Mount Holly hears plan after phenols found at former treatment plant; monitoring and remedial testing to proceed

Engineers from HDR told Mount Holly City Council on March 23 that phenolic compounds were detected in sediment and groundwater at the former wastewater treatment plant site, and they described a planned assessment and remediation pathway required by the North Carolina Department of Environmental Quality (NCDEQ).

Barry Sharon of HDR said the base contract for decommissioning the plant was awarded last summer and totals about $10 million; the council previously voted to convert the site into a park extension and the city is working to finish grading and other work under a roughly $15 million grant. Sharon said the project team expects to spend roughly $13 million of the grant to date and is coordinating with the grant administrator on which additional site work (including parking and stormwater modifications) the grant will cover.

HDR senior geologist Mark Fardy described the environmental findings and next steps. City staff collected basin sediment samples in October 2025 that returned phenol compounds above NCDEQ allowable (2L) limits; subsequent temporary groundwater monitoring wells also showed phenols above those limits. In response, HDR and the city submitted a limited environmental assessment and then a groundwater assessment work plan; field mobilization has begun to implement that plan.

Fardy said the work plan calls for installing seven permanent monitoring wells (BG1, BG2, and MW1–MW5), three soil borings in the former basins and four surface‑water samples in the Kataba River. Soil removed from basin borings will be sent to a treatability lab to evaluate which active amendments work on site‑specific soils. "Based on that report and the data contained in that report, NCDEQ requested that the city submit a groundwater assessment work plan which we did," Fardy told council.

HDR anticipates active remediation may involve one or two injection events of biological amendments to stimulate microbes that break down phenols in groundwater. The consultants said remediation will likely be paired with institutional controls such as a groundwater‑use restriction (prohibiting potable or irrigation wells on the site) and that four seasons of sampling will be needed to characterize seasonal variability — a process that means the restriction and cleanup timeline will likely exceed a year.

Council discussed logistics: monitoring wells will be sited and installed to minimize interference with future park uses (most will be flush with the ground; some may have short protective posts where necessary). Staff also said grant timing matters; the city extended its grant deadline to June 30, 2026 and is pursuing further extension with the state legislature while working to maximize work that can be paid from the grant.

Fardy and Sharon emphasized that, based on concentrations reported so far, the compounds exceed groundwater standards but are not at levels that pose immediate direct exposure risk for normal park use: "As long as the kids aren't digging to six feet to interact with the water, it's safe," Fardy said when asked about potential risks to children.

Next steps are fieldwork for about a week of sampling, lab analysis, treatability testing on basin soils and then design and implementation of any approved remedial injections and long‑term monitoring required by NCDEQ. The council did not take a vote on remediation actions at the meeting; staff and consultants will return with additional results and recommendations.