Assessment Comments
Assessment is based on: (1) the results of monthly monitoring at the IDNR fixed ambient station at the Highway 38 bridge north of Olin from 2004 through 2006 (STORET station 10530001), (2) results of IDNR bacteria monitoring in 2010-12 conducted as part of the city/county beach monitoring program, (3) information from the report "Statewide Assessment of Freshwater Mussels (Bivalva, Unionidae) in Iowa Streams" by Arbuckle et al. (2000), (4) results of IDNR freshwater mussel surveys in July & August 2012, and (5) fish sampling conducted by IDNR Fisheries Bureau in 2003.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 5a) based on results of ambient bacterial water quality monitoring from 2010-12. The Class B(WW1) aquatic life are assessed (evaluated) as "fully supported" (IR 2a) based on results of ambient water quality monitoring from 2004-06 and on results of an IDNR Fisheries Bureau fish survey in 2003. The previous impairment of the freshwater mussel community of this segment is de-listed based on results of new (2012) mussel surveys. Fish consumption uses remain not assessed (IR 3a) due to the lack of fish contaminant monitoring in this river segment. The sources of data for this assessment include (1) the results of monthly monitoring at the now-abandoned IDNR fixed ambient station at the Highway 38 bridge north of Olin from 2004 through 2006 (STORET station 10530001), (2) bacterial monitoring conducted from 2010-12 at three Wapsipinicon River stations monitored as part of IDNR’s city/county beach monitoring program: Anamosa Boat Ramp (station 15530002), Newport Mills Access (15530003), and Olin Access (station 15530006), (3) information from the report "Statewide Assessment of Freshwater Mussels (Bivalva, Unionidae) in Iowa Streams" by Arbuckle et al. (2000), (4) results of IDNR surveys of freshwater mussels at four sites in July and August 2012, and (5) IDNR Fisheries Bureau biological sampling in 2003. [Notes: (1) Routine ambient monthly monitoring at IDNR station 10530001 was discontinued in 2006. (2) Limited monitoring was conducted in this assessment segment by USGS in June 2008 near Anamosa (station 05421740). Two samples were analyzed for E. coli and for pH. This amount of data does not meet IDNR’s data quantity requirements for Section 305(b) reporting or Section 303(d) listing.]
EXPLANATION: The Class A1 uses are assessed (monitored) as "partially supported" based on violations of state criteria for indicator bacteria (E. coli) at monitoring stations sampled as part of the IDNR city/county beach monitoring program. Results of bacteria monitoring conducted at three stations as part of the city/county beach program 2010 through 2012 suggest moderately high levels of E. coli in this river segment. The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2010 through 2012 at the city/county beach station at Anamosa Access were as follows: the 2010 geometric mean was 1,602 orgs/100 ml, the 2011 geometric mean was 365 orgs/100 ml and the 2012 geometric mean was 153 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Eleven of the 21 samples (52%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.
The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2010 through 2012 at the city/county beach station at Newport Mills were as follows: the 2010 geometric mean was 1,486 orgs/100 ml, the 2011 geometric mean was 616 orgs/100 ml and the 2012 geometric mean was 157 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Fourteen of the 21 samples (67%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.
The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2010 through 2012 at the city/county beach station at Olin Access were as follows: the 2010 geometric mean was 924 orgs/100 ml, the 2011 geometric mean was 433 orgs/100 ml and the 2012 geometric mean was 123 orgs/100 ml. Two of the three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Thirteen of the 21 samples (62%) exceeded the Class A1 single-sample maximum criterion of 235 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 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 Section 303(d) impaired. Although geometric means were exceptionally high (>1,000 orgs/100 ml) during the flood conditions that occurred during the recreation season of 2010, geometric means were subtantially lower (~300 to 600 orgs/100 ml) during the recreation season of 2011 when flows were not as extreme as in 2010. Thus, this segment of the Wapsipinicon River likely has moderately high levels of indicator bacteria during most years (i.e., recreation season geometric means from ~300 to 600 orgs/100 ml) and thus the Class A1 uses are assessed as "partially supporting".
Despite the results of bacterial monitoring that suggest impairment of the Class A1 uses, the results of ambient water quality suggest “full support” of the Class B(WW1) aquatic life uses due to (1) the lack of violations of Iowa Class B(WW1) water quality criteria for dissolved oxygen and ammonia-nitrogen in the 36 samples collected from January 2004 through November 2006 at the IDNR fixed ambient station near Olin and (2) the lack of violations of Class B(WW1) water quality criteria in the 10 samples from this station analyzed for pesticides and toxic metals during the 2004-2006 period. One of the 36 samples analyzed for pH did exceed the Iowa Water Quality criterion to protect Class A1 and Class B(WW1) uses: the pH in the sample collected on November 5, 2003, was 9.3 units, thus exceeding the Class A1/B(WW1) criterion of 9.0 pH units. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), however, a violation frequency of less than 10 % for conventional parameters such as pH does not suggest impairment of aquatic life or primary contact recreation uses. Thus, the percentage of violations of the pH criterion at this station does not suggest an impairment of designated uses. Because the data upon which this assessment is based are now more than five years old, the assessment type is changed from “monitored” (a higher confidence assessment) to “evaluated” (a lower confidence assessment). As water quality data age, they are less able to represent current water quality conditions.
Results of IDNR surveys of freshwater mussels at four sites in this assessment segment during 2012 suggest that the biological impairment based on the apparent decline of freshwater mussels no longer exists. The following is a summary of these surveys:
--Number of freshwater mussel species from surveys conducted in 1984 (Frest (1987), in 1998 (Arbuckle et al. 2000), and IDNR Watershed Improvement Section staff (J. Kurth) in 2012:
1984 1998 2012
Site 20: 5 1 10
Site 33: 2 0 3
Site 37: 1 0 3
Site 65: 8 4 9
The original impairment was based on a comparison of sampling results from 1998 and 1999 (Arbuckle et al. 2000) to results from stream sites surveyed in 1984 and 1985 by Frest (1987). Impairment 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 to the 1998-99 period suggested an impairment of the aquatic life uses. Based on IDNR’s assessment approach, the degree of decline (~65%) in the number of freshwater mussel species in this segment suggested “partial support” (impairment) of the Class B(WW) aquatic life uses for purposes of both Section 303(d) listing and 303(d) reporting. Results of the IDNR's surveys in 2012, however, show recovery in the number of freshwater mussel species at the sites used to identify the original impairment (Sites 20 and 65), with twice as many species found at Site 20 in 2012 than were found in 1984, and more mussel species were present at Site 65 in 2012 than in 1984. Due to the lack of a protocol for identifying biological thresholds that indicate "full support" of a freshwater mussel community, this impairment was moved from Category 5b of Iowa's 2010 Integrated Report to IR Category 3a (insufficient information to develop an assessment of support of uses) for Iowa’s 2012 Integrated Report.
The results of the 2003 IDNR Fisheries bureau fish sampling suggest that the aquatic life uses of this segment are fully supported. This evaluated biological assessment was based on data collected in 2003 by the IDNR Fisheries Bureau. 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 fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2003 FIBI score was 46 (fair). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score 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. This assessment is considered evaluated because the drainage area (1596 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 the FIBI 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.
Fish consumption uses remain not assessed due to the lack of fish contaminant monitoring information for this river reach.
