Civil Engineering Reference
In-Depth Information
What remains to be said is that the process leaves some unanswered
questions. As a big technological artifact in the environment, a bridge is,
after all, relatively benign. It is a concrete or steel structure that in itself
(leaving aside the traffic on it) usually does not pollute. How do we judge
whether its extent of environmental impact, say two acres of disrupted wet-
land, added stormwater spilling from the bridge into the harbor, and a rare
woodcock or two killed by a truck, is worth so much bother? Would it be
better to disregard these arguably minor impacts, build the project quickly,
and put the saved funds toward mitigating more severe environmental harms
in other locations?
At the project site, how do we weight the relative harms from wetlands
disruption, stormwater discharge, bird deaths, and release of toxic buried
sediments? How much worse is it to harm a pair of blue-winged teal than
to lose an acre of wetland, or let road dust and grime (washed off with rain
and snow) cause water turbidity? And how much should be spent to mitigate
one impact compared to the others?
These are questions to which the EIS analyses cannot provide a tech-
nical answer. Or at least there is no methodology that can provide diverse
stakeholders, having different interests, an answer they would readily con-
sider scientifically reliable. After all, bird impact studies, stormwater studies,
aquatic wildlife studies, and wetlands habitat studies are done by different
kinds of scientists. Relative harms, and reductions in harm, seem incom-
mensurable—we do not reliably know how to compare them according to
one measurable value standard.
Even without providing answers to these tough questions, the EIS
does an important job for citizens of Great Lake City. It reveals the envi-
ronmental issues that require public debate. It provides clarity on the subset
of problems for which scientific answers are available. And if properly done,
it also exposes the residual subset for which scientific analysis cannot, at
reasonable cost or in reasonable time, tell citizens how to decide.
These questions will have to be resolved by precedents from bridge
projects in other localities, by negotiations and parrying among stakeholders,
by lawsuits initiated by those who think they can get a better outcome in
court, and ultimately by political decisions. What is clear is that it is best
to have citizens who are informed about infrastructure and knowledgeable
about the stakes involved.
WHAT IS A SUSTAINABLE BRIDGE?
As worries about sustainability have swept the design professions, one of
the sustained debates has been about the definition of sustainability. We do
in the rest of this chapter get to our ideal of a sustainable bridge, but we
