Ottumwa Lagoon IA 04-LDM-1014
Wapello County S25T72NR14W at Ottumwa.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trophic
- Hypereutrophic
- Trend
- Unknown
- Created
- 3/19/2019 10:14:38 AM
- Updated
- 6/11/2019 1:27:22 PM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2008 | Class BLW | Fish Kill: Caused By Petroleum Spill | Fish kill investigation: Iowa DNR | Assessment Error |
The Class A1 (primary contact recreation) uses are assessed (evaluated) as “not supported” due to aesthetically objectionable conditions caused by poor water transparency due to algal blooms and high levels of inorganic turbidity. The Class B(LW) (aquatic life) uses are assessed (monitored) as “not supported” due to a fish kill in 2006 and excessive nutrient loading, nuisance blooms of algae, siltation and organic enrichment. Fish consumption uses are not assessed due to the age of the data. Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2006 and 2010 through 2014 by Iowa State University (ISU), (2) information from the IDNR Fisheries Bureau, and (3) results of a fish kill investigation in August of 2006.
NOTE: The 2006 fishkill was determined to be natural causes, rather than from petroleum. This needs to be revisited and removed as a potential cause of impairment - JMM 3/19/2019 Ottumwa Lagoon was only sampled once by ISU during 2010-2014 sampling seasons. This is due to a lack of boat accessibility due to the lake being in a drawn status for repairs to be made to the stormwater system. Because there is only one sampling event in one year of data upon which to base an assessment, this assessment is considered "evaluated" (of lower confidence) rather than "monitored." For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Ottumwa Lagoon are assessed (evaluated) 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 survey from 2013 (approximately 1 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 83, 73, and 87 respectively for Ottumwa Lagoon. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Ottumwa Lagoon in the Hypereutrophic category. These values suggest very high levels of chlorophyll a and suspended algae in the water, extremely poor water transparency, and extremely high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 1 samples. The previous assessment from 2012 will keep the lake as “not supported” due to aesthetically objectionable conditions caused by poor water transparency due to algal blooms and high levels of inorganic turbidity. Note:A TMDL for algae, turbidity, and chlordane at Ottumwa Lagoon was prepared by DNR and approved by EPA in 2005; thus, this waterbody was placed in Category 4a of Iowa's 2006 Integrated Report. Because the fish kill-related impairment is not covered by this TMDL, this waterbody is placed in Category 5b of Iowa's 2016 Integrated Report. The level of inorganic suspended solids was extremely high at Ottumwa Lagoon, and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Ottumwa Lagoon (29 mg/L) was ranked 136th among the 138 lakes by the ISU lake survey. Data from the 2013-2013 ISU lake survey suggest a moderately large population of cyanobacteria exists at Ottumwa Lagoon. These data show that cyanobacteria comprised 49% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (27.1 mg/L) was ranked 87th of the 138 lakes sampled. The Class B(LW) (aquatic life) uses are assessed (evaluated) as "fully supported." Results of the ISU lake survey from 2013 show there were no violations of the criterion for ammonia in 1 sample (0%), no violations of the criterion for dissolved oxygen in 1 sample (0%), and no violations of the criterion for pH in 1 sample (0%). Based on DNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/evaluated) of the Class B(LW) uses of Ottumwa Lagoon. Based on DNR’s assessment methodology these results do not suggest impairment of the Class B(LW) uses at Ottumwa Lagoon. In the previous assessment 2016 cycle, the Class B(LW) (aquatic life) uses were assessed (monitored) as “not supported” based on information from the DNR Fisheries Bureau, results of a fish kill investigation, and results from the ISU lake surveys. A fish kill occurring on August 17, 2006 at Ottumwa Lagoon was attributed to a spill of petroleum products due to pumping of a local gas station that had been contaminated by fuel (pollutant/human). The number and type of fish killed was not reported. At the time of this assessment there are no records that DNR sought/received restitution for this fish kill. However, during a 2019 review of the Iowa DNR fish kill database an email from field office 6 was located that indicated that the fish kill was actually due to natural causes due to water levels being lowered in the system. The fish had been dead or dying over several days prior to the groundwater remediation at the LUST (leaking underground storage tank) site. Thus, the assessment of aquatic life use support for this stream segment is being moved from impairment Category 5a of Iowa’s Integrated Report to Catagory 3 not assessed due to assessment error. Fish consumption uses are considered to be not assessed due to the age of the data. The previous assessment of fish consumption was assessed as (monitored) as “fully supported.”