PORTSMOUTH, N.H. — A construction company says it will challenge violations and nearly $330,000 in fines proposed by the Occupational Safety and Health Administration over possible mercury exposure at Eversource’s Schiller Station in Portsmouth, New Hampshire.

Connecticut-based Manafort Brothers, Inc., began mercury and asbestos abatement and demolition at the power plant last year.

OSHA said Friday it found Manafort wasn’t taking steps to reduce mercury exposure and protect workers. It cited Manafort for eight violations concerning mercury, respirators, protective clothing and sanitary conditions.

Manafort said it stopped work at Schiller in June over concern about possible mercury exposure so that it could assess the situation, along with experts and consultants. It cooperated with OSHA in its investigation. Manafort restarted work in September, following a review of work procedures and employee practices; it felt its employees were protected.