Point Hollow Creek (aka White Pine Cr.) IA 01-TRK-165

Sources of Data:

Presumptive Class A1 - Indicator Bacteria:

Presumptive Class A2 - Indicator Bacteria:

Class A - pH:

Class BCW1 - Conventional Parameters:

Class BCW1 - Biological Sampling:

Benthic Macroinvertebrates:

Overall Assessment:

Class BCW1- Fishkill Assessment:

The Class BCW1 use assessment based on the 2017 fish kill placed this segment in Category 4d. The fish kill was caused by a “pollutant” or was suspected to be caused by a “pollutant”; therefore, the presumptive Class BCW1 use was considered impaired. However, because restitution for the fish killed was received, the presumptive Class BCW1 use was placed in Category 4d (impaired but TMDL not required). DNR feels that (1) TMDLs should not be required for a fish kill caused by a one-time illegal or unauthorized release of a pollutant where enforcement action was taken and (2) enforcement action is more appropriate and effective for addressing a spill-related impairment than the TMDL process.

Details about the 2017 fish kill can be found here:https://programs.iowadnr.gov/fishkill/Events/948

Class BCW1 - Continuous Monitoring:

Continuous dissolved oxygen (DO) monitoring data collected in 2012 for the DNR/SHL coldwater stream sampling project at station 11310006 were examined for DO criteria violations. The lowest DO concentration recorded in 51 days of continuous monitoring was 6.3 mg/L. The daily DO minimum concentration failed to meet the 24-hour DO criterion (5 mg/L) in 0 of 51 days. The percentage exceeding (0%) was less than (passing) the 10% impairment threshold used to assess conventional water quality parameters. The associated statistical analysis confidence level was high (>90%). The 16-hour DO criterion (7 mg/L) was exceeded in 4 of 51 days. The percentage exceeding (7.8%) was less than (passing) the 10% threshold; however, the statistical analysis confidence level was not high (<90%). Based on these data, the BCW1 aquatic life use is assessed as not impaired for DO. 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.

Continuous stream temperature monitoring data collected in 2012 for the DNR/SHL coldwater stream sampling project at stations 11310006 and 11310005 were examined for temperature criteria violations. At station 11310006, the maximum stream temperature recorded during the sensor deployment period was 18.6 degrees (C). The BCW1 temperature criterion of 20 (C) was exceeded in 0 of 51 days. The percentage exceeding (0%) was less than (passing) the 10% impairment threshold with high statistical confidence (>90%). At station 11310005, the maximum daily temperature was 27.3 degrees (C). The BCW1 temperature criterion of 20 (C) was exceeded in 78 of 111 days between 6/21/2012 and 10/9/2012. The percentage exceeding (70%) was greater than (failing) the 10% impairment threshold with high statistical confidence (>90%). Based on these data, the BCW1 use is assessed as impaired for water 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.

The substantially different continuous monitoring results obtained from stations 11310006 and 11310005 suggest that the stream temperature regime is not consistent throughout the entire stream segment. Additional continuous monitoring and an assessment of coldwater inputs (e.g., groundwater seeps and springs) in the vicinity of the sampling sites might be needed to determine whether the BCW1 use is the appropriate designated use for the entire segment or just certain areas within the segment.