Cleaning of Mercury Contamination in Gabraith Street
in Squamish, B.C. Canada
8 March 2004
Presented by Lindsey Dunn
Saleh Salim
Introduction
Canadian Occidental Petroleum Ltd. (COPL) operated chlor-alkali plant from 1965-1991
Property owned by BC Rail and BCR Properties Ltd., plant owned by FMC of Canada Ltd.
Location
The plant is located on Gabraith Street in Squamish British Columbia, Canada.
45 acres just south of downtown Squamish
The property is enclosed by the Howe (South), Cattermole Creek (West), and Mamquam Blind Channel (East)
The soil on site is a dredged sediment over formal tidal floats and saltwater marches
Chlor-Alkali Processes
Caustic soda and chlorine are produced by the electrolysis of an aqueous solution of sodium chloride (brine)
Approximately 4.2% of mercury released in atmosphere from chlor-alkali
Due to environmental concerns, mercury processes since abandoned and ion-exchange membrane technology used
Source of Mercury Contamination
Plant discharged and spilled mercury into the land, water, and air as a result of plant processes.
“Old Lagoon” was named as it was a main discharge area for discharge sludge from wastewater treatment diluted with saltwater
From 1965-1974 (pre-environmental standards) plant discharged 2-31 kg/day or 1000-10,000 kg/year of mercury into the environment
1974-1991: 1 kg/day or 370 kg/year discharged
Resulting Contamination
On site: the soil contained 65,635 m3 of waste with Hg levels > 2ppm, 22,905 m3 of special waste (Hg >100 ppm), ground water found to have unacceptable Hg levels (>2ppm)
– “Old Lagoon” held 36,000 m3 of Hg contaminated sludge, half of which could be considered “special waste”, ground water held dissolved mercury at levels 100x standards)
– Surface vegetation found to have elevated levels of mercury Off site: High levels of Hg found in sedimentation of water ways
Channel, Creek Highest levels found in Mamaquam Blind Channel at SW corner of
property near dock Howe Sound lake bottom organisms, aquatic vegetation, and general
aquatic life (fish, birds, crabs, ect) found to have mercury traces
Risks associated with Mercury
Mercury causes adverse effects to the human and environmental health
Mercury changes to methylmercury by a chemical reaction in organic environments
Methymercury then has the ability to bio-accumulate within a food chain where by humans are at the greatest risk as the rate in which mercury is removed from the body cannot match the rate in which it is ingested.
Problems due to Contamination
Canadian Occidental petroleum Ltd(COPL) forced to change name to Nexen
Nexen paid Millions Site left unused Over 1700 rails cars of contaminated
soil shipped to landfill
Environmental Impacts
Kills Aquatic life Destroys vegetation Make land unusable Effects can be seen
in generations to come
Alternative Remediation Technique
Precipitate Flotation method Causes heavy metals to precipitate with
iron elements in soil Completely leaves site pollutant free Compact device allowing onsite
cleaning up Separates contaminates from soil, thus
allowing soil to be buried back onsite
Remediation Efforts
COPL and BC Rail agreed to complete voluntary clean-up but never completed work
Mandatory remediation was then required to a depth of 3 m
Difficulties included the hydrostatigraphy, tidal influences, presence of surface impoundments in the form of effluent and peroxide ponds, hydroecolgocial complexity
Cost equal to $45 million Carried out by Nexen Inc. (formally COPL)
Remediation Techniques
Ground water recovery and treatment
Contaminated soil and sludge excavation and stabilization
Soil Washing
Techniques Considered
Electrochemical Remediation Technologies (ECRTs)– Strong electrical current sent through ground to
remove metals and mercury– Limited because not economical for large areas
– Location concerns: If mercury were to be mobilized it could send a large amount of concentrated mercury directly into aquatic environment surrounding site
New Mercury Capturing Technique Presented by Noram Engineering and
Constructors Ltd at 2002 Remediation Technologies Symposium
Uses lignin derivatives and a flocculating agent to remove and stabilize metal contaminants from contaminated water
Uses a lignin-ferric absorbent material to capture and immobilize metals in soil
Groundwater Remediation
Technique similar to wastewater treatment of suspended soils
Lignin dissolved in captured groundwater so that it bonds to free mercury
Coagulate to form colloidal lignin-mercury particles Ferric chloride added to flocculate the mix and
cause mercury to fall out of suspension Result is groundwater with Hg < 1g/l and a non-
leaching mercury sludge
Soil Remediation
Soil mixed with a solid ferric-lignin adsorbent
Absorbent captures mercury in order to stabilize and immobilize
Contaminated soil extracted and disposed