Wolf Creek IA 02-CED-530
mouth (S29 T87N R11W Black Hawk Co.) to confluence with Twelvemile Cr. in S19 T86N R13W Tama Co.
- Assessment Cycle
- 2018
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 5/13/2019 1:17:49 PM
- Updated
- 7/16/2019 2:37:21 PM
Assessment Summary
The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring conducted from 2012 through 2014 and based on results of biological sampling conducted in 2004. Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this assessment segment. The primary sources of data for this are (1) the results of DNR/SHL monthly ambient water quality monitoring conducted on Wolf Creek near LaPorte City (STORET station 10070002) during the 2014-2016 assessment period, (2) DNR/SHL REMAP biological sampling conducted in 2004 near LaPorte City, and (3) USGS monitoring at station 05464220 near Dysart from September 2012 to September 2013.
Assessment Explanation
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at Iowa DNR ambient station 10070002 at La Porte City were as follows: the 2014 geometric mean was 200 orgs/100 ml, the 2015 geometric mean was 406 orgs/100 ml, and the 2016 geometric mean was 459 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Sixteen of the combined 24 samples (67%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported."
Results of chemical/physical water quality monitoring at Iowa DNR ambient station 10070002 at La Porte City also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.3 mg/L), 36 Dissolved Oxygen samples (minimum = 6.9 mg/L), 35 pH samples (range = 7.4 to 8.4), 36 Temperature samples (maximum = 23.5°C), 36 Chloride samples (maximum = 33 mg/L), or 36 Sulfate samples (maximum = 72 mg/L) occurred during monitoring from January 2014 to December 2016.According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.
Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this river segment. Previous assessments were based on results of fish contaminant monitoring conducted by USGS in 1995 as part of the NAWQA project. These data are now considered too old (greater than 10 years) to accurately characterize current water quality conditions.
Assessment Key Dates
8/19/2004 | Biological Monitoring |
1/9/2014 | Fixed Monitoring Start Date |
12/6/2016 | Fixed Monitoring End Date |
Methods
150 | Monitoring data more than 5 years old |
220 | Non-fixed station physical/chemical monitoring (conventional pollutant only) |
230 | Fixed station physical/chemical (conventional plus toxic pollutants) |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
330 | Fish surveys |
380 | Quantitative physical habitat assessment |
420 | Indicator bacteria monitoring |