A couple days ago the FERC issued a notice that the final Environmental Impact Statement for the Atlantic Coast Pipeline would be finished on June 30, 2017.  After the EIS is available, there is a 90 day decision deadline, basically an opportunity for other federal agencies to weigh in on the EIS.  So on September 28, 2017, the EIS is expected to be approved.

The ACP will not be able to begin construction before that date.  When, exactly, it will begin construction is unknown.  Dominion had previously hoped to begin construction in the summer of 2017, but unless you consider the end of September to be the summer that looks pretty unlikely.