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Superior MGP Semi-Annual Progress Report
Reporting Period: January 1, 2014 to June 30, 2014
Submitted on September 15, 2014
Background
The Superior MGP operated from 1889 to 1904, and company records were available to estimate the amounts of gas and by products generated. The Superior shoreline has been filled and modified since 1904 including the creation of the land now occupied by Graymont, an industrial boat slip that has been dredged several times to depths of 25 feet or more, the creation of the land and lagoons used by the City of Superior wastewater treatment plant, and generally extending the shoreline out into Superior Bay.
Environmental investigations at the Superior MGP have been conducted since 2001 and an excavation to remove source materials containing VOC, PAH, and coal tar was conducted in 2008. Chemical oxidation (Cool Ox) was also used at the time of the excavation. Several rounds of groundwater monitoring have delineated a stable plume of VOC and PAH. Soil sampling and analysis from numerous borings, test trenches, and surface samples have delineated VOC and PAH concentrations exceeding WDNR standards. To date, no vapor intrusion investigations have been conducted.
Based on the investigative and remedial work completed to date, Superior Water Light and Power requested a data review to determine if the following closure plan was acceptable to WDNR:
1. Construct soil covers over areas that exceed surficial direct contact standards.
2. Demonstrate natural attenuation for groundwater remediation.
3. Conduct a vapor intrusion investigation and provide mitigation/remediation as needed.
The response from WDNR indicated that the three items need to be supplemented with the following remedial activities:
1. Additional soil removal in the vicinities of MW-3 and MW-4 to address âhot spotâ contamination.
2. Complete investigation and assessment of the sediments in the industrial boat slip.
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First Half 2014 Progress Report
Superior Water Light and Power set aside ongoing planning efforts for the soil, groundwater, and vapor intrusion remedies to engage expert legal assistance in the area of sediment remediation. The potential burden of engaging multiple parties with adversarial legal positions to address sediment cleanup has caused the need for this deliberation. The results of prior sediment investigations led Superior Water Light and Power to believe that the MGP has no impact on the sediments. The company is now weighing options for pursuing site closure under alternative regulatory scenarios including the Voluntary Party Liability Exemption program. We have also set aside a groundwater monitoring report from 2013, pending a decision on the closure strategy for the site.
Also during this reporting period, WDNR apparently reassigned project managers for the Superior MGP, although no formal notifications or other communications have been made. Superior Water Light and Power assumes a kickoff meeting with the new project manager will be the first order of business, and that future plans and expectations for the project will be discussed.
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