Assessment Comments
Assessment is based on (1) results of bacteria monitoring at Site 26 of the Upper Iowa River Watershed (UIRW) project from 2010 through 2012, (2) results of IDNR/SHL biological monitoring in 2003, 2011 & 2012, (3) results of Section 319 bacterial/chemical/physical water quality monitoring at three monitoring stations from April 2010 to November 2011, (4) results of water quality monitoring in 2010 and 2011 at STORET station 12030012), and (5) results of a 2012 IDNR trout reproduction survey.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses)).] This stream segment is identified as an Outstanding Iowa Water under the antidegradation policy in the Iowa Water Quality Standards.
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” (IR 5p) due to levels of indicator bacteria that exceed state water quality criteria. The presumptive Class A2 (secondary contact recreation) uses are also assessed (monitored) as “not supported” (IR 5p). The Class B(CW1) coldwater aquatic life uses are assessed (evaluated) as "fully supported" (IR 2a) based on results of biological monitoring in 2003, 2011 and 2012. Fish consumption uses remain “not assessed” (IR 3a) due to lack of fish contaminant monitoring in this stream segment. Sources of data for this assessment include (1) results of monitoring for indicator bacteria conducted at Site 26 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 190050003) from April 2010 through October 2012, (2) results of IDNR/SHL biological monitoring in 2003, 2011 and 2012, (3) results of Section 319 bacterial/chemical/physical water quality monitoring at three monitoring stations (STORET stations 13030002, 13030003, and 13030005) from April 2010 to November 2011, (4) results of chemical/physical water quality monitoring from August 2010 to September 2011 at STORET station 12030012), and (5) results of a 2012 trout reproduction survey.
EXPLANATION: The Class A1 (primary contact recreation) uses and the Class A2 (secondary contact recreation) uses are both 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 20 samples collected during the recreational seasons of 2010 through 2012 at UIRW Site 26 were as follows: the 2010 geometric mean was 669 orgs/100 ml, the 2011 geometric mean was 46 orgs/100 ml and the 2012 geometric mean was 112 orgs/100 ml. Only the 2010 geometric mean exceeded the Class A1 criterion of 126 orgs/100 ml. Although the 2011 and 2012 geometric means met the Class A2 geometric mean criterion of 630 orgs/100 ml, the 2010 geometric mean (669 orgs/100 ml) slightly exceeds this criterion. Seven of the 20 samples (35%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; 2 of the 20 samples (10%) exceeded the Class A2 single-sample maximum criterion of 2,880 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 are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
Additional bacteria monitoring was conducted in this assessment segment during the 2010-2012 period. The following is a summary of bacterial monitoring (geometric means of E. coli) from Section 319 monitoring at three stations on Waterloo Creek from April 2010 to November 2011 (approximately 20 samples were analyzed in 2010 and approximately 10 samples were analyzed in 2011):
Site/Station 2010 Class A1 GM 2011 Class A1 GM
Site 1 (STORET station 13030002) 1,960 522
Site 2 (STORET station 13030005) 2,309 339
Site 5 (STORET station 13030003) 1,247 123
Site/Station 2010 Class A2 GM 2011 Class A2 GM
Site 1 (STORET station 13030002) 1,697 522
Site 2 (STORET station 13030005) 2,048 339
Site 5 (STORET station 13030003) 1,026 123
These results show that nearly all recreation season geometric means for 2010 and 2011 exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml; only the geometric mean at Site 5 for the 2011 recreation season met the Class A1 criterion. From 14% to 25% of the samples analyzed exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. These results also show that all geometric means for the 2010 recreation season exceeded the Class A2 geometric mean criterion of 630 orgs/100 ml. Six samples at each site (~20%) exceeded the Class A2 single-sample maximum criterion of 2,880 orgs/100 ml. All geometric means from the 2011 recreation season, however, met the Class A2 criterion. 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 are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, both the results of Section 319 bacterial monitoring in 2010 and 2011 and the results of Upper Iowa River watershed bacterial monitoring from 2010 to 2012 show impairment of both the Class A1 and Class A2 uses in this assessment segment.
The Class B(CW1) coldwater aquatic life uses are assessed as “fully supporting” based on results of (1) biological monitoring in 2003, 2011 & 2012, (2) chemical/physical water quality monitoring conducted as part of Section 319 monitoring from April 2010 to November 2011, (3) results of chemical/physical monitoring conducted at IDNR STORET station 12030012 from August 2010 to September 2011 and (4) an IDNR-Fisheries Bureau evaluation of Iowa trout streams.
The Class B(CW1) aquatic life uses were assessed (evaluated) as “fully supporting” based on biological data collected in 2003, 2011 and 2012 as part of the IDNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2003 CBI scores were 75 and 82. The 2011 CBI score was 48. The 2012 CBI scores were 49, 75 and 90. The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the CBI scores with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 4/6 times in a 10-year period. This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”. This segment had multiple samples collected in a 10-year period (2003-2012). Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.
Results of Section 319 chemical/physical water quality monitoring in 2011 also suggest “full support” of the Class B(CW1)aquatic life uses of this stream segment. Seven samplings were conducted in 2011 at the three monitoring stations in this segment (Waterloo Creek sites 1, 2, and 5). Results of monitoring for dissolved oxygen show that two of the combined 21 samples violated the Class B(CW1) criterion for temperature of 7 mg/l (9.5% violation). The two violations of the Class B(CW1) dissolved oxygen criteria occurred at Waterloo Creek Station 5 and were 6.7 mg/l on August 24, 2011 and 6.6 mg/l on September 6, 2011. According to the IDNR assessment methodology, if the percentage of sample that violate water quality criteria for conventional parameters such as dissolved oxygen is less than 10%, the aquatic life uses should be assessed as “fully supported”. Additional monitoring for dissolved oxygen, pH, and ammonia was conducted at STORET Station 12030012. None of the nine samples collected between August 2010 and September 2011 violated the Class A2 criterion for either of these parameters. Monitoring at the three 319 stations and at station 12030012 show no violations of the Class A2 criterion for water temperature (20C) in the combined 42 samples collected from August 2010 to November 2011.
In addition, an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2012, also suggests the Class B(CW1) uses are "fully supported". According to the updated summary, Waterloo Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit fairly consistent natural reproduction and maintain a viable population of brown trout without any stocking (Category I stream). This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.
Taken together, the results of biological, chemical/physical water quality monitoring, and trout stream evaluation all suggest that that Class B(CW1) aquatic life uses of this stream segment should be assessed as “fully supporting”.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.
