Tetes Des Morts Creek IA 01-TRK-121

[Note:  Although the A2 uses were previously assessed as impaired (5p), this impairment had not been identified on either the 2012 or 2014 Section 303(d) lists.  Thus, this impairment is added to the current (2016) Section 303(d) list.]  

The Class A1 and A2 uses remain 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 21 samples collected during the recreational seasons of 2010 and 2011 at the Section 319 monitoring station Tetes Des Morts Site 3 were 713 and 106 orgs/100 ml, respectively.  The geometric mean of indicator bacteria (E. coli) in the 24 samples collected during these recreational seasons at Tetes Des Morts Site 2 were 1,578 and 822 orgs/100 ml, respectively.  Three of the four recreation season geometric means exceed Iowa’s Class A1 geometric mean criterion of 126 E. coli  orgs/100 ml and, three of four 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.  Eight of the 21 samples (37%) at Site 3 exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml, and 20 of 24 samples (83%) 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 2 of 21 samples (10%) exceeding this criterion at Site 3 and five of 24 samples (21%) 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 addition, 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 2010, 2011 and 2014 as part of the IDNR/SHL 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 2010 FIBI score was 59 (good) and the BMIBI score was 55 (fair).   The 2011 FIBI score was 70 (good) and the BMIBI score was 59 (good).  The 2014 FIBI score was 74 (excellent) and the BMIBI score was 54 (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 1994-2008.  The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.  This segment passed the FIBI BIC 3/3 times and passed the BMIBI BIC 0/3 times in the last five years (2010-2014).    

Water quality data were collected from April to October of 2011 at the Section 319 project sites:  Site 2 at the Highway 52 bridge (STORET station 12490004) and Site 3 at the High Road Bridge (STORET station 13490002).  The results of this monitoring do not suggest impairment of the Class B(WW1) aquatic life uses.  Two of the 11 samples collected at Site 2 violated the Class B(WW1) criterion for dissolved oxygen of 5 mg/l:  the sample collected on August 8th contained 4.9 mg/l and the sample collected on July 19th contained 4.5 mg/l.  At Site 3, one of the 11 samples violated the dissolved oxygen criterion:  the sample collected on July 11th contained 2.6 mg/l.  According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as dissolved oxygen, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b).  According to IDNR’s assessment/listing methodology, however, the results from these two stations on Tete Des Morts however, do not indicate that significantly greater than 10% of the samples exceed the Class B(WW1) criterion for dissolved oxygen.  Thus, these results suggest that the Class B(WW1) uses should be assessed (monitored) as “fully supported.”

Despite the results of chemical monitoring that suggest good water quality in Tete de Morts 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 fish contaminant monitoring in this stream reach.