Assessment Comments
Assessment based on 2006 and 2011 IDNR/SHL biological monitoring data: CBI = 20, 37, 44 and 47; CW BIC = 60.
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.
SUMMARY: The Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses remain “not assessed” due to the lack of sufficient water quality data or other information upon which to base an assessments. The Class B(CW1) coldwater aquatic life uses are assessed (evaluated) as “partially supporting” due to a biological impairment. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment. The source of data used for this assessment is biological monitoring conducted on Pecks Creek in 2006 and 2011 as part of the IDNR/SHL TMDL sampling project.
EXPLANATION: The presumptive Class A1 and A2 uses of this stream remain “not assessed” due to the lack of information upon which to base an assessment. Single samples of E. coli were collected at two monitoring sites on this stream in August 2006: (1) STORET station 11220012 near Osterdock (TMDL site No. 326) and (2) STORET station 11220013 near Osterdock (TMDL site No. PeC2). The level of E. coli in the sample from TMDL site 326 was 290 orgs/100 ml; the level in the sample from TMDL site PeC2 was 64 orgs/100 ml. This small amount of data (total of two samples from two stations) neither meets IDNR guidelines for developing Section 305(b) water quality assessments nor allows calculation of summary statistics (i.e., geometric mean) needed to develop an assessment of the degree to which the Class A uses are supported.
The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2006 and 2011 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 2006 CBI scores were 20 and 37. The 2011 CBI scores were 44 and 47. The aquatic life use support was assessed (evaluated) as partially supporting (=PS), 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 0/4 times in a six-year period (2006-2011).
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 in a five-year period to be considered “monitored”. This segment had multiple samples collected in a six-year period (2006-2011). 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). Despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2012 Section 303(d) list of impaired waters.
As part of the 2002 REMAP project, stream physical habitat assessment found adverse conditions that are thought to contribute to the biological impairment. These include, bank instability, flow impoundment, and excessive silt deposition. Beaver activity in the vicinity of the sample site has been observed and is suspected to be a major source of habitat alteration.
Similar to the case for assessing support of the Class A uses of this stream, insufficient water quality data are available from the two TMDL monitoring sites on this stream to develop an assessment for the support of the Class B(CW1) coldwater aquatic life uses. Single samples were collected at both stations in August 2006. The levels of ammonia and pH at both stations (TMDL site No. 326 and TMDL site No. PeC2) were below the Class B(CW1) chronic criteria. This small amount of data, however, neither meets IDNR guidelines for developing Section 305(b) water quality assessments nor allows calculation of summary statistics (e.g., percent violations based on at least 10 samples) needed to develop an assessment of the degree to which the aquatic life uses are supported.
Fish consumption uses remain “not assessed” due to lack of fish contaminant monitoring in this stream segment.
