Assessment Comments

Assessment is based on (1) IDNR monthly ambient monitoring station at Hwy 61 bridge NW of Maquoketa, (2) IDNR/UHL TMDL monitoring, (3) freshwater mussell survey, and (4) EPA/IDNR fish tissue (RAFT) monitoring NE of Maquoketa in 1997, 1999, and 2001.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses were assessed (monitored) as "not supported" and the Class B(WW) aquatic life uses were assessed (evaluated) as "fully supported / threatened" with a declining water quality trend.   Fish consumption uses remain "fully supported."  Sources of data for this assessment include (1) results monthly monitoring from October 1999 through September 2001 at the IDNR ambient station at the Hwy 61 bridge NW of Maquoketa, (2) results from 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), and (4) U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 1999 northeast of Maquoketa.   EXPLANATION:  The Class A (primary contact recreation) uses were assessed as "not supported."  The geometric mean of indicator bacteria (fecal coliforms) in the 15 samples not materially affected by surface runoff during the recreational seasons of 2000 and 2001 at the IDNR ambient monitoring station exceeded the Iowa water quality criterion to protect primary contact recreation uses.   For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff.   According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff."  The geometric mean of fecal coliform bacteria in the 15 non-runoff-affected samples was 326 orgs/100 ml, with seven samples (47%) exceeding the EPA-recommended single-sample maximum value of 400 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean is greater than 200 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 at the five TMDL stations during the recreational season of 2001 support this assessment:  geometric means in seven samples at these stations ranged from 697 to 830 organisms/100 ml (N=7) with from 47 to 71% of the samples exceeding the single-sample maximum value of 400 organisms/100 ml.   The Class B(WW) aquatic life uses uses were assessed as "fully supported" based on results of monitoring from the IDNR ambient station NW of Maquoketa in 2000 and 2001 and from the five stations from Maquoketa to Canton monitored in 2001 in support of TMDL development for this river reach.   Monitoring at these stations show no violations of Class B(WW) water quality criteria for conventional or toxic pollutants.   Results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams, 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") from the mid-1980s to the late 1990s.   For purposes of Section 305(b) reporting, 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.   This assessment included the following factors:  (1) the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey and (2) the number of mussel species found in the 1998-99 survey.   Greater than a 50% decline in species richness from the 1984-84 to the 1998-99 period suggests an impairment of the aquatic life uses.   In addition, low species richness in the 1998-99 survey suggests potential impairment.   For purposes of Section 305(b) assessment only, staff of the IDNR Water Quality Bureau used results from Arbuckle et al.  (2000) to define categories of species richness for Iowa's mussel communities:  less than three species indicates low species richness and "nonsupport" or "partial support" of aquatic life use; from four to seven species indicates moderate species richness and potential minor impacts (="fully support / threatened"); more than seven species indicates high species richness and "full support" of 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 -100%.   Based on these results, the full support of aquatic life uses suggested by results of IDNR ambient and TMDL monitoring is downgraded to "fully supported / threatened" with a declining water quality trend.   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 instream 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.   Fish consumption uses remain assessed as "fully supported" based on the 1997, 1999 and 2001 EPA/DNR fish tissue (RAFT) samplings on the Maquoketa River northeast of Maquoketa.   This site is sampled for common carp on an every-other-year basis as part of RAFT trend monitoring.   Results from all three samplings show that levels of all contaminants in the composite samples of whole-fish carp were less than ½ of the respective FDA action levels and DNR levels of concern.   This site will again be sampled in 2003.