Western Railroad Discussion > Dumbarton Bridge questions

If (Big one) the Dumbarton Bridge was replaced, is there a need for swing bridges on the bay and the Newark Slough? There is no commercial traffic south of the ROW, there are no recreational marinas either. Maybe barge traffic to San Jose, but using Google sat view, I looked all over, and found no docks anywhere. I wonder how often a pleasure sailboat comes down that far. As for the slough, would.ny be deep enough othere than paddle or outboard craft. How high is the current bridge off the water at high tide?

Second question is what are the two pipe lines to the north of the ROW? Part of them extend half way out in the bay form the Redwood City side.

Thanks in advance.

CPRR Wrote:
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> If (Big one) the Dumbarton Bridge was replaced, is
> there a need for swing bridges on the bay and the
> Newark Slough? There is no commercial traffic
> south of the ROW, there are no recreational
> marinas either. Maybe barge traffic to San Jose,
> but using Google sat view, I looked all over, and
> found no docks anywhere. I wonder how often a
> pleasure sailboat comes down that far. As for the
> slough, would.ny be deep enough othere than paddle
> or outboard craft. How high is the current bridge
> off the water at high tide?
>
> Second question is what are the two pipe lines to
> the north of the ROW? Part of them extend half way
> out in the bay form the Redwood City side.
>
> Thanks in advance.

CP,

I suspect the ship and/or boat traffic would have to be answered by the Coast Guard. As for the Pipe(s). They are I believe part of the San Francisco water supply.

J.

The pipeline is part of the Hetch Hetchy Water Project bringing water to the San Francisco Peninsula.

I would assume the bay south of the Dumbarton Bridge is still classed as a navigable water way by the Coast Guard so some means of allowing boat traffic through would have to be made, although it doesn't need to be a swing-span, a lift bridge would also work. The second bridge over the Newark Slough could be converted to a solid bridge if the Coast Guard were to deem that waterway not navigable for boat traffic. 

If the channel is navagible per the Coast Guard and the new bridge is only for passenger traffic, then the best solution may be to ramp up to an overhead clearance that obviates the need for a movable span.
This would lower operating costs and increase schedule reliability.
Locomotive hauled trains cope with 3% grades.  The biggest safety/operating challange is stopping distances at passenger speeds on the descending side.

On March 2, 2019, paulp started a thread titled "Dumbarton Passenger Crossing" on the Passenger section, that asked some similar questions. I responded on 3-4 with some details of the bridge layout. Perhaps someone who knows how can copy it here, I don't know how. 

Coast Guard controls when and if a bridge must open. The main swing span on the bay might (big if) be made fixed if there is sufficient evidence of no commercial need for a moveable span for any traffic to the south end of the bay. Sailboats would likely be the only user needing any significant clearance.

The small swing span in the slough could be made fixed if the salt ponds are decommissioned eliminating the need for the dredge barge that is the only user now. 

Getting Facebook involved with appropriate guidance from railroad engineers and not a consultant with an eye for only a fancy new bridge project could save untold millions.

Hope this helps

Sailing vessels need about 60 feet of clearance. Occasional traffic transits past the bridge. I been there numerous times. With sea levels rising more traffic will be possible to Alviso.

Posted from Android

xrds72 Wrote:

> On March 2, 2019, paulp started a thread titled
> "Dumbarton Passenger Crossing" on the Passenger
> section, that asked some similar questions. I
> responded on 3-4 with some details of the bridge
> layout. Perhaps someone who knows how can copy it
> here, I don't know how. 

Link to the thread: https://www.trainorders.com/discussion/read.php?4,4744544,4746167#msg-4746167

Your text:

About 9 or 10 years ago when I worked for Caltrain they were looking closely at the design requirements for rebuilding the route across the Dumbarton Bridge. As part of that effort I put together a schematic of the layout from the Chilco Rd crossing (end of in-service track in Redwood City) to what was at that time the end of in-service track on the Newark side. Total of about 6.7 miles. 

From west to east:
From the Chilco crossing to the west end of the bridge is about 11030' (2.1 mi) with the Willow Rd crossing in front of Facebook at about 0.6 mi
Once you get to the bridge, it is the next 1730' (0.33 mi) that was the timber portion destroyed by fire in the early 80's
Next you have 3920' (0.75 mi) of concrete ballast deck and 3 open deck truss spans to the 300' swing span and then 1580' (0.30 mi) of 3 more open deck truss and concrete ballast deck spans
Then you have 8100' (1.53  mi) on the ground to the 180' swing span over the salt pond channel and another 8300' (1.58  mi) to the in service track on the Newark side.

The 180' swing span could possibly be made a fixed span, with Coast Guard approval, if the dredging barge that worked the salt ponds was de-commissioned and the salt ponds were returned to natural conditions (a big plus for the environmental arguments). 

Several other environmental requests were looked at to provide passage for small animals through the track structure (essentially box culverts)

Track for the entire length would have to be rebuilt. 

Caltrain has a large file with all of this info.

Thanks guys, lots of good information.

Posted from iPhone

xrds72 Wrote:
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> Getting Facebook involved with appropriate
> guidance from railroad engineers and not a
> consultant with an eye for only a fancy new bridge
> project could save untold millions.

I'm good friends with a number of senior people at FB. Give me a month or two and I'll see where they're at, but last I checked it is a fairly serious effort on their part.