DNR opens contamination case after Thomas Street tests find lead, dioxins and groundwater chemicals

The Wisconsin Department of Natural Resources told the City of Wausau's Economic Development Committee on March 3 that Phase 2 testing of the Thomas Street corridor found contamination in one portion of the project area and that the agency has opened an environmental contamination case.

Jane Gray, a hydrogeologist and program coordinator with the DNR's Remediation and Redevelopment Program for the West Central Region, said soil samples from Area A (borings SB3 and SB4) showed shallow-fill exceedances for lead and dioxins and furans in the 2'4 foot interval. Deeper, saturated samples in the same borings also contained volatile organic compounds, including naphthalene, trimethylbenzene and xylenes, as well as pentachlorophenol (PCP). Groundwater samples reflected similar compounds, the DNR presentation said.

Why it matters: The DNR said the shallow lead and dioxin/furan exceedances and evidence of deeper groundwater-related contamination require formal action. On Feb. 11 the DNR issued a responsible-party letter to the city under the agency's NR 700 process, initiating a contamination case and spelling out next steps and deadlines.

What the DNR is requiring: According to Jane Gray, the responsible-party letter requires the city to hire a qualified environmental consultant within 30 days of receipt (deadline cited as March 13) and to submit a site investigation work plan within 60 days (deadline cited as April 12). The work plan will guide further delineation of the nature, extent and potential source of contamination and inform next steps.

Other areas: Gray told the committee that Areas B, C and D (other portions of the project map) showed either no residual contaminant level (RCL) exceedances in soil or only limited, vertically constrained groundwater-pathway exceedances that the DNR judged de minimis. Area B had an estimated (J-flag) arsenic detection in groundwater but no evidence of a hazardous substance discharge at that parcel; Areas C and D had PAH and selenium detections in shallow soil that DNR said were not impacting groundwater and required no action.

Public concern and DNR method: A resident, Tom Killian, had pointed to dioxin TEQ numbers in public comment and said some samples appeared to exceed a roughly 4.8 nanograms-per-kilogram screening value for residential soil. Gray said DNR calculates dioxin/furan TEQ using the 2005 World Health Organization toxic equivalence factors and compares the TEQ to the direct-contact RCL for 2,3,7,8-TCDD (approximately 4.8 ng/kg). She added the DNR was meeting with the state Department of Health Services this week to clarify TEQ questions statewide.

Next steps for the city: Staff told the committee they expect to seek authorization from the finance committee next week to hire a consultant. The consultant and the city will prepare the site investigation work plan for DNR review. Gray said DNR will rely on the responsible party and consultant's work plan to determine whether additional delineation (including off-site) is necessary; for fill-related sources, DNR generally focuses delineation on parcel lines but will decide case-by-case based on the work plan and data.

What was not decided: The DNR's issuance of the responsible-party letter starts a regulatory process; the committee did not vote on remediation actions at the meeting. The DNR's determinations about whether impacts are from fill, the precise lateral extent of contamination, and the final remedial approach will be informed by the consultant's forthcoming investigation and by DNR review.

The committee was told staff will return to the committee in April with development plans for Areas B, C and D and further updates on Area A after consultant work begins.