The discount on light rail tunneling continues. Sound Transit said Wednesday that the contractor that lost out on the longer and much more lucrative University of Washington-to-Capitol Hill route presented a proposal to dig the light rail tunnels from Capitol Hill to downtown that will cost 12% less than the agency expected to pay.

According to the Sound Transit announcement, JCM U-Link Joint Venture sent in a bid of $153.6 million to do the job — 12%, or $20.7 million, below the Sound Transit engineer’s estimate of $174.3 million. JCM U-Link lost out on the bidding for the UW-Cap Hill route when contractor Traylor Frontier-Kemper presented a plan to build the tunnels that will pass underneath the Montlake cut and up Capitol Hill for $309 million back in March. That bid came in 22% below ST engineer estimates.

So, what’s with all these, um, bargains? Seattle Transit Blog says ST may never see the savings:

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There’s no way for Sound Transit to know what’s going to happen to these costs – if there were, they’d be the most effective commodities traders in the world! But this goes both ways. At the beginning of Sound Move, for instance, most materials and real estate were much less expensive than they are now – but during the late 90s and early 2000s, construction cost inflation was far higher than the consumer price index, the number we normally associate with inflation. Today’s estimates were largely made at the peak of the real estate boom, but as the markets have been rebounding, future contracts may not see double digit percentage savings.

Meanwhile, neither of the lowest bidding contractors worked on the troublesome Beacon Hill tunneling which ran into those pesky sandy voids. The Beacon Hill contractor was Obayashi Corporation. Maybe they can pass on some advice to the new guys.

Photograph: cdine from the CHS flickr pool