Red Haw Lake IA 04-LDM-1073

Results of IDNR beach monitoring from 2012 through 2014 suggest that the Class A1 uses are "Fully Supported." Levels of indicator bacteria at Red Haw Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2012 (15 samples), 2013 (28 samples) and 2014 (29 samples), as part of the IDNR beach monitoring program.   According to IDNR’s assessment methodology two conditions need to be met for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period are less than the state's geometric mean criterion of 126 E.  coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state's single-sample maximum value of 235 E.  coli orgs/100 ml. If a sampling season geometric mean exceeds the state criterion of 1000 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period and/or if significantly more than 10% of the samples in any one of the three recreation seasons exceed Iowa's single-sample maximum value of 235 E.  coli orgs/100 ml, the Class A1 uses should be assessed as “partially supported.” This assessment approach is based on U.S.   EPA guidelines (see pgs 3-33 to 3-35 of U.S.   EPA 1997b).

At Red Haw Beach, the geometric means from 2012, 2013 and 2014 were all below the Iowa water quality standard of 126 E.  coli orgs/100 ml.   The geometric mean was 12 E.  coli orgs/100 ml in 2012, 12 E.  coli orgs/100 ml in 2013 and 13 E.  coli orgs/100 ml in 2014.   The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E.  coli orgs/100 ml) was 0% in 2012, 7% in 2013 and 3% in 2014.   None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses.   According to IDNR's assessment methodology and U.S.  EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses.

Red Haw Beach was assessed as "partially supported" for the 2008 assessment/listing cycle. Based on IDNR’s assessment methodology 2 consecutive assessment/listing cycles without violations of the geometric mean criterion and without significantly greater than 10% of the samples violating the single-sample maximum criterion are necessary to propose delisting based on bacteria violations. There were no violations of the geometric mean criterion for the 2014 or current 2016 assessment listing cycle and there were less than 10% of the samples exceeding the single-sample maximum criterion. Therefore, the impairment for indicator bacteria is suggested for delisting for the 2016 assessment/listing cycle.

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Red Haw Lake are assessed (monitored) as "fully supported" based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 60, 61, and 58 respectively for Red Haw Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Red Haw Lake in the Eutrophic category. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and relatively low levels of phosphorus in the water column. The data show one violation of the Class A1 criterion for pH in 15 samples.

The level of inorganic suspended solids was relatively low at Red Haw Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Red Haw Lake (2.5 mg/L) was ranked 39th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a moderately large population of cyanobacteria exists at Red Haw Lake. These data show that cyanobacteria comprised 90% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (29.4 mg/L) was ranked 93rd of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (monitored) as "fully supported." Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and one violation of the criterion for pH in 15 samples(7%). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Red Haw Lake.

The Class C (drinking water) uses are not assessed due to the lack of recent information upon which to base an assessment. The only parameter collected as part of the ISU lake surveys relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU surveys from 2010-2014 show that nitrate levels are extremely low at this lake (maximum value = 0.2 mg/l; median = 0.1 mg/l), these data are not sufficient for developing a valid assessment of support of the Class C uses.

Fish consumption uses are assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Red Haw Lake in 2007 and 2008, and 2012.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.    The fish contaminant data generated from the 2007 RAFT sampling conducted at Red Haw Lake showed that levels of mercury were sufficiently high for concern and thus justified follow-up monitoring.    Results from the 2007 sampling showed that the level of mercury in the sample of largemouth bass fillets (0.516 ppm) exceeded the 1 meal/week consumption advisory trigger level (0.30 ppm) as defined in Iowa’s revised (2007) fish consumption advisory protocol.    According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.    Follow-up sampling conducted in 2008 showed that levels of mercury in largemouth bass (0.428 ppm) again exceeded the 1 meal/week trigger level (0.30 ppm).    Thus, a 1 meal/week advisory was issued for this lake, and the fish consumption uses were assessed as “partially supported”.   Fish contaminant monitoring in 2012 again showed levels of mercury in largemouth bass tissue plugs that exceed the 1 meal per week trigger level of 0.3 ppm:  the average level of mercury in the five tissue plugs was 0.41 ppm (SD = .10 ppm; maximum = 0.52 ppm).  Thus, the consumption advisory remain in effect, and the fish consumption uses remain assessed as "partially supporting".