Assessment Comments
Assessment is based on results of (1) TMDL-related monitoring at two stations in 2007 and 2008 (11100001 and 12100002), (2)IDNR/UHL biological monitoring in 2004, 2007 and 2008: FIBI = 69 (good), 78 & 82 (excellent); BMIBI = 71, 72 (good), 82, 83 (excellent); (3) results of a fish kill investigation in July 2008; (4) ISU statewide survey of freshwater mussels in 1998-99.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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 also now presumptively designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria (E. coli) at two stations sampled as part of TMDL monitoring. This represents a new impairment for this assessment segment. The source of data for this assessment is the results of TMDL-related water quality monitoring at sites (LiCr2 (11100001) and at site 154 (12100002) near Brandon in 2008. The Class B(WW1) aquatic life uses are assessed (evaluated) as "not supported" based on results of a fish kill investigation in July 2008 and results of the 1998-99 statewide assessment of freshwater mussels in Iowa streams by Arbuckle et al. (2000). However, results of IDNR TMDL-relatedwater quality monitoring in 2008 and results of IDNR/UHL biological (biocriteria) monitoring in 2004, 2007 and 2008 both suggest "full support" of these aquatic life uses based on sampling of the fish and benthic macroinvertebrate communities. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
EXPLANATION: The presumptive Class A1 uses are assessed as "not supported" based on results of ambient monitoring for indicator bacteria (E. coli) at two monitoring stations in 2008. At site LiCr2 downstream from Brandon, the geometric mean level of indicator bacteria (E. coli) in the 11 samples collected during the recreational season of 2008 (997 orgs/100ml) far exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. At site 154 upstream from Brandon, the geometric mean level of indicator bacteria (E. coli) in the 11 samples collected (4,498 orgs/100ml) far exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Ten of the 11 samples (91%) exceed Iowa’s single-sample maximum criterion of 235 orgs/100 ml at both monitoring stations. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’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 3-35of U.S. EPA 1997b).
Results of a fish kill investigation in July 2008 suggest that the Class B(WW1) uses should be assessed (evaluated) as "partially supported." The kill occurred approximately 48 hours prior to the investigation on July 9, 2008. The kill occurred along 4.2 miles of Lime Creek northeast of Brandon and affected approximately 2,720 fish. High water occurred during, or after, the kill event because some fish were observed 2-3 feet above the water level present during the day of investigation. Fish carcasses were easily identifiable to family group, but identification to species was not possible for most Cyprinidae species due to poor physical condition of specimens. The following species were positively identified: Common Shiner, Creek Chub, Northern Hogsucker, Northern Logperch, Rock Bass, Smallmouth Bass, and Stonecat. It is likely that high water flows flushed a significant number of dead fish from the investigated area, and decay and predation further reduced counts of small-bodied fishes. The estimated value of the fish was $3,004.36. No definite source for the fish kill was found, however, two feedlots and an herbicide over-application were investigated.
According to IDNR’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 (2006-2009) 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 was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5).
Results of TMDL-related chemical/physical water quality monitoring conducted in from September 2007 through December 2008 do not suggest impairment of the presumptive Class B(WW1) aquatic life uses. Approximately 14 samples were collected at each monitoring station. None of the combined 28 samples collected violated Class B(WW1) criteria for dissolved oxygen, pH, temperature, or the temperature/pH-dependent Class B(WW1) chronic criteria for ammonia (none of the 28 samples analyzed contained a detectable levels of ammonia (detection level = 0.05 mg/l). The maximum temperature at station LiCr2 was 22.2 C; the maximum temprature at station 154 was 23.9 C.
Results from the IDNR/UHL biocriteria sampling in 2004, 2007 and 2008 suggest that the Class B(WW1) uses are "fully supported." The 2004 BMIBI scores were 71, 70 (both good). The 2007 FIBI scores were 78 and 82 (exellent) and the BMIBI score was 82 (excellent). The 2008 FIBI score was 69 (good) and the BMIBI score was 83 (excellent). The aquatic life use support was assessed as fully supported (=FS), based on a comparison of the 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 natural substrate BMIBI BIC for this ecoregion is 70. This segment passed the FIBI BIC 3/3 times and passed the BMIBI BIC 4/4 times in the past five years. This aquatic life use assessment is considered "monitored" because there were two or more samples collected in multiple years from 2004-2008.
Results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams, however, suggest an impairment to the aquatic life uses of this stream segment. [Note: because the data from Arbuckle et al. (2000) are now older than five years, the assessment category is changed from a “monitored” (i.e., a higher confidence assessment) to “evaluated” (i.e., lower confidence assessment). Despite this change in assessment category, the impairment indicated by these data remains in IR Category 5 (i.e., Section 303(d) list) until more recent data suggest a good cause for de-listing.] As part of this study, sampling results from 1998 and 1999 (Arbuckle et al. 2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987). For purposes of Section 303(d) listing, this assessment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey. For stream segments having four or more species reported for the 1984-95 survey, results of this comparison were used by staff of the Iowa DNR to assess the degree to which the aquatic life uses of the sampled stream segments are supported. Greater than a 50% decline in species richness from the 1984-85 to the 1998-99 period suggests an impairment of the aquatic life uses. Species richness of freshwater mussels at the one sample site in this segment of Lime Creek was 9 in the 1984-85 period and was 0 in the 1998-99 period for a percent change of minus 100%. Based on these results, the aquatic life uses were assessed as “not supported.” As presented by Arbuckle et al. (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high instream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
