Assessment Comments
Assessment remains based on results of (1) 2004-2007 IDNR/UHL biocriteria sampling data, (2) results of monitoring for indicator bacteria conducted at Site 29 of the Upper Iowa River Watershed, (3) EPA/IDNR fish contaminant monitoring in 2002 and (4) a 2006 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life 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), this segment is also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption) uses.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The presumptive Class A2 (secondary contact recreation) uses remain assessed (monitored) as “fully supported.” The Class B(CW1) coldwater aquatic life uses remain assessed (monitored) as "fully supported" based on the IDNR/UHL biological sampling data and the May 2006 summary of trout reproduction in Iowa streams as prepared by the IDNR Fisheries Bureau. Fish consumption uses are assessed (evaluated) as “fully supported” based on results of fish contaminant monitoring in 2002. Sources of data for this assessment include (1) results of IDNR/UHL biological monitoring from 2004-2007, (2) results of monitoring for indicator bacteria conducted at Site 29 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 190050007) from April 2004 through October 2006, (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring near Churchtown in 2002, and (4) a 2006 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as impaired due to violations of Iowa’s water quality criteria for indicator bacteria. The presumptive Class A2 (secondary contact recreation) uses remain assessed (monitored) as “fully supported.” The geometric mean of E. coli in the 21 samples collected at UIRW site 29 during the recreational seasons of 2004 through 2006 was 623 orgs/100 ml. This geometric mean far exceeds the Class A1 criterion of 126 orgs/100 ml but is just below the Class A2 criterion of 630 orgs/100 ml. Fourteen of the 21 samples (67%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.; 4 of the 21 samples (19%) exceeded Iowa’s Class A2 single-sample maximum criterion (2,880 orgs/100 ml.). According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean of E. coli is greater than the applicable state criterion, the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Thus, the presumptive Class A1 uses for this segment of French Creek are assessed as “not supported,” and the presumptive Class A2 uses are assessed as “fully supported.”
The assessment of the Class B(CW1) aquatic life uses was based on biological data collected between 2004 and 2007 as part of the IDNR/UHL stream biocriteria project. A series of eight (8) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data and supplemental IDNR Fisheries Bureau data. The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. Sites that score 5-8 are fully supporting (FS), sites that score 2-4 are partially supporting (PS), and sites that score 0-1 are not supporting (NS). When fish sampling is not conducted, assessments are based on benthic macroinvertebrate data only. Non-fish sampled sites that score 3 or 4 are fully supporting (FS), sites that score 1 or 2 are partially supporting, and sites that score 0 are not supporting (NS). The 2004 coldwater biological indicator scores were 4/4 and 3/4. The 2005 scores were 3/4, 4/4. The 2007 score was 8/8. The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for this Section 305(b) report. The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2008 and with assistance from the IDNR Fisheries Bureau.
In addition, based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, the Class B(CW1) uses are assessed as "fully supported". According to the updated summary, French Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit fairly consistent natural reproduction and maintain a viable population of the listed species without any stocking. This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.
Fish consumption uses remain assessed (evaluated) as “fully supporting” based on results of U.S. EPA / IDNR fish tissue (RAFT) monitoring near Churchtown in 2002. The composite samples of fillets from white sucker and brown trout collected in 2002 had extremely low levels of contaminants. Neither sample contained levels of contaminants that approached even one-half the respective FDA action levels or IDNR levels of concern. Levels of primary contaminants in the composite sample of white sucker fillets were as follows: mercury: 0.022 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of brown trout fillets were as follows: mercury: 0.028 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. The fish contaminant data upon which this assessment is based are now more than five years old; therefore, this assessment of fish consumption uses is now considered "evaluated" (of lower confidence) instead of "monitored" (of higher confidence).
