West Branch Floyd River IA 06-FLO-1558

The Class B(WW2) aquatic life uses are assessed (evaluated) as "partially supported" based on the occurrence of a fish kill that occurred south of Sioux Center on August 10, 2016. An estimated 37,910 fish were killed in 4.5 miles of stream due to an unknown source/unknown cause. The valuation of the fish was $10,001.16 and the investigation expenses were $816.82. Information about the kill:

Investigated on 8/13 - 8/14/2016.This kill looks to have occurred 4-6 days ago based on the level of decomposition and scavenger activity. Many fish were deteriorated heavily. This stream bed is extremely hard to traverse in places because of heavy siltation and mud shorelines. The kill looks to have occurred when water levels were 6 inches to 1 foot higher than current level. The beginning of the kill is fairly well defined and located on the map in report. There were no dead fish upstream from this location.A source could not be determined by ESD. No restitution will be sought.

According to the DNR 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. If 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, however, there was no evidence that Iowa DNR had sought or received restitution for the value of the fish killed or for the costs of investigation. Thus, this impairment is placed in Category 5b of Iowa's 2018 Integrated Report.

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “partially supporting” based on the results of DNR/SHL biological sampling conducted in 2001. A series of biological metrics which 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 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 2001 FIBI score was 22 (poor) and the BMIBI score was 63 (good). The aquatic life use support was assessed 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 1994-2008. The FIBI BIC for this ecoregion is 43 and the BMIBI BIC for this ecoregion is 54. This segment failed the FIBI BIC and passed the BMIBI BIC in 2001.

This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over a recent five-year period. 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 DNR’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). DNR 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 was previously on Iowa’s Section 303(d) list and thus remains on Iowa’s Section 303(d) list of impaired waters (IR Category 5b-t).

Historic fish kill information:

A pollutant-caused fish kill occurred near Sioux Center on October 29, 2012. An estimated 190,000 fish were killed due to a wastewater pond discharge from a packing plant into a tributary of the West Branch Floyd River. Wastewater entered the West Branch of the Floyd River through a small tributary/ditch. Dead fish were observed at the confluence of the small tributary/ditch and the West Branch of the Floyd River (Section 28, T95N, R45W) and the fish kill extended downstream 11 miles(Section 28, T94N, R45W). According to the DNR 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. If 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 (2016), however, there was no evidence that Iowa DNR had sought or received restitution for the value of the fish killed or for the costs of investigation. Thus, this impairment was placed in Category 5b of Iowa's 2014 Integrated Report.

Two previous fish kills occurred on this stream in September 2003. The first of the two kills occurred on or before September 11, 2003. A cause of this kill could not be identified (cause = unknown). An estimated 40 fish were killed (five common carp and 35 “minnow” species). No estimated value of the fish killed was provided. No estimate of the length of this stream affected by the kill was provided. No responsible party was identified. The location point for this kill is the SE ¼ of the SE ¼ of Section 19, T96N, R44W, Sioux County. According to the DNR investigation, the Sioux Center area had recently received heavy rains. The second of the two kills occurred on or before September 13, 2003. No cause of the kill was determined, possibly due to the time that elapsed between the kill and the DNR investigation. An estimated 100 fish were killed; all fish were non-game fish (“minnows”). No estimated value of the fish killed water provided; no estimate of the length of stream affected was provided. No responsible party was identified. The location point for the kill is Section 17 of T94N, R45W, Sioux County. According to the DNR investigation, approximately 100 dead chubs and minnows were observed and appeared to have been dead for several days. Although a cause of the kill was not identified, DNR staff reported that water levels were extremely low at that time due to drought conditions, thus making fish susceptible to any kind of pollution that might have washed into the stream from the recent rainfall. These kills and others that occurred in small streams in northwest Iowa from September 11-15, 2003 were believed related to a rainfall event that followed a prolonged dry period. Based on the summaries of the kills provided by DNR field staff, the possibility exists that both kills occurred at the same time and were related to the same runoff event. None of the investigations of these kills, however, suggested a specific pollutant-related cause. Thus, this impairment was appropriate for Category 3b of Iowa’s 2006 Integrated Report (=list of waters in need of further investigation).

This stream segment’s fish community was sampled on September 4, 2015, as part of the DNR Watershed Improvement and Water Monitoring sections’ fishkill follow up monitoring program. Sampling methods described in DNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s assessment/listing methodology) were followed. Approximately 820 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 3,515 fish per mile compared to the Level IV ecoregion 47a average of approximately 524 fish per mile; 78% of the expected fish taxa for this ecoregion were sampled. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the October 2012 fish kill event. Thus, the impairment of aquatic life uses due to the 2012 fish kill was de-listed in 2016.