Assessment Comments
Assessment based on 2006 IDNR/UHL biological monitoring: FIBI = 42 (fair), BMIBI scores = 17, 14, 19 (all poor). Non-riffle FIBI BIC = 32, BMIBI BIC = 62.
Basis for Assessment
SUMMARY: This evaluated biological assessment was based on data collected in 2006 as part of the DNR/UHL stream REMAP project. A series of biological metrics that 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 benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2006 FIBI score was 42 (fair) and the BMIBI scores were 17, 14, and 19 (all poor). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The non-riffle FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. Even though this site passed the FIBI BIC and failed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small general use stream and doesn’t fall in the calibrated watershed size. However, the 2004 assessment (see below) will explain in detail the water quality problems found in this stream.
2004 SUMMARY: The general uses of this stream are assessed (monitored) as "not supported" due to impacts of poorly treated and untreated wastewater discharged to the stream. This assessment is based on IDNR complaint records of March 26, 2002 and July 19, 2002. The IDNR investigations resulting from these complaints documented toilet paper in the stream in March 2002 and the covering of the stream bottom with a "gray deposit" in July 2002. Photographs from citizens in July 2002 show large colonies of bloodworms (Chironomids) in the stream, thus suggesting both organic enrichment and low levels of dissolved oxygen. IDNR staff have corresponded with both the Wright County sanitarian and the Wright County Board of Supervisors to address this problem. Households in the watershed of Buttermilk Creek were notified by the Wright County Sanitarian in December 2003 and again in March 2004 that, according to state and county regulations, they must properly maintain their septic systems and update these systems if necessary to alleviate pollution problems in Buttermilk Creek.
2004 EXPLANATION: The water quality conditions reported by citizens and documented by IDNR field staff potentially violate several of Iowa's narrative water quality standards designed to protect general uses of Iowa's surface waters (e.g., livestock and wildlife watering, aquatic life and noncontact 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;
Based on the information received by IDNR on this stream, the general uses are assessed (monitored) as "not supported" due to water quality impacts from poorly-treated and untreated domestic sewage being discharged to Buttermilk Creek.
