Rhine Creek IA 02-IOW-6412

The presumptive Class (BWW1) aquatic life uses of this stream remain assessed (monitored) as "partially supported" due to the occurrence of a fish kill in November 2012. Approximately 2,190 fish were killed in over one mile of stream. The value of the fish was reported as $213.60. The cause of the kill was identified as a pesticide spill. The following is from the DNR fish kill investigation:

"The source [of the pesticide(s) that caused the kill] originated from corn and soybean rinsate tanks. The valves apparently had been tampered with and released several hundred gallons of mixture that entered Rhine Creek. Johnson County, Oxford Township, Sec 21 T80N, R8W. The kill started in section 21 (UTM X = 600495, Y = 4619636) and extended approximately 1.0 miles to the confluence with Clear Creek in Sec 28 (UTM X = 601528, Y = 4618729)."

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. 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, there was no indication that DNR has sought or received restitution for this fish kill. Thus, this assessment segment remains in Category 5b of Iowa’s Integrated Report.

The assessment of support of the general uses of this stream segment is based on results of observations and biological monitoring conducted by DNR staff on September 28, 2005, as part of a use attainability analysis for Rhine Creek in Johnson County near the outfall of Oxford WWTP. The following comments from the UAA are relevant to this assessment:

"Aquatic Vegetation Comments: Rocks [sic] attached to algae on rocks. Comments: Water was green in color, muck/silt for the most part."

These comments suggest potentially poor water quality conditions that may, upon further investigation, constitute violations of several of Iowa's narrative water quality standards (IAC 61.3(2)) designed to protect general uses of Iowa's surface waters (e.g., livestock and wildlife watering, aquatic life and non-contact recreation). Based on the information available, however, the UAA comment does not appear to suggest violation of any of the following narrative criteria (DNR rationales are in parentheses):
--such waters shall be free from substances from point source dischargers that will settle to form sludge deposits. (No “sludge deposits” are mentioned in UAA recommendation documents, and “muck” (which was a commonly-used term for silt/mud substrate by one of the lead UAA field staff) does not indicate presence of “sludge”.)
--such waters shall be free from floating debris, oil, grease, scum and other materials from wastewater discharges or agricultural practices in amounts sufficient to create a nuisance. (Although water was noted as “green,” thus suggesting a high chlorophyll concentration, no “debris, oil, grease, scum, or other materials” are mentioned in UAA reports; thus the UAA comments do not suggest a violation of this narrative water quality criterion.)
--such waters shall be free from materials from wastewater discharges or agricultural practices producing objectionable color, odor, or other aesthetically objectionable conditions. (The only potential violation of this narrative criterion mentioned in the UAA was the “green” color of the water in Rhine Creek. While a potential violation is suggested, high levels of chlorophyll in Iowa streams are not atypical and may or may not be related to wastewater discharges.)
--such waters shall be free from substance attributable to wastewater discharges or agricultural practices in concentrations or combinations which are acutely toxic to human, animal, or plant life. [There is no suggestion of a “toxic condition” in the UAA recommendation documents or on the UAA field sheets.]

Based on the information from the September 2005 UAA, and based on the potential for water quality impacts from inadequately-treated domestic sewage, the general uses of this stream segment suggest a potential impairment of the general uses of this stream. Such waters, although not appropriate for addition to Iowa’s Section 303(d) list of impaired waters, are appropriate for addition to Iowa’s list of waters in need of further investigation (WINOFI). Thus, the general uses of this assessment segment remain in Category 3b of Iowa’s Integrated Report.Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment categories are considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).