Upper Iowa River IA 01-UIA-245

Assessment Comments

Assessment remains based on results of fish contaminant monitoring conducted near Lime Springs in 2006 as part of the U.S. EPA/IDNR fish contaminant (RAFT) monitoring program.

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.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses.   The stream remains designated for aquatic life uses (now termed Class B(WW1) aquatic life uses).   Thus, for the current (2012) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are considered "not assessed" due to the age of the biological data upon which the previous assessments of these uses ("fully supported") were based.   Fish consumption uses remain assessed (monitored) as “fully supported” (IR 2a) based on results of fish contaminant monitoring conducted near Lime Springs in 2006 as part of the U.S.  EPA/IDNR fish contaminant (RAFT) monitoring program.  

EXPLANATION:  The presumptive Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of data for indicator bacteria upon which to base an assessment.   Upstream sites on the Upper Iowa River are monitored by as part of the Upper Iowa River Watershed Project, but these sites are located approximately five miles into Minnesota and are thus are too far removed to be useful for assesing the Class A1 uses of this segment in Iowa.

The Class B(WW1) aquatic life uses also remain “not assessed.”  The most recent (2004) assessment of the Class B(WW) uses for this stream segment (“fully supported”) was based on results of biological monitoring conducted as part of an IDNR stream use assessment in 1995.   Because the data upon which this assessment was originally based have aged beyond 10 years--and are thus are considered too old to characterize current water quality conditions--the Class B(WW1) uses of this segment are now considered "not assessed".  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Lime Springs in 2006.   The composite samples of fillets from smallmouth bass and golden redhorse (Moxostoma erythrurum) collected near Lime Springs in 2006 were analyzed only for mercury.   These samples were collected as part of RAFT follow-up monitoring to better define the boundaries of the existing fish consumption advisory issued in 2006 for the Upper Iowa River from the Lower Dam upriver to the county road W20 bridge NW of Decorah.   The level of mercury in the composite sample of golden redhorse fillets was 0.22 ppm.   The level of mercury in the composite sample of smallmouth bass fillets was 0.25 ppm.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   The results from the 2006 sampling near Lime Springs suggest that levels of mercury in fish from this segment of the Upper Iowa River are below IDNR/IDPH advisory trigger levels.   Thus, the fish consumption uses are assessed as “fully supported.”