Assessment Comments

Assessment is based on (1) results of an IDNR investigation of a fish kill in April 2004, (2) results of the 2008 IDNR/UHL biological monitoring data: FIBI = 24 (poor); BMIBI = 70 (good). Riffle habitat FIBI BIC = 53; BMIBI BIC = 62, and (3) IDNR TMDL-related monitoring near Ellsworth in 2007 and 2008.

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 presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to the levels of indicator bacteria that exceed water quality criteria.   This assessment represents a new impairment for this stream segment.   The source of data for this assessment is the results of TMDL-related monitoring conducted near Ellsworth (ldc-2; STORET station 11400004) from July 2007 through December 2008.   Although chemical water quality monitoring data from this station show no violations of aquatic life criteria, the presumptive Class B(WW1) aquatic life uses of this stream remain assessed (monitored) as “partially supported” due to a fish kill in April 2004.   The kill was caused by animal waste.   Although the party responsible for the kill was identified, IDNR records do not indicate that IDNR sought restitution for the value of the fish killed or for the costs incurred by DNR during the investigation of the kill.   Thus, this impairment is appropriate for Category 5b of Iowa’s 2010 Integrated Report (=Section 303(d) list).   Additionally, the 2008 results of IDNR/UHL biological monitoring suggest "evaluated" partial support of aquatic life uses.    

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 27 samples collected during recreational seasons of 2007 and 2008 (359 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Seventeen of the 27 samples (63%) exceed Iowa’s single-sample maximum value 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 level 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).  

Results of TMDL-related chemical/physical water quality monitoring conducted in 2007-2008 do not suggest impairment of the presumptive Class B(WW1) aquatic life uses.   None of the 32 samples collected violated Class B(WW1) criteria for dissolved oxygen (minimum value:  7.9 mg/l), and none of the 32 samples violated the temperature/pH-dependent Class B(WW1) chronic criteria for ammonia.  

The occurrence of a fish kill in 2004, however, indicates impairment of the aquatic life use of this stream segment.   This kill occurred on April 19, 2004; the cause of the kill was attributed to animal waste.   An estimated 15 fish (“minnows”) were killed; no estimate of the value of the fish killed was provided.   No estimate of the length of stream was provided.   The party responsible for the kill was identified.   According to the IDNR investigation, a commercial applicator dumped approximately 3,000 gallons of manure after he became stuck while land-applying the manure in a farm field roughly three miles northeast of Randall.   Although dumping the manure allowed the applicator to free his equipment, the manure reached a broken tile line at the end of the field.   An unknown amount of manure reached Long Dick Creek through this tile line.   The applicator acted quickly to place dams (1) in front of the tile line break and (2) below the tile line to block manure coming out of the line from reaching the creek.   The applicator pumped manure from behind the dams into a honey wagon.   He also flushed contamination out of the tile line with about 1600 gallons of clean water.  

According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.   If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing.   Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b.   The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.

Bioassessment explanation:  The assessment of the presumptive Class B(WW1) aquatic life uses was based on data collected in 2008 as part of the IDNR/UHL biological monitoring program.    A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.    The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.    The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).    The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).    The 2008 FIBI score was 24 (poor) and the BMIBI score was 70 (good).   The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.    The riffle habitat FIBI BIC for this ecoregion is 53 and the BMIBI BIC is 62.    Even though this site failed the FIBI BIC and passed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.  

This biological assessment is considered “evaluated” (of lower confidence) due to the lack of a biological assessment protocol for general use-only streams.   IDNR’s existing protocol has been calibrated to aquatic life reference conditions in wadeable Class B(LR) and Class B(WW) streams.    The aquatic environment of most general use streams is one of extremes in water quality.    Consequently, general use-only streams tend to have biological diversity that is low relative to more stable aquatic environments of Class B(LR) and Class B(WW) streams.    Thus, the use of biological assessment methods developed for the ecologically more stable and diverse Class B(LR) streams to assess general use reaches will likely overstate the existence of impairment.