EPC briefing details Sydney Mine Superfund site, groundwater restrictions and ongoing monitoring

Hillsborough County Environmental Protection Commission staff on April 17 gave a briefing on Superfund sites in the county and provided detailed updates on the Sydney Mine Superfund site located in the Energy Industrial Park.

“Allison Alisa Amram, a professional geologist in EPC’s waste division, described a Superfund site as ‘a piece of property that has environmental contamination that is so bad it's considered to be a significant risk to public health, welfare, or the environment,’” the commission record shows.

Amram summarized federal and state roles: the U.S. Environmental Protection Agency manages Superfund (the National Priorities List and response authority under CERCLA), while the Florida Department of Environmental Protection reviews technical work and enforces state cleanup standards. EPC’s role is informational; the commission does not exercise Superfund regulatory authority.

Key details Amram provided about the Sydney Mine site included:

- Location and history: the site sits within a former phosphate-mined area in the Energy Industrial Park (south of Route 60, east of Valrico). From 1973 to 1981 Hillsborough County leased land for three unlined waste-disposal ponds used for waste oils and sludges. - Early cleanup actions: Hillsborough County excavated wastes, incinerated material on-site and constructed a slurry wall (clay barrier) around the three ponds in 1984; monitoring followed and the site was placed on the National Priorities List (Superfund) in 1989. - Current contamination and scope: soils and wastes were removed; groundwater remains the only affected medium. A benzene plume has been delineated to Florida cleanup target levels. More recent monitoring identified 1,4-dioxane above Florida cleanup target levels in several monitoring wells, prompting an approved work plan to further delineate the extent of the 1,4-dioxane plume. - Restrictions and reuse: EPA and DEP groundwater-use restrictions cover portions of the Energy Industrial Park; the Superfund area includes a three-pond (9-acre) core with additional land-use restrictions (no residential, recreational, educational or agricultural uses) and prohibitions on digging that could disrupt the protective slurry wall.

Amram also said Hillsborough County has 12 active Superfund/NPL sites in the county, four delisted sites and two sites that proceeded under Superfund alternatives where responsible parties conducted agreed cleanups. She noted that most local Superfund sites stem from historical unlined landfills or waste ponds and that the last county Superfund listing occurred in 2010.

Commissioners asked about public exposure and redevelopment. Amram said public exposure is limited where properties are served by public water and sewer; the water-management district controls new well permitting, which prevents new potable wells from being permitted where groundwater is restricted. Commissioners asked about long-term persistence of pesticides in groundwater and about how redevelopment and brownfields incentives differ from Superfund processes. Amram said brownfields programs focus on redevelopment-time cleanups and incentives, while Superfund sites are nationally prioritized—she noted recent legislative changes under review could affect brownfields eligibility.

The EPC voted 6-0 to receive the Superfund briefing. Commissioners emphasized the county’s prior cleanup actions (excavation, slurry wall and monitoring) and asked staff to keep the commission informed as delineation work for 1,4-dioxane proceeds.