrogen concentration of 12.5 mg/l.
An additional fish kill occurred on this segment on September 18, 2002. The kill was caused by discharge of cattle manure from an open feedlot. (NOTE: this is the same feedlot responsible for the September 2001 fish kill.) Approximately 8988 fish were killed in a 4.3 mile stretch of stream. The estimated value of these fish was $2093.01.
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 (2007-2009) 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. Thus, this assessment segment will remain in Category 5b of Iowa’s 2010 Integrated Report.
Results of biological data collected in 1999 and 2002 as part of the IDNR/UHL biocriteria and REMAP projects also suggest "partial support" of the aquatic life uses. The 1999 FIBI score was 30 (fair) and the BMIBI score was 47 (fair). The 2002 FIBI score was 5 (poor) and the BMIBI score was 30 (poor). Thus, the aquatic life use support was assessed (monitored) as partially supporting (=PS), 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 1994-2004. The FIBI BIC for this ecoregion is 43 and the BMIBI BIC for this ecoregion is 54. This segment passed the FIBI and BMIBI BICs 0/2 times in the last 10 years.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous 10 years (1999-2008); however, the multiple samples were not collected during 2004-2008. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.
