I agree that jack shields have been used successfully in the past and will be used successfully in the future. Their use here was a complete failure though, so unless the contractor was totally incompetent in the use of the technology (which I am not privvy about, but kind of doubt as it would have been bid out to a different more competent contractor by now), the failure speaks about whether the technology was appropriate for this specific tunnel or not. And the reality is that it was not appropriate for this tunnel. While I understand why LIRR was reluctant to have both tracks out at the same time, with proper planning this could have been built cut and cover over a week and have both tracks back on with slow speed restrictions while the concrete cures completely. I am guessing that now the plan is to take both tracks out only after ESA opens, so that the reduction in capacity to Penn is less of a problem, but I still do not see why this could not be done with a short closure.jlr3266 wrote:Jack shields have been used successfully all over. The problem was not the technology. LIRR also insisted that both mainline tracks could not come out together for bridging the area to allow cut and cover construction. The shield was the only remaining feasible option.
In general, the MTA has become too concerned with complaints, both from the riding public and the politicos, to the point where necessary projects get way over budget in order to "minimize inconvenience" or get delayed again and again while looking for a "better" solution which might not even exist.