Data Sources:

Presumptive Class A1 - Indicator Bacteria:

Presumptive Class A1 - pH:

Class BWW1 - Binomial Parameters:

Class BWW1 - Toxic Parameters:

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Overall:

Class BWW1 - Fish kill Assessment:
The Class BWW1 aquatic life use assessment based on the 2016 fish kill placed this segment in Category 5b. The fish kill was caused by a “pollutant” or was suspected to be caused by a “pollutant”; therefore, the Class BWW1 use was considered impaired. Because the source of the pollutant was not identified and/or the enforcement actions taken against the responsible party have not been resolved, the Class BWW1 use was placed in Category 5b. Due to uncertainty regarding the recovery of the aquatic life following the fish kill, any existing fish kill 5b impairment will remain in Category 5b until more recent sampling has shown recovery of the aquatic community or the responsible party has paid restitution.

Details about the 2016 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/916

Class BWW1 - Nutrient Impact Assessment:
Monitoring data collected from the DNR/SHL ambient fixed station near Hurtsville (10490001) during the 2010-2014 data assessment period were sufficient to complete a Nutrient Impact Assessment (NIA). Data analysis methods and screening benchmark values for nutrient stressor and response parameters described in the DNR’s 2016 NIA methodology were used to examine for nutrient impacts often associated with low biotic index scores and violations of dissolved oxygen (DO) criteria. Nutrient stressor: The median concentration of total phosphorus (TP) was 0.22 mg/L among samples collected during the June 15- October 15 index period. The TP benchmark (0.10 mg/L) was exceeded in 18 of 20 samples. The percentage exceeding (90%) was greater than (failing) the 50% threshold with high statistical confidence (> 90%). Nutrient response parameter: The median concentration of algal chlorophyll A suspended in water (WCHLA) was 11 ug/L. The WCHLA benchmark (20 ug/L) was exceeded in 2 of 20 samples. The percentage exceeding (10%) was less than (passing) the 50% threshold with high statistical confidence (> 90%). The median rating of filamentous algae coverage (FLMA) on hard substrates was 0 (absent). The FLMA benchmark (3; 50%-75%) was exceeded in 0 of 8 observations. The percentage exceeding (0%) was less than (passing) the 50% threshold with high statistical confidence (> 90%).

The results of this “evaluated” assessment indicate the presence of elevated levels of the nutrient stressor parameter (TP) and low levels of the nutrient response parameters, WCHLA and FLMA. This combination of results is interpreted as representing a moderate risk of aquatic life use impairment due to nutrient enrichment. Continuous monitoring data were not available to examine for violations of DO criteria; however, the benthic macroinvertebrate index (BMIBI) results described suggest full attainment of aquatic life uses. Based on the assessed risk level, the stream segment is considered a moderate priority for follow-up nutrient impact monitoring.

Class HH-F - Toxic Parameters: