Assessment Comments
Assessment is based on: (1) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011 and (2) results of IDNR physical/chemical water quality monitoring conducted at Bloody Run Creek from January 2010 through December 2012 at Site 1 (STORET station 10220003).
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life 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 coldwater aquatic life use (now termed Class B(CW1) 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 “partially supported” (IR 5p) due to levels of indicator bacteria that slightly exceed the Class A1 criterion. The presumptive Class A2 (secondary contact recreation) uses, however, are assessed (monitored) as “fully supported” (IR 2a). The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "fully supported" (IR 2a) based on (1) a summary of trout reproduction in Iowa streams and (2) results of ambient chemical/physical water quality monitoring conducted from 2010 through 2012. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this coldwater stream. Sources of data for this assessment include (1) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011 and (2) results of IDNR physical/chemical water quality monitoring conducted at Bloody Run Creek from January 2010 through December 2012 at Site 1 (STORET station 10220003). Despite the very slight bacterial impairment, the results of chemical and bacterial monitoring over the 2010-12 period, and the historical water quality monitoring data for this stream segment, suggest that this segment of Bloody Run has exceptional water quality and fully supports its designated uses for Class B(CW1) coldwater aquatic life.
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported.” The geometric means of indicator bacteria (E. coli) in the 24 monthly samples collected during the recreational seasons of 2008 through 2010 at Bloody Run Creek Site 1 were as follows: the 2010 geometric mean was 179 orgs/100 ml, the 2011 geometric mean was 73 orgs/100 ml and the 2012 geometric mean was 45 orgs/100 ml. Only one of the three recreation season geometric means (2010) exceeds, and very slightly exceeds, the Class A1 criterion of 126 orgs/100 ml. The 2011 and 2012 geometric means are far below the Class A1 criterion of 126 orgs/100 ml. All three annual geometric means for the period 2010 to 2012 (68, 40, and 31 orgs/100 ml, respectively) are well below the Class A2 geometric mean criterion of 630 orgs/100 ml. Three of the 24 recreation season samples (12%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; only one of the 36 samples (3%) exceeded the Class A2 single-sample maximum criterion of 2,880 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 should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, based only on the 2010 recreation season geometric mean, the Class A1 primary contact recreation uses are assessed (monitored) as “impaired.”
The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as “fully supported.” This assessment is based in part on the updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011. According to this summary, this reach of Bloody Run Creek is in the category of Iowa trout streams that have fairly consistent natural reproduction and are capable of maintaining a viable population for the target trout species without any stocking. The Class B(CW1) aquatic life uses were also assessed (monitored) as "fully supported" based on results of water quality monitoring at Site 1 on Bloody Run Creek from 2010 through 2012. None of the 36 monthly samples analyzed for dissolved oxygen, ammonia, temperature, pH, chloride and sulfate violated the respective Class B(CW1) aquatic life criteria.
Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.
