Assessment Comments
Assessment is based on: (1) results of IDNR/UHL monthly ambient water quality monitoring conducted on Lizard Creek at Highway 169 at Fort Dodge (STORET station 10940001, formerly station 500990) from 2004-2006, (2) results of IDNR/UHL biological (biocriteria) monitoring in 2002, (3) IDNR/UHL biological (REMAP) monitoring in 2004, and (4) information from the 1998-99 statewide survey of Iowa's freshwater mussels (Arbuckle et al. 2000).
Basis for Assessment
[Note: Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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) and the results of an Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses remain assessed (monitored) as "partially supported" based on 2002 and 2004 IDNR/UHL biological monitoring data and on information from the 1998-99 statewide survey of Iowa's freshwater mussels (Arbuckle et al. 2000). As have results of previous water quality monitoring, results of ambient water quality monitoring from 2004-2006 continue to suggest "full support" of the Class B(WW1) aquatic life uses. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment. The sources of data used for this assessment include (1) results of IDNR/UHL monthly ambient water quality monitoring conducted on Lizard Creek at Highway 169 at Fort Dodge (STORET station 10940001, formerly station 500990) from 2004-2006, (2) results of IDNR/UHL biological (biocriteria) monitoring in 2002, (3) IDNR/UHL biological (REMAP) monitoring in 2004, and (4) information from the 1998-99 statewide survey of Iowa's freshwater mussels (Arbuckle et al. 2000).
EXPLANATION: The Class A1 uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.
The geometric mean level of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2004 through 2006 (78 orgs/100ml) is well-below, and meets, the Iowa Class A1 water quality criterion of 126 orgs/100ml. Five of the 24 samples (21%) 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 of E. coli is less than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). These EPA guidelines state, however, that if more than 10% of the samples exceed the state’s single-sample maximum criterion, the primary contact recreation uses should be assessed as “partially supported.” According to IDNR’s assessment/listing methodology, these results suggest that significantly greater than 10% of the samples exceed IDNR’s single-sample maximum criterion, thus suggesting that the Class A1 uses should be assessed as “partially supported/impaired.” Thus, while the geometric mean is below the Class A1 standard and suggests “full support,” the percentage of violations of Iowa’s single-sample maximum criterion is significantly greater than 10 percent and thus suggests impairment (partial support) of the Class A1 uses of this river segment. Although the percentage of samples greater than Iowa’s single-sample maximum criterion suggests impairment of the Class A1 uses, the difference between impairment and “full support” is only one sample violation. Thus, these results suggest generally low levels of indicator bacteria in this segment of Lizard Creek.
The Class B(WW1) aquatic life uses remain assessed (monitored) as "partially supported" based on 2002 and 2004 IDNR/UHL biological monitoring data and results of the 1998-99 statewide survey of freshwater mussels. The 2002 biocriteria FIBI score was 85 (excellent) and the BMIBI score was 57 (good). The 2004 REMAP FIBI score was 71 (good) and the BMIBI scores were 49, 49 (fair). The FIBI average was 78 and the BMIBI average was 52. The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The riffle-site FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62.
The results of the statewide assessment of freshwater mussels also suggest the potential for an impairment of the aquatic life uses due to a decline in the community of freshwater mussels in this stream segment. This segment of Lizard Creek was sampled as part of the 1998-99 statewide study of freshwater mussels in Iowa streams and rivers (Arbuckle et al. 2000). 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). On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa streams and rivers from the mid-1980s to the late 1990s. For stream segments having four or more species reported for the 1984-95 survey, 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. The results of this sampling on this segment of Lizard Creek, however, do not meet IDNR guidelines for developing a monitored assessment of support for the aquatic life uses that is appropriate to support addition of this waterbody to Iowa's Section 303(d) list. That is, 303(d)-level assessment decisions are developed only for those stream segments having an average of four or more species reported in the 1984-85 (Frest) survey due to the difficulty of interpreting status of mussel communities showing relatively low species richness during the both the historical (1984-85) and current (1998-99) surveys. This information can be used, however, to indicate the potential for an impairment of the aquatic life uses and to indicate the need to conduct additional sampling. Species richness of freshwater mussels at the four sample sites in this segment of Lizard Creek was 0, 1, 2, and 3 in the 1984-85 period and was 0, 1, 0, 0 in the 1998-99 period, respectively, for an average 1984-85 species richness of approximately 2 and a percent change of minus 50%. Based on these results, the aquatic life uses are assessed (evaluated) as “partially supported."
Conversely, results of ambient chemical/physical monitoring continue to suggest very good chemical/physical water quality in Lizard Creek. None of the 36 samples collected during the 2004-2006 assessment period at Hwy 169 station violated Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen (the minimum dissolved oxygen concentration (8.4 mg/l) is relatively high for ambient monitoring stations and suggests excellent water quality). In addition, no violations occurred in the 14 samples analyzed for toxic metals or in the three samples analyzed for pesticides.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
