The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1891-07-10

river, thus keeping large quantity out
OF Tinker creek, where it goes at pres
emit. 1t therefore postpones to some ex-
tent the day when the creek will receive
the greatest quantity Of sewage that it
can safely dilute. From the plan it will
readily be seen which territory can be
made to drain directly into the river
and which must continue to drain into
Lick run and Tinker creek.
The outfall into the creek or river
must be so built that the sewage is dis
charged into the current, which secures
its more rapid dilution and prevents de-
posits along the shores and banks.
ALIGNMENT OF MAIN SEWERS AND DRAINS
After having shown in the first report
how much sewage and storm water could
DO economically carried into tho Roa-
noke river, it is left for me to state how
the remaining territory should hereafter
DO treated. AS the city area is made
more and more impervious by the con-
struction of buildings and pavements,
less w"ter percolates into tho ground
and correspondingly more flows Off into
the cutters, sewers, drains and streams
1t is hardly questionable that Roanoke
will be large city, and that its popula-
tion will in a few decades amount to
more than 100000 persons. Tho CORE
spending roof and pavement area will
cause the accumulation of largo guam
tity OF water, which must be carried off
artificiallY. Tho magnitude of this guam
tity Of water is not conceived of at the
present day by those not familiar with
the subject.
The plan designed for you is calcu-
lated on the basis that the built-up part
of your city will eventually be as densely
populated as that of Norfolk, Washing
ton, Lynchburg, etc. The sizes of the
drains have been calculated accordingly.
The table appended to the first report
was compiled from the best sources,
and shows the amounts of the heaviest
rainfalls and their frequency. The
diagram now appended shows the guam
tity of storm water which has been as
sumed to reach tho sewers during
heavy storms, and for which provisions
should be made when building new
drains.
The quantity of sewage which has
been assumed to enter Tho sewers is
soventy-iive gallons per head per day,
one-ha)f of this amount to run oil in
eight hours. AS the sewage will vary,
therefore, according to tho population
the calculations have been based on tho
assumption that in the business portion
of tho city tho average population is
sixty per acre. In the territory adjoin-
ing tho business portion the population
was assumed at fifty; further away at
forty, and in the extreme limit at TWEEN
ty por aero. The maximum rainfall for
which the system is provided has been
assumed at three inches per hour. (See
table appended to report of April is,
1S9I).
The amount of roof water entering
the separate" sewers is estimated at
eight times the maximum flow of sew
age.
The storm-watcr intercep tor proposed
in previous report will, from time to
time, relieve the central part of the city
from flooding. When, however, the
territory becomes so we'll built up that
the quantity of water is greater than
tho interceptor will carry, it will be
necessary to relieve it. This can he
done by the drain starting at the head
of the interccptor at Morman's Brook,
and following the brook to the railroad
and thence along Railroad avenue to
Lick run. The present drain on Camp
bell street should likewise be extended
to the interception and built as shown
on the profile and plan. Lick run
should be embodied in drain built
along it's present line, and of the dimen-
sions and with the slopes given on the
plan.
a number of othnr plans for dealing
with the problem have been studied, but
this one is found to be the best and at
the same time the least expensive one
in the future, besides allowing of gradual
extension as the requirements for drain
age may demand. The present drain on
Campbell street will eventually DO used
to its full capacity. That part of Trout
run between Railroad avenue and Camp
bell street can be entirely abandoned
and closed up when the Railroad avenue
drain is built. is size would not have
been sufficient tc drain the water ult-
mately entering it, and therefore another
drain would have been necessary on
Railroad avenue in any event.
The portion of Lick run already con-
verted into drain below Holiday street
will be of sufficient size, with the grade
given on tho profile, to convey all the
water reaching it in the future.
The quantity OF storm water collected
on the above mentioned limos and carried
by the Campbell street drain before it ar
rivcs at Lick run will be 225 cubic feet
per second. The quantity of storm-water
reaching tho drain on Railroad avenue
above it's junction with Lick run will be
about 345 cubic feet per second, and the
quantity in the drain constituting the
Lick run, just before it Joins the
Railroad avenue drain, is 40 cubic
feet per second. According to the
formula from which tho diagrams
above mentioned have been prepared, it
will be noticed that the lower sewers
need not be calculated for "A capacity
equal to tho sum of the branches. The
element Of time is an important factor
in the question, and allows OF a com
parative reduction Of size towards tho
outfall. In accordance with this, tho
quantities in thu three sewers reaching