Ottumwa Lagoon IA 04-LDM-1014

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 storm water 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 2016 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 IDNR 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 (monitored) as “not supported” based on information from the IDNR Fisheries Bureau, results of a fish kill investigation, and results from the ISU lake surveys.  A fish kill occurred on August 17, 2006 at Ottumwa Lagoon.   The fish kill 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 IDNR sought/received restitution for this fish kill.  

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 (2008-2011) 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 is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing.    Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b.   The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.   For previous assessment/listing cycles, IDNR had considered fish kill-impaired (IR 5b) waters with no subsequent kills in the three year subsequent to the kill as appropriate for de-listing and for movement to IR categories 2b or 3b (i.e., Iowa’s list of waters in need of further investigation).   Due, however, to EPA uncertainty regarding the full recovery of the aquatic life following the kill, any existing fish kill (5b) impairment will remain in IR Category 5b until more recent monitoring has shown full recovery of the aquatic communities affected by the kill.   Thus, this assessment segment will remain in Category 5b of Iowa’s 2012 Integrated Report.    

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 samples(0%), no violations of the criterion for dissolved oxygen in 1 samples(0%), and no violations of the criterion for pH in 1 samples(0%). Based on IDNR'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 IDNR’s assessment methodology these results do not suggest impairment of the Class B(LW) uses at Ottumwa Lagoon.   However, information from the IDNR Fisheries Bureau suggests that Ottumwa Lagoon is not meeting its aquatic life uses due to siltation, a large population of rough fish, and frequent inputs from storm sewers.  Thus, the fish kill and information from the IDNR Fisheries Bureau suggest impairment (nonsupport) of the Class B(LW) uses at Ottumwa Lagoon.

Fish consumption uses were assessed (monitored) as “fully supported” based on results of ongoing U.S.  EPA/IDNR fish contaminant (RAFT) monitoring at Ottumwa Lagoon in 2000, 2002, 2004, and 2006.   Recent fish contaminant monitoring (2004 and 2006) has shown that levels of contaminants are below IDNR/IDPH advisory trigger levels.   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.   A fish consumption advisory had been in place at Ottumwa Lagoon since 2001.   Levels of chlordane in channel catfish fillets had exceeded the trigger level for technical chlordane (0.6 ppm for a one meal per week advisory).  

The level of technical chlordane in the composite sample of fillets from channel catfish collected for the 2000 RAFT program was 0.87 ppm; this level is greater than the IDPH/INDR trigger level of 0.6 ppm for a one meal per week consumption advisory.    For the 2002 RAFT sampling, the composite samples of fillets from common carp and channel catfish had generally low levels of contaminants.   Levels of primary contaminants in the composite common carp fillets were low and do not suggest a fish contaminant problems (mercury: 0.095 ppm; total PCBs: 0.106 ppm; and technical chlordane: 0.240 ppm).   With the exception of chlordane, levels of primary contaminants in the composite sample of channel catfish fillets were also relatively low (mercury: 0.021 ppm; total PCBs: 0.143 ppm).   The level of chlordane in the sample of channel catfish fillets (0.78 ppm), however, exceeded the IDNR/IDPH trigger level of 0.60 ppm for a one meal per week consumption advisory (this levels is well below the “do not eat” trigger level for chlordane of 5.0 ppm).   Because the level of chlordane in the 2000 sample of channel catfish fillets (0.87 ppm) had also exceeded this trigger level, continuance of the existing advisory was justified.   As per Iowa’s revised protocol, the type of advisory, however, was changed from a “do not eat” to a “one meal per week” advisory.    

The 2004 RAFT follow-up sampling at Ottumwa Lagoon showed that levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: <0.0181 ppm; total PCBs: 0.12 ppm; and technical chlordane: 0.45 ppm.    The level of chlordane in this sample of (0.45 ppm), however, was below the IDNR/IDPH trigger level of 0.60 ppm for a one meal per week consumption advisory.   According to the IDNR/IDPH advisory protocol, if two consecutive samplings show that contaminant levels are below the trigger level in fillet samples, an existing consumption advisory can be removed.   The 2006 RAFT follow-up sampling at Ottumwa Lagoon showed that levels of technical chlordane in channel catfish (0.3 ppm) were again below the IDNR/IDPH trigger level of 0.60 ppm for a one meal per week consumption advisory.   The levels of PCBs in channel catfish (0.133 ppm) were also below the IDNR/IDPH trigger level.   Therefore, the one meal per week consumption advisory for Ottumwa Lagoon was removed and the fish consumption uses are assessed as “fully supported” for the 2010 assessment/listing cycle.