Narrative

Narrative

Narrative

[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses.  Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses.  According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.  Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.] 

SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain assessed monitored) as impaired (“partially supported”) (IR 5p) due to monitoring in 2011 and 2013 that showed levels of indicator bacteria (E. coli) exceeding state water quality criteria.  The presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported” (IR 2a) based on results of chemical/physical monitoring from 2010-2013.  The source of data for this assessment is the results of USGS ambient water quality monitoring conducted on Onion Creek near USGS station 05451754 (USGS Site 3) near Montour.  USGS issued a report in 2009 summarizing water quality for this stream and other streams sampled in 2006 on the Meskwaki Indian Settlement (see http://pubs.usgs.gov/sir/2009/5105/). 

EXPLANATION: The presumptive Class A1 uses are assessed (monitored) as "partially supported" based on results of USGS ambient monitoring near Montour in 2011 and 2013.  The geometric mean level of indicator bacteria (E.  coli) in the five samples collected during the 2011 recreation season at station 05451754 (USGS Site 3) was 956 orgs/100ml, and the geometric mean of the five samples collected during the recreation season of 2013 at USGS Site 3 was 698 orgs/100 ml.  These geometric means exceed the Iowa Class A1 water quality criterion of 126 orgs/100ml.  Eight of the 10 samples (80%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b).  The number of samples collected at this station (five during 2011 and five during 2013) is relatively low and does not meet IDNR guidelines for developing a “monitored” (higher confidence) assessment (i.e., at least 10 samples collected over a three-year period).  Despite the relatively low number of samples, the relatively high geometric means of indicator bacteria in this stream segment (956 and 698 orgs/100 ml) constitute overwhelming evidence of impairment of the presumptive Class A1 uses.  According to Iowa’s listing methodology, overwhelming evidence of bacterial impairment occurs when the E. coli geometric mean of at least five samples collected at regular intervals over a summer recreational season that meet credible data requirements would exceed Iowa’s geometric mean criterion even if the remainder of the seven samples needed for a high-confidence (“monitored”) assessment all had E.  coli levels equal to the IDNR’s detection level (i.e., 10 orgs/100 ml).  If two samples all with E.  coli levels of 10 orgs/100 ml are added to the Onion Creek Site 3 dataset for 2011, the resulting geometric mean (260 orgs/100 ml) still exceeds the Class A1 geometric mean criterion of 126 orgs/100 ml and thus suggests overwhelming evidence of impairment of the presumptive Class A1 use. 

Results of the USGS ambient water quality monitoring from October 2012 through August 2013 showed no violations of Class B(WW1) water quality criteria in the five samples from USGS Site 3 that were analyzed for pH, and ammonia.  One of five samples (20%) violated the Class B(WW1) criterion for dissolved oxygen.  This sample was collected on October 23, 2012 during extreme low-flow conditions (0.41 cfs).  This isolated/low-flow violation of the dissolved oxygen criterion does not suggest impairment of the Class B(WW1) aquatic life uses.  In addition, none of the five samples analyzed for toxic metals and pesticides during the 2012-2013 period exceeded the respective Class B(WW1) chronic criteria.  These results suggest “full support” of the presumptive Class B(WW1) aquatic life uses of this stream. 

Narrative

[Note 1: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.] [Note 2: A relatively recent expansion of the Mesqwaki Settlement to the west resulted in the inclusion of nearly the entire length of Onion Creek on Settlement land. Thus, as the Settlement is sovereign land and is not under jurisdiction of the governments of the United States or the state of Iowa, this stream is not subject to impaired waters listings from the state of Iowa. Consequently, this stream will be considered "not assessed" for the current assessment/listing cycle. The assessment narrative below is that which would have accompanied the stream if under the jurisdiction of the state of Iowa.] [Note 3: USGS has continued to monitor Onion Creek. The two USGS stations monitored in 2006 were again monitored from September 2010 to October 2012. SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain assessed monitored) as “not supported” (IR 5p) due to monitoring in 2006 that showed levels of indicator bacteria (E. coli) exceeding state water quality criteria. The presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported” (IR 2a) based on results of chemical/physical monitoring in 2006 and from 2010-2012. The sources of data for this assessment are the results of USGS ambient water quality monitoring conducted on Onion Creek near at two locations from April through December 2006 and from September 2010 to October 2012: (1) station 05451753 (USGS Site 2) below Highway 30 and (2) station 05451754 (USGS Site 3) near Montour. USGS issued a report in 2009 summarizing water quality for this stream and other streams sampled in 2006 on the Meskwaki Indian Settlement (see http://pubs.usgs.gov/sir/2009/5105/). EXPLANATION: The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of USGS ambient monitoring near Montour in 2006. The geometric mean level of indicator bacteria (E. coli) in the seven samples collected during the 2006 recreation season at station 05451754 (USGS Site 3) (993 orgs/100ml) far exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Six of the seven samples (86%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). The number of samples collected at this station (seven) is relatively low and does not meet IDNR guidelines for developing a “monitored” (higher confidence) assessment (i.e., at least 10 samples collected over a three-year period). Despite the relatively low number of samples, the relatively high geometric mean of indicator bacteria in this stream segment (993 orgs/100 ml) constitutes overwhelming evidence of impairment of the presumptive Class A1 uses. According to Iowa’s 2010 listing methodology, overwhelming evidence of bacterial impairment occurs when the E. coli geometric mean of at least five samples collected at regular intervals over a summer recreational season that meet credible data requirements would exceed Iowa’s geometric mean criterion even if the remainder of the 10 samples needed for a high-confidence (“monitored”) assessment all had E. coli levels equal to the IDNR’s detection level (i.e., 10 orgs/100 ml). If four samples all with E. coli levels of 10 orgs/100 ml are added to the Onion Creek Site 3 dataset for 2006, the resulting geometric mean (250 orgs/100 ml) still exceeds the Class A1 geometric mean criterion of 126 orgs/100 ml and thus suggests overwhelming evidence of impairment of the presumptive Class A1 use. The geometric mean level of indicator bacteria (E. coli) in the six samples collected during the 2006 recreation season at station 05451753 (USGS Site 2) (175 orgs/100ml), however, only slightly exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Two of the six samples (33%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Because additional sampling could easily produce a geometric mean level below the geometric mean criterion of 126 orgs/100 ml, the USGS data from this station do not suggest impairment of the presumptive Class A1 uses. Note: USGS monitoring from 2010 to 2012 did not include monitoring for indicator bacteria (E. coli). Results of the USGS ambient water quality monitoring from April through December 2006 showed no violations of Class B(WW1) water quality criteria in the approximately five samples from USGS Site 2 and the approximately 8 samples from USGS Site 3 that were analyzed for dissolved oxygen, pH, and ammonia. In addition, none of the samples analyzed for toxic metals and pesticides exceeded the respective Class B(WW1) chronic criteria. These results suggest “full support” of the presumptive Class B(WW1) aquatic life uses of this stream. Similarly, None of the eight samples analyzed at USGS stations 05451754 and 05451753 (total of 16 samples) between September 2010 and October 2012 violated the respective Class B(WW1) aquatic life criteria for pesticides (e.g., chlorpyrifos and dieldrin), toxic metals (e.g., Ag, Al, As, Cd, Ni, Pb, Se, and Zn), chloride, sulfate, pH, or ammonia. One of the eight samples (12%) violated the Class B(WW1) criterion for dissolved oxygen of 5.0 mg/l: the sample collected on October 23, 2012, had a dissolved oxygen concentration of 3.3 mg/l. According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as dissolved oxygen, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, however, the results from USGS station 05451754 do not indicate that significantly greater than 10% of the samples exceed either the Class B(WW1) criteria for dissolved oxygen. Thus, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

