Assessment Comments
Assessment based on results of (1) IDNR/UHL biological monitoring in 2007, 2009 and 2010, (2) LTRMP ambient water quality monitoring from 2000-04, (3) an IDNR investigation of a fish kill in August 2005, and (4) a Section 319 monitoring project from July 2009 to November 2010.
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, 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 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 and A2 (primary and secondary contact recreation) uses are both assessed (monitored) as “not supported” due to violations of Iowa water quality criteria for indicator bacteria. These are new impairments for this assessment segment. The Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" based on (1) results of biological monitoring in 2007, 2009 & 2010 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 monitoring at two sites (Tetes Des Morts Sites 2 and 3) conducted as part of a Clean Water Act Section 319 water quality project from July 2009 through November 2010, (2) results of IDNR/UHL biological monitoring in 2007, 2009 and 2010, (3) 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 (4) results of an IDNR investigation of a fish kill in August 2005.
EXPLANATION: The Class A1 and A2 uses are assessed (monitored) as “not supported due to levels of indicator bacteria (E. coli) that exceed the respective Class A1 and A2 geometric mean criteria. The geometric mean of indicator bacteria (E. coli) in the 15 samples collected during the recreational seasons of 2009 and 2010 at the Section 319 monitoring station Tetes Des Morts Site 3 were 4,574 and 713 orgs/100 ml, respectively. The geometric mean of indicator bacteria (E. coli) in the 15 samples collected at Tetes Des Morts Site 2 were 3,031 and 1,070 orgs/100 ml, respectively. All of these recreation season geometric means far exceed Iowa’s Class A1 geometric mean criterion of 126 E. coli orgs/100 ml and, they also exceed the Class A2 geometric mean criterion of 630 E. coli orgs/100 ml, thus indicating nonsupport of both the Class A1 and A2 water contact recreation uses. Thirteen of the fifteen samples (87%) at Site 3 exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml, and 14 of fifteen samples (93%) exceeded this criterion at Site 2. The percentages of violations of the Class A2 single-sample maximum criterion (2,880 orgs/100 ml) were much lower with 5 of 15 samples (33%) exceeding this criterion at Site 3 and four of 15 samples (27%) exceeded this criterion at Site 2. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than the respective criterion (126 orgs/100 ml for Class A1 and 630 orgs/100 ml for Class A2)., the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). In additional, the percentage of samples with levels of E. coli that exceeded Iowa single-sample maximum criteria indicate impairment of the contact recreation uses for both Class A1 and A2 uses at both monitoring sites.
Regarding the Class B(WW1) aquatic life uses, this assessment, in part, was based on data collected in 2007, 2009 and 2010 as part of the IDNR/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 2007 FIBI scores were 50 (fair) and 64 (good) and the BMIBI scores were 64 (good) and 49 (fair). The 2009 FIBI score was 65 (good) and the BMIBI score was 37 (fair). The 2010 FIBI score was 59 (good) and the BMIBI score was 55 (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. This segment passed the FIBI BIC 3/4 times and passed the BMIBI BIC 1/4 times in the last four years.
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 (i.e., "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 and 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 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.
