Assessment Comments
Assessment based on (1) results of IDNR/SHL biological sampling in 2002, 2004 and 2012, (2) results of IDNR/SHL ambient monthly water quality monitoring conducted from March to November 2001 and from April to September 2005 in support of TMDL development, (3) results of Section 319 bacteria monitoring from June 2009 through November 2010, (4) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2004 and (5) results of IDNR Fisheries Bureau fish sampling in 2005.
Basis for Assessment
[Note: Prior to the 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, this segment is also now presumptively 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 presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as "not supported" (IR 5p) due to levels of indicator bacteria that violate state water quality criteria. Although recent (2012) biological monitoring suggests "full support" of the Class B(WW1) aquatic life uses, these uses remain assessed as "partially supported" (IR 5b-v) based on results of previous IDNR/SHL biological (biocriteria) sampling in 2002 and 2004 and on IDNR Fisheries Bureau sampling in 2005. This assessment is also based on results of Section 319 project water quality monitoring for indicator bacteria conducted at BHC Site 13 (STORET station 13380010) from June 2009 to November 2010. This current aquatic life assessment indicates that the aquatic life uses in this segment are fully supporting; however, because the assessment is evaluated (i.e., another biological sampling showing "full support" is needed), this waterbody remains in IR Category 5b-v. Fish consumption uses remain assessed (monitored) as "fully supported" (IR 2a) based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2004. Note: USGS conducted monitoring in this assessment segment at station 05463500 at Hudson in October 2010. Too few data were produced from this monitoring during the 2010-2012 assessment period (one sample) to be of use for assessment for purposes of either Section 305(b) reporting or Section 303(d) listing.
Note: A TMDL for indicator the bacteria impairments in the adjacent downstream segment of Black Hawk Creek (IA 02-CED-0370_1) was approved by EPA in 2006. This TMDL, however, did not include the current segment (IA 02-CED-0370_2); thus, this impairment is considered appropriate for Category 5p of Iowa's Integrated Report.
EXPLANATION: The presumptive Class A1 uses are assessed as "not supported" based on results of Section 319 monitoring for indicator bacteria (E. coli). The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2009 and 2010 at Section 319 monitoring station BHC 13 were as follows: the 2009 geometric mean was 1,195 orgs/100 ml and the 2010 geometric mean was 765 orgs/100 ml. Both geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Eighteen of the 21 samples (86%) exceeded the Class A1 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 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). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”
The Class B(WW1) aquatic life uses are assessed as “fully supporting” based on data collected in 2002, 2004 and 2012 as part of the IDNR/SHL stream biocriteria project. The 2002 FIBI score was 61 (good) and the BMIBI score was 64 (good). The 2004 FIBI score was 44 (fair) and the BMIBI score was 41 (fair). The 2012 FIBI score was 61 (good) and the BMIBI score was 65 (good). The 2005 IDNR Fisheries Bureau FIBI was 62 (good). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52. This segment passed the FIBI BIC 4/4 times and passed the BMIBI BIC 2/3 times in the past 11 years. This aquatic life use assessment would be considered "monitored" because there were two or more samples (FIBI) collected in multiple years in a five year period however, the data used for the assessment are now more than five years old. Old data can't accurately characterize current water quality conditions; therefore, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). This current assessment indicates that the aquatic life uses in this segment are fully supporting; however, because the assessment is evaluated, this waterbody remains in IR Category 5b-v.
Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Hudson in 2004. The composite samples of fillets from channel catfish and smallmouth bass had very low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.072 ppm; total PCBs: 0.092 ppm; and technical chlordane: 0.044 ppm. Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.098 ppm; total PCBs: 0.09 ppm; and technical chlordane: < 0.03 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 levels of contaminants do not exceed any of the Iowa advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory.
