Assessment Comments
Assessment remains based on (1) 2002 IDNR/UHL biological monitoring data: FIBI = 22 (poor), BMIBI = 24 (poor). FIBI BIC = 33; BMIBI BIC = 41 and (2) USGS monitoring in 1998 and 1999 near Bloomfield, West Grove, and Paris.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream 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.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (evaluated) as "not supported" based on results of IDNR/UHL biological and water quality monitoring conducted as part of the REAMP project in 2002. In addition to the IDNR/UHL REMAP monitoring in 2002, chemical water quality data collected by USGS in 1998 and 1999 were also used for this assessment. Note: monitoring was again conducted by USGS in this assessment segment beginning in 2009. These data, along with any subsequent data collected in 2010, will be used to develop the 2012 Section 305(b) assessment.
EXPLANATION: The Class B(WW2) aquatic life uses remain assessed (evaluated) as “not supported" based on biological data collected in 2002 as part of the IDNR/UHL REMAP project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were 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 2002 FIBI score was 22 (poor) and the BMIBI score was 24 (poor). The aquatic life use support was assessed as not supporting (=NS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41.
This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years from 2004-2008. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.
As part of the REMAP project, diurnal dissolved oxygen and temperature monitoring conducted during July 2002 found dissolved oxygen levels sagging to approximately 4.2 mg/L during night hours. Additional sampling data are needed to evaluate the extent, causes and sources of this water quality problem. Stream physical habitat assessment found excessive sediment deposits and a lack of instream cover that could also contribute to the biological impairment. The wide-shallow channel probably contributes to observed high stream temperature (>36C) and high rates of biological community respiration and primary production.
Previous Section 305(b) assessments suggest that chemical water quality may, in fact, contribute to the low biotic index values seen in REMAP monitoring. Results of chemical water quality monitoring conducted in 1998 and 1999 by the U.S. Geological Survey at three stations on this segment of the Fox River (Bloomfield (S27, T69N, R13W), West Grove (NW1/4, S27, T69N, R15W), and Paris (NE1/4, S24, T69N, R15W)) (see May et al. 1999 and Nalley et al. 2000) showed no violations of Class B(WW2) water quality criteria for dissolved oxygen, pH, and ammonia-nitrogen in the 12 samples collected at the Bloomfield or Paris stations. At the West Grove (most upstream) station, however, two of 12 samples violated the Class B(WW2) criterion for dissolved oxygen, and three of 12 samples violated Class B(WW2) chronic criteria for ammonia-nitrogen. These violations were used to identify an impairment of the aquatic life uses of this assessment segment fro the 2002 through 2006 listing cycles. Based on IDNR’s 2008 Section 303(d) listing methodology, however, these results do not suggest that significantly more than 10 percent of the samples exceed Iowa’s Class B(WW2) criterion for dissolved oxygen or Class B(WW2) chronic criteria for ammonia and thus do not suggest an impairment of the Class B(WW2) aquatic life uses due to either parameter. Both ammonia and "low DO" were included on Iowa's approved 2006 Section 303(d) list, and, as explained in Notes 1 and 2 below, both are proposed for de-listing for the 2008 cycle. Because, however, more than one violation of the chronic criterion for ammonia occurred, this potential impairment will be added to Iowa's list of waters in need of further investigation.
Note 1: Based on consultation with other Region 7 states and U.S. EPA Region 7 staff in 2007, IDNR's methodology for assessing impairments due to violations of chronic criteria for toxic parameters (e.g., ammonia and toxic metals) was changed. Prior to the 2008 listing cycle, IDNR followed a U.S. EPA recommendation (U.S. EPA 1997b, page 3-18) that more than one violation of a water quality criterion for a toxic pollutant in an abundant data set indicates an impairment of aquatic life uses. Because no state in Region 7 collects ambient data with the frequency necessary to accurately identify compliance with a chronic criterion (i.e., to allow calculation of a short-term (4-day or 30-day averages)), Region 7 states concluded that another assessment approach (e.g., the 10% rule) was more appropriate. Thus, for the 2008 listing cycle, IDNR identified aquatic life impairments for toxic parameters when significantly more than 10% of the samples exceeded a chronic criterion.
Note 2: The identification of a Section 303(d) impairment of the Class B(WW2) aquatic life uses due to low dissolved oxygen for the 2006 listing cycle was in error. As stated in IDNR's 2006 listing methodology (http://wqm.igsb.uiowa.edu/wqa/303d/2006/IA_2006_Methodology_final.pdf (pages 37-38)), such impairments were identified only if significantly more than 10% of the samples collected were in violation of the appropriate dissolved oxygen criterion. Based on this methodology, the occurrence of two violations in the 12 samples collected during the 1998-99 period is not significantly greater than a 10% violation frequency; thus, this impairment should have been de-listed for the 2006 cycle. This low DO impairment is now proposed for de-listing for the current (2008) cycle.
Of the 12 samples analyzed for toxic metals in 1998-99, one sample at each station exceeded a state water quality criterion. The samples collected at all three stations on June 10, 1999, exceeded the Class B(WW2) chronic water quality criterion for copper (55 ug/l): the level at Bloomfield was 120 ug/l, at Paris 90 ug/l, and at West Grove 110 ug/l. These samples were collected during a high flow event on the Fox River; the June 10 stream flow was 599 cfs at Bloomfield. 1,140 at Paris, and 1,170 cfs at the West Grove station. According to IDNR's 2008 listing methodology, the percentage of samples exceeding chronic criteria for these metals does not suggest impairment of the Class B(WW2) aquatic life uses.
