North Branch Turkey River IA 01-TRK-223

The presumptive Class A1 (primary contact recreation) uses remain assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. Based on the approximately eight monthly samples collected during the recreation seasons of 2012, 2013, and 2014, the geometric means at station TRN-10 are as follow: 413 orgs/100 ml, 1,062 orgs/100 ml, and 214 E. coli orgs/100 ml., respectively. All three geometric means exceed the Class A1 geometric mean criterion of 126 orgs/100 ml. Sixteen of the combined 23 samples (70%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’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, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”

Results of chemical/physical water quality monitoring from April 2012 to November 2014 at Station TRN-10 do not suggest impairment of the Class B(WW2) aquatic life uses. There were no violations of Class B(WW2) water quality criteria for ammonia (16 samples), dissolved oxygen (24 samples), temperature (24 samples), or chloride (16 samples). One of the 24 samples (4%) analyzed for pH, however, violated the Class B(WW2) criterion of 9.0 pH units. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as pH suggests impairment of aquatic life uses. Based on DNR’s assessment methodology, however, these results suggest that the frequency of violations is not significantly greater than 10 percent; thus, these results do not suggest impairment of the Class B(WW2) aquatic life uses. Thus, the Class B(WW2) aquatic life uses are assessed (monitored) as “fully supported”.

In agreement with the water quality sampling, this monitored biological assessment based on data collected in 2013-2016 as part of the DNR Fisheries Bureau sampling project also suggests that theClass B(WW1) aquatic life uses are "fully supporting". A series of biological metrics that 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 fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2013-2016FIBI scores were 69, 69 (both good) and 72, 79 (both excellent). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. While it is still undetermined if the Fisheries sampling sites contain stable riffle habitat, this segment passed the riffle FIBI BIC (4/4 times). The riffle habitat FIBI BIC for this ecoregion is 65.

This aquatic life assessment is now considered "monitored" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years in the most recent five year period (2012-2016) to be considered “monitored”. This segment had foursamples collected in the previous five years (2012-2016).