When the benthic macroinvertebrate community structure significantly diverges from unimpacted control sites of comparable physical and chemical characteristics. In addition, this use will be considered impaired when toxicity (as defined by relevant, field-validated, bioassays with appropriate quality assurance/quality controls) of sediment associated contaminants at a site is significantly higher than controls.
When the benthic macroinvertebrate community structure does not significantly diverge from unimpacted control sites of comparable physical and chemical characteristics. Further, in the absence of community structure data, this use will be considered restored when toxicity of sediment-associated contaminants is not significantly higher than controls.
Removal may occur if:
- Known contaminant sources contributing to sediment contamination and degraded benthos have been identified and control measures implemented; and
- All remediation actions for contaminated sediments are completed and monitored according to an approved plan; or
- The benthic community within the site being evaluated is statistically similar to a reference site with similar habitat and minimal sediment contamination.
Sources of Pollution or Problem
- Contaminated sediments; spills of chemicals within the watershed; atmospheric deposition
- Sediment, nutrients, and bacteria as a result of nonpoint, or diffuse, sources of pollution; urban stormwater runoff; sewer overflows; noncontact cooling water
- Dams, drop structures, concrete-lined channels, and poorly-sized culverts and stream crossings; shoreline alteration, such as sheet piling, that doesn’t provide high-quality habitat
- Discharges of water with elevated temperatures
Results from the benthos assessments in 2012 & 2014 are still pending. The data from 2012 is being reassessed using the same statistical analysis as the 2014 data. The final report will include both data sets and final conclusions and is expected in early 2016.
Sources of contamination to the benthic community within the AOC need to be remediated. The following actions need to be completed in order to determine contamination related management actions.
- Assess areas on the Milwaukee River from Estabrook Park dam downstream to the estuary.
- Assess the potential impacts to sediments from other manufactured gas plants within the AOC.
- Review and act upon sediment assessment data from other areas of the AOC. This includes, but is not limited to, Kinnickinnic River/Turning Basin, Menomonee River from confluence with Little Menomonee to the harbor and existing Milwaukee River data.
The status and condition of the benthic community in the AOC needs to be determined. The next step will be to evaluate the findings of the USGS benthos study and then assess the need to supplement the study to adequately characterize the range of benthic conditions in the AOC. A target adjustment may also be needed depending on the results of the study.
The following management actions are necessary to move towards removing this impairment. This list is not complete. The actions that have been implemented are italicized.
1) Sources of contamination to the benthic community within the AOC need to be remediated.
- Complete the assessment and cleanup of PCBs at the Cedar Creek Superfund Alternative Site.
- Complete the management of sediments containing PAHs and metals from the Burnham Canal Superfund Alternative Site.
- Complete the assessment of contaminated sediment and evaluate and implement clean up related to the Solvay Coke Superfund Alternatives Site.
- Blatz Pavilion, Lincoln Park Phase 1 and Phase 2 Contaminated Sediment Remediation
- Kinnickinnic River Legacy Act Cleanup
A full assessment of the impairment cannot be made until the final data from 2012 and 2014 are received from USGS. Given the disturbance found in some of the AOC waterways, it is unlikely that high quality benthic communities can be established at all sites. For instance, the inner harbor has high degrees of disturbance, sediment deposition and lack of suitable habitat that tend to be dominated by very tolerant organisms. Changes in the habitat in this area are unlikely. Refinement of the target may be needed, taking into consideration the achievability of targets for BUI removal and the varied benthic conditions throughout the AOC.
Photo courtesy of Milwaukee Riverkeeper