Assessment Comments
Basis for Assessment
SUMMARY: Continue to use the assessments of the Class A (primary contact recreation) uses ("not supporting") and the Class B(LW) aquatic life uses ("partially supporting") developed for the 1998 and previous reports. Fish consumption uses were assessed as "fully supported / threatened." EXPLANATION: The assessment of the Class A primary contact uses remains based on observations of combined sewer overflows discharging to the Ottumwa Lagoon by DNR staff in June 1995 (see above assessment for the 1996 report). Due to recent expansion of the DNR WQ monitoring network, routine water quality monitoring by ISU Limnology began at Ottumwa Lagoon summer 2000. Data from this monitoring will enable development of an updated assessment for the Class A uses and an assessment of the Class B(WW) aquatic life uses for the 2002 report. Based on results of recent EPA/DNR fish tissue (RAFT) monitoring, fish consumption uses were assessed as "fully supporting/threatened." RAFT monitoring in 1998 showed that levels of all contaminants in the sample of largemouth bass fillets were well below ½ of respective FDA action levels and DNR levels of concern, but that the level of technical chlordane in the sample of common carp fillets (0.39 ppm) was greater than the FDA action level of 0.30 ppm. Follow-up (RAFT) monitoring was conducted in 1999. Levels of technical chlordane in samples of common carp fillets (0.24) were less than the FDA action level, while levels in the sample of channel catfish fillets (0.32 ppm) slightly exceeded the FDA action level of 0.30 ppm. Based on DNR's 305(b) assessment methodology, the occurrence of levels above 1/2 the FDA action level for chlordane in the absence of a fish consumption advisory suggests that fish consumption uses should be assessed as "fully supported / threatened." Samples of carp and channel catfish were collected from this lake for the 2000 RAFT program. If chlordane levels in the sample of channel catfish again exceed the FDA action level, a fish consumption advisory will be issued for this lake in summer 2001.
