Little Rock River IA 06-BSR-1798

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 18 samples collected at the IDNR/SHL TMDL monitoring station near Doon during summer recreational seasons of 2002-2003 (311 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Ten of the 18 samples (56%) exceed Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’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 "impaired" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).  

The assessment of the Class B(WW2) aquatic life uses is changed from "partially supported" (IR 5b) to "not assessed" (IR 3a) based on results of a fish kill follow-up survey in September 2015.  A fish kill occurred in this stream segment on or before September 3, 2013.   A total of 522 fish were killed over 1.75 miles of stream.  The value of the fish was reported as $2,349.35.   The cause of the kill was identified as a spill of animal waste from an open cattle feedlot.   The following is from the fish kill investigation report:  

"Runoff from two open feedlots.   Dead fish were observed downstream of the confluence of two small drainage ways on the Little Rock River.   IDNR enumerated all dead fish – there are no expansions.    This was possible because the event did not impact large numbers of small fish (minnows/shiners) and the kill extended 1.75 miles."

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 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 (2016), there was no indication that DNR had sought or received restitution for this fish kill.   Thus, this assessment segment was placed in Category 5b of Iowa’s 2014 Integrated Report (=303(d) list).

This stream segment’s fish community was sampled on September 3, 2015, as part of the IDNR Watershed Improvement and Water Monitoring sections’ fish kill follow up monitoring program.  Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s assessment/listing methodology) were followed.  Approximately 985 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 5,640 fish per mile compared to the Level IV ecoregion 47a average of approximately 525 fish per mile; 89% of the expected fish taxa for this ecoregion were sampled.  For detailed results of this sampling, see https://programs.iowadnr.gov/bionet/Fish/Session/1693.  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 September 2013 fish kill event.  Thus, the assessment of aquatic life use support for this stream segment is being moved from impairment Category 5b of Iowa’s Integrated Report to Category 3a (designated use not assessed). 

Results of chemical/physical water quality monitoring conducted by IDNR/SHL from March 2002 through December 2003 in support of TMDL development suggested relatively good water quality in this stream and "full support" of aquatic life uses.   None of the 21 samples collected had levels of dissolved oxygen, pH, or ammonia-nitrogen that violated state water quality standards (these samples were not analyzed for toxic metals or pesticides).   These results, although somewhat limited in terms of parameter coverage, suggested "full support" of the Class B(WW2) aquatic life uses. These data, however, have aged beyond 10 years and are thus no longer useful for characterizing current water quality conditions.

Previous assessments of the Class B(WW2) aquatic life uses were based on biological data collected in 2000 as part of an IDNR Fisheries stream sampling project: Manchester research station.   These data are now considered too old to be useful for characterizing current water quality or biological conditions.   As water quality data age, they are less able to represent current water quality conditions.   As data age beyond ten years, their ability to represent current water quality conditions is increasing suspect.   Additional monitoring is needed in this assessment segment to update status of its aquatic communities.