South Skunk River IA 03-SSK-934
from the Ames Water Works dam in River Valley Park at Ames (S36 T84N R24W Story Co.) to the Co. Rd. at north line of S6 T85 R23W Story Co (approximately 1 mile NNE of Story City)
- Assessment Cycle
- 2024
- Release Status
- Pending
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 11/1/2023 8:12:53 AM
- Updated
- 12/20/2023 9:44:36 AM
Assessment Summary
The Class A1 use was assessed as “not supported” due to levels of indicator bacteria that violated state water quality criteria. The Class BWW1 use was assessed as "not supported" based on biological sampling data. All other designated uses were "not assessed."
Assessment Explanation
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2012-2014 10850003 South Skunk River Upstream
of Ames (US1) Prairie Rivers/City of Ames 26 WQ CY 2020-2022 99990168 South Skunk @ W Riverside Rd
(Ames) Prairie Rivers/City of Ames 26 WQ CY 2020-2022 99990169 South Skunk River @ Broad St
(Story City) Iowa DNR 6 BIO See Below 38 South Skunk River Ames Site ID Data Source ID # Samples / # Years 2012 Geometric Mean 2013 Geometric Mean 2014 Geometric Mean Annual Geometric Mean
Violation # Violations % Violations Significantly >10%
Violations Assessment Type Support Level 10850003 6 22 / 3 46 94 223 Yes 7 32% Yes Evaluated Not
Site ID Data Source ID # Samples per Year (2020/ 2021/2022) 2020 Geometric Mean 2021 Geometric Mean 2022 Geometric Mean Violates Annual Geometric Mean? # 2020 SSM violations / SSM Violations needed for impairment # 2021 SSM violations / SSM Violations needed for impairment # 2022 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 99990168 26 7/8/8 103.2 97.9 131.0 YES 2/3 1/3 1/3 NO Evaluated WINOFI 99990169 26 7/8/8 425 133.8 175.9 YES 6/3 3/3 4/3 YES Evaluated WINOFI The bacteria samples
were collected by the Prairie Rivers Watershed Group and Story County
Conservation with the analyses conducted by the City of Ames. Since the data
were not collected under a DNR-approved quality assurance plan, the
assessment was considered "evaluated" instead of
"monitored". According to Iowa DNR’s assessment/listing
methodology, impairments based on “evaluated” assessments are of lesser
confidence and are not appropriate for Section 303(d) listing (Category 5 of the
Integrated Report). The Iowa DNR does, however, consider these impairments as
appropriate for listing under Category 3b of the Integrated Report (waters
potentially impaired and in need of further investigation). Site ID Data Source ID # Samples / # Years Maximum Value Mean Value Median Value # Violations % Violations Significantly >10%
Violations Assessment Type Support Level 10850003 6 33 / 3 8.6 8.1 8.1 0 0% No Evaluated Full Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations % Acute/ Chronic Violations Significantly >10%
Violations Assessment Type Support Level 10850003 6 Ammonia 33 / 3 1.7 0.15 0.05 0 / 0 0% / 0% No Evaluated Full 10850003 6 Chloride 33 / 3 100 43 35 0 / 0 0% / 0% No Evaluated Full 10850003 6 Dissolved oxygen 33 / 3 16.2 10.7 10.2 NA / 0 NA / 0% No Evaluated Full 10850003 6 pH 33 / 3 8.6 8.1 8.1 0 / NA 0% / NA No Evaluated Full 10850003 6 Sulfate 33 / 3 110 46 41 0 / NA 0% / NA No Evaluated Full 10850003 6 Temperature 33 / 3 27.5 12 12.4 0 / 0 0% / 0% No Evaluated Full BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/Thermal BM Sample Gear BMIBI score BMIBI Class 47b BMIBI BIT BMIBI Pass/Fail 38 9/19/22 254.3 47b MS/WW Surber 55 Good 62 Fail 38 8/31/17 254.3 47b MS/WW Surber 58 Good 62 Fail BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/Thermal Riffle Stream? FIBI score FIBI Class 47b FIBI BIT FIBI Pass/Fail 38 9/19/22 254.3 47b MS/WW No 39 Fair 32 Pass 38 8/31/17 254.3 47b MS/WW No 70 Good 32 Pass Community Assessment Type Assessment Result Support Level IR Category Reason Benthic Macroinvertebrates Evaluated Fail (0/2) Not Fish Evaluated Pass (2/2) Full Assessment was evaluated because the samples used for the Overall Evaluated Fail Not 5bv the assessment were not collected in a recent five year
period.
Class A1 - Indicator Bacteria: 2012-2014
Class A1 - Indicator
Bacteria:
Class A1 - pH: 2012-2014
Class BWW1 - Binomial Parameters: 2012-2014
Class BWW1 - Biological Sampling:
Benthic Macroinvertebrates:
Fish:
Overall:
Class HH - No Data
Assessment Key Dates
9/19/2022 | Biological Monitoring |
1/10/2012 | Monitoring Start |
9/4/2014 | Monitoring End |
8/31/2017 | Biological Monitoring |
4/15/2020 | Monitoring Start |
10/19/2022 | Monitoring End |
Methods
150 | Monitoring data more than 5 years old |
200 | Physical/Chemical Monitoring |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
330 | Fish surveys |
420 | Indicator bacteria monitoring |