Brushy Creek IA 04-RAC-1209
from confluence with unnamed tributary (S6 T82N R34W Carroll Co.) to headwaters in S27 T84N R36W Carroll Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 7/18/2019 2:08:57 PM
- Updated
- 8/5/2019 12:49:09 PM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2008 | Class BWW1 | Fish Kill: Due To Unknown Toxicity | N/A | Assessment Error |
The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses remain assessed as "partially supported" based on results of the DNR investigation of a fish kill in May 2014. Results of 2009 DNR/SHL biological sampling, however, suggested that the aquatic life uses should be assessed as "fully supporting". Due to the occurrence of the 2014 pollutant-caused fish kill, the aquatic life uses of this assessment segment are considered "partially supported" and remain on Iowa list of impaired waters. The historic Class B(WW1) aquatic life uses impairment based on a 2005 fish kill is proposed for de-listing for this cycle. The 2005 fishkill occurred in the immediate downstream segment and the impairment and fish kill information can be found there: https://programs.iowadnr.gov/adbnet/Segments/1818
The fish kill occurred on or before May 25, 2014. The kill began on an unnamed tributary of Brushy Creek near Halbur in Carroll County and was attributed a spill of anhydrous ammonia at a local co-op. An estimated 50,100 fish were killed over 5.45 miles of stream. The value of the fish killed was estimated a $4,550.38, and the investigation costs were $720.38. Although the party responsible for the kill was identified (local co-op), restitution for the fish killed or costs of investigation have not been received by DNR at the time of the current assessment. The following is from the Iowa DNR fish kill investigation report: Anhydrous ammonia spill from co-op. Fish Kill started at UTM, Zone 15, E 336945, N 4652200, NW quarter of section 18, T83N, R35W in Unnamed Tributary on south side of Halbur, Carroll County, IA and moved downstream into Brushy Creek ending at UTM, Zone 15, E 341075, N 4647620, Intersection of sections 27, 28, 33, and 34 of T83N, R35W of Carroll County, IA. 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. Thus, this assessment segment will remain in Category 5b of Iowa’s Integrated Report.
In contrast to the 2014 fish kill data, subsequent biological sampling conducted in 2009 by DNR/SHL suggested "full support" of the aquatic life uses of this segment. This evaluated biological assessment was based on data collected in 2009 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 biological 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 2009 FIBI score was 28 (fair) and the BMIBI score was 47 (fair). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54.
Even though this site passed both the FIBI and BMIBI BICs (using the FIBI UAV of 7 points and BMIBI UAV of 8 points), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small presumed B(WW1) (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.