Assessment Comments
Assessment remains based on results of (1) 2005 and 2007 IDNR/SHL biological sampling data, (2) results of monitoring for indicator bacteria from 2008-2010 at Site 29 of the Upper Iowa River Watershed, (3) EPA/IDNR fish contaminant monitoring in 2002 and (4) a 2011 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, 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.] This stream segment is identified as an Outstanding Iowa Water under the antidegradation policy in the Iowa Water Quality Standards.
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are 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 are also assessed (monitored) as “not supported” due to high levels of indicator bacteria. The nonsupport of Class A2 uses represents a new impairment for this assessment segment. The Class B(CW1) coldwater aquatic life uses remain assessed (monitored) as "fully supported" based on the IDNR/SHL biological sampling data and the February 2011 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/SHL biological monitoring in 2005 and 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 2008 through October 2010, (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring near Churchtown in 2002, and (4) a 2011 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses are both assessed 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 21 samples collected during the recreational seasons of 2008 through 2010 at Upper Iowa River station 29 were as follows: the 2008 geometric mean was 323 orgs/100 ml, the 2009 geometric mean was 2,562 orgs/100 ml and the 2010 geometric mean was 1,122 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml; the 2009 and 2010 geometric means exceed the Class A2 geometric mean criterion of 630 orgs/100 ml. Nineteen of the 21 samples (90%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; five of the 21 samples (24%) exceeded the Class A2 single-sample maximum criterion of 2,880 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).
The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2005 and 2007 as part of the IDNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2005 CBI scores were 82 and 85. The 2007 CBI score was 72. The aquatic life use support was assessed (monitored) as fully supporting (=FS), based on a comparison of the CBI scores with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 3/3 times in a three-year period (2005-2007).
In addition, based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011, 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).
