The Portland daily press., 1884-10-11

should be conveyed to the outlet, will
amount to about thirty cubic feet per second
during the hours of greatest use of water
in the day, and during a heavy fall of rain
To discharge this volume of sewage il the
| first half of an ebb tide will require a reser-
voir having an area Of about five and one
quarter acres. Such reservoir can be To-
Gated al Pomroy's Rock
The high water level of this reservoir
could not be II wer than about mean high
TIDE, or say 90 feet above mean low
water.
sewer discharging into this reservoir
and preserving its outward flow when the
reservoir comes to be full must have its
crown not lower than mean high tide. This
requirement fixes the level for our proposed
lntercepting sewer which is to discharge by
gravity. have designed grade for the
sewer OF one foot in two thousand which
will bring the crown Level at our proposed
temporary outlet on East Commercial street
about II. 10 feet above mean low water, or 3
feet above high water. The mean tide will
rise IN the sewer at this point about nine
inches in depth.
The height of the crown at the junction
of Portland and Forest streets. the beginning
of the new sewer as now proposed, will be
1901 feet above mean low tide. Here the
invert, or water line, of the sewer will be
OBI I06G ABOVE mean nigh TIDE.
sewer in this location aud at this eeva-
ton will eventually take the drainage of
about 1925 acres, of ground west of
"Horse Pond" TO Libby's corner; about 1877
acres of ground near the northern portion of
st. John street aud extending from the
Maine Central r. r. and Portland street to
the County road; about "A. 46 acres near
the Western Promenade; about 37.08 acres
to near Melen street, about 1875 90 acres to
near Oxford street; about GIFT acres to near
Anderson street; and about 1904 acres to
near Tukey's bridge, making in all about
500 26 acres.
The area available for building, north
easterly of the neighborhood of Portland
and st. John streets, excluding Deerine's
Oaks, which could not be drained by this
sewer, is about 1915 acres.
OF the total area of the district available
for buildings, then, about 821 per cent
would be drained by this proposed sewer
The sewage from the remaining III per
cent must finally be pumped. The aals
covered by tide water, below behring's
bridge are not included in the above esii-
mated areas.
Of the sewers now built in this district the
discharge from an aggregate length of about
49, $50 feet would be drained through the
new sewer, and that from length of about
Is, 1876 feet would still go on to the cove. If
the discharge OF sewage is in proportion to
the length of sewers, about three quarters of
all the flow, except in heavy storms, will be
taken by the new sewer. But it is probable
that the sewage near the outlets is not so
great per lineal foot as in the upper sections.
in which case less than one-fourth of the
sewage now discharged in the cove would
continue to be so discharged after the com
pletion OF the new sewer.
cir mcfo / ioIr IL
nuisance IN this district, to the extent that it
is caused by the discharge of sewage, would
be so far abated by the gravity sewer that
the collection and pumping of the sewage
from the loW-lying area might be postponed
for some years. But if, on trial, this should
prove not 10 be the case, then the work for
that section of the district might proceed.
Should it be determined that an expendi-
| tnre sufficient to relieve the entire district
must be made Immediately, would not
change the plan as herein indicated, but
gravity discharge, and another for pump
ing. This is in the interest both of economy
and efficiency.
The sizes estimated to be suitable for the
gravity sewer are as follows:
1880 feet to Portland and Forest Streets. 2ou
$3.50 " Portland near State street,. 24//x36H
1920 I" Oxford street. 28Hx4OH
$500 s Anderson street :. ......... 2SUx42n
4O6O {" East Commercial .30"x45"
These sizes provide for the discharge, car
rjed on to the outlet, of about three cubic
feet per second for 100 acres area, for all the
territory having sewers terminating above
behring's bridge, and one aud one-half Gu
bic feet per second for 100 acres area for all
that drains below behring's bridge. This
difference is made for the reason that storm
water discharged into the cove below
i(aHrIHO'S hau q 10
percentage of sewage mixed with it than
would be allowable in the creek above Deer
ing's bridge. For the lower area where we pro-
vide for carrying to the outlet the least
amount oil storm water, about half the
storms of year would be wholly carried by
the sewer in addition to the maximum flow
OF sewage, such as occurs only few hours
in each day, from fully occupied territory
The other half of the storms, about thirty
IN each year, would furnish more or less
storm water to be discharged through the
overflow sewers into the present natural
channels. As rule the sewage, once adj
mitted to the new sewer, together with its
added quantity of storm water, may remain
in the sewer aud 60 on to the outlet without
mixing With The storm water which passes
through the overhows.
make the approximate estimate of the
cost OF the gravity sewer, provided no ledge
is encountered, and subject to some changes
upon more complete knowledge of the
ground, to be about $65, 000
The low-lying interceptlng sewer, for the
pumping system should be located in the
proposed Marginal Way. The sizes for cor
responding engths will be somewhat small
er than othe gravity sewer, and the cost,
including pumping apparatus and station, for
the length TO be required in the immediate
| future may be roughly set at about SIS, 900,
exclusive OF any construction of the Margin
al Way.
have recommended alb I'VE such new sew
er work as | consider Immediately necessary
But this is not all that think it desirable
for the city to do upon the sewers. The
present construction aud mode of manage
ment should be modified.
| The chief need in this respect is the ven
tilation of the sewers. The principle to be
adopted is The diffusion and dissipation of
the sewer air in the outer air. This can be
accomplished by providing numerous small
outlets at short intervals all over the sewer
age system. The most approved practice is
| to have numerous manholes, rising to the
surface oIss the street, with perfor-
now exist should be put upon the Portland
sewers. Advantage may be taken to put
one in when the street is dug up to get at a
sewer for cleaning, as | am told is not I'M
| frequently done. The usual distance apart
tor manholes on all small sewers is one hun
dTed feet, with one at every change of grade
| or direction of the sewer. Good results in
ventilation have been attained by m4king
small perforations in the traps of the catch
basins, or street culverts, where the man
holes are too iufreuueut tt, serve the nnrDOsa