Jordan Creek IA 05-CHA-1330

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 16 samples collected during the recreational seasons of 2010 through 2012 at Jordon Creek at County Road J32 were as follows: the 2010 geometric mean was 1,317 orgs/100 ml, the 2011 geometric mean was 251 orgs/100 ml, and the 2012 geometric mean was 656 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Fourteen of the 16 samples (88%) 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 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). 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.  

The Class B(WW2) aquatic life uses are assessed (evaluated) as “partially supporting“ based on biological data collected in 1999-2002 as part of an IDNR Fisheries stream sampling project: Chariton research stations and on data collected in 2012 by IDNR/SHL for TMDL/SI purposes. 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 1999-2002 Fisheries FIBI scores were 25 (poor) and 26, 37 (fair). The 2012 FIBI score was 24 (poor) and the BMIBI score was 13 (poor). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI scores with biological assessment criteria established for previous Section 305(b) reports. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC is 41. This segment passed the FIBI BIC 1/4 times in the last 16 years and failed the BMIBI BIC in 2012.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR 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”. This segment had multiple samples collected in the previous 16 years (fish); however, the multiple samples were not collected during a recent five-year period. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t.

Because the biological impairment of the Class B(WW2) uses is based on an “evaluated” (lower confidence) assessment, the IDNR assessment/listing methodology indicates that this assessment segment should be placed into IR Category 3b (potentially impaired; in need of further investigation). In their May 23, 2006 transmittal letter for Iowa’s 2004 Section 303(d) list, however, U.S. EPA Region 7 informed IDNR that biological impairments based on bioassessment data from the IDNR Fisheries Bureau, even though IDNR/SHL bioassessment protocols were not strictly followed, should nonetheless be placed into IR Category 5. Thus, this waterbody was placed into Category 5b of Iowa’s 2006 Integrated Report and will remain on Iowa’s future Section 303(d) lists.

Results of ambient chemical/physical water quality monitoring do not suggest impairments of the Class B(WW2) aquatic life uses of this stream segment. Results of chemical/physical water quality monitoring at Jordan Creek at County Road J32 suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 22 Ammonia samples (maximum = 0.7 mg/L), 36 Dissolved Oxygen samples (minimum = 5.1 mg/L), 36 pH samples (range = 6.6 to 8.3), 36 Temperature samples (maximum = 28.2° c), 15 or Chloride samples (maximum = 16 mg/L) occurred during monitoring from March 2012 to October 2014.According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW2) aquatic life uses. Based on results of this monitoring, this stream segment does not show a dissolved oxygen-related impairment of its Class B(WW2) aquatic life uses. 

However, the results of additional continuous monitoring for dissolved oxygen (DO) and temperature do suggest impairment of the Class B(WW-2) uses. Continuous monitoring data collected in 2012 by IDNR/SHL for TMDL/SI purposes were examined for DO and stream temperature criteria violations. The lowest DO concentration recorded in 29 days of continuous monitoring was 1.6 mg/L. The daily DO minimum concentration failed to meet the 24-hour DO criterion (4 mg/L) in 19 of 29 days and the 16-hour DO criterion (5 mg/L) in 9 of 29 days. The percentages exceeding the 24-hour and 16-hour DO criteria (65.5% and 31.0%, respectively) were greater than (failing) the 10% impairment threshold used to assess conventional water quality parameters. The associated statistical analysis confidence level was high (>90%). The maximum stream temperature recorded during the sensor deployment period was 34.9 degrees (C). The temperature criterion for warmwater interior streams (32 C) was exceeded in 14 of 29 days. The percentage exceeding (48.3%) was greater than (failing) the 10% impairment threshold with high statistical confidence (>90%). Based on these data, the B(WW1) aquatic life use is assessed as impaired for DO and temperature. The assessment type is “evaluated” because it is based on data collected from a single year within the current data assessment period. In order to meet the requirements for a “monitored” assessment, the IDNR’s continuous monitoring assessment methodology requires monitoring data from two or more years within the assessment period.

Although this stream is not designated for Class C drinking water uses, Jordan 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. For example, the mean level of atrazine in the 18 samples collected at Station RA-37 from 2012 through 2014 (2.9 ug/l) approaches but is below the atrazine MCL of 3 ug/l, thus suggesting relatively low contributions of atrazine to Rathbun Reservoir. The maximum level of atrazine during the 2012-14 period was 13.0 ug/l.