Lake Icaria IA 05-NOD-1398

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Lake Icaria are assessed (monitored) as "partially supported" 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 64, 64, and 63 respectively for Lake Icaria. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Lake Icaria in the Eutrophic category. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and moderately high levels of phosphorus in the water column. The data show one violation of the Class A1 criterion for pH in 15 samples. While the TSI value for Secchi depth in Lake Icaria is below the impairment trigger of 65 for the 2016 reporting cycle, Lake Icaria was listed as "partially supporting" the Class A1 uses for the 2014 reporting cycle due to aesthetically objectionable conditions caused by poor water clarity.   Based on IDNR's assessment methodology, median-based TSI values for Secchi depth must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state’s Section 303(d) list (IR Category 5).    Therefore, Lake Icaria remains assessed as "partially supported" due to poor water clarity for the 2016 assessment cycle.      

Note:  A TMDL for siltation at Lake Icaria was prepared by IDNR and approved by EPA in 2002; thus, this waterbody was placed into IR Category 4a (TMDL approved) for the 2004 and 2006 assessment/listing cycles.   Data for the 2008 assessment show that water quality had improved and Lake Icaria was listed as Category 2a from  2008-2012.  However, recent water quality data suggests water quality is degrading.  Since all impairments for Lake Icaria were addressed in the 2002 TMDL, it will be listed as Category 4a for the 2016 assessment/listing cycle.  

The level of inorganic suspended solids was moderately high at Lake Icaria, and does suggest that non-algal turbidity may contribute to the impairment at this lake. The median level of inorganic suspended solids in Lake Icaria (6.2 mg/L) was ranked 98th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a large population of cyanobacteria exists at Lake Icaria, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 94% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (35.7 mg/L) was ranked 105th of the 138 lakes sampled. This median is in the worst 25% of the 138 lakes sampled. The presence of a large population of cyanobacteria at this lake suggests a potential violation of Iowa's narrative water quality standard protecting against the occurrence of nuisance aquatic life. This assessment is based strictly on the distribution of the lake-specific median cyanobacteria values from 2010-2014. Median levels greater than the 75th percentile of this distribution were arbitrarily considered to represent potential impairment. No other criteria exist, however, upon which to base a more accurate identification of impairments due to cyanobacteria. Assessments based on level of cyanobacteria will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence) to account for this lower level of confidence.

Note: The City of Corning applies copper sulfate (an algaecide) to Lake Icaria in the event of an algae bloom (Iowa Water Web).  

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” based on information from IDNR’s Fisheries Bureau and results of the ISU lake surveys.   Information from the IDNR Fisheries Bureau indicates that extensive soil conservation practices have been implemented in the watershed that likely will reduce nutrient loading and siltation impacts in Lake Icaria. Common carp were not eradicated during the renovation and the water quality has suffered.  The lake has issues with turbidity and lack of vegetation due to a high abundance of common carp. Results of the ISU lake survey from 2010-2014, however, show there were no violations of the criterion for ammonia in 15 samples(0%), 3 violations of the criterion for dissolved oxygen in 15 samples(20%), and one violation of the criterion for pH in 15 samples(7%). 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(LW) uses of Lake Icaria.

The Class C (drinking water) uses are not assessed due to the lack of recent information upon which to base an assessment. The only parameter collected as part of the ISU lake surveys relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU surveys from 2010-2014 show that nitrate levels are relatively low at this lake (maximum value = 2.1 mg/l; median = 0.2 mg/l), these data are not sufficient for developing a valid assessment of support of the Class C uses.

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.   EPA/IDNR fish contaminant (RAFT) monitoring at Lake Icaria in 2010.   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: 0.0322 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: 0.21 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 2010 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.