Biology Reference
In-Depth Information
extended three miles into the bay. Keller had that pipeline flushed and
plugged with concrete. On the landward side, he had thousands of feet of
leaky fuel line removed, as well as lots of surrounding soil. Keller believes
he got lucky because the base was built atop some very fine silt and clay
soils. “The soils were extremely tight. Water could not move through them
at all, so we had no contaminant plumes,” says Keller. “Even in a firefight-
ing training area, where soldiers basically poured fuel on trash and set it
on fire, we only had to go 7 feet down and 10 feet beyond the concrete pad
in each direction to get all the contaminants. In 40 different wells we sam-
pled on the base, there was no contamination.”
Once the base was clean enough, the restoration engineers moved in.
Initially, one of their most critical tasks was to build a rather unusual pipe-
line from the shoreline out to a spot five miles into the bay where it was
deep enough for tugs and barges to maneuver. Without the pipe, engi-
neers could not import the key ingredient in their design: dredged sed-
iment. But with the help of the pipeline, 10 million cubic yards of sedi-
ment—offloaded from barges out in the bay and mixed with water into a
slurry—could be pumped through the pipeline and onto subsided areas.
In some places, land levels were more than eight feet below sea level. Even
better, the project was putting sediments that harbors and marinas wanted
removed from their channels and berths to good use elsewhere in the
bay—fulfilling a regional “beneficial reuse” goal.
To lay the section of pipeline crossing the soft wetland surface, work-
ers made a temporary road for their heavy equipment out of huge
wooden timbers and rafted-up rubber mats. As Polson remembers, “We
built that over Christmas during bad weather with tides so high our mats
were floating. It was pretty dicey.” Once built, however, the pipe allowed
crews to work year-round in the marsh, instead of pausing between Feb-
ruary and August, when Clapper Rails and Salt Marsh Harvest Mice
might be raising young. The pipe is much less disruptive than alternative
methods of moving sediment: haulers, backhoes, and other noisy, smelly
machinery.
On the site itself, the pipe snakes in and out of various giant pits. Work-
ers can move the slurry spray around as they prepare each unit. One day,
the units will be a mix of seasonal wetlands, wildlife corridors, tidal wet-
lands, tidal pannes, and ponds. “We're setting a template for a functional
wetland, so species can move back in and propagate,” says Polson. “We're
trying to give them the right set of conditions—elevation, sediment, sub-
strate, water, hydrology—to get things going in the right direction. You
look at natural analogs and do your best to copy them.”
By 2050, visitors should be able to see a pretty good copy of the 2,500
acres of wetlands that historically covered the Hamilton shore.