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The Tybee High
It's not about margaritas anymore
Will harbor deepening punch
a hole in the aquifer's most vulnerable point off the shores of Tybee
Island?
by: Lynn Hamilton and Joel Worth
"To dig
or not to dig," Armstrong professor Chris Schuberth writes on the board when he
first meets his Introduction to Geology students.
He's talking
about the Georgia Ports Authority's (GPA's) proposal to deepen the Savannah
harbor. GPA wants to deepen the harbor to provide for bigger ships. The
Authority claims a deeper harbor will boost area economy and provide jobs.
But some citizens, including a number of scientists, are
concerned about the possible impact on the floridan aquifer from which
Savannah-area residents draw their fresh water. Schuberth says it's a question
of whether deepening will cause salt water intrusion into the aquifer's natural
fresh water reserve.
These days, Schuberth is talking about the
"Tybee high." No, it's not that pleasant sensation one gets from sitting at a
beach bar, drinking margaritas. The Tybee high is a geological formation within
the aquifer, a point where the aquifer buckles and comes close to the earth's
surface. The Tybee high isn't visible to the naked or even sub-aquatic eye. It's
underneath the Savannah River off Tybee.
"The Tybee high would
be there for the GPA deepening proposal to slice into it and possibly,
we don't know for sure perforate the upper protective sedimentary layer, called
the aquitard that prevents salt water from the river entering the fresh water of
the aquifer," says Schuberth. "Something like punching a hole in the ceiling of
the tunnel under the English Channel and seawater thereby pouring
in."
Schuberth, a board-certified geologist describes it this way:
"The Tybee High is simply a structural feature, a slight upward flexing of the
sedimentary strata that brings deeper layers closer to the surface and localized
where it is located. If you hold a copy of your Tybee News in both of your
hands, and gently push each side of the newspaper together, it would either
'bend' downward or else 'bend' upward. In the case of the Tybee high the bend is
upward." The official geological term for this is "anticline."
The Tybee high is not a new discovery. It was first noticed in the initial US
Army Corps of Engineers study, relevant to harbor deepening feasibility, in
1996. The Corps concluded that there was no danger to the aquifer, even given
its closeness to the earth's surface at the Tybee high point.
Schuberth says, "Some of us, myself included, years ago, made reference to the
Tybee high at Stakeholder Evaluation Group (SEG) meetings." Problem is,
Schuberth says, the SEG has no real power.
"If I come forward
with an objection, they take it under advisement," says the geologist who
describes the SEG as "emasculated." SEG, he says, has "no kill switch
authority," i.e. it has no absolute power to veto the project. As a consequence,
"the only voices the ports are listening to are federal and state agencies the
Environmental Protection Division, Department of Natural Resources, and the
United States Fish and Wildlife Service," he says. "They are the juggernaut.
We're the minions."
Schuberth says the Tybee high didn't get any
real attention until plans emerged for another port on the South Carolina side
of the Savannah River about ten miles downstream from the Savannah port.
"That port would be essentially constructed over the Tybee
high," says Schuberth. "So the Tybee high suddenly gained 'sunlight.'" he says.
Hope Moorer who works for GPA says a recent study has raised
questions about "fractures in the confining layer" of the aquifer, the confining
layer being what keeps it separate from the river. There have also been
questions raised about "any potential effects that deepening might have in
conjunction with these fractures," Moorer says.
She adds that a
lot of the studies being conducted relevant to the harbor deepening project will
be completed soon. If studies show that deepening poses a danger to the aquifer,
the GPA will, indeed, not dig, she says.
"We live here and
depend on that aquifer as well. If the aquifer, if our source of drinking water
is going to be damaged, that's not something we would be able to go forward with
here," says Moorer.
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