Assessment Comments
Assessment is based on: (1) results of ambient water quality monitoring conducted by USGS at Omaha, NE, (station 06610000) from February 2004 through December 2006, (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Council Bluffs in 2005, (3) information from Nebraska fisheries biologists, and (4) assessment information from Nebraska DEQ’s 2008 Integrated Report (http://www.deq.state.ne.us/).
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “fully supported” based on data and information from the Nebraska DEQ. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on information from local fisheries biologists on impacts related to flow modification and habitat alterations in this segment of the Missouri River. The fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2005. The sources of information for this assessment include (1) results of ambient water quality monitoring conducted by USGS at Omaha, NE, (station 06610000) from February 2004 through December 2006, (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Council Bluffs in 2005, (3) information from Nebraska fisheries biologists, (4) personal communication with staff of the Nebraska DEQ, and (5) assessment information from Nebraska DEQ’s 2008 Integrated Report (http://www.deq.state.ne.us/).
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as “fully supported” based on the assessment of primary contact recreation uses identified for this segment of the Missouri River by the Nebraska Department of Environmental Quality (NDEQ) for their 2006 and 2008 Section 303(d) listing cycles. This assessment represents a de-listing of Iowa’s 2006 bacteria impairment for this assessment segment. The rationale for this delisting is as follows. A draft version of Nebraska’s 2006 Integrated Report stated that the recreation uses of this segment of the Missouri River (NDEQ MT1-10000) were impaired due to high levels of indicator bacteria. Based on this information, Iowa DNR mistakenly placed this impairment on its 2006 Section 303(d) list. According to staff of the Nebraska DEQ, however, this impairment was de-listed during Nebraska’s 2006 Integrated Reporting cycle: samples of E. coli collected from this segment of the Missouri River in 2005 yielded a recreation season geometric mean of 72 orgs/100 ml (N=22), indicating that the bacterial impairment should be de-listed. Nebraska’s 2008 Integrated Report also shows that recreation uses for Missouri River segment MT1-10000 are fully supported. Thus Iowa DNR is de-listing this impairment for the current (2008) Integrated Reporting cycle.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on the assessment developed for previous reporting cycles (i.e., habitat alterations and flow modifications that resulted from development of the river for navigation uses in the mid-Twentieth Century). This assessment was developed in consultation with the Missouri River fisheries biologist for the state of Nebraska. Results of ambient water quality monitoring conducted by USGS during the 2004-2006 assessment period, however, suggest good water quality in this river segment. No violations of Class B(WW1) criteria occurred in the 42 samples analyzed during this period for ammonia (maximum of 0.4 mg/l) or pH (range from 7.7 to 8.7 pH units). Levels of toxic metals (e.g., selenium and arsenic) and pesticides (e.g., dieldrin and DDE) in the 42 samples collected were below their respective Class B(WW1) criteria. One of 41 samples violated the Class B(WW1) criterion for dissolved oxygen: the sample collected on June 28, 2005 contained 4.9 mg/l, thus slightly violating the Class B(WW1) criterion of 5.0 mg/l. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), however, the percentage of violations at this station during the 2004-2006 period for dissolved oxygen (2%) does not suggest a water quality impairment. These guidelines allow up to 10% violations of conventional parameters such as dissolved oxygen, pH, and water temperature before impairment of water quality is indicated.
Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring south of Council Bluffs in 2005. The composite samples of fillets from common carp and flathead catfish had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.117 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of flathead catfish fillets were as follows: mercury: 0.039 ppm; total PCBs: 0.102 ppm; and technical chlordane: <0.03 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. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 2005 RAFT sampling conducted in this assessment segment: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
