If they are getting federal money for this project (a good bet), then they need to get necessary environmental permits. That includes either avoiding "Section 4(f)" resources (historic properties, parklands, archaeological sites, etc.) or proving to the government's satisfaction (in this case, probably the FTA) that there's no feasible alternative.

It could be that it's either impossible to avoid hitting the headhouse, or that they could do it but it would be unreasonable because the alternatives are not as good at meeting the needs of the project, or if it would impose dramatically higher costs to the project.

If this is being funded entirely by their own revenue stream or by state funds, the rules are somewhat looser.

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Boom, boom, acka-lacka-lacka boom.
Boom, boom, acka-lacka boom boom.