Buttermilk Creek IA 04-UDM-1826

The presumptive Class A1 (primary contact recreation) uses remain assessed (evaluated) as "not supported" due to levels of indicator bacteria (E. coli) that violate state water quality criteria. The geometric mean level of indicator bacteria (E. coli) in the 13 samples collected in the recreational seasons of 2006 and 2007 at Site BMC1 (294 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Nine of the 13 samples (69%) exceed Iowa’s single-sample maximum criterion of 235 orgs/100 ml. At Site BMC3, the geometric mean level of indicator bacteria (E. coli) in the 10 samples collected in the recreational seasons of 2006 and 2007 was 161 orgs/100ml, thus slightly exceeding the Iowa Class A1 water quality criterion of 126 orgs/100ml. Six of the 10 samples (60%) 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 DNR’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 3-35 of U.S. EPA 1997b). Sufficient (i.e., weekly) data for E. coli existed for Site BMC1 from early July through mid-September 2006 to allow calculation of several 30-day/five-sample geometric means for this stream. All five of these 30-day geometric means exceeded the Class A1 criterion of 126 orgs/100 ml (range: 570 to 855 orgs/100 ml). Note: although results of bacterial monitoring suggest impairment of the Class A1 uses, the levels of bacteria in Buttermilk Creek are low relative to most other small streams where geometric mean values can be considerably larger, sometimes by an order of magnitude.

The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting” based on biological data collected in 2006 and 2007. These data suggest, but do not conclusively demonstrate, impairment of the presumptive Class B(WW1) aquatic life uses of this stream. Biological assessments were conducted on Buttermilk Creek in 2006 and 2007 as part of an DNR/SHL stream biological monitoring 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 14, 20 and 23 (all poor). The 2007 FIBI scores were 39, 44 (both fair) and 55 (good) and the 2007 BMIBI score was 38 (fair). 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 1994-2008. The non-riffle FIBI BIC for this ecoregion is 32, the riffle habitat FIBI BIC is 53 and the BMIBI BIC for this ecoregion is 62. One site (BMC1) passed the non-riffle habitat FIBI BIC 2/2 times while the other two sites (BMC2 and BMC3) passed the riffle habitat FIBI BIC 0/2 times. All three sites passed the BMIBI BIC 0/5 times in the last 11 years. Even though this site failed the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.

This biological assessment is considered “evaluated” (of lower confidence) due to the lack of a biological assessment protocol for headwater streams. Prior to the changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this stream was classified only for general uses due to the inability of the stream to support a viable aquatic community at low-flow conditions. DNR’s existing biological assessment protocol, however, was calibrated to aquatic life reference conditions in larger wadeable streams with perennial flow. The aquatic environment of most headwater streams is one of extremes in water quality. Consequently, intermittent headwater streams tend to have biological diversity that is low relative to more stable aquatic environments of larger streams with perennial flow. Thus, the use of biological assessment methods developed for the ecologically more stable and diverse streams will likely overstate the existence of impairment in headwater streams. For these reasons, headwater stream reaches that show a failure to meet regional expectations for aquatic biota (fish or aquatic macroinvertebrates) will not be added to Iowa’s Section 303(d) list of impaired waters (Category 5 of the Integrated Report). The assessment type for these assessed waters will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to “monitored" (indicating an assessment with relatively high confidence). Such waters will be placed in either Category 2b or 3b of the IR and thus will be added to the state’s list of “waters in need of further investigation”.

Based on information from the Wright County Sanitarian, and based on recent water quality investigations conducted by DNR staff (see "Buttermilk Creek Objectionable Conditions Impairment Update," Iowa DNR 2009), the historical impacts of poorly treated and untreated wastewater, as documented in 2002, appear to have been addressed. The background of this impairment is as follows. DNR complaint records of March 26, 2002 and July 19, 2002 described toilet paper in the stream and the covering of the stream bottom with a "gray deposit.” Photographs from citizens in July 2002 showed large colonies of bloodworms (Chironomids) in the stream, thus suggesting both organic enrichment and low levels of dissolved oxygen. The water quality conditions reported by citizens and documented by DNR field staff potentially violated narrative water quality in the Iowa Water Quality Standards designed to protect general uses of Iowa's surface waters from nuisance and aesthetically objectionable conditions. Based on this information, Buttermilk Creek was assessed as Section 303(d) impaired and was added to the state list of impaired waters in 2004. In response to the pollution problems in this stream, DNR staff 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.

Recent evidence, however, suggests improved water quality conditions in Buttermilk Creek. Information received by DNR in March 2009 from the Wright County Sanitarian note the following corrective actions: (1) elimination of discharge from a residential septic tank that was believed to be a significant source of pollutant loading to the stream; (2) other (relatively minor) problems with residential septic tanks have been identified and are being addressed; (3) additional sources of residential wastewater identified through watershed investigations conducted by the Natural Resources Conservation Service (NRCS) are being investigated by the Wright County Sanitarian; and (4) volunteers have recently conducted a stream clean-up on Buttermilk Creek, thus removing various trash and debris from the stream. Local opinion is that water quality conditions of Buttermilk Creek have improved considerably relative to those reported and documented by volunteer monitors in 2002. Based on this information, the impairment due to violations of Iowa’s narrative water quality criteria protecting against nuisance and aesthetically objectionable conditions was removed from Iowa’s 2008 Section 303(d) list.

The results of DNR/SHL TMDL-related monitoring in 2006 and 2007 do not suggest chemical water quality problems in this stream segment and thus provide additional evidence of improved water quality conditions in Buttermilk Creek. This monitoring showed no violations of Class B(WW1) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 16 samples collected at Site BMC1, or in the 13 samples collected at site BMC3, from June 2006 through April 2007. Although the sampling interval was relatively short (i.e., June 2006 through April 2007), levels of DO remained strong (minimum values of 6.6 and 6.5 mg/l at Sites BMC1 and BMC3, respectively, and levels of ammonia remained very low, with maximum values of 0.26 mg/l and 0.41 mg/l at Sites BMC1 and BMC3, respectively; none of these levels approached chronic Class B(WW1) ammonia criteria (early life stages present).