Honey Creek IA 05-CHA-1337

The Class A2 (primary contact recreation) uses are assessed (evaluated) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 11 samples collected during the recreational seasons of 2010 through 2012 at Honey Creek were as follows: the 2010 geometric mean was 533 orgs/100 ml, the 2011 geometric mean was 607 orgs/100 ml, and the 2012 geometric mean was 1,692 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Eight of the 11 samples (73%) exceeded the Class A1 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 are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).In the 2014 assessment/listing cycle, the presumptive Class A1 uses were listed as (monitored) "not supported" due to levels of indicator bacteria that exceeded state water quality criteria. Therefore, due to the lack of new data collected during the 2012 -2014 sampling seasons, the Class A1 uses will remain listed as "not supported" for the 2016 assessment/listing cycle.

Results of chemical/physical water quality monitoring at Honey Creek suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 24 Ammonia samples (maximum = 1 mg/L), 38 pH samples (range = 6.7 to 8.2), 38 Temperature samples (maximum = 29.8° c), or 17 Chloride samples (maximum = 40 mg/L) occurred during monitoring from March 2012 to October 2014.One of the 38 samples (3%) analyzed for Dissolved Oxygen (minimum = 3.9 mg/L) violated the Class B(WW2) criteria during the 2012-2014 monitoring period. 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 Ammonia, pH, Temperature, Chloride, or Sulfate suggests impairment of aquatic life uses. Because the frequency of violations for this parameters is not greater than 10 percent, these results do not suggest impairment of the Class B(WW2) aquatic life uses.

Although this stream is not designated for Class C drinking water uses, Honey Creek does flow into Rathbun Reservoir which is used as a source of drinking water for a public water supply. Thus, the seasonal elevation of pesticide levels in this stream and other tributaries of Rathbun Reservoir presents a continuing concern for full support of the Class C (drinking water) uses designated for the Chariton River immediately downriver from Rathbun Reservoir. Fortunately, however, the levels of atrazine in Honey Creek during the 2012-2014 period do not suggest a serious threat to support of drinking water uses in Rathbun Reservoir. For example, the mean level of atrazine in the 18 samples collected during the 2012-14 period at station RA-40 (3.1 ug/l) is slightly above the atrazine MCL of 3 ug/l, thus suggesting relatively low contributions of atrazine to Rathbun Reservoir. The maximum level was 21.0 ug/l.