We’ve been asking for weeks for an explanation of the claim that it would be cheaper to start building rail and then tear down any work as opposed to waiting until after clearing key hurdles like the lawsuit, the mayoral election and the federal funding guarantee to start construction.

Today, HART sent an answer to the Honolulu City Council, and I got my hands on a copy.

In it, new HART chief Dan Grabauskas says it would cost only $5 million to tear down $114 million worth of work between now and Jan. 31, 2013. By contrast, waiting until that date to start construction would add $22 million in delay claims, $109 million in escalated materials costs and $68 million in staff costs because of the late end of construction, according to Grabauskas.

Together, that’s a difference of $194 million, which HART says makes starting construction now financially prudent. Here’s the full letter:

HART Cost To Tear Down