Assessment Comments
Assessment is based on: (1) the results of ambient monthly water quality monitoring from January 2004 through December 2006 at the IDNR/UHL ambient city monitoring station located upstream from Mason City (STORET station 10170002) and (2) the results of biological monitoring conducted by the IDNR Fisheries Bureau near Fertile in 2000. The assessment is also based, in part, on historical water quality studies conducted for the Lehigh Portland Cement Company.
Basis for Assessment
[Note: Prior to the current (2008) Section 305(b) cycle, this river 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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), and due to results of an 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 are assessed (monitored) as "not supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported " based on results of (1) ambient water quality monitoring from 2004 through 2006 and (2) biological monitoring conducted by the IDNR Fisheries Bureau in 2000. Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment. The sources of data for this assessment include (1) the results of ambient monthly water quality monitoring from January 2004 through December 2006 at the IDNR/UHL ambient city monitoring station located upstream from Mason City (STORET station 10170002) and (2) the results of biological monitoring conducted by the IDNR Fisheries Bureau near Fertile in 2000. The assessment is also based, in part, on historical water quality studies conducted for the Lehigh Portland Cement Company.
EXPLANATION: The Class A1 primary contact recreation uses are assessed (monitored) as "not supported" based on results of ambient monitoring for indicator bacteria (E. coli). Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.
The geometric mean level of indicator bacteria (E. coli) in the 34 samples collected during the recreational seasons of 2004 through 2006 (492 orgs/100ml) far exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Twenty-three of the 34 samples (68%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from 2004-2006 and on results of biological monitoring conducted in 2000. Results of monthly ambient water quality monitoring at the IDNR/UHL station upstream from Mason City from January 2004 through December 2006 showed no violations of Class B(WW1) water quality criteria for either conventional or toxic parameters. No violations occurred in the approximately 40 samples analyzed for dissolved oxygen, pH, and ammonia-nitrogen, in the 14 samples analyzed for toxic metals, or in the approximately 10 samples analyzed for pesticides.
The assessment is also partially based on data collected in 2000 as part of a DNR Fisheries stream sampling project: Manchester research station. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data. The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 evaluated Fish IBI = 63 (good). The aquatic life use support was assessed (evaluated) as Fully Supporting (=FS), based on a comparison of the F-IBI score 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 1994-2001.
Although these results suggest "full support" of the Class B(WW1) aquatic life uses, the results of water quality studies conducted in 1994 and 1995 for the Lehigh Portland Cement Company showed relatively low diversity of the fish community downstream from Mason City. The results from these studies continue to suggest the possibility of threats to full support of the aquatic life uses within the Mason City urban/industrial area. These studies are now quite old (over 10 years), and their ability to characterize current water quality conditions is doubtful. Follow-up monitoring is needed to better determine the status of the aquatic communities of this reach of the Winnebago River and to determine whether the Class B(WW1) uses may be impaired.
Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.
