The record-union., 1899-05-23

San Francisco, May 20, 1899.
70 the Hon. Board of Trustees of Sac
ramento-Gentlemen: As your consult
ing engineer in the matter of the pro-
posed extension of Sacramento's sewer
system, the question has been submit
ted to me as to whether the city should
now issue bonds to the amount Of Slzo,-
COU for sewers as projected by your city
Engineer and reported on by him under
date of May a, 1897, and May 70,
1898.
The proposed sewers are to carry
both sewage proper and surface drain
age to the main sewer already on 5
street, terminating at a pumping sta
tion at the foot of S street, where a
delivery into the river is to be erected
The S-street main sewer has been in
service only two years. Until within the
past few months, it delivered its flow
into a rectangular stump at the base
of the levee, from which it was pumped
by centrifugal pumps into the river
Leakage of soil water from without into
the sewer and into the sump entrained
earth and sand particles, gradually in
creasing the permea bility of the sur
rounding ground and undermining the
street surface, until the sewer and
sump gave way and the volume of flow
from the river through pervious layers
under the levee became alarming
The sewer has been closed with con-
crete bulkhead about midway between
Front street and the levee, and its flow
is now handled by a single centrifugal
pump, being kept temporarily in service
until proper treatment shall have been
decided upon.
While the pumps on S street were dis
mantled, the old pump on Y street
which discharges through a long pipe
line into the river, was doing good
service.
The dry weather flow of the S-street
sewer consists of soilwater, the over
flow from cesspools and some sewage
received direct from house drains, with
out the intervention of cesspools. Dur
ing wet weather this is augmented by
the surface drainage. from roofs, yards,
streets and open places, all of which
finds its way sooner or later into the
sewers
For many years it has been the prac-
tice TO pump all the city's water-car-
ried waste into the river. When the
city shall have been we'll severed and
all sewage proper is dehyered into the
sewers without the intervention of cess
pools, its total quantity may be approx
imated on the basis of fifty gallons per
inha bitant. 1t will be augmented to
some extent by soil water. that will find
its way into the drains no matter how
much care is exercised in laying them,
and the maximum hourly rate of flow
Will be about twice the average rate.
For determining the capacity of main
sewers, rate of five gallons per in
habitant per hour may be assumed as
the maximum. For a population of
100000 the maximum IA te of flow will
be about 1872 cubic feet per second, and
the aggregate flow in twenty-four hours
about 100000 to 5000, ,0G0 gallons.
Surface drainage will increase as the
proportion of impervious to pervious
surface increases. 1t will be relatively
greatest from the well-paved business
section of the city. L will increase
also as facilities for the quick, direct
flow of the runoff from the street and
yard surface into sewers are improved
In other words, the maximum rate at
which the runoff will present itself at
the outfall point will be increased as
the paved and rooted areas increase and
as sewers are extended. 1t is also de-
pendent upon the rate and duration Of
rainfall.
Violent storms are of extremely rare
occurrence in Sacramento, and it is
particularly noteworthy that none have
occurred in the last few years. There
is no guide, however. to the frequency
of their occurrence nor to the maxi
mum rate of rainfall, except the rec
ords of the past.
Rainfall in Sacramento in excess of
one inch in twenty-four hours has been
noted by the United States Weather
Bureau as follows: (The Sacramento
Station of that department was estab
lished in July, 1879
1S7S-January 10th, 1e3 inches; 10Th
1.19; 22d, 1.61; 24th, 1.12; February
18th, 1O1.
1sI9-February 9th, 140 inches;
March 9th, 1.9I; December 18th, 141
1SS0-January 9th. 125 inches; April
18th, 1.s4; Goth, SIS; Dist, 3.09; De-
cember I'd, 2.05; 18th, 1.41; 20th, 119;
9th, LOS.
1Ss1-January Goth, 266 inches; 3Oth.
1.35; February Sd, LIP; 10th. 112;
December 4th, 1.41.
1sS2-March 18th, 1.30 inches; Oc-
tober Sd, 1.S2; November Sd, 1.16.
1CCo-J diludiS ISL, 1.5U inches:
March Goth, 161.
1SS4-February 18th, 1.22 inches:
March 9th. 122; 9th, 2.62: April 9th
1.3I; October 18th. 1.52; December
18th, 1.33; Goth, 1.32; 23d. 1.3S; 18th,
242
lSSo-November 1th, l inch; 18th.
BOZ; 18th, 2.30; 24th, 1.93; December
21st. 2.S1; 9th. 1.42.
1SS6-January 10Th, 130 inches; 10Th
1.43; 23d, 2.50; February 4th, 115.
1SSl-February 4th, 1.13 inches; 5th.
LIB; April 9th, LOG
1SsS-January Sd, 14O inches: No
vember 10th, 1.95; December 9th, 1.1O
1ss9-March 18th, 23S inches, May
9th. 1-94; October 20th, la; 21st, !. .J2;
22d, 132
1S90-January 10th, 102 inches; 25th
1.34; February 10th, 116; 18th, 1.2S;
December 3d. .
1s91-February 10th, 1.S6 inches;
22d, 1.O4; 23d, l. %
1S92-January 26th, inch: Feb
ruary 10th. 1.10; May 18th. 1.1e: No
vember 9th. 1.16; 2sth. 1.26: Both,
3.26; December Sd, 112; 9th. 1.s6.
4/ =. IEr. w.
r.