Unnamed Tributary to Snyder Creek IA 02-IOW-6401
mouth (S36 T79N R6W Johnson Co.) to headwaters in NE1/4 S18 T79N R5W Johnson Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 8/30/2016 10:28:23 AM
- Updated
- 12/29/2016 3:54:14 PM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2010 | Class BWW1 | Toxics: Unknown Toxicity | UAA surveys: Iowa DNR | Assessment Error |
The general uses of this stream are assessed as "not supported" due to impacts of poorly-treated wastewater discharged to the stream that result in a violation of Iowa’s narrative water quality criteria (IAC 61.3(2)). The basis for assessment is the results of a use attainability analysis (UAA) conducted by Iowa DNR staff in September 2006. Waters assessed as “monitored/not supported” are appropriate for addition to Iowa’s Section 303(d) list of impaired waters and will thus be placed in Category 5a of Iowa’s Integrated Report. The presumptive Class A1 (primary contact recreation) remain “not assessed” due to lack of sufficient information. Although previously assessed as "impaired" (IR Category 5), the presumptive Class B(WW1) aquatic life uses are now considered “not assessed” (IR 3a) due to the lack of information upon which to base an assessment. This is the same assessment as that developed for the previous (2014) Integrated Reporting cycle with the following exceptions: (1) the previous impairment due to "unknown toxicity" is de-listed and (2) due to a change in Iowa DNR’s assessment database, impairments of general uses can now be tracked; thus, this impairment is moved from the aquatic life placeholder to “general uses” (see Note below).
Note: Due to limitations in Iowa DNR's previous assessment database, the impairment of general uses in this assessment segment was originally applied to the presumptive Class B(WW1) aquatic life uses and was attributed to "unknown toxicity" due to "wastewater". Due to database improvement, this impairment can now be more accurately applied to this segment's "general uses" and attributed "wastewater" that led to to violations of Iowa's narrative water quality criteria as described below. The source of the impairment is now identified as a "municipal wastewater treatment plant".] EXPLANATION: The assessment of support of the general uses of this stream segment remains based on results of observations and biological monitoring conducted by IDNR staff on September 21, 2006 as part of a use attainability analysis for an unnamed tributary to Snyder Creek in Johnson County near the outfall of the Sunrise Mobile Home Park WWTP. The following comments from the UAA regarding the predominant substrate of this stream segment are relevant to this assessment (see http://programs.iowadnr.gov/uaa/search.aspx)
“There was a layer of approximately 12 inches of “floc” throughout the majority of the assessed reach that had a sewage odor.”
These comments suggest poor water quality conditions and potential 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):
--such waters shall be free from substances from point source dischargers that will settle to form sludge deposits;
--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;
--such waters shall be free from materials from wastewater discharges or agricultural practices producing objectionable color, odor, or other aesthetically objectionable conditions;
--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.
Based on the information from the September 2006 UAA, the general [aquatic life[ uses of this stream segment are assessed (monitored) as "not supported" due to water quality impacts from poorly-treated domestic sewage. Waters assessed as “monitored/not supported” are considered appropriate for addition to Iowa’s Section 303(d) list of impaired waters.