Narrative

Insufficient water quality information available to assess use support. Thus, this waterbody is considered Not Assessed.

Narrative

[Note 1: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current (2010) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.] [Note 2: A relatively recent expansion of the Mesqwaki Settlement to the west resulted in the inclusion of nearly the entire length of Onion Creek on Settlement land. Thus, as the Settlement is sovereign land and is not under jurisdiction of the governments of the United States or the state of Iowa, this stream is not subject to impaired waters listings from the state of Iowa. Consequently, this stream will be considered "not assessed" for the current (2010) assessment/listing cycle. The assessment narrative below is that which would have accompanied the stream if under the jurisdiction of the state of Iowa.] SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed monitored) as “not supported” due to levels of indicator bacteria (E. coli that exceed state water quality criteria. The presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported” based on results of chemical/physical monitoring in 2006. The source of data for this assessment is the results of USGS ambient water quality monitoring conducted on Onion Creek near at two locations from April through December 2006: (1) station 05451753 (USGS Site 2) below Highway 30 and (2) station 05451754 (USGS Site 3) near Montour. USGS issued a report in 2009 summarizing water quality for this stream and other streams sampled in 2006 on the Meskwaki Indian Settlement (see http://pubs.usgs.gov/sir/2009/5105/). EXPLANATION: The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of USGS ambient monitoring near Montour in 2006. The geometric mean level of indicator bacteria (E. coli) in the seven samples collected during the 2006 recreation season at station 05451754 (USGS Site 3) (993 orgs/100ml) far exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Six of the seven samples (86%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). The number of samples collected at this station (seven) is relatively low and does not meet IDNR guidelines for developing a “monitored” (higher confidence) assessment (i.e., at least 10 samples collected over a three-year period). Despite the relatively low number of samples, the relatively high geometric mean of indicator bacteria in this stream segment (993 orgs/100 ml) constitutes overwhelming evidence of impairment of the presumptive Class A1 uses. According to Iowa’s 2010 listing methodology, overwhelming evidence of bacterial impairment occurs when the E. coli geometric mean of at least five samples collected at regular intervals over a summer recreational season that meet credible data requirements would exceed Iowa’s geometric mean criterion even if the remainder of the 10 samples needed for a high-confidence (“monitored”) assessment all had E. coli levels equal to the IDNR’s detection level (i.e., 10 orgs/100 ml). If four samples all with E. coli levels of 10 orgs/100 ml are added to the Onion Creek Site 3 dataset for 2006, the resulting geometric mean (250 orgs/100 ml) still exceeds the Class A1 geometric mean criterion of 126 orgs/100 ml and thus suggests overwhelming evidence of impairment of the presumptive Class A1 use. The geometric mean level of indicator bacteria (E. coli) in the six samples collected during the 2006 recreation season at station 05451753 (USGS Site 2) (175 orgs/100ml), however, only slightly exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Two of the six samples (33%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Because additional sampling could easily produce a geometric mean level below the geometric mean criterion of 126 orgs/100 ml, the USGS data from this station do not suggest impairment of the presumptive Class A1 uses. Results of the USGS ambient water quality monitoring from April through December 2006 showed no violations of Class B(WW1) water quality criteria in the approximately five samples from USGS Site 2 and the approximately 8 samples from USGS Site 3 that were analyzed for dissolved oxygen, pH, and ammonia. In addition, none of the samples analyzed for toxic metals and pesticides exceeded the respective Class B(WW1) chronic criteria. These results suggest “full support” of the presumptive Class B(WW1) aquatic life uses of this stream.