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Projects
Project Name: Remediation
of French Cable Wharf Site
Project Location: Dartmouth,
Nova Scotia – (CFB Halifax)
Owner’s Name: Department
of National Defence
Project Description:
The Canadian
Federal Government committed to the remediation
of contaminated sites with funding identified
in the 2003 and 2004 Federal budgets. The objective
of the increased funding was to reduce environmental
liability through accelerated clean-up of contaminated
sites. French Cable Wharf is a Department of National
Defence (DND) property that was identified as
having the potential to reduce environmental liability
to the Federal government through remediation.
French Cable Wharf is located on the Dartmouth
waterfront in the area of Halifax Harbour referred
to as the Narrows. This area has been inhabited
and industrialized for over 100 years resulting
in historical contamination of the site. During
operational years, French Cable Wharf was the
site of a coal fired heating plant and underground
fuel line for refueling ships. Assessment of contamination
at the site identified polycyclic aromatic hydrocarbon
and metals likely originating from coal ash. Limited
petroleum hydrocarbon contamination was also identified,
likely related to the former underground fueling
lines.
Remediation
at the French Cable Wharf site location posed
several challenges to the project:
- limited space for equipment operation and
staging
- adjacent to a salt water marine environment
- tidal zone excavation
- CN rail track crossing
- tight completion schedule (3 weeks from award)
- weather (late March – Snow/Rain)
- existing wharf infrastructure
- breakwater reconstruction
Dexter Construction
was required to excavate and dispose of approximately
1800 cubic metres of soil, rock and debris. The
excavated material consisted of over 2100 tonne
of polycyclic aromatic hydrocarbon (PAH) and heavy
metals contaminated soil, approximately 400 cubic
metres of oversize rock and over 150 tonne of
debris (steel cables and creosote timbers) from
the vicinity of the French Cable Wharf (FCW) site
in Dartmouth.
The excavated material was screened on site to
remove oversize rock and debris. The oversized
material was screened until the material was free
of contaminated soil, and then reinstated in the
excavation as backfill. The undersize (100 mm
minus) contaminated material was then transported
to an off-site, temporary stockpiling area for
sampling and testing. The temporary stockpiles
required polyethylene liners, covers and netting
to prevent erosion and lose of soil from the stockpiles
prior to disposal. Based on the results of the
Consultant (CBCL Ltd) testing the final disposal
/ treatment options were confirmed. The site,
once excavated was to be reinstated with clean
surge rock and a gravel surface to form a suitable
storage or parking area for future use.
The site excavation
was completed to a depth of approximately 3 metres
(low water – tidal limit) with environmental
considerations for potential siltation into the
marine environment. An environmental contingency
plan was established for the site, including provision
of a silt curtain if necessary.
Dexter Construction, working in conjunction with
Envirosoil Limited was able to provide an economical
treatment and disposal solution for all the soil
and debris at the site. All the soil was impacted
with PAH therefore all the screened soil was transported
to the Envirosoil facility in Bedford for treatment
via Low Temperature Thermal Desorption. As the
representative sampling and testing of the screened
stockpiled soil revealed, the metals concentrations
and leachability within the soil were suitable
for disposal at a local landfill facility once
the soil has been treated for organic contaminates
(PAHs), thus a complete solution was available.
In summation of the project, Dexter Construction
and Envirosoil were able to complete the project
on schedule and within budget and provide a complete
solution to the entire project resulting in a
successful remediation to the satisfaction of
DND.
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