The 1958 bridge carrying Alameda Avenue over I-25 doesn't have room underneath for additional lanes, and is subject to flooding during storms. CDOT photo.

CDOT will be opening bids next month for a new Alameda Avenue bridge over the freeway, opening up room under the bridge for additional through lanes and rebuilding the drainage system to prevent the flash-flooding problem there.

The total project cost is expected to be $37.4 million, with $36 million of it coming from federal stimulus funds under the American Reinvestment and Recovery Act.

The project will replace the bridge, an original Valley Highway span dating from the 1958 full opening of the city’s first freeway. It will be large enough to allow eight through lanes plus auxiliary lanes to pass underneath on I-25, eventually eliminating the 1,000-foot choke point between Alameda and Santa Fe Drive where lane-drops at the exits force rush-hour backups. That final expansion, estimated several years ago at $84 million, will have to wait for funding of a reconstruction of the Santa Fe interchange.

But the new Alameda bridge is the first piece to be put in place. Getting stimulus funding for it allows it to be done now.

While the immediate benefits won’t include extra lanes, drivers will benefit from the elimination of the flooding problem.

The project will include reconstruction of the cofferdam and pump house that have been inadequate to handle stormwater runoff that collects in the low point of the underpass. Almost from the time the Valley highway opened, whenever there was heavy rain, water collected at Alameda and the nearby Logan Street underpasses.

The T-REX project eliminated the problem at Logan.

Finally, the contract will pave I-25 in concrete through the underpass.

Diagram from the Valley Highway Environmental Impact Study highlights the deficiencies around the Alameda bridge.

This work is part of the larger Valley Highway Project, which I’ve nicknamed Son of T-REX. When completed – and there is no date yet because complete funding hasn’t been identified – I-25 will be eight lanes wide through here and traffic should flow a lot better.

A number of drivers have been critical that T-REX stopped at Logan Street and didn’t go farther north to eliminate the choke point between Santa Fe Drive and Alameda.

There’s an easy explanation for that.

Lack of money.

T-REX could only be funded as far north as Logan because going any farther meant tearing down and replacing the old rickety I-25 bridges over Broadway and the railroads west of there. CDOT didn’t have enough money for that when T-REX kicked off.

But thanks to aggressive work by CDOT and the Colorado congressional delegation, the state was able to obtain surplus federal funds and earmarked transportation money so that, in a separate project while T-RX was underway, CDOT was also able to replace those Broadway bridges.

It then kicked off the Valley Highway Project environmental study, aimed at getting clearance for expansion and upgrades from Broadway to Sixth Avenue, the west on Sixth to Federal Boulevard.

The total project includes not only this new Alameda bridge, but when future funding is available:

• A new Alameda interchange that will replace the substandard northbound entrances with a dramatic flyover ramp from the west side of the highway at Alameda.
• A complete reconstruction of the Santa Fe interchange to eliminate the unsafe and substandard left-lane entrance ramps.
• Widening I-25 from Alameda to Sixth Avenue.
• Reconstructing the Sixth Avenue Freeway between Federal and I-25.
• Closing the Bryant Street interchange on Sixth Avenue.
• Reconfiguring the Federal interchange with Sixth.
• Replacing the Sixth Avenue bridge over the South Platte River.
• Reconfiguring the Broadway interchange on I-25.
• Grade-separating the mainline railroad tracks from Santa Fe and Kalamath Street.

CDOT diagram shows the planned configuration for the reconstructed Alameda Interchange -- a single-point access on the west side of the highway from Alameda for northbound entrances, to replace substandard short ramps on the east side.