Wouldnt the elevated gjrr block the street grid from crossing over the pike and west station? Thats probably why that option hasnt been proposed.
On Google Earth I'm measuring 1,400 feet from the east end of the West Station platforms to the start of my proposed GJ viaduct, with allowance for room for the Worcester line to curve under the proposed viaduct. At 1.5% GJ RR grade, that provides a rise of 21 feet. If the grade could be 2%, then the vertical rise in the 1,400 feet would be 28 feet. I'm not sure what the maximum grade on a railroad can be. Of course if the Worcester Line is not raised up at the throat as shown in the typical section in Stefal's post above, then that would help.I think the operational question is whether there is enough room between West Station and the Throat to get the Grand Junction up to the required viaduct elevation, given RR grade constraints. Note in the proposals the Worcester Line is also somewhat elevated at the Throat, so that increases the elevation needed for Grand Junction even more.
Your calculations assume the grade of the Worcester Line is flat (0%). Is it?On Google Earth I'm measuring 1,400 feet from the east end of the West Station platforms to the start of my proposed GJ viaduct, with allowance for room for the Worcester line to curve under the proposed viaduct. At 1.5% GJ RR grade, that provides a rise of 21 feet. If the grade could be 2%, then the vertical rise in the 1,400 feet would be 28 feet. I'm not sure what the maximum grade on a railroad can be. Of course if the Worcester Line is not raised up at the throat as shown in the typical section in Stefal's post above, then that would help.
I don't know. This is just a concept and a topographical survey and a 30% design would be needed to validate things.Your calculations assume the grade of the Worcester Line is flat (0%). Is it?
1.5% is the FRA max grade. Anything higher needs a waiver, and waivers are usually only granted in very specific cases like a fixed bridge replacing a movable bridge (all of the T's over-grade inclines were on former movable bridges). 1% is the recommended grade.On Google Earth I'm measuring 1,400 feet from the east end of the West Station platforms to the start of my proposed GJ viaduct, with allowance for room for the Worcester line to curve under the proposed viaduct. At 1.5% GJ RR grade, that provides a rise of 21 feet. If the grade could be 2%, then the vertical rise in the 1,400 feet would be 28 feet. I'm not sure what the maximum grade on a railroad can be. Of course if the Worcester Line is not raised up at the throat as shown in the typical section in Stefal's post above, then that would help.
They have to be at the same level because all of the West platforms are on the mainline. The tracks tie in beforehand, and there's a quick set of pick-a-platform crossovers for changing tracks...so it all has to be at the same level. Now...West itself is a godawful mess of a design that needs a ton of finishing work before it's ready for prime time. Its layout is self-alienating from its surroundings, the mission statement on the attached (and ever shrinking) storage yard is completely incoherent, the busway-on-stilts is ludicrously overcomplicated, and the platform setup is excessive for the services that would actually use it (as well as taking a giant punt on whether the GJ itself has the capacity to run the Purple Line shuttle they envision on it, because that *still* has not been studied well enough to be proven). The 'throat' saga has simply created a giant singularity time-and-resource suck that prevents any further refining work on those troubleshoots.Also I'm thinking the West Station platforms for the GJ (if passenger service runs on it in the future) could be a few feet higher than the platforms for the Worcester branch, thus providing a bit more room for the ramp up to the GJ viaduct I'm proposing.
16 ft feels low for me if we're stacking the tracks - I don't have a table in front of me, but as I recall the Worcester Main here is Plate C, 15'6" bilevel, then figure another 2-3 feet for electrification... I think you'd need about 19ft of vertical clearance, +2 for decking. That's just about perfectly 1.5% grade, which admittedly might be a touch tough coming out from a dead stop @ West.1.5% is the FRA max grade. Anything higher needs a waiver, and waivers are usually only granted in very specific cases like a fixed bridge replacing a movable bridge (all of the T's over-grade inclines were on former movable bridges). 1% is the recommended grade.
You only need to rise ~18 feet (16 for the physical structure over the roadway, up to +2 for decking/ballast) above Pike grade to overpass the highway and meet Interstate highway vertical clearances.
16 ft. is just for where the GJ has to pass over the highway for switching sides. If you're stacking the mainline...yes, absolutely you have to do it as Plate C + 2.5 ft. for 25 kV electrification, which is an 18 ft. minimum. And weight-rate the upper deck for 286,000 lb. railcars per new-construction guidelines. And have an open enough airflow design to diesel-vent the lower level properly. While you can trace a path to absolute engineering feasibility, I don't think the cost is going to be something MassDOT wants to swallow. Stacking tracks is probably not going to be an option they entertain in any way/shape/form because of the endemic cost increasers.16 ft feels low for me if we're stacking the tracks - I don't have a table in front of me, but as I recall the Worcester Main here is Plate C, 15'6" bilevel, then figure another 2-3 feet for electrification... I think you'd need about 19ft of vertical clearance, +2 for decking. That's just about perfectly 1.5% grade, which admittedly might be a touch tough coming out from a dead stop @ West.
Those sound like reasonable issues. Thanks!I reached out to the project team and they responded saying that a stacked rail viaduct has been considered but the problem is that they would need a lot of runway for the grade to go up and there isn't enough space between West Station and the potential viaduct to do that and to have the necessary switches between the rail lines. Additionally, they pointed out that a rail viaduct would require much heavier infrastructure due to the rail weight and that there would be a lot of noise from the locomotives getting up to the viaduct level.
Those sound like reasonable issues. Thanks!
River induced flooding is not the only concern. That whole area is subject to stormwater induced flooding as well. I doubt putting the Worcester Line in a trench is going to fly.But what about splitting the difference: having the lower rail line slightly below grade and the upper rail line slightly above grade? This would create less of a climb situation for the locomotives. I know there'd be drainage/flooding concerns for the lower rail line, but we'd be talking about a much smaller footprint for the two-track bed (compared to a highway) and it would be a couple hundred feet away from the river (nonetheless mitigation approaches required, but doable?).
If the feds are being absolutists about the flood control, I doubt flipping the modes is going to substantially redirect the meat of their complaint. The FRA can be tasked with being just as P.I.T.A. a vector as the FHA for that sticking point.But what about splitting the difference: having the lower rail line slightly below grade and the upper rail line slightly above grade? This would create less of a climb situation for the locomotives. I know there'd be drainage/flooding concerns for the lower rail line, but we'd be talking about a much smaller footprint for the two-track bed (compared to a highway) and it would be a couple hundred feet away from the river (nonetheless mitigation approaches required, but doable?).