Missouri River IA 06-WEM-1708

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria.  The geometric means of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2012 through 2014 at Missouri River near Council Bluffs were as follows: the 2012 geometric mean was 92 orgs/100 ml, the 2013 geometric mean was 188 orgs/100 ml, and the 2014 geometric mean was 423 orgs/100 ml.  Two of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  Eight of the combined 20 samples (40%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported".

The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" (IR Category 4c, non-pollutant stressor) 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 2010-2012 assessment period, however, suggest good water quality in this river segment.   Monitoring showed no violations of Class B(WW1) water quality criteria for 29 Ammonia samples (maximum = 0.1 mg/L), 29 pH samples (range = 7.7 to 8.6), 30 Temperature samples (maximum = 29.3° c), or 24 Chloride samples (maximum = 20.5 mg/L) occurred during monitoring from July 2012 to December 2014. One of the 30 samples (3%) analyzed for Dissolved Oxygen (minimum = 4.5 mg/L) violated the Class B(WW1) criteria during the 2012-2014 monitoring period. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as Dissolved Oxygen suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant monitoring south of Council Bluffs in 2013 and 2014.   The composite samples of fillets from channel catfish and flathead catfish had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.13 ppm; total PCBs: 0.6 ppm; and technical chlordane: <0.2 ppm.  The total PCBs (sum Aroclors) composite value is above the 1 meal/week advisory threshold.  TThis composite value generated from this monitoring data are sufficiently high for concern and to justify follow-up monitoring.  According to IDNR's assessment methodology, the single occurrance of a contaminant above the advisory trigger level neither warrants issuance of an advisory not indicated impairment of the fish consumption uses: two consecutive sampoings that show contaminant levels above the trigger level are needed to justify impairment. Levels of primary contaminants in the composite sample of flathead catfish fillets were as follows: mercury: 0.173 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 results of fish contaminant monitoring in this assessment segment from the 2013 and 2014 sampling, however, show that the levels of contaminants do not exceed any of Iowa' advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.

Previous fish consumption uses remain  was assessed  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.   The results of fish contaminant monitoring in this assessment segment from the 2005 RAFT sampling, however, show that the levels of contaminants do not exceed any of Iowa' advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.