Lower Pine Lake IA 02-IOW-758
Hardin County S4T87NR19W 0.5 mi E of Eldora.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Hypereutrophic
- Trend
- Stable
- Created
- 10/16/2018 10:43:00 AM
- Updated
- 4/10/2019 1:46:34 PM
The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to high levels of indicator bacteria that exceed Iowa’s water quality standards, and aesthetically objectionable conditions caused by algae blooms and turbidity. The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to high levels of nutrients that contribute to nuisance algae blooms and results of a fish kill investigation in April 2009. Fish consumption uses are considered “not assessed” due to the age of the data upon which the previous assessment (“fully supported”) was based. Sources of data for this assessment include (1) results of IDNR/UHL beach monitoring from 2014 through 2016, (2) results of the statewide survey of Iowa lakes conducted from 2012 through 2016 by Iowa State University (ISU), (3) information from the IDNR Fisheries Bureau, (4) results of a fish kill investigation in April 2009, and (5) results of U.S. EPA/IDNR fish tissue monitoring in 2003.
Results of DNR beach monitoring from 2014 through 2016 suggest that the Class A1 uses are "partially supported." Levels of indicator bacteria at Pine Lake South Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2014 (16 samples), 2015 (19 samples) and 2016 (18 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 Pine Lake South Beach, the geometric mean from 2014 was below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric means from 2015 and 2016, however, were greater than the Iowa water quality standard of 126 E. coli orgs/100ml and therefore suggests impairment of the Class A1 uses. The geometric mean was 67 E. coli orgs/100 ml in 2014, 136 E. coli orgs/100 ml in 2015 and 132 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 19% in 2014, 47% in 2015 and 39% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2015 and 2016. 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 Lower Pine 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 14 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 67, 71, and 73 respectively for Lower Pine Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Lower Pine Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest very high levels of chlorophyll a and suspended algae in the water, poor water transparency, and very high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 15 samples. Note:A TMDL for organic enrichment at Lower Pine Lake was prepared by DNR and approved by EPA in 2002; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because the Section 303(d) impairment due to indicator bacteria (aka, "pathogens") was not addressed in the TMDL, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle and remains in Category 5a for the 2016 assessment/listing cycle. The level of inorganic suspended solids was moderately high at Lower Pine Lake, and does suggest that non-algal turbidity may contribute to the impairment at this lake. The median level of inorganic suspended solids in Lower Pine Lake (3.3 mg/L) was ranked 73rd among the 138 lakes by the ISU lake survey. Data from the 2012-2016 ISU lake survey suggest a moderate population of cyanobacteria exists at Lower Pine Lake. These data show that cyanobacteria comprised 47% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (12.9 mg/L) was ranked 61st of the 138 lakes sampled. The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to a fish kill that occurred in April of 2009. The fish kill was attributed to natural causes (fluctuating water temperatures). The 2009 kill affected approximately 2500 fish; mostly bluegill and crappie. No estimate of the value of these fish was made. According to DNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2010-2012) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.”If a cause of the kill was not identified during the DNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.”Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation. Information from the DNR Fisheries Bureau also suggests that the Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to nutrient loading that leads to nuisance algae blooms. Information from the DNR Fisheries Bureau suggests that this lake has no submergent vegetation and a moderate common carp population that leads to occasional algae blooms.Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 15 samples(0%), one violation of the criterion for dissolved oxygen in 15 samples(7%), and no violations of the criterion for pH in 15 samples(0%). 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 Lower Pine Lake.