Avenue Of The Saints Lake IA 02-SHL-1790

The Class B(LW) (aquatic life) uses are assessed (monitored) as "not supported" due to violations of the Class B(LW) criterion for pH. Information from the DNR Fisheries Bureau suggests that water quality and the fishery are extremely poor at this lake. Blue-green algae blooms and summer fish kills are frequent. 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 7 violations of the criterion for pH in 15 samples(47%). Based on DNR's assessment methodology these violations are significantly greater than 10% of the samples and therefore suggest impairment (not supported/monitored) of the Class B(LW) uses of Avenue Of The Saints Lake.

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, 68, and 76 respectively for Avenue Of The Saints Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Avenue Of The Saints 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 extremely high levels of phosphorus in the water column.

The level of inorganic suspended solids was high at Avenue Of The Saints Lake, and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Avenue Of The Saints Lake (10.2 mg/L) was ranked 122nd among the 138 lakes by the ISU lake survey.

Data from the 2012-2016 ISU lake survey suggest a large population of cyanobacteria exists at Avenue Of The Saints Lake, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 96% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (66.8 mg/L) was ranked 124th 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 2012-2016. 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.

A fish kill occurred in Avenue of the Saints Lake on or before May 15, 2015. An estimated 1,250 Black Bullhead were killed. No estimates of the value of the fish killed or the costs of the Iowa DNR investigation of the kill were provided. Based on the investigation conducted by the DNR Fisheries Bureau, the kill was attributed to natural causes. The following is from the report of the fish kill investigation:

Assumed to be an epizootic outbreak within the bullhead population that was caused by spawning stress and less than great water quality conditions—a bacterial or viral infection killed a portion of the bullhead population.

This is the same assessment as that developed for the 2016 assessment/listing cycles. The continuance of the IR Category 3b listing is based on DNR's 2016 assessment methodology that states the following: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 (2014-2016) 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” and will be placed in IR subcategories 3b and will be added to the state list of waters in need of further investigation. Thus, this assessment segment will remain in Category 3b of Iowa’s 2018 Integrated Report.

Fish consumption uses were assessed (monitored) as “partially supported” based on results of U.S. EPA/DNR fish contaminant (RAFT) monitoring at Avenue of the Saints Lake in 2013. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. The fish contaminant data generated from the 2013 RAFT sampling conducted at Avenue of the Saints Lake show that levels of mercury are sufficiently high for concern and thus justify follow-up monitoring. Results from the 2013 sampling show that the level of mercury in the sample of largemouth bass fillets (0.786 ppm) exceeds the 1 meal/week trigger level (0.30 ppm) as defined in Iowa’s revised (2007) fish consumption advisory protocol. According to DNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. Thus, follow-up monitoring is needed at Avenue of the Saints Lake. Levels of primary contaminants in the composite sample of 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 Avenue of the Saints Lake show the need for follow-up monitoring.