Bear Creek IA 06-LSR-1833

The assessment of the presumptive Class B(WW1) aquatic life uses remains based on data collected in 2002 as part of the IDNR/SHL stream REMAP project.  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 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).  The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).  The 2002 FIBI score was 27 (fair).  The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI score 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 43.  Even though this site failed the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.  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). 

This assessment is considered “evaluated” (of lower confidence) due to the lack of a biological assessment protocol for general use-only streams.  IDNR’s existing protocol has been calibrated to aquatic life reference conditions in wadeable Class B(WW2) and Class B(WW1) streams.  The aquatic environment of most general use streams is one of extremes in water quality.  Consequently, general use-only streams tend to have biological diversity that is low relative to more stable aquatic environments of Class B(WW2) and Class B(WW1) streams.  Thus, the use of biological assessment methods developed for the ecologically more stable and diverse Class B(WW2) streams to assess general use reaches will likely overstate the existence of impairment.  For these reasons, general use-only stream reaches that show a failure to meet regional expectations for aquatic biota (fish or aquatic macroinvertebrates) of Class B(WW2) streams, 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 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”.

The presumptive Class B(WW1) aquatic life uses are also assessed as “partially supported” (IR 3b) due to a fish kill that occurred on or before September 28, 2015, 4 miles NW of Meriden at K and L avenue bridges.  The following are notes from the fish kill investigation:

FO3 received a page early on Saturday morning from a chub fisherman near Meriden in Cherokee County.  He said there were “hundreds” of dead chubs and minnows under a bridge north of Meriden in Bear Creek.  Bear Creek flows northeasterly from that point about one mile and discharges into Mill Creek.  Water quality parameters were normal with high DO and low ammonia.  Dead fish were only observed under two bridges.  The second bridge, on C16 right before Bear Creek enters Mill Creek, had a few floaters that appeared to come from a pooled area under the bridge at L Avenue where most of the dead fish were observed, just south of County Road C16.  Flows in the creeks were high from rains in the area over the past few weeks.  No dying fish were observed.  This area had received approximately 1 inch of rain during the previous two days.  We contacted two cattle facilities in the area but saw no evidence of runoff.  It is possible some pollutants entered the stream and were washed away by the time we responded.  Fisheries personnel did not conduct a count as no obvious source was determined.  It is also possible that DO levels dropped in the pooled water overnight, killing fish, and then returned to normal.  It is also possible that the fish died of “natural” causes.

No estimates were provided for the number of fish killed, the value of the fish killed, or the cost of the Iowa DNR investigation.  The kill affected approximately 1 mile of stream. 

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 (2002-2005) 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 was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.”  Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5).  Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.