Assessment Comments
Assessment remains based on (1) results of water quality monitoring in 2006 by the Lake Delhi Watershed Association at two locations on the Maquoketa River (below Backbone Lake (STORET station 15280001) and approximately 4 miles SE of Dundee (STORET station 15280002)) and (2) biological monitoring in 2001 by the IDNR Fisheries Bureau: FIBI = 45, 45 (fair). Non-riffle FIBI BIC = 44.
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 and due to the completion of a Use Attainability Analysis in 2007, 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 remain assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class B(WW1) uses remain assessed (evaluated) as “fully supported” based on results of biological (fish) monitoring in 2001 by the IDNR Fisheries Bureau. Fish consumption uses are not assessed due to lack of fish contaminant monitoring in this assessment segment. Sources of data used for this assessment include (1) results of water quality monitoring in 2006 by the Lake Delhi Watershed Association at two locations on the Maquoketa River (below Backbone Lake (STORET station 15280001) and approximately 4 miles SE of Dundee (STORET station 15280002)) and (2) biological monitoring in 2001 by the IDNR Fisheries Bureau.
EXPLANATION: The Class A1 (primary contact recreation) uses remain assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric mean of E. coli in the seven samples collected by the Lake Delhi Watershed Association at the monitoring station downriver from Backbone Lake was 1,066 orgs/100 ml; five of the seven samples (71%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Similarly, the geometric mean of E. coli in the seven samples collected at their monitoring station downriver from Dundee was 2,198 orgs/100 ml; six of the seven samples (86%) exceeded Iowa’s 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 the geometric mean 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). Although IDNR’s listing methodology requires that a minimum of ten E. coli samples be collected over a three-year period to support a Section 303(d) listing, this segment is being added to Iowa’s 2010 Section 303(d) list based on overwhelming evidence of impairment. That is, even if three additional samples had been collected, and each of these three samples had less than 10 orgs/100 ml (the INDR detection level), the resulting geometric means of E. coli at these two stations(262 orgs/100 ml at station 15280001 and 436 orgs/100 ml at station 15280002) would still have exceeded Iowa’s Class A1 criterion of 126 orgs/100 ml. Thus, the Class A1 uses of this segment are assessed (“monitored”) as “not supported,” and this impairment is being added to Category 5a of IDNR’s 2010 Integrated Report (Iowa’s Section 303(d) list).
The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supported” based on results of biological monitoring. The evaluated assessment was based on data collected in 2001 as part of an IDNR 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 (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2001 FIBI scores were 45, 45 (fair). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI 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 1994-2004. The non-riffle FIBI BIC for this ecoregion is 44. This segment passed the FIBI BIC 2/2 times in 2001.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years within a five-year period to be considered “monitored”. This segment had multiple FIBI samples collected in 2001; however, the multiple samples were not collected during the five-year period and were not collected in multiple years. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
Results of chemical/physical water quality monitoring in 2006 are consistent with the assessment of aquatic life uses as “fully supported.” Water quality monitoring conducted from April to June 2006 by the Lake Delhi Watershed Association at stations 15280001 and 15280002 showed no violations of Class B(WW1) criteria for dissolved oxygen, ammonia, or pH in the combined 10 samples collected.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.
