The 28th/24th Avenue South improvement project extends from South 188th Street to South 204th Street in the city of SeaTac. It was designed to reduce traffic on Highway 99 near Sea-Tac Airport.

The project involved rebuilding the existing two-lane road into a four-lane arterial, including turn lanes and new signalized intersections. That required placement of about 33,000 square yards of 8-inch-thick concrete pavement using fixed forms and a Gomaco GP2000 slipform paving machine.

The median was finished off with extensive landscaping and mortar-set river rocks to give it a unique look.

Related work involved relocating existing overhead utility lines underground along with new water, sanitary sewer, storm drainage and gas lines. Also, three cast-in-place underground detention vaults were installed.

The city of SeaTac bid the project with two pavement alternates — one with concrete and one with asphalt. Gary Merlino Construction was the low bidder on both alternates, with its asphalt bid $203,755 lower than its concrete bid. The city decided to go with concrete after doing a life-cycle cost analysis.