Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 2008 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, (4) results from the IDNR beach monitoring program, and (5) IDNR fish contaminant monitoring in 2013.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to high levels of algae that violate Iowa's narrative criteria protecting against aesthetically objectionable conditions. Violations of Iowa’s water quality criterion for indicator bacteria also contribute to this impairment. The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.” The previous impairment for pH is suggested for de-listing. Fish consumption uses are assessed as "fully supporting." Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 2008 by University Hygienic Laboratory (UHL),(3) information from the IDNR Fisheries Bureau, (4) results from the IDNR beach monitoring program, (5) IDNR fish contaminant monitoring in 2013.
EXPLANATION:Results of IDNR beach monitoring from 2012 suggest that the Class A1 uses are “partially supported." Levels of indicator bacteria at Kent Park Lake beach were monitored once per week during the primary contact recreation seasons (May through August) of 2012 (18 samples) as part of the IDNR beach monitoring program. According to IDNR’s assessment methodology two conditions need to be met for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period are less than the state’s geometric mean criterion of 126 E. coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state’s single-sample maximum value of 235 E. coli orgs/100 ml. If a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if significantly more than 10% of the samples in any one of the three recreation seasons exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A1 uses should be assessed as “partially supported.” This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
NOTE 1: Note: A TMDL for the algae and pH impairments at Kent Park Lake was prepared by Iowa DNR and was approved by U.S. EPA in June 2015 see http://www.iowadnr.gov/Environment/WaterQuality/WatershedImprovement/WatershedResearchData/WaterImprovementPlans/PublicMeetingsPlans.aspx). Due to completion of the TMDL, the algae impairment for this lake is moved to IR Category 4a (impaired; TMDL approved). The pH impairment is proposed for de-listing for the current (2014) cycle due to new data. The Class A1 primary contact recreation uses remain impaired (IR Category 5a) due to the bacteria impairment that is not covered by the June 2015 TMDL.
NOTE 2: Based on consultation with EPA Region 7 staff in 2011, IDNR’s methodology for assessing impairments based on the geometric mean water quality criterion was changed. Prior to the 2012 listing cycle, IDNR calculated geometric means for lakes based on a 30-day periods within the recreational season. Any violation of one of these 30-day periods within 3 years resulted in an impairment of the Class A1 uses of that lake. Because water quality standards do not identify a 30 day period but instead a recreational season, Region 7 concurred that the approach used for rivers and streams with less frequent bacteria data (seasonal geometric means) would be appropriate for identifying §303(d) impairments at lake beaches. Thus, for the 2014 listing cycle, IDNR identified primary contact recreation impairments for lakes when the geometric mean of all samples from the recreation season of a given year exceeded the geometric mean criterion. This does not impact the way IDNR assesses beaches for closure to protect the recreating public in the short term.
At Kenk Park Lake beach, the geometric mean from 2012 was below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 58 E. coli orgs/100 ml in 2012. The percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was 28% in 2012. The results from 2012 are significantly greater than 10% of the samples and therefore also suggest impairment of the Class A1 uses. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest the Class A1 uses are “partial supported.”
For the 2014 reporting cycle, the Class A1 (primary contact recreation) uses for Kent Park Lake are assessed (monitored) as “partially supported” due to high levels of algal turbidity. Using the median values from the ISU and UHL lake surveys from 2008-2012 (approximately 14 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 68, 64, and 65 respectively for Kent Park Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Kent Park Lake in between the eutrophic and the hypereutrophic categories. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, poor water transparency, and high levels of phosphorus in the water column.
NOTE: The trophic state index value for chlorophyll a at Kent Park Lake is below the impairment trigger of 65. However, Kent Park Lake was assessed as "partially supporting" the Class A1 uses due to algae for the 2010 assessment/listing cycle. Based on IDNR's assessment methodology, two assessment/listing cycles with TSI values less than or equal to 63 are necessary to suggest de-listing of the algae impairment. Therefore, Kent Park Lake will remain assessed as "partially supported" for the 2014 Integrated Report.
The levels of inorganic suspended solids at this lake were moderately high and do and may contribute to the impairment at this lake. The median level of inorganic suspended solids in Kent Park Lake (2.8 mg/L) and ranked 53rd of the 134 lakes sampled by the ISU and UHL programs.
Data from the 2008-2012 ISU and UHL surveys suggest a moderate population of cyanobacteria exists at Kent Park Lake, which does not contribute to impairment at this lake. These data show that cyanobacteria comprised 70% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (20.1 mg/L) and ranked 72nd of the 134 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed as “fully supported” based on information from IDNR’s Fisheries Bureau and results from the ISU and UHL lake surveys. The ISU and UHL lake surveys data from 2008-2012 show no violations of the Class B(LW) criteria for ammonia in 14 samples,pH in 14 samples, or dissolved oxygen in 214 samples. Kent Park Lake was assessed as "partially supporting" the Class A1,B(LW) uses for the 2010 assessment/listing cycle due to violations of the pH criteria. Based on IDNR's assessment methodology 2 consecutive assessment/listing cycles where there are not significantly greater than 10% of the samples violating the standard are necessary to suggest de-listing of the pH impairment. Because violations of the pH criteria were not significantly greater than 10% for the 2012 assessment/listing cycle or the current 2014 assessment/listing cycle, the pH impairment for Kent Park Lake is suggested for delisting.
Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring at Kent Park Lake in 2013. The composite samples of fillets from largemouth bass and channel catfish had low levels of contaminants. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.107 ppm. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: total PCBs: <0.6 ppm; and technical chlordane: <0.2 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 fish contaminant data generated from the 2013 RAFT sampling conducted at this lake show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
