0 + 28.2 reads 28.2 feet, the symbol 1 + 14.6 at
manhole No. 2 indicates that this connection point is
114.6 feet from the reference point 0 + 00. You can
now easily determine the distance between all the
remaining connection points on the plan. Although
you can read the distances between points on the plan
view, you might note that you cannot determine the
depth at which the pipe is to be laid in the ground
from this view. Another view is required and that is
the profile view. The profile view will be discussed
in paragraph c following. Now, from figure 3-18 you
can see that the main sewer line is to be connected to
a septic tank whose dimensions are given as 6 feet by
8 feet by 22.5 feet. Again it would be necessary to
refer to the profile view to determine at what
Figure 3-20. Leaching tank.
elevation (depth below building level) the bottom of
the tank is required to be placed. Note that you are
uses both a septic tank and a subsurface sand filter as
directed to see enlarged view AA of the septic tank
the final sewage disposal point. Because of the long
for details of the required construction. Finally, the
pipe runs and the use of the sand filter, both a plan
outfall of the septic tank is connected to a subsurface
and profile view of the system are required to inform
sand filter via a distribution box. The plan tells you
the pipe fitters of construction requirements.
that the filter consists of distribution lines laid above
a separate system of drain lines. Note that only the
3-14. SEWERAGE SYSTEM PLANS
distribution lines are connected to the distribution
box. The under drain lines form a separate system.
a. Topography. Unless a sewerage plan is
Note that the extent of the subsurface sand filter is
prepared for a specific location and facility, it will
not completely specified in figure 3-18. The actual
represent only a typical plan for the type of facility
size of the filter must be determined at the site by the
covered. The topography and disposal facilities at
performance of the soil absorption test. The same
the building site will determine the actual piping
test must be performed to determine the necessary
layout and arrangement. For example, the plan
percolation area when a leaching tank is used as the
illustrated on figure 3-14 is based on the assumption
disposal field.
of a uniform slope downward to the right. If the
actual slope at the site is different the plan would
c. Details From Profile View. Figure 3-23 is
have to be rearranged to suit the topography.
the profile view that complements the plan of figure
3-18. The profile is taken along the path of sewage
b. Details From Plan View. If you start at the
flow in the manner of an alined section. To provide
left side of figure 3-18, you can see that five
for easier reading, note that the vertical scale is
buildings are to be connected to the main sewer line
expanded so that one square equals 1 foot, whereas
by five 4-inch vitrified tile pipe sections. The pipe
for the horizontal scale, one square equals 10 feet.
sections are to be installed laterally. Two manholes
Note that the floors of the buildings are shown at an
are to be provided, one at each end of the main sewer
elevation of 200 feet. It is common practice to assign
line. The first manhole is given as the zero reference
a convenient round number to this reference point.
point for all other measurements. The point of
The actual elevation might have been 196 or 207 feet,
connection of the first lateral is given as 0 + 28.2 feet.
but for purposes of convenience the round number
These numbers indicate the distance between
200 is used. All elevations are then referenced to this
connection points in hundreds of feet plus feet and
point. Note that the laterals shown on figure 3-18
decimal fractions of a foot. For example the symbol
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