Assessment Comments
Assessment is based on (1) results of IDNR/UHL ambient water quality monitoring conducted in 2002 and 2003 in support of TMDL development and (2) occurrence of a fish kill in September 2013.
Basis for Assessment
[Note Prior to the 2008 Section 305(b) cycle, this river 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.gov/Portals/idnr/uploads/water/standards/files/swcdoc2.pdf) and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW2) uses).]
SUMMARY: The Class A1 (primary contact recreation) uses remain assessed (evaluated) as "not supported" (IR 5a) due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW2)aquatic life uses are assessed as "partially supported" (IR 5b) due to a fish kill caused by animal waste in September 2013. The sources of data for this assessment include (1) results of IDNR/UHL ambient water quality monitoring conducted in 2002 and 2003 as part of TMDL monitoring (TMDL station 6; STORET station 11600005) and (2) results of an IDNR fish kill investigation in September 2013. Previous assessments of support of aquatic life uses were also based on results of biological monitoring by the IDNR Fisheries Bureau in 2000. These data have aged beyond 10 years aren are thus no longer useful for characterizing current water quality conditions.
EXPLANATION: 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/UHL 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 "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
The Class B(WW-2) (aquatic life) uses are assessed (monitored) as "partially supported" due to the occurrence of a fish kill in September 2013. The kill occurred 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. DNR 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 (January 2014), 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).
In contrast to the fish kill impairment, results of chemical/physical water quality monitoring conducted by IDNR/UHL 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.
Previous assessments of the Class B(WW2) aquatic life uses were based on 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.
