Wolf Creek IA 05-CHA-1339
mouth (S15 T71N R21W Lucas Co.) to confluence with unnamed tributary in E 1/2 NW 1/4 S8 T70N R22W Wayne Co.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Stable
- Created
- 10/27/2025 3:08:56 PM
- Updated
- 1/13/2026 9:15:07 AM
The presumptive Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW2 use was assessed as “not supported” based on biological sampling data and assessed as "WINOFI" on continuous dissolved oxygen and temperature monitoring data. Note: A TMDL for indicator bacteria was approved by EPA in March 2025 for this segment. The approval of this TMDL moved the bacterial impairment for this segment from Iowa's Impaired Waters List (Category 5a of the IR) to IR Category 4a (impaired; TMDL completed).
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description USACE 12 WQ CY 2010-2012 15590003 Wolf Creek at CR H50/430th (Site RA-41) USACE 12 WQ CY 2010-2012 15930007 Wolf Creek at CR S23/100th (Site RA-44) Iowa DNR 6 BIO & WQ See Below 207 Wolf Creek Chariton Iowa DNR 6 BIO See Below 1418 Wolf Creek Slab Castle Wildlife Area Site ID Data Source ID # Samples / # Years 2010 Geometric Mean 2011 Geometric Mean 2012 Geometric Mean Annual Geometric Mean Violation # Violations % Violations Significantly >10% Violations Assessment Type Support Level 15590003 12 19 / 3 959 185 2469 Yes 15 79% Yes Evaluated Not 15930007 12 15 / 3 470 138 632 Yes 8 53% Yes Evaluated Not Benthic Macroinvertebrates: Site ID Date Drainage Area (mi2) Ecoregion Major Drainage BM Sample Gear BMIBI score BMIBI Class 40a BMIBI BIT BMIBI Pass/Fail 1418 8/15/23 70.1 40a MO ArtSub 32 Fair 41 Fail 207 9/11/19 65.7 40a MO Surber 37 Fair 41 Fail Site ID Date Drainage Area (mi2) Ecoregion Major Drainage Riffle Stream? FIBI score FIBI Class 40a FIBI BIT FIBI Pass/Fail 1418 8/15/23 70.1 40a MO NA 21 Poor 33 Fail 207 9/11/19 65.7 40a MO NA 45 Fair 33 Pass Community Assessment Type Assessment Result Support Level IR Category Reason Benthic
Macroinvertebrates Monitored Fail (0/2) Not Fish Evaluated Fail (1/2) WINOFI Assessment was monitored because the samples
used to complete Overall Monitored Fail Not 5bv the (BMIBI) assessment were collected in the
last five years.
Presumptive Class A1 - Indicator Bacteria: 2010-2012
Class BWW2 - Biological Sampling:
Fish:
Overall:
Class BWW2 – Continuous Monitoring Data:
The results of continuous dissolved oxygen (DO) and temperature monitoring in
2012 for the DNR/SHL sampling project do suggest impairment of Class BWW2
aquatic life uses. The lowest DO concentration recorded in 69 days of
continuous monitoring was 2.1 mg/L. The daily DO minimum concentration failed
to meet the 24-hour DO criterion (4 mg/L) in 29 of 69 days and the 16-hour DO criterion
(5 mg/L) in 9 of 69 days. The percentages exceeding the 24-hour and 16-hour DO
criteria (42.0% and 13.0%, respectively) were greater than (failing) the 10%
impairment threshold used to assess Binomial water quality parameters. The
associated statistical analysis confidence level for the 24-hour analysis
result was high (>90%), while the confidence level for the 16-hour analysis
result was not high (<90%). The maximum stream temperature recorded during
the sensor deployment period was 34.2 degrees (C). The temperature criterion
for warm water interior streams (32 C) was exceeded in 15 of 69 days. The
percentage exceeding (21.7%) was greater than (failing) the 10% impairment
threshold with high statistical confidence (>90%). Based on these data, the BWW2
aquatic life use was assessed as impaired for DO and temperature. The
assessment type is “evaluated” because it is based on data collected from a
single year within the current data assessment period. In order to meet the
requirements for a “monitored” assessment, the DNR’s continuous monitoring
assessment methodology requires monitoring data from two or more years within
the assessment period.