Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-07-02

are left manholes in the roof, which will
be fitted with iron frames and covers, rls-
concrete roof AS soon the concrete Is
sufficiently dry earth and soil will be
heaped upon the roof and around the man
holes and the earth will be covered with
grass sod.
The filter beds will then be chambers
entirely inclosed all sides, but
having ample ventilation and light
through the openings In the roof, and hav-
somewhat above the level Of the rest of
the structure. from which a covered pas
sage leads by an easy descent to the floor
of the filter.
beds there will be open courts with con-
crete floors, to which the sand used In the
filtering process may be removed and
washed and stored.
There Is In all this work but a small use
of steel or Of any other material than ce-
ment and stone. Throughout the walls OF
concrete are small tie rods OF iron to give
the material greater conference, and aside
from a few girders set between the col
umns near the chamber entrances upon
which temporary flooring may be laid lead
ing from the doorsll to the floor of the
chamber, there is very little steel used.
Arranged in Groups.
The beds are arranged in several groups,
some to the east and some to the west of
LIST street. At the eastern extremity OF
the Howard University reservoir there is
being constructed a clearwater reservoir.
in which will be collected the water as 1t
comes from the filters. A short distance
west of this oontainer pumping station is
under construction, which is intended to
raise the water from Howard University
reservoir to the filter beds.
Through the center of each chamber and
beneath the floor run large mains leading
to the clearwater reservoir. These mains
have openings every fourteen feet through
the floor of the filter. On top of the floor
there will be laid at right angles to the
mains benea tn several sections of terra
Gotta pipe with wide interstices at the
Joints. These will be covered well with
gravel, and over all a medium grade of
sand will be spread to depth of four
feet This forms the medium OF filtration.
When the plant is in operation water Will
cover this sand to depth of about four
feet.
At the normal rate of filtration each bed
will supply 300O,GO0 gallons of filtered
water each day. 1t is proposed to have
only about twenty-five of the beds In use
at one time, leaving four in reserve. This
is done in order that any one of them may
be repaired or have the sand removed or
renewed as required.
Capacity of the Plant.
1t will be seen that the normal capacity
of the plant will be 75,OO0,0OO gallons a day,
which is likely to be ample for some time to
come, the present consumption by the city
being only about 6O00O,OO0 gallons daily.
This is considered by some to be an ex-
cessive quantity of water to be utilized by
a city of the size of Washington 1t is
equal to 200 gallons for each inhabitant,
and in several cities of the east the con-
sumption and waste amounts to only 1OO
gallons a day for each citizen However
should there be demand for a greater
supply than the filter produces at its nor
| NAL rate, the speed of filtering may be in
creased so as to give an additional Il 900 ,OOC
gallons from the twenty-five chambers.
The rate of filtration, or the speed at
which water passes through the filter, is
governed by the outlet valves of the cham
| bers The function of the pumping station