LEROY TWP. – Approximately 4,700 gallons of acid was spilled Wednesday at a natural gas drilling pad near Towanda Creek in Bradford County.

Chief Oil and Gas, operator of the Yoder well site off Southside Road, said the release was discovered at approximately 1 p.m. Wednesday by workers at the site. Several dead fish were observed in a plunge pool within a tributary to Towanda Creek near the pad, the company said.

“There were a few dead minnows observed, localized in a small plunge pool, but there was no evidence of HCL and normal pH readings and live fish were noted further downstream in the tributary that leads to Towanda Creek,” the company said in a statement.

Hydrochloric acid is a highly corrosive mineral acid used in natural gas drilling to clear drilling mud and concrete from a well bore before hydraulic fracturing. Exposure in humans can cause irritation of the eyes, skin and mucous membranes, and in high concentrations laryngitis, bronchitis and pulmonary edema, according to the U.S. Occupational Safety and Health Administration. Extremely high concentrations can cause death.

Chief claims approximately 4,000 gallons of the spilled acid was contained by a plastic liner surrounding the well pad, and the majority of fluid that left the pad was captured by a sediment pond below.

About 50 gallons left the sediment pond but appeared to be contained within a small pool next to the pond, the company said in a statement.

“No evidence of any runoff into Towanda Creek. Chief and DEP will continue to take readings and monitor,” the company said.

The state Department of Environmental Protection and the Bradford County Emergency Management Agency were notified and response measures were implemented, the company added. Chief, DEP and the state Fish & Boat Commission are continuing to take readings at the site. Chief spokeswoman Kristi Gittins said clean-up of the spill was nearing completion Thursday evening.

DEP officials could not be reached for comment Thursday evening.

By Matt Hughes