Tar ponds cleanup plan undergoes
some minor revisions
By Nancy King
Cape Breton Post
Wed., Nov. 28, 2007
SYDNEY - A component of the Sydney
tar ponds cleanup plan is undergoing a
significant design change, with the decision
to abandon construction of a steel
channel through the site.
The Sydney Tar Ponds Agency is now
reviewing a recommendation by design
engineer Earth Tech/CBCL to pump
water flowing from two brooks around
the tar ponds to isolate the area during
solidification and stabilization work
while constructing the channels in the
hardened cement mixture. It is now considering
the design recommendations
and will soon decide how the project
will proceed.
The initial design called for using
steel sheet piling to construct the channel
to build a new brook alignment, with
water from the two brooks that pass
through the ponds, the Wash Brook and
the Coke Ovens Brook, flowing through
it. The channel, which was expected to
take about 18 months to complete,
would manage water flow during the
solidification and stabilization of the tar
ponds and allow brook water to move
freely to the harbour, and prevent flooding
of surrounding communities.
Last winter, a drill rig collected core
samples from both the north and south
tar ponds to ensure officials knew such
things as the height of the bedrock
and the soil conditions.
"When that information came back,
it was more detailed information than
what we had before," noted Frank Potter,
CEO of the Sydney Tar Ponds Agency.
"There were two issues that came up,
one was that the bedrock was higher
than we had seen in other bore holes
that were randomly picked in the ponds
and there was more of a sandy material
down there than initially thought."
As a result, the design consultant had
to change the style of the steel sheet piling
to be used in the channel, to a more
expensive material. But as they proceeded
with the design work and determined
the length and depth of material needed,
it was discovered it would add significantly
to the cost, placing it over budget,
Potter said.
Instead, the consultant re-evaluated
alternative options and recommended
blocking off the two brooks and pumping
water around the ponds while the
solidification and stabilization proceeds.
"The original approach would have
had us spend 18 months building the
brooks and then let the water flow
through for the remaining six or so
years," Potter said. "This way what we’ll
do is simply just block it off and pump it.
We don’t have to pump the whole
amount all the time but we’ll pump it as
we work in certain areas."
The change won’t have any impact on
the overall timeline for the cleanup project,
although the short term schedule
will change because the pump around
solution is actually quicker, he noted.
Depending on weather conditions and
other factors, solidification could begin
next year, a bit ahead of schedule, Potter
said.
"We’re still dealing with the water,
still moving it around, but instead of
flowing the water through a newly constructed
channel we’re going to physically
pump it around the portions of the
site that we’re working in," he said
As for whether the situation should
have been foreseen, Potter said these
sorts of projects begin with a concept
and a limited amount of information
and then go on to the detailed design
stage to ensure they don’t encounter any
surprises later on that would force them
to change course midstream.
There have been some other small
changes to other components of the
cleanup effort as more detailed information
was obtained, Potter added, such as
deciding to construct a larger building
than originally envisioned on Ferry
Street to wash trucks and clean debris
coming out of the tar ponds.
nking@cbpost.com
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