Assessment Comments
Assessment remains based on (1) results of monitoring from May to October 2010 at Station WQ-01 of the Catfish Creek Watershed Project and (2) results of routine water quality monitoring conducted from 2000 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA. No additional data have been generated for this waterbody by the LTRMP since 2004.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” due to levels of indicator bacteria (E. coli) that exceed state water quality criteria. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported" based on results ambient water quality monitoring conducted from 2000-2004. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach. The sources of data for this assessment includes (1) results of monitoring from May to October 2010 at Station WQ-01 of the Catfish Creek Watershed Project (quality assurance/project plan available upon request) and (2) the results of routine water quality monitoring conducted at station CF00.3M from 2000 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA (see http://www.umesc.usgs.gov/data_library/water_quality/water_quality_page.html). No additional data have been generated for this waterbody by the LTRMP since 2004.
EXPLANATION: The Class A1 (primary contact recreation) uses remain assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric mean of indicator bacteria (E. coli) in the 11 samples collected approximately every two weeks during the recreational season of 2010 at Site WQ-01 of the Catfish Creek Watershed Project (2,390 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml). Nine of the 11 samples (82%) exceeded Iowa’s 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 the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
The assessment of the Class B(WW1) uses remains based on results of IDNR/LTRMP chemical/physical monitoring at station CF00.3M from January 2000 through September 2004. Due to budgetary problems, monitoring was not conducted at this station from September 2002 through March 2004. Samples were collected monthly. The parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll. A summary of these data show no violations of the Class B(WW1) water quality criteria for temperature, pH, or dissolved oxygen 43 samples collected. One of 43 samples did exceed the Class B(WW1) chronic criterion for ammonia nitrogen: the sample collected on August 25, 2004 contained 0.68 mg/l of ammonia nitrogen. This level slightly exceeded the temperature/pH-dependent chronic criterion of 0.55 mg/l. According to U.S. EPA guidelines for Section 305(b) reporting, if, for a dataset where at least 10 samples have been collected over a three-year period, up to one sample can violate water quality criteria without indicating impairment; however, if more than one sample exceeds the criterion, impairment (“partial support”) is indicated (see pg 3-18 of U.S. EPA 1997b). Thus, the single violation in the 43 samples collected over the three-year period at Catfish Creek does not indicate impairment of aquatic life uses. The assessment type for this assessment is changed from monitored (a higher confidence assessment) to an “evaluated” (lower confidence assessment) due to the age of the data upon which the assessment is based (i.e., greater than five years).
Fish consumption uses remain "not assessed" due to the lack of monitoring in this stream reach.
