[Note: A TMDL for pathogen indicators in this segment of the Maquoketa River was prepared by DNR and approved by EPA in 2006. Thus, this impairment remains in Category 4a of Iowa's Integrated Report. 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).]

The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at the Maquoketa River west of Maquoketa (station 10490004) were as follows: the 2014 geometric mean was 451 orgs/100 ml, the 2015 geometric mean was 318 orgs/100 ml, and the 2016 geometric mean was 2231 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Eighteen of the combined 24 samples (75 %) 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 Iowa DNR’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 "not supported."

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 DNR 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 ten 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 sampling conducted in 2003, 2005, 2012, 2013 and 2014 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, 2012, 2013 and 2014 as part of the DNR/SHL large river stream sampling project and 2003 DNR 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)and the 2005 FIBI score was 60 (good). The 2003 Fisheries bureau FIBI score was 48 (fair). The 2012, 2013 and 2014 BMIBI scores were 45, 50, 50 (all fair) and 58 (good). 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 1994-2008. 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 14 years and passed the BMIBI BIC 1/4 times in the past five years. This assessment is considered evaluated because the drainage areas (754, 813 and 940 mi2) above the sampling sites were greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this segment passed the FIBI BIC and failed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment don'tfall in the calibrated watershed size.

Fish consumption uses are assessed (monitored) as "fully supported" based on the 2012, 2014, and 2016 Iowa DNR fish tissue 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 fish contaminant trend monitoring. The whole-fish samples of common carp from these three years had generally low levels of the primary contaminants: mercury: maximum of 0.06 ppm; total PCBs: maximum of 0.162 ppm; and technical chlordane: maximum of 0.042 ppm. The results therefore, continue to suggest "full support" of the fish consumption uses.