Assessment Comments
Assessment based on: (1) results of IDNR/SHL monthly ambient water quality monitoring conducted on Lizard Creek at Highway 169 at Fort Dodge (STORET station 10940001, formerly station 500990) from 2010-2012, (2) results of IDNR/SHL biological (biocriteria) sampling in 2011 & 2012, (3) IDNR/SHL biological (REMAP) sampling 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 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" (IR 5a) due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" (IR 5b-v) based on 2004, 2011 and 2012 IDNR/SHL biological sampling 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 2010-2012 continue to suggest excellent water quality and "full support" of the Class B(WW1) aquatic life uses. Fish consumption uses remain "not assessed" (Ir 3a) 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/SHL monthly ambient water quality monitoring conducted on Lizard Creek at Highway 169 at Fort Dodge (STORET station 10940001, formerly station 500990) from 2010-2012, (2) results of IDNR/SHL biological (biocriteria) sampling in 2011 and 2012, (3) IDNR/SHL 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 means of indicator bacteria (E. coli) in the 25 samples collected during the recreational seasons of 2010 through 2012 at IDNR station 10940001 near Fort Dodge were as follows: the 2010 geometric mean was 217 orgs/100 ml, the 2011 geometric mean was 493 orgs/100 ml, and the 2012 geometric mean was 58 orgs/100 ml. All three geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml. Ten of the 25 samples (40%) 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 are "not supported" (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 “impaired.”
The Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" based on 2004, 2011 and 2012 IDNR/SHL biological sampling data and results of the 1998-99 statewide survey of freshwater mussels. The 2004 REMAP FIBI score was 70 (good). The 2011 FIBI score was 75 (excellent) and the BMIBI score was 41 (fair). The 2012 BMIBI scores were 33 (fair) and 60 (good). 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 1994-2008. 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 in the last nine years and passed the BMIBI BIC 0/3 times in the last five years.
This aquatic life assessment is now considered "monitored" 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 recent five-year period to be considered “monitored”. This segment had multiple BMIBI samples collected in the previous five years (2008-2012). However, despite this change in assessment methodology and type, this waterbody remains on Iowa’s Section 303(d) list of impaired waters (IR Category 5b-v).
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 2010-2012 assessment period at Hwy 169 station violated Class B(WW1) water quality criteria for dissolved oxygen, pH, temperature, ammonia-nitrogen, chloride, or sulfate (the minimum dissolved oxygen concentration (7.7 mg/l) is relatively high for ambient monitoring stations and suggests excellent water quality).
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
