Assessment Comments

Assessment is based on: (1) results of USGS ambient water quality monitoring conducted on the Maquoketa River near Spragueville, IA from February 2008 through December 2010 and (2) results of fish tissue monitoring conducted in 2006, 2008, and 2010 near Maquoketa for the U.S. EPA/IDNR (RAFT) fish tissue monitoring program.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed as “not supported” due to high levels of indicator bacteria; this is a new impairment for this assessment segment.   The Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” based on results of chemical water quality monitoring by USGS conducted from 2008 through 2010.   Fish consumption uses remain assessed as “fully supported” based on fish contaminant monitoring in 2006, 2008, and 2010.   The sources of data for this assessment are (1) results of USGS ambient water quality monitoring conducted on the Maquoketa River near Spragueville, IA (USGS station 05418600) from February 2008 through December 2010, (2) results of IDNR monitoring at STORET station 10490003 near Maquoketa from October to December 2010, and (3) results of fish tissue monitoring conducted in 2006, 2008, and 2010 near Maquoketa for the U.S.  EPA/IDNR (RAFT) fish tissue monitoring program.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria.   Results of USGS monitoring in 2009 and 2010 showed that recreation season (March-November) geometric means based on the 14 samples collected were well above Iowa’s Class A1 water quality criterion of 126 orgs/100 ml:  the 2009 geometric mean was 919 orgs/100 ml and the 2010 geometric mean as 1677 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses are "not supported".   Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”  

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of water quality monitoring by the U.S.   Geological Survey near Spragueville from 2008 through 2010.   No violations of state water quality criteria occurred in the 30 samples analyzed for dissolved oxygen, pH, ammonia, chloride, chlorpyrifos, DDE, and dieldrin.   Similarly, no violations of Class B(WW1) criteria occurred in the three samples collected by IDNR from October to December of 2010.  

Fish consumption uses are assessed (monitored) as "fully supported" based on the 2006, 2008, and 2010 EPA/IDNR fish tissue (RAFT) samplings on the Maquoketa River northeast of Maquoketa.   This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring (due to a change in the design of the RAFT program, all of Iowa’s 10 trend sites were sampled in 2005 and 2006; all ten sites were then monitored as part of the 2008 RAFT sampling).   The whole-fish samples of common carp from these three years had generally low levels of the primary contaminants: mercury:  maximum of 0.136 ppm; total PCBs: maximum of 0.45 ppm; and technical chlordane: maximum of 0.059 ppm.   While results from these samplings show that levels of chlordane and mercury are well below levels of concern, the level of total PCBs in the sample of whole-fish common carp from the 2006 sampling (0.45 ppm) exceeds the 1 meal/week trigger level as defined in Iowa’s revised (2006) fish consumption advisory protocol.  

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   The levels of total PCBs in the sample of whole-fish common carp collected in 2006 exceeded the 1 meal/week trigger level as defined in Iowa’s revised (2006) fish consumption advisory protocol.   According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level does not suggest impairment of the fish consumption uses but does suggest the need to conduct additional fish contaminant monitoring.   The IDNR/IDPH advisory protocol states that two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   The results for the  whole-fish sample from the 2006 sampling on the Maquoketa River did not warrant issuance of an advisory but did indicate the need to conduct additional monitoring to better define contaminant levels in fish from this river segment.   Additional monitoring in 2008 and 2010, however, showed that levels of total PCBs were below the advisory trigger level (0.105 ppm and 0.107 ppm).   The results therefore, suggest "full support" of the fish consumption uses.