Kent Park Lake IA 02-IOW-694
Johnson County S24T80NR8W 2.5 mi. W of Tiffin.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 10/15/2018 10:21:16 AM
- Updated
- 4/5/2019 1:24:39 PM
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.” 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 2012-2016 by Iowa State University (ISU), (2) information from the IDNR Fisheries Bureau, (3) results from the IDNR beach monitoring program, (4) IDNR fish contaminant monitoring in 2013.
Results of DNR beach monitoring from 2014 through 2016 suggest that the Class A1 uses are "partially supported." Levels of indicator bacteria at F. W. Kent Park Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2014 (15 samples), 2015 (16 samples) and 2016 (15 samples), as part of the DNR beach monitoring program. According to DNR’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 1000 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period and/or 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). At F. W. Kent Park Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 73 E. coli orgs/100 ml in 2014, 17 E. coli orgs/100 ml in 2015 and 19 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 47% in 2014, 6% in 2015 and 13% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2014. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses. For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Kent Park Lake are assessed (monitored) as "not supported" due to poor water transparency and aesthetically objectionable conditions caused by algae blooms based on information from the ISU lake survey. Using the median values from these surveys from 2012-2016 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 70, 69, and 74 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 high levels of chlorophyll a and suspended algae in the water, very poor water transparency, and very high levels of phosphorus in the water column. The data show 2 violations of the Class A1 criterion for pH in 15 samples (13%). The level of inorganic suspended solids was low at Kent Park Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Kent Park Lake (1.6 mg/L) was ranked 9th among the 138 lakes by the ISU lake survey. 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. Not all of the section 303(d) impairments identified for the current (2018) assessment/listing cycle (indicator bacteria), however, are addressed in the TMDL. Thus, this waterbody remains in Category 5a (impaired; TMDL required) for the 2018 assessment/listing cycle. Data from the 2012-2016 ISU lake survey suggest a moderately large population of cyanobacteria exists at Kent Park Lake. These data show that cyanobacteria comprised 93% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (25.5 mg/L) was ranked 94th of the 138 lakes sampled. The Class B(LW) (aquatic life) uses are assessed (monitored) as "fully supported." Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 15 samples(0%), 2 violations of the criterion for dissolved oxygen in 15 samples(13%), and 2 violations of the criterion for pH in 15 samples(13%). Based on DNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Kent Park Lake.