Assessment Comments

Assessment is based on results of (1) IDNR monthly ambient monitoring station at Hwy 61 bridge NW of Maquoketa from 2006-08, (2) IDNR/UHL TMDL monitoring in 2004-06, (3) ISU statewide freshwater mussell survey in 1998-99, (4) EPA/IDNR fish tissue (RAFT) monitoring NE of Maquoketa in 2005 2006, and 2008, (5) IDNR/UHL biological monitoring in 2003, 2005 and 2007, and (6) IDNR Fisheries bureau sampling in 2003.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to levels of indicator bacteria that exceed state water quality criteria.   The Class B(WW1) aquatic life uses remain assessed (evaluated) as "not supported" due the apparent elimination of the freshwater mussel community from this river segment.   Fish consumption uses remain assessed as "fully supported" based on results of fish contaminant monitoring in 2003, 2005, 2006, and 2008.   Sources of data for this assessment include (1) results monthly monitoring from January 2006 through August 2008 at the IDNR ambient station at the Hwy 61 bridge NW of Maquoketa (station 10490002), (2) results from IDNR/UHL monthly TMDL monitoring conducted just upstream from Canton (TMDL station 23; STORET station 1149009) from April through September 2005, (3) results from IDNR/UHL monthly TMDL monitoring conducted further upstream from Canton near Benedict Hollow (station 11530003) from April through September 2005, (4) 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 2005, 2006, and 2008 northeast of Maquoketa, (5) IDNR/UHL biological monitoring in 2003, 2005 and 2007 and (6) IDNR Fisheries bureau sampling 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 5b (impaired; TMDL required).  

EXPLANATION:  The Class A1 (primary contact recreation) uses are 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 21 samples collected during the recreational seasons of 2006 through 2008 at the IDNR ambient monitoring station NW of Maquoketa exceeded the Iowa water quality criterion to protect primary contact recreation uses.   The geometric mean of E.  coli bacteria in the 21 samples from the IDNR station at Hwy 61 bridge NW of Maquoketa was 737 orgs/100 ml, thus far exceeding Iowa’s geometric mean criterion of 126 orgs/100 ml; 12 samples (57%) exceeded Iowa’s single-sample maximum criterion sample maximum criterion of 235 orgs/100 ml.   Similarly, results from the two IDNR/UHL monthly TMDL monitoring stations also suggest impairment of the Class A1 uses:  at the monitoring station just upstream from Canton (TMDL station 23), the geometric mean of the 12 samples collected was 270 orgs/100 ml with 7 samples (58%) exceeding the single-sample maximum criterion; at the station upstream from Canton near Benedict Hollow, the geometric mean of the 10 samples collected was 269 orgs/100 ml with 5 samples (50%) exceeding the single-sample maximum criterion.   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/UHL ambient station NW of Maquoketa from 2006 through 2008 and from the two TMDL stations upstream from Canton monitored in 2005 in support of TMDL development for this river reach suggest “full support” of the Class B(WW1) uses.   Monitoring at these three stations show no violations of Class B(WW1) water quality criteria for conventional pollutants in the combined 53 samples analyzed or for toxic pollutants in the 2 samples analyzed at the IDNR/UHL ambient monitoring station NW of Maquoketa (toxic pollutants were not analyzed at the two TMDL stations upstream from Canton).  

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) 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 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.     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.   (Note:  because the data from Arbuckle et al.   (2000) are now older than five years, the assessment category is changed from a “monitored” (i.e., a higher confidence assessment) to “evaluated” (i.e., lower confidence assessment).   Despite this change in assessment category, the impairment indicated by these data remains in IR Category 5 (i.e., Section 303(d) list) until more recent data suggest a good cause for de-listing.)  

Results of biological monitoring conducted in 2003, 2005 and 2007 suggest that the Class B(WW1) aquatic life uses should be assessed (evaluated) as “partially supported”.   This biological assessment was based on data collected in 2003, 2005 and 2007 as part of the IDNR/UHL stream sampling project and 2003 IDNR Fisheries sampling.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological 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).   The 2005 FIBI score was 60 (good) and the BMIBI score was 34 (fair).   The 2007 BMIBI scores were 42 and 47 (both fair).   The 2003 Fisheries bureau FIBI score was 48 (fair).   The aquatic life use support was assessed (evaluated) as partially supporting (=PS), 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 site passed the FIBI BIC 3/3 times in the past six years and passed the BMIBI BIC 0/3 times in the past four years.   This assessment is considered evaluated because the drainage area (754, 813 and 939 mi2) above this sampling sites was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed the FIBI BIC and failed to meet the BMIBI BIC, 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.

According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report).   IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).   However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.  

Fish consumption uses are assessed (monitored) as "fully supported" based on the 2005, 2006 and 2008 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 level of total PCBs in the 2005 whole-fish common carp sample was <0.09 ppm and the level of total PCBs in the 2008 whole-fish common carp sample was 0.105 ppm.    

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, however, showed that levels of total PCBs were below the advisory trigger level (0.105 ppm).    If levels of total PCBs exceed the one meal/week advisory level, follow-up monitoring will be conducted 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.