Assessment Comments
Assessment is based on results of Iowa DNR bacterial monitoring from 2010 to 2012. Assessment of aquatic life uses remains based on statewide assessment of freshwater mussels in Iowa (Arbuckle et al. 2000). This assessment is also based on results of a fish kill investigation in June 2011 and results of IDNR fish kill follow-up sampling in October 2013.
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, this segment is also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary 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 levels of indicator bacteria (E. coli) that exceed Iowa’s geometric mean criterion. The source of data for this assessment is IDNR bacterial monitoring during the recreation seasons of 2010 through 2012 at STORET station 15310001 approximately 5 miles east of Cascade. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "not supported" (IR 5b) based on information from the report "Statewide Assessment of Freshwater Mussels (Bivalva, Unionidae) in Iowa Streams" by Arbuckle et al. (2000). 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). On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa streams and rivers from the mid-1980s to the late 1990s. The assessment of support of the Class B(WW1) aquatic life uses is also based on (1) results of an IDNR investigation of a pollutant-caused fish kill in June 2011 and (2) IDNR fish kill follow-up monitoring on October 8, 2013. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
EXPLANATION: The Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” based on results of IDNR bacteria monitoring from 2010-12. The geometric means of indicator bacteria (E. coli) in the 19 samples collected during the recreational seasons of 2010 through 2012 at station 15310001 were as follows: the 2010 geometric mean was 3,647 orgs/100 ml, the 2011 geometric mean was 1,552 orgs/100 ml and the 2012 geometric mean was 717 orgs/100 ml. All three geometric means far exceed the Class A1 criterion of 126 orgs/100 ml. Eighteen of the 19 samples (95%) exceeded the Class A1 single-sample maximum criterion sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”
For purposes of Section 303(d) listing, the assessment of the Class B(WW1) aquatic life uses remains 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 Water Quality Bureau 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 two sample sites in this segment of Whitewater Creek was 8 and 3, respectively, in the 1984-85 period (average of 5 species) and was zero at both sites in the 1998-99 period for an average percent change of minus 100%. Based on these results, the aquatic life uses are assessed (monitored) 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.
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). Despite this change in assessment type, this waterbody remains in IR Category 5b.
The assessment of the Class B(WW1) aquatic life uses is also based on results of an IDNR investigation of a fish kill on June 19, 2011 caused by animal waste. Approximately 104,000 fish were killed over nearly 18 miles of stream. The value of the fish was reported as $96,482.22; the cost of the DNR investigation was estimated as $1,190.07. The cause of the kill was identified as animal waste from hog and cattle feedlots. According to the IDNR fish kill report (https://programs.iowadnr.gov/fishkill/detail.aspx?fkid=830), the kill was caused by ammonia toxicity associated with manure discharge as determined by IDNR Field Office #1 field tests. An open hog lot and a cattle operation were on site. The kill originated in the SW 1/4 of Section 18, T88N, R1E in Whitewater Creek (1 mile SE of Epworth) and proceeded downstream to the NE 1/4 of Section 26, T87N, R1W (Highway 151 Bridge) for a total distance of 17.95 miles. Observations of fish and invertebrates at the stream suggest a complete kill in the upper 2.5 miles of the assessment area (Lone Pine Rd to Pilot Grove Road) and an extensive kill from Pilot Grove Rd to East Pleasant Grove Rd (3.2 additional miles). From East Pleasant Grove Rd to the confluence with Curran Branch (5 miles) a moderate to partial kill appeared to have occurred. In the downstream 7 plus miles of assessed stream a partial kill appears to have occurred with additional dead fish floating in from upstream areas."
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 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 is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required). IDNR records show that the party responsible for the kill was identified, and IDNR sought and has received restitution for the value of the fish killed and the costs incurred by IDNR during investigation of the kill. Thus, this assessment segment was appropriate for Category 4d of Iowa’s 2014 Integrated Report.
This stream segment’s fish community was sampled on October 8, 2013, as part of the IDNR Watershed Improvement and Water Monitoring sections’ fishkill follow up monitoring program. Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s 2014 assessment/listing methodology) were followed. Approximately 550 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 5,500 fish per mile compared to the Level IV ecoregion 47f average of approximately 1,500 fish per mile; 89% of the expected fish taxa for this ecoregion were sampled. For detailed results of this sampling, see https://programs.iowadnr.gov/bionet/Sites/961. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the June 2011 fish kill event. Thus, the assessment of aquatic life use support for this stream segment is being moved from impairment Category 4d of Iowa’s Integrated Report to Category 3a (designated use not assessed).
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
