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[quote user="riprap"]<p>How many RRs have built trenches ala the UP (ex-SP) trench going through the inner suburbs of LA, or the one that was built through the downtown of Reno after the UP took over the line? This may seem like a naive question, but isn't it quite easy for rainwater or other things to build up there? What are the acknowledged advantages and disadvantages of building trenches? Would running a trench, for example, be as risky as having a busy mainline running at street-level (I'm talking about something like Stockton, CA, where the RR actually runs on the street, I believe, as well as not having its own trench?) One that would come to my mind is that it would be quite difficult for RR personnel to get emergency equipment into/out of said trench if a derailment or accident happened in one. Although I don't know for sure, my hunch is that not too many have been built, b/c I haven't read or seen about too many around the US.....</p> <p>Riprap</p>[/quote]<br><br>There are several hundred U.S. examples of railroads depressed below grade to avoid at-grade crossings with roadways. Look around any major city. Often the railway is partially depressed and the roadway is partially raised.<br><br>The only advantage (from a railway's point of view) of depressing the railway below grade is to avoid grade crossings and the significant maintenance and liability costs they incur. The disadvantages are many. Precipitation is not a major issue so long as the bottom of the trench is above existing storm sewer inverts and above the water table, but in many cases they are not, in which case pumping stations must be constructed, powered, operated, and maintained. Track maintenance is problematic as access can be severely restricted for off-track equipment. Capacity for future expansion is of course seldom provided so some of these depressed grades that seemed like a good idea 40 years ago now are a bete noire (the El Paso trainway, for instance). Access to industries is either by long leads with lots of grade crossings, or none at all. Cost of construction is very high because the depressed grade will cut through dozens of utilities, all of which have to be rerouted or somehow dealt with, because the depressed grade is often up against existing structure foundations that have to be shored, and because the railway has to keep operating at the same time.<br><br>There can also be significant issues with train-handling if sufficient space can't be found for runout for the gradient in and out of the trench. That in turn can limit train tonnage and length.<br><br>S. Hadid<br>
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