Consultants: 1,4‑Dioxane exceeded Massachusetts guideline in five Gardner landfill monitoring wells

Civil Environmental Consultants told the Gardner Board of Health on Feb. 24 that recent groundwater sampling at the closed West Street landfill detected 1,4‑dioxane at concentrations ranging roughly from 1.5 to 8 parts per billion (ppb) in five of 11 monitoring wells, above Massachusetts' drinking‑water guideline of 0.3 ppb.

The finding matters because the 0.3 ppb value used by the state and referenced by the consultants is a drinking‑water guideline intended to limit lifetime cancer risk; the U.S. Environmental Protection Agency has a closely aligned value (about 0.35 ppb). John Tavolianza, a licensed site professional with Civil Environmental Consultants, said the wells that exceeded the guideline were primarily in the northwest portion of the property and that the detections resulted from a change in laboratory method that lowered the method detection limit.

CEC explained that the landfill has 11 groundwater monitoring wells and four surface‑water sample locations. The company said the historical laboratory method had a reporting limit around 250 ppb; at the…