Clear Creek IA 02-IOW-1937

Assessment Comments

Assessment is based on (1) results of violations of narrative WQ criteria as documented by volunteer monitors and (2) a July 2009 memorandum from IDNR Field Office 6.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general 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), this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses.    According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.    Thus, for the current (2010) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]  

SUMMARY:  The general uses and the presumptive Class A1 (primary contact recreation) uses of this stream are assessed (monitored) as "fully supported" based on a follow-up investigation by IDNR field office staff of historical impacts of poorly-treated and untreated domestic  wastewater discharged to the stream near Conroy, IA.   The presumptive Class B(WW1) aquatic life uses are "not assessed" due to lack of information upon which to base an assessment.   This assessment represents a de-listing of the wastewater-related impairments that have existed for this stream segment since Iowa’s 2004 Section 303(d) listing cycle.    The source of information upon which these delistings are based is a July 7, 2009 memorandum from IDNR Field Office 6 staff describing improved water quality conditions in this segment of Clear Creek.    This is the same assessment as that developed for the next upstream segment of Clear Creek (IA 02-IOW-001615_0).  

EXPLANATION:  Historically the water quality conditions in this segment of Clear Creek as documented by volunteer monitors and by IDNR staff potentially violated several of Iowa's narrative water quality standards designed to protect general uses of Iowa's surface waters.    The assessment of impairment was originally based on results of the an IDNR/IOWATER “snapshot” monitoring event in September 2003 that showed presence of toilet paper, floating sewage material, and a strong sewage smell coming from a tile line that discharges to the uppermost reaches of Clear Creek near Conroy, IA (see IDNR Water Fact Sheet 2005-2:  Snapshot Events; see also Neely et al.    2003.    Old Man’s Creek and Clear Creek, east-central Iowa:  the role of volunteers in a snapshot sampling (available at http://wqm.igsb.uiowa.edu/iowater/SnapshotResults/Oldmans.pdf )).    Subsequent investigations by volunteer (IOWATER) monitors and by IDNR staff confirmed that these impacts existed.    Based on these investigation, the general uses of this stream, as well as the presumptive aquatic life uses and the presumptive primary contact recreation uses of this segment, were assessed as impaired for the 2004 listing cycle.    This impairment remained on Iowa’s 2006 and 2008 Section 303(d) lists.    Due to the February 2008 EPA approval of changes to Iowa Water Quality Standards that presumed Class A1 and Class B(WW1) uses for all Iowa perennial streams, this impairment was added to the presumptive Class A1 (primary contact recreation) and Class B(WW1) aquatic life uses o this segment of Clear Creek.  

A follow-up investigation by staff from IDNR Field Office 6 (Washington, IA) on July 1, 2009 showed improved water quality conditions with no evidence of untreated or poorly-treated wastewater being discharged to the stream.    Thus, the general uses and the presumptive Class A1 uses are assessed as “fully supported” for the current (2010) assessment/listing cycle, and the wastewater-related impairment of these uses is proposed for de-listing.   The wastewater-related impairment identified for the 2008 cycle was incorrectly applied to the Class B(WW1) aquatic life uses:  there were (and are) no data available upon which to develop a valid assessment of the degree to which the aquatic life uses of this stream segment are supported.   Thus, the wastewater-related impairment of the aquatic life uses is delisted, and these uses are considered "not assessed" for the 2010 cycle due to the lack of water quality information upon which to base an assessment.