by Sand Box John
ASCE report says tunnel feasible through Tyson on Dulles route
American Society of Civil Engineers press release.
American Society of Civil Engineers Tunnel Review Panel full report
Background
Tyson tunnel option review panel appointed press release
Washington Post
07 27 2006 Wolf, Davis Say Tunnel May Delay Dulles Rail
04 26 2006 Tunnel Back On Table for Dulles Rail
08 01 2006 Virginia to Review Rival Bid For Tysons Rail Extension
The diameter of the proposed tunnel bore using the earth pressure balance tunnel boring machine is 41' 7" (12.7m). The inside diameter is 37' 8" (11.48m). (See pages 16 and 17 in the Tunnel Review Panel full report.) That’s a single tunnel large enough for two tracks stacked on one side of the tunnel with 15' (4.57m) wide platforms next to them on both levels. What I find bazaar is they are proposing to bore the full 4.2 mile (6.75km) length of the tunnel at this diameter. That's a tunnel large enough for 4 tracks, 2 tracks on each level or a tunnel with 2 tracks and 2 platforms over it‘s full length! They only need roughly 3000' (914.4m) of this tunnel diameter in the four stations along the 22,176' (6,759.26m) length of the tunnel.
The sectional drawings of stations in the report bare no resemblance to any of the existing stations in subway on the WMATA metrorail system. Hell their smaller then the single track side platform train rooms at Wheaton and Forest Glen.
I do understand the objectives of the tunneling option and how this fits into Fairfax County’s land use plan in the Tyson area. What I have a problem with is the station designs completely disregards and throws out the classic WMATA barrel vault subway station design.
I still believe that the proposed change I submitted into record of the of Preliminary Engineering Design Refinements Environmental Assessment is a more cost affective solution.
My proposal was to make the Pike Seven station in the ditch of the median of Leesburg Pike elevated in the median at the same location as the station in subway as shown in the Final Environmental Impact Statement. Shorten the bored tunnel roughly 800' (243.8m) by moving the west tunnel portals from the median Leesburg Pike VA-7 at the east end of the Pike Seven station platform to the northeast corner of the Leesburg Pike VA-7 Chain Bridge Road VA-123 interchange and make the tunnel cut and cover.
This configuration would have eliminate one 3.00% grade, one 2.75% grade and replace another 2.75% grade with a 2.09% grade. It would also eliminate the need for an ejector pumping station in the tunnel.
The only problem with my proposed vertical alignment is it required the modification to half of the Leesburg Pike VA-7 Chain Bridge Road VA-123 interchange to accommodate the relocated west tunnel portals.
American Society of Civil Engineers press release.
American Society of Civil Engineers Tunnel Review Panel full report
Background
Tyson tunnel option review panel appointed press release
Washington Post
07 27 2006 Wolf, Davis Say Tunnel May Delay Dulles Rail
04 26 2006 Tunnel Back On Table for Dulles Rail
08 01 2006 Virginia to Review Rival Bid For Tysons Rail Extension
The diameter of the proposed tunnel bore using the earth pressure balance tunnel boring machine is 41' 7" (12.7m). The inside diameter is 37' 8" (11.48m). (See pages 16 and 17 in the Tunnel Review Panel full report.) That’s a single tunnel large enough for two tracks stacked on one side of the tunnel with 15' (4.57m) wide platforms next to them on both levels. What I find bazaar is they are proposing to bore the full 4.2 mile (6.75km) length of the tunnel at this diameter. That's a tunnel large enough for 4 tracks, 2 tracks on each level or a tunnel with 2 tracks and 2 platforms over it‘s full length! They only need roughly 3000' (914.4m) of this tunnel diameter in the four stations along the 22,176' (6,759.26m) length of the tunnel.
The sectional drawings of stations in the report bare no resemblance to any of the existing stations in subway on the WMATA metrorail system. Hell their smaller then the single track side platform train rooms at Wheaton and Forest Glen.
I do understand the objectives of the tunneling option and how this fits into Fairfax County’s land use plan in the Tyson area. What I have a problem with is the station designs completely disregards and throws out the classic WMATA barrel vault subway station design.
I still believe that the proposed change I submitted into record of the of Preliminary Engineering Design Refinements Environmental Assessment is a more cost affective solution.
My proposal was to make the Pike Seven station in the ditch of the median of Leesburg Pike elevated in the median at the same location as the station in subway as shown in the Final Environmental Impact Statement. Shorten the bored tunnel roughly 800' (243.8m) by moving the west tunnel portals from the median Leesburg Pike VA-7 at the east end of the Pike Seven station platform to the northeast corner of the Leesburg Pike VA-7 Chain Bridge Road VA-123 interchange and make the tunnel cut and cover.
This configuration would have eliminate one 3.00% grade, one 2.75% grade and replace another 2.75% grade with a 2.09% grade. It would also eliminate the need for an ejector pumping station in the tunnel.
The only problem with my proposed vertical alignment is it required the modification to half of the Leesburg Pike VA-7 Chain Bridge Road VA-123 interchange to accommodate the relocated west tunnel portals.
John in the sand box of Maryland's eastern shore.
