Lower Pine Lake IA 02-IOW-758

Results of IDNR beach monitoring from 2012 through 2014 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 2012 (16 samples), 2013 (30 samples) and 2014 (16 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 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 means from 2012, 2013 and 2014 were all below the Iowa water quality standard of 126 E.  coli orgs/100 ml.   The geometric mean was 50 E.  coli orgs/100 ml in 2012, 45 E.  coli orgs/100 ml in 2013 and 67 E.  coli orgs/100 ml in 2014.   The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E.  coli orgs/100 ml) was 19% in 2012, 17% in 2013 and 19% in 2014.   None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses.   According to IDNR's assessment methodology and U.S.  EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses. While the levels of indicator bacteria for  Pine Lake South Beach are not significantly greater than 10% of the samples and do not exceed the state's single season geometric mean criterion of 126 E.  coli orgs/100 ml for the 2016 reporting cycle,  Pine Lake South Beach was listed as "partially supporting" the Class A1 uses for the 2014 reporting cycle due to indicator bacteria.   Based on IDNR's assessment methodology, indicator bacteria violations must be not violation for two consecutive assessment cycles before a lake can be removed from the state’s Section 303(d) list (IR Category 4a).    Therefore,  Pine Lake South Beach remains assessed as "partially supported" due to violations of the criterion for indicator bacteria for the 2016 assessment cycle.    

For the 2016 assessment/listing cycle, however, 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 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 67, 70, and 72 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 IDNR 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 (4.59 mg/L) was ranked 86th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a moderately large population of cyanobacteria exists at Lower Pine Lake. These data show that cyanobacteria comprised 83% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (28.7 mg/L) was ranked 90th 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 IDNR’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 IDNR 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 IDNR 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 IDNR 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 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and no violations of the criterion for pH in 15 samples(0%). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(WW-1) uses of Lower Pine Lake.

The level of support of the Class HH-fish consumption uses is changed from “fully supporting” to “not assessed” due to the age of the data upon which the previous assessment was based.  The previous assessment was based on results of U.S. EPA / IDNR fish tissue (RAFT) monitoring at Lower Pine Lake in 2003.   The composite samples of fillets from channel catfish and largemouth bass had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: <0.0181 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.048 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   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).   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 2003 RAFT sampling conducted at Lower Pine 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.