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 2006-2008, (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 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 "not supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (evaluated) 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). Similar to results of previous water quality monitoring, results of ambient water quality monitoring from 2006-2008 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 2006-2008, (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 "not supported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the 22 samples collected during the recreational seasons of 2006 through 2008 (132 orgs/100ml) slightly exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Nine of the 22 samples (41%) 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 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). Despite the indication of a bacterial impairment for the 2010 assessment/listing cycle, levels of indicator bacteria (E. coli) are relatively low in this segment of Lizard Creek. A comparison of geometric mean levels from the previous three assessment cycles shows a tendency to meet Iowa’s Class A1 geometric mean criterion of 126 orgs/100 ml: 2004 cycle: 107 orgs/100 ml (N=24); 2006 cycle: 119 orgs/100 ml (N=24); 2008: 71 orgs/100 ml (N=24). Thus, the impairment suggested by the 2010 cycle geometric mean of 132 orgs/100 ml should be considered minor with a good possibility that future monitoring will again show lower levels of E. coli and compliance with the Class A1 criterion.
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 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. This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 0/3 times in the last seven years.
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 between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous seven years (2002-2008); however, the multiple samples were not collected during 2004-2008. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.
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 33 samples collected during the 2006-2008 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 (8.1 mg/l) is relatively high for ambient monitoring stations and suggests excellent water quality). In addition, no violations occurred in the five samples analyzed for toxic metals.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
