Assessment Comments

Assessment is based on results of (1) IDNR monthly ambient monitoring station at Hwy 61 bridge NW of Maquoketa from 2002-04, (2) IDNR/UHL TMDL monitoring in 2001, (3) ISU statewide freshwater mussell survey, (4) EPA/IDNR fish tissue (RAFT) monitoring NE of Maquoketa in 2001 and 2003, and (5) IDNR/UHL biological (REMAP) monitoring in 2003 [FIBI = 58 (good), BMIBI = 57 (good). FIBI BIC = 36; BMIBI BIC = 51].

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses were assessed (monitored) as "not supported" due to levels of indicator bacteria that exceeded state water quality criteria.   The Class B(WW) aquatic life uses were assessed (monitored) as "not supported" due the apparent elimination of the freshwater mussel community from this river segment.   Fish consumption uses remain "fully supported" based on results of fish contaminant monitoring in 1999, 2001, and 2003.   Sources of data for this assessment include (1) results monthly monitoring from January 2002 through December 2004 at the IDNR ambient station at the Hwy 61 bridge NW of Maquoketa (station 10490002), (2) results from IDNR/UHL monthly monitoring conducted at five locations between Maquoketa and Canton from March to November 2001 as part of monitoring in support of TMDL development, (3) results of monitoring at one site for the 1998-99 statewide assessment of freshwater mussels in Iowa streams (Arbuckle et al.  2000), (4) U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 1999, 2001, and 2003 northeast of Maquoketa, and (5) IDNR/UHL biological (REMAP) monitoring in 2003.

Note:  A TMDL for pathogen indicators in this segment of the Maquoketa River was prepared by IDNR and approved by EPA in 2006.   Because, however, the Section 303(d) impairment related to decline in the freshwater mussel community of this river segment was not addressed in the TMDL, this waterbody remains in IR Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle.

EXPLANATION:  The Class A (primary contact recreation) uses were assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.   The geometric mean of indicator bacteria (E.  coli) in the 24 samples collected during the recreational seasons of 2002 through 2004 at the IDNR ambient monitoring station exceeded the Iowa water quality criterion to protect primary contact recreation uses.   Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, this exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of the 2006 Section 305(b) assessments and Section 303(d) listings.   The geometric mean of E.  coli bacteria in the 24 samples was 221 orgs/100 ml, with 12 samples (50%) exceeding Iowa’s single-sample maximum value 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 are "not supported" (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).  

Results of monitoring from the monthly IDNR ambient station NW of Maquoketa from 2002 through 2004 and from the five stations from Maquoketa to Canton monitored in 2001 in support of TMDL development for this river reach suggest “full support” of the Class B(WW) uses.   Monitoring at these stations show no violations of Class B(WW) water quality criteria for conventional pollutants in the approximately 36 samples analyzed or for toxic pollutants in the approximately 10 samples analyzed.  

As noted in previous Section 305(b) assessments for this river segment, results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams (Arbuckle et al.  2000), however, suggest a potential impairment to the aquatic life uses of this stream segment.   As part of this study, sampling results from 1998 and 1999 (Arbuckle et al.  2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987).   In general, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa’s streams and rivers from the mid-1980s to the late 1990s.   Results of this comparison were used by staff of the Iowa DNR Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported.   For purposes of Section 303(d) listing, this assessment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey.   Greater than a 50% decline in species richness from the 1984-85 period to the 1998-99 period suggests an impairment of the aquatic life uses.   The confidence level of this assessment is relatively high; thus the assessment type is considered “monitored” in the context of Section 305(b) reporting.   According to Iowa DNR’s assessment methodology, waterbodies identified as “impaired” based on a “monitored” assessment are candidates for Section 303(d) listing.   Species richness of freshwater mussels at the one sample site in this stream segment was 5 in the 1984-85 period and was 0 in the 1998-99 period for a percent change of minus 100%.   Based on these results, the “full support” of aquatic life uses suggested by results of chemical monitoring from IDNR ambient and TMDL monitoring programs is downgraded to "non-support" for purposes of both Section 303(d) listing (greater than 50% decline in species richness) and Section 305(b) reporting (low species richness reported in the 1998-99 survey).   As presented by Arbuckle et al.  (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high in-stream levels of nutrients (phosphorus and nitrogen).   Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness.   Additional monitoring is needed to better define the biological status of this stream segment as well as the site-specific causes and sources of impairments of these uses that may exist.  

Results of biological monitoring conducted in 2003 suggest that the Class B(WW) aquatic life uses should be assessed (evaluated) as “fully supported”.   This biological assessment was based on data collected in 2003 as part of the DNR/UHL stream REMAP project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2003 FIBI score was 58 (good) and the BMIBI score was 57 (good).  The aquatic life use support was assessed (evaluated) as Fully Supporting (= FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.   This assessment is considered evaluated because the drainage area (748 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.

Fish consumption uses are assessed as "fully supported" based on the 2003 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.   The whole-fish sample of common carp had generally low levels of the primary contaminants:  mercury: 0.07 ppm; total PCBs: 0.333 ppm; and technical chlordane:< 0.03 ppm.   While results from the 2003 sampling 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 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.   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.   Although this scenario does not apply to the fish contaminant data generated from the 2003 RAFT sampling conducted in this assessment segment, levels of contaminant are sufficiently high for concern and justify follow-up monitoring.

While results from the 2003 sampling 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 exceeds 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.   And, according to the IDNR/IDPH advisory protocol, the single result for a whole-fish sample from the 2003 sampling on the Maquoketa River does not warrant issuance of an advisory but does indicate the need to conduct additional monitoring to better define contaminant levels in fish from this river segment.   Thus, follow-up monitoring will be conducted in 2006 to better determine (1) levels of PCBs in the edible portions (fillets) of fish in this river segment and (2) whether a 1 meal/week consumption advisory for PCBs needs to be issued.