Citing continued growth in both flights and airlines, Denver International Airport is upping by 50% a previously announced gate-expansion project. The airport now plans to add 39 gates across all three of its concourses by 2021. At a cost of $1.5 billion, the improvements would increase the airport’s total gate count to more than 145.

Originally announced in August as a 26-gate expansion, the bond-funded project calls for extending the ends of existing concourses to accommodate the new gates. A similar approach was used to facilitate a $46-million, five-gate expansion at the west end of Concourse C, completed in 2014.

Project design and construction firms already have been selected, pending approval by Denver’s city council and mayor. HNTB won a $65-million contract to design additional gates for the west ends of Concourses A and B, which will be built by a joint venture of Turner and Flatiron under a $700-million construction management-at-risk (CMR) agreement.

Jacobs was awarded a separate, $65-million design contract for projects at the east ends of Concourses B and C, with a Holder-FCI joint venture performing CMR services for $655 million.

All four contracts are for five years, with provisions for extensions if the scope of work should change.

WSP USA is providing program management services for the expansions under a $45-million contract awarded earlier this year. No changes to that deal will be made for the additional gates.

Construction would begin in 2018, with all gates scheduled to become operational by 2021. The project would be performed concurrently with a four-year, $650-million terminal makeover, being performed as a part of a $1.8-billion public-private partnership with a group led by Ferrovial Airports of Spain.

According to an airport spokesman, Denver International Airport expects its 2017 passenger volume to exceed 60 million, 20% above its design capacity. The original expectation that the majority of the airport’s flights would be connections has changed; origination-destination passengers now account for about 60% of DIA's traffic. The airport currently handles nearly 1,550 daily flights with 25 airlines.