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

The presumptive Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses are both assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.  The geometric mean of indicator bacteria (E. coli) in the samples collected during the recreational season of 2010 at stations 11310005 (16 samples) and 11310006 (nine samples) (917 and 358 orgs/100 ml, respectively) both exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml).  Six of the nine samples (67%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml at station 11310006, and 12 of 16 samples (75%) exceeded the single sample maximum criterion at station 11310005.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). 

The geometric mean of the 10 samples collected during calendar year 2010 at station 11310006 (461 orgs/100 ml) is below the Class A2 geometric mean criterion of 630 E. coli orgs/100 ml, thus indicating full support of the Class A2 water contact recreation uses.  The geometric mean of the 17 samples collected at station 11310005 (990 orgs/100 ml), however, exceeded the Class A2 criterion.  Two of the 10 samples (20%) from station 11310006 exceeded Iowa’s Class A2 single-sample maximum criterion of 2,880 orgs/100 ml, and six of 17 samples from station 11310005 exceeded this criterion.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than the respective criteria (126 orgs/100 ml for Class A1 and 630 orgs/100 ml for Class A2), the contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, both the Class A1 and Class A2 water contact recreation uses for this segment are assessed as "not supported".    

The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2009 and 2012 as part of the IDNR/SHL coldwater stream sampling project.  A series of biological metrics which reflect coldwater stream water quality and habitat integrity were calculated from the biological sampling data.  The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa that were collected in the stream sampling reach.  The biological metrics were combined to make a coldwater benthic index (CBI).  The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).  The 2009 CBI score was 27.  The 2012 CBI scores were 31, 52 and 55.  The aquatic life use support was assessed (monitored) as partially supporting (=PS), based on a comparison of the CBI scores with biological impairment criteria (BIC) established for the 2012 Section 305(b) report.  The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011.  The CW BIC is 60 and this segment passed the CW BIC 0/4 times in a four-year period (2009-2012).  This aquatic life assessment is now considered "monitored" because there were multiple samples collected in multiple years in a recent five year period. 

Results of chemical/physical water quality monitoring from March to July 2010 at these two stations show no violations of Class B(CW1) water quality criteria for ammonia, dissolved oxygen, pH, chloride, or sulfate occurred in the approximately 25 combined samples from these two stations that were analyzed from March to July 2010.

Continuous dissolved oxygen (DO) monitoring data collected in 2012 for the IDNR/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 B(CW1) 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 IDNR’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 IDNR/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 B(CW1) 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 B(CW1) 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 B(CW1) aquatic life 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 IDNR’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 B(CW1) designated aquatic life use is the appropriate designated use for the entire segment or just certain areas within the segment.

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.