Assessment Comments
Assessment remains based on results of (1) IDNR/UHL biocriteria monitoring in 2001, (2) LTRMP ambient water quality monitoring from 2000-04, and (3) an IDNR investigation of a fish kill in August 2005.
Basis for Assessment
[Note: Prior to the current (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), this segment is also now presumptively 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 “not assessed” due to the lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (monitored) as "partially supported" based on (1) results of biological monitoring in 2001 and (2) occurrence of a fish kill in August 2005. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach. The sources of data for this assessment include (1) results of IDNR/UHL biological (biocriteria) monitoring in 2001, (2) results of routine water quality monitoring conducted at station TM04.1 from 2000 through 2004 by IDNR staff of the Upper Mississippi River Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA, and (3) results of an IDNR investigation of a fish kill in August 2005.
EXPLANATION: The Class A1 uses are “not assessed” due to the lack of water quality information upon which to base an assessment. LTRMP monitoring does not include sampling for indicator bacteria.
Regarding the Class B(WW1) aquatic life uses, this assessment, in part, was based on data collected in 2001 as part of the DNR/UHL stream biocriteria project. 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 2001 FIBI score was 58 (good) and the BMIBI score was 47 (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 FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.
In addition to biological monitoring, the IDNR/LTRMP staff at Bellevue supplied water quality data for 36 samples collected from Tete de Mortes Creek during the period January 2000 through September 2004 (no sampling was conducted at LTRMP station TM04.1M from October 2002 through March 2004, and no LTRMP monitoring has been conducted at this station since September 2004). Samples were collected approximately monthly; samples were collected during all months of the year. The parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll. A summary of these data show no violations of the Class B(WW1) water quality criteria for temperature, pH, dissolved oxygen, or ammonia-nitrogen in the 43 samples collected over the 2000-04 period.
Despite the results of chemical monitoring that suggest good water quality in Tete de Mortes Creek ("full support" of the Class B(WW1) uses), the results of biological monitoring suggest an impairment ("partial support") of the aquatic life uses. Because stream biota (fish and aquatic macroinvertebrates) integrate water quality impacts over the long-term, the results of biological monitoring are typically weighted more than results of chemical monitoring when determining support of aquatic life uses for purposes of Section 305(b) reporting. This approach is consistent with recommendations in U.S. EPA's guidelines for Section 305(b) reporting (see U.S. EPA 1997b, page 3-21). Thus, considering the "full support" suggested by results of chemical monitoring, and the "partial support" suggested by results of biological monitoring, the aquatic life use of this segment of this stream remain assessed as "partially supported."
The occurrence of a fish kill in August 2005 also suggests only "partial support" of the Class B(WW1) aquatic life uses of this stream. This kill occurred on or before August 18, 2005; no cause of the kill was identified. An estimated 3,363 fish were killed with an estimated value of $12,000. Game fish killed included channel catfish (53), flathead catfish (18), smallmouth bass (370), and walleye (141). The kill affected approximately two miles of stream. No responsible party was identified. The timing an location of the kill, however, suggests that a pollutant caused the kill. 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 (2002-2005) 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, will be placed into Integrated Report subcategory 5b (=Section 303(d) list). 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.
Fish consumption uses remain "not assessed" due to the lack of monitoring in this stream reach.
