The Slog got the pictures but here are the details on a most telling set of signs that have suddenly appeared in the lot that will someday be the home of Capitol Hill’s light rail station.
Come January, the laser art installation will be removed, the lot will begin to be filled with equipment and, as the signs note, Denny Way between 10th and Broadway will be closed until 2016.
Here is the long-term Sound Transit schedule from some of their community forum meeting materials.
JCM U-Link Joint Venture won the contract to handle digging the $150 million tunnel from Capitol Hill to downtown. Ladies and gentlemen, we are about to enter Phase 2: Excavation and Tunneling.
JCM U-Link Joint Venture won the contract to handle digging the $150 million tunnel from Capitol Hill to downtown. Here’s how Sound Transit describes the work planned for the three-year period:
Denny Way Closure
A portion of Denny Way between Broadway and 10th Ave. will be closed to traffic for approximately 6 years while the light rail station is under construction (see map ). The construction wall surrounding the work site will be extended across Denny, preventing public access to that portion of the street. A gate at either end of the road will allow construction vehicles into and out of the site.
One of the first tasks the contractor will undertake is to construct a portion of the walls that will surround the construction site for the next 6 years. The wooden walls are expected to be between 8 feet high facing Broadway and up to and 24 feet high facing 10th Ave. The final height of the wall is subject to further design work. Sound Transit will be working with the community and local artists to design graphics for the exterior surface of the walls.
During this phase the contractor will grade the site to make it level, and begin digging out the area for the station. The excavation for the station is approximately 400 feet long, 100 feet wide, and 60 feet deep. All of the excavated dirt (also known as spoils) will be hauled away in trucks. The trucks will travel along the haul route identified by the City of Seattle – leaving the site they will travel west on Olive Way to I-5 and coming to the site they will travel east up Denny Way. The final disposal site for excavated material will be determined by the contractor. The majority of the hauling during this phase will take place during the daytime and, at times, possibly extending into the evening. Once the excavation reaches the bottom of the station (approx. 60 feet down), a concrete slab 10 feet thick will be poured at the bottom of the excavation.
Tunnel Boring Machine
After the concrete slab is poured, the digging of the two tunnels to Pine Street will begin. A single tunnel boring machine (TBM) will be launched from the bottom of the station excavation. The TBM is scheduled to excavate an average of 40 feet of tunnel every day. As it bores through the ground, the TBM will also place the concrete rings that form the exterior surface of the tunnel. Dirt from the excavation travels through the machine and onto a conveyance system which brings it back out to the surface to be hauled away.
When the TBM reaches Pine Street, the TBM will be disassembled and transported back to the Station site, where it will be reassembled to dig the second tunnel between Capitol Hill and Pine Street. The tunneling is done in this direction because there is not sufficient room for all the equipment needed to extract the excavated dirt at Pine Street.
For safety, schedule and other reasons, the tunneling operations must continue around the clock. In order to minimize the traffic impact of the trucks hauling away dirt, most of the hauling is expected to be done in the evening and at night (7 pm to 7 am). Sound Transit has applied for a variance from the Major Project Permit in order to do the truck hauling at night (10 pm to 7 am).
So, some of the first work you’ll see in 2010 is the erection of the giant sound walls encircling the construction zone. The construction walls are designed to limit noise and dust from the station work site. The walls will be 8′ tall on the Broadway side, 16′ on the 10th Ave. Sound Transit says it is planning an art effort to make the walls more interesting and will also look into adding some kind of plexiglass view areas so you can peer in to see the work being done at the site. Here’s more on the walls and other early Phase 2 construction work from our coverage of a June Sound Transit meeting.
Not mentioned in the summary of Phase 2 from Sound Transit is a process we’re interested in involving the application of “cement, cement kiln dust, calcium chloride or other high pH materials” into the soil to improve the performance of the tunnel boring equipment. We’re kind of interested in this line we found buried in a Sound Transit specification for the work:
Do not use high pH soil stabilizers during periods of rain or if rain is forecast.
That should be interesting.
Sound Transit is also busy rewiring utilities in the area to patch cable and electrical service to nearby residences around the construction zone. They’ve also had to some clipping and clearing in the northwest corner of Cal Anderson park as that area will be part of the construction — though they’ve pledged to be extremely careful with the Chinese Scholar Tree rooted in the area.
Meanwhile, we also need to get more information on the noise variance application that Sound Transit has reportedly submitted to request permission from the city’s Department of Planning and Development for round-the-clock construction work at the site starting in 2011. No word yet on when the DPD will be scheduling the public meetings that are part of the approval process.
We also need to follow up with the Seattle Department of Transportation about pedestrian safety improvements in the works for the area as truck traffic to and from the construction site increases. Of course, SDOT’s been pretty busy up here lately so they might be behind on the crosswalk end of things.