require that ballast be cleaned every 1 to 3 years, heavy-traffic roads every to 3 to 5 years, and
light-traffic lines every 5 to 8 years.
LONGITUDINAL OR SIDE DITCH
The effectiveness of the supplementary drains discussed in paragraph 2.15 depends upon
a side or longitudinal drain large enough to carry off all the water collected by the supplementary
ones. The usual practice is to provide a large ditch running parallel to the tracks, leading the
water to a natural stream at its intersection with the right of way, as figure 2.6 shows.
Sometimes a pipe is substituted for the ditch. The size of the side ditch depends on the needs of
the trackage to be drained. To have sufficient capacity, the ditch should never be less than 1
foot deep or less than 1 foot wide at the bottom, as shown in figure 2.7. Its sides should be
made on a slope of no more than 1 unit high to 1 1/2 units across; for example, if the height is
2 feet, then the horizontal dimension of the side should not be less than 3 feet. The grade of
the main ditch should be at least 0.3 percent. Where water movement is so rapid that scouring
(erosion) occurs, the ditch should be paved.
In a wet cut, two serious difficulties pertaining to the main longitudinal drains arise.
First, the original cost of railroad construction prohibits sufficient width for an ordinary side
ditch. Second, the usual profile of a wet cut is nearly level, making it difficult to obtain a
satisfactory grade for the side ditch. The solution lies in using large pipe drains instead of
ditches. Subparagraph a describes the pipes used in longitudinal ditches; Subparagraph b, the
procedures for cleaning the pipes.
a. Pipe drains. Because pipes offer lower resistance to the flow of-water than do ditches
and because of their greater capacity for their size, they are ideal for use in a nearly level wet cut.
The installation of this type of side drain is shown in figure 2.9. The main pipe must be at least
10 inches in diameter, and it may be either corrugated steel or vitrified sewer pipe. The grade
may be as little as 0.25 percent. To insure that water can get into the drain all along its length,
corrugated steel pipe must be perforated. For the same reason, the joints of vitrified sewer pipe
are opened about one-half inch. The pipes must be covered with gravel, cinders, stone, or straw
so that dirt cannot get in and clog the pipe.
b. Methods of cleaning longitudinal drains. Once a satisfactory longitudinal drain has
been installed, the track supervisor has to direct his attention to keeping it clean. Pipe drains do
not offer a serious problem, since storm water washes them clean. However,