Pile driving in the river is expected to start within the next day or two (it was supposed to start today, but the winds scuttled that, too). Engineers said it should be at least 18 months before there are any changes to the traffic flow on either side of the river.

The biggest changes in the configuration of the bridges will be the new ramps allowing for access from southbound I-295 to the bridges and from the bridges to northbound DC295, meaning that much of the neighborhood cut-through traffic and bad flow on Pennsylvania Avenue should be mitigated, though residents who oppose the expansion of the bridges' capacity--such as the Capitol Hill Restoration Society--differ with DDOT on the benefits of the project.

The third span--a "local street that happens to cross a river," in the words of DDOT's Bart Clark--will be built with streetcar tracks included in the two curb lanes, and will also include wide pedestrian/cycling paths, bulb-out bridge overlooks (where you can stop and look at the view without impeding the flow), and even osprey nest perches down by the water. This span, allowing local traffic to cross the river without having to mix with high-speed freeway traffic as it currently does, will reach street level at O Street on the west side of the river, which will also make for an easy connection to the Anacostia Riverwalk Trail. And all new bridges will be built with shoulders, to help lessen backups when there are accidents.

One additional change in all of this is that the Anacostia Community Boathouse operations, which are currently nestled between the existing spans, will be permanently moved northeast, to the Anacostia marina, and the old red brick buildings will be demolished. (A temporary structure is being built to get their operations moved by spring.)

For the next few months, pile driving and some off-roadway clearing and minor lane shifts on DC-295 will be the extent of the construction, but by late spring or early summer there will begin to be work underway on both O Street and M Street

I've added new graphics to my 11th Street Bridges page that show the plans for the new bridges. It will be an interesting project to watch over the next few years.

In addition, demolition work on the existing ramps to and from RFK has perked back up again, and there will be lane closures on the portion of the freeway that connects to Pennsylvania Avenue within the next few weeks. (If you saw the variable message sign at the Sixth Street SE exit that said "Freeway to be closed on or about 1/9/2010," it was a bit of a verbiage boo-boo that was meant to alert drivers to the coming lane closures, and is being fixed.)

There was a decent amount of press at the briefing (both Dr. Gridlock and Bob Marbourg were in the house, so you know it was serious), and I'll be updating this entry as stories come online, most of which will no doubt give more focus to the changes coming to the east side of the river than I have here (though I have posted some enlarged graphics that show both sides of the river). Here's the DDOT press release, fact sheet, and FAQ.

UPDATE: Links to Dr. Gridlock, WTOP, and City Paper. And WUSA. (I won't bother with pieces written right off the press release.)

UPDATE II: A bike-centric look at the plans from WashCycle.