Beaver Creek IA 02-CED-555
mouth (S34 T90N R14W Black Hawk Co.) to confluence with South Beaver Cr. in S25 T90R R17W Butler Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 5/13/2019 1:39:21 PM
- Updated
- 7/17/2019 2:34:08 PM
The Class A1/A3 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class A2 (secondary contact recreation uses) are assessed as “fully supporting”. The Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” based on results of DNR ambient water quality monitoring, DNR/SHL biological data and DNR Fisheries data. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment. The sources of data for this assessment are (1) the results of DNR monthly ambient monitoring from 2014 through 2016 at the county road T75 bridge approximately 3.5 miles northwest of Cedar Falls (STORET station 10070001), (2) the results of DNR/SHL biological sampling in 2003, 2012-2015 and (3) 2001 DNR Fisheries sampling.
The Class A3 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at DNR ambient station 10070001 were as follows: the 2014 geometric mean was 104 orgs/100 ml, the 2015 geometric mean was 473 orgs/100 ml, and the 2016 geometric mean was 166 orgs/100 ml. Two of the three recreation season geometric means exceeded the Class A3 geometric mean criterion of 126 orgs/100 ml. Thirteen of the combined 24 samples (54%) exceeded Iowa’s Class A3 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported." However, The Class A2 Only (primary contact recreation) uses are assessed (monitored) as "fully supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at DNR ambient station 10070001 were as follows: the 2014 geometric mean was 104 orgs/100 ml, the 2015 geometric mean was 473 orgs/100 ml, and the 2016 geometric mean was 166 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A2 Only geometric mean criterion of 630 orgs/100 ml. Two of the combined 24 samples (8%) exceeded Iowa’s Class A2 Only single-sample maximum criterion of 2880 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because none of the recreation seasons geometric means exceeded criteria for Class A2 uses, these uses are assessed as "fully supported." The assessment of the Class B(WW1) aquatic life uses as “fully supporting” remains partially based on results of biological monitoring conducted in 2003, 2012-2015 by DNR/SHL as part of the REMAP and large river sampling projects and on data collected in 2001 by the DNR Fisheries bureau. A series of biological metrics which reflect 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 and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2001 DNR Fisheries FIBI score was 62 (good) and the 2003 DNR/SHL FIBI score was 45 (fair). The 2012-2015 BMIBI scores were 56, 57, 64 (all good) and 76 (excellent). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52. This segment passed the FIBI BIC 2/2 times in the last 16 years and passed the BMIBI BIC 4/4 times in the last five years.
This aquatic life assessment is now considered "monitored" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”. This segment had four BMIBI samples collected between 2012 and 2016.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach.