Site Remediation: Dry Cleaning Legacy, Nova Scotia

Jacques Whitford Environment

Keeping our clothes smart and fresh comes at a cost to the environment. Dry cleaning involves chlorinated solvents which sometimes used to leak and contaminate soil and groundwater in older establishments. Today there is much more environmental awareness and dry cleaners have advanced with closed loop operations and better staff training.

Jacques Whitford Environment was called in to clean up the soil and groundwater contamination under a dry cleaning store in a shopping mall in Dartmouth, Nova Scotia. The owners wanted complete remediation done in a short period, and at the same time they wanted the mall to stay open to customers. The contamination identified during an environmental site assessment included perchloroethylene (PCE) and daughter products produced by biodegradation over 15 years, such as trichloroethylene (TCE), cis-1,2 dichloroethylene and vinyl chloride.

A multi-disciplinary team of engineers, geoscientists and contractors conducted the remediation by first removing the contaminated soil from an area 30 m x 30 m under the mall’s concrete floor slab. The excavation was 7 metres deep and required sheet piling, bracing supports and dewatering.

For the in-situ remediation of the groundwater, potassium permanganate in aqueous solution (3%) was added to oxidize the contaminants. Over 200,000 litres of the solution (KMnO4) was gravity fed into approximately 100 shallow screened injection wells inside the mall.

Before returning the area back into tenant spaces, the team installed a sub-slab vapour extraction system, as well as provisions for remote access ground water monitoring and future injection well applications.

Monitoring for a year after completion in October 2000 has shown that the dissolved total chlorinated solvents have been reduced by over 95%. The project’s capital cost was $3 million.–BPCCE

Prime consultant: Jacques Whitford Environment (JWEL) (Gordon G. Check, P.Geo.)

Contractor: PCL Constructors Canada