2. depends on how competently the pipeline is operated. And the likely answer to that is "not very".
Transcanada does not exactly have a stellar record. Their Keystone phase 1 pipeline sprung 14 leaks in its first two years of operation. Across their network, they average better than 70 spills per year.
I wouldn't trust these guys to operate a garden hose, much less a pipeline carrying dibit over a major aquifer.