Wolf Creek IA 05-CHA-1339

The presumptive Class A1 (primary contact recreation) 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 19 samples collected during the recreational seasons of 2010 through 2012 at site RA-41 (downstream) were as follows: the 2010 geometric mean was 959 orgs/100 ml, the 2011 geometric mean was 185 orgs/100 ml, and the 2012 geometric mean was 2,469 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Fifteen of the 19 samples (79%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. The geometric means of indicator bacteria (E. coli) in the 15 samples collected during the recreational seasons of 2010 through 2012 at site RA-44 (upstream) were as follows: the 2010 geometric mean was 470 orgs/100 ml, the 2011 geometric mean was 138 orgs/100 ml, and the 2012 geometric mean was 632 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Eight of the 15 samples (53%) 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 since, the Class A1 uses will remain listed as "not supported" for the current assessment/listing cycle.

Results of chemical/physical water quality monitoring at site RA-41 (downstream) suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 28 Ammonia samples (maximum = 0.7 mg/L), 53 pH samples (range = 7 to 8), 53 Temperature samples (maximum = 27.5° c) or 34 Chloride samples (maximum = 14 mg/L) occurred during monitoring from March 2012 to October 2014. One of the 53 samples (2%) analyzed for Dissolved Oxygen (minimum = 3.2 mg/L) violated the Class B(WW2) criteria during the 2012-2014 monitoring period. Additionally results of chemical/physical water quality monitoring at site RA-44 (upstream) also suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 21 Ammonia samples (maximum = 0.7 mg/L), 35 pH samples (range = 7 to 7.9), 35 Temperature samples (maximum = 25.1° c) or 14 Chloride samples (maximum = 13 mg/L) occurred during monitoring from March 2012 to October 2014. One of the 35 samples (3%) analyzed for Dissolved Oxygen (minimum = 3.6 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 Dissolved Oxygen suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW2) aquatic life uses. Additionally, the results of chemical/physical water quality monitoring at the DNR biological reference site Wolf Creek near Chariton also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW2) water quality criteria for 6 Ammonia samples (maximum = 1 mg/L), 6 Dissolved Oxygen samples (minimum = 6.9 mg/L), 6 pH samples (range = 7.5 to 7.9), 6 Temperature samples (maximum = 23.5° c), 6 Chloride samples (maximum = 11 mg/L), or 6 Sulfate samples (maximum = 45 mg/L) occurred during monitoring from July 2015 to September 2015.

Results of biological sampling from DNR/SHL suggest that the Class B(WW2) uses should be assessed (monitored) as "partially supported." This biological assessment was based on data collected in 2012 and 2015 as part of the DNR/SHL stream biocriteria and TMDL/SI sampling projects. A series of biological metrics which 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 benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2015 FIBI score was 17 (poor) and the BMIBI scores were 37, 43 (both fair). The 2012 FIBI score was 23 (poor) and the BMIBI score was 27 (poor). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41. This segment passed the FIBI BIC 0/2 times and passed the BMIBI BIC 1/3 times in the last five years. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.

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 over a recent five-year period to be considered “monitored”.

Although this stream reach is not designated for Class C drinking water uses, Wolf Creek does flow into Rathbun Reservoir which is used as a source of drinking water for a public water supply. The seasonal elevation of pesticide levels in the Chariton River 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. The mean level of atrazine in the 19 samples collected from 2012-14 at Station RA-41 (5.4 ug/l) is above the atrazine MCL of 3 ug/l, thus suggesting relatively low contributions of atrazine to Rathbun Reservoir. Similarly, at station RA-44, the mean level of atrazine in the 17 samples collected from 2012-14 (9.2 ug/l) is above the atrazine MCL of 3 ug/l, thus suggesting relatively moderate contributions of atrazine to Rathbun Reservoir.