Assessment Comments
Assessment of the Class A1 uses is based on results of bacterial monitoring in 2012 at Station 15280002 approximately 4 miles SE of Dundee. Assessment of the Class B(WW1) uses remains based on 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)).
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/evaluated ”. Fish consumption uses remain 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 by the Lake Delhi Watershed Association at two locations on the Maquoketa River [below Backbone Lake (STORET station 15280001) in 2006 and approximately 4 miles SE of Dundee (STORET station 15280002) in 2006 and 2012.
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 in 2006 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 in 2006 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 was 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 were assessed (“monitored”) as “not supported,” and this impairment was added to Category 5a of IDNR’s 2010 Integrated Report (Iowa’s Section 303(d) list).
The results of more recent monitoring in 2012, however, suggest a significant decline in bacteria levels. The geometric mean of E. coli in the seven samples collected in May and June 2012 at the monitoring station downriver from Dundee was 123 orgs/100 ml and was thus below the Class A1 criterion; only one of the seven samples (14%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml (the 2006 geometric mean at this station was 2,198 orgs/100ml). The results from monitoring in 2012 do not suggest impairment of the Class A1 uses, but they are not sufficient for removing the existing bacterial impairment. That is, (1) too few data were collected over the 2010-2012 data collection period to meet Iowa DNR’s guidelines for data quantity (at least 10 samples over a three-year period) and (2) removal of a bacterial impairment requires that geometric mean levels of E. coli must all be less than the applicable state water quality criterion for two consecutive listing cycles (i.e., five consecutive years). Thus, the impairment of the Class A1 uses will remain. If sufficient additional data are collected during the 2013-2014 period that show a continued decline in bacteria levels and compliance with the Class A1 water quality criterion, this impairment may be removed.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supporting” based on results of chemical/physical water quality monitoring in 2006. 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. The results of monitoring from these stations are consistent with the assessment of aquatic life uses as “fully supported.”
The assessment of support of the Class B(WW1) aquatic life uses is no longer based on the results of biological monitoring conducted by IDNR Fisheries in 2001. According to Iowa DNR’s assessment/listing methodology, any non-303(d) Section 305(b) an assessments based on data that have aged beyond 10 years likely does not represent current conditions is thus not included in the current assessment cycle. Previous assessments based on these data remain in IDNR’s on-line assessment database, ADBNet. The previous assessments of the Class B(WW1) uses were based in part 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 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.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.
