The New York herald., 1876-03-20

| The following able letter the advisability Of
utilizing salt water has been addressed to Commits
sionsr Levy by Mr. samuel MeEroy, the eminent civil
I.engneer:-
BRooKLYS March !, 1870
To Commissioner j. p. LEvY-
SIR-In reply TO your request for some information
in regard to the present state of the croton supply
submit, in brief, the following remarks:--
PRESENT FUTURE DEMAND
The population OF New York was IN 1895, 26s 0S9;
1850 5l5 547 1870 942 202 double in about fifteen
years previous 1850 and did not quito double the
twenty years. The facilities for suburban life
so much improved that il not likely TO keep up this
for tho island proper but IL would not be safe
the supply is administered TO assume conditions
Of increase in water demand less in aggregate than
twice the present demand in twenty-four years. or in
the year 1900 The present use is about 1ooOoO,O 900
gallons per day. Assuming that tho eventual density
of population will equal that existing below Four
tcenth street. the aggregate for the upper fourteen
fifth square miles Will be about 900 0OO total OF
21lO,OOO. For some years Now York below Fourteenth
has not increased ITS census, the expansion
taking place in the upper city on the island.
LOSS OF HEAD
In consequence of tho expansion and tho defective
arrangement OF tho lower tho supply OF the
upper city has gradually diminished the delivery to
the lower districts, much that tho effective head
at Canal street reduced time TO thirty-iye
thiry-eight feet and the Battery about cgh-
teen feet, although the flow line Of the reservoirs
when full stands at 115 feot above tide.
This loss of head in the lower city may be- and has
been in part relieved by the OF larger trunk mains;
but the gradual increase OF population up town will
increase this tendency, and has almost made clear
that supply from Long Island New Jersey il it
could be Obtained by pumping, would be great benefit
III lost quantity and pressure below rwenty-third
supply, at the time 1t nauguratcd engineer
1 ing mistake.
PROSPECTIVE SUPPLY
The minimum flow OF the CrOton IN the dryer
OF the year does exceed ~ 900 to 81 900 600
gallons per day, determined by reported gauges.
The balance OF the daily Is made up from the
age reservoir in the city and Croton Valley rhls
serve, with full reservoirs s In tho city, ll70 600 0O0
Croton Lake, 800 600 O0O and Boyds Corners Resor-
vo OO0 COO 600 about go Oc0 600 gallons IN all.
To this IL IL claimed that the natural lakes OF the
upper Croton Valley, for three feet in depth, make
aggregate OF 600 600, 00O For dry u 100
days this controls o. 100000 gallons per day, 50 that
II the minimum run OF The Groom at Me dam holds for
100 days all these reserves would be exhausted Pract
caly, then, New York IS approaching the present
capacity OF supply OF the entire reserve now controlled
The future demand is sure TO increase, and IL Is
claimed that the Croton Valley, with area OF 33s
square miles, adequate to provide for 200 900 900
gallons per day by the construction OF additional
ge reservoirs, as TO receive twothrds in all oil tho
800 600 600 estimated as an average river ow at tho
Croton In TINS connection, however there arc
! Two three things TO be considered.
The first is that there reasonable limit to the
dram OF the city the water How OF these 33S square
miles OF the Croton Valley to be determined by The
uses health and comfort of the future population OF
this large district. The superior claim tho city Is
admiIted but can never reach practical conisca
ton Of the water ilow
The second is that the engineers who dcduced a re-
servo storage OF l5oo00,000 or 10000, 900 per day
from the flow Of tho valley took erroneous
basis, since the only area from which the surplus
be impounded Is that portion which IL pract-
cable TO construct and supply storage Tho
first built instead OF being located at low point in
the valley, as to control largo drainage
actually but on an upper branch or the west branch
of the Croon, twenty -four miles above the dam and
600 feet above tide or 43l feet above the dam The
site deemed available is Brcwstcrs
the middle branch, about eighteen miles above the
dnm. calculated to hold =, 700 OOO, 900 gallons.
Now If assume that these three branches a re-
ofl0 600 900 900 gallons be made, Will repre-
100 900 aday Tor 100 days. aud the
condition, growth and necessities OF the Croon Valley
Itself below those points so to show that the city
not reasonably depend on anything moro than seq
OF those S3S square miles assumed Tor superficial
estimates which may not exceed one-third OF this
The city will hnd the problem of additional sup
ply lar less easy tnah the puoisheu reports make H.
aud Is fortunate that the OF this sub
Jcct IS IN the hands of engineer who does not tako
Tor granted what has been assumed in former years,
and, n man of thoroughly disciplined professional
llc such engineer would never have expended the
capital Tor storage reserve within the city limits
absqCbed by the reservoir until he had first
cured the sites, and bu at least In part the catch
inent works, which would insure to New York tho
actual available delivery and reserve OF the Croton
Valley For want of these the reservoir day
painfully crippled IN its and Its rcsuppy.
ADVANTAGE
Now York Is in conuition today which taxes
the capacity OF her water works, and II is by no
means clear that tho Cr0ton Valley DO oc-
cupied as to double the present supply. What
this field may YIELD and at whatever lavshncss OF
outlay the wisdom OF using, the chcapncss Of pumping
engines, drawing their supply from tidal rivers each
side OF the city, and tho advantage OF using salt
Tor fires cleaning baths, and other sup.
Elemental purposes fully apparent now. and Will
grow as tho city expands In area and popula-
ton.
Engineers familiar with the action of the sewers un-
dcrsand that the ordinary daily waste from baths
water closets, street hoses aud other purposes for
which fresh water Is required Is very large Tho
supply OF fresh water actually needed for drinking.
cooking, washing and manufacturing might DO nearly
confined to It's proper uses and the aggregate in
OF such discrimination would DO practically
or less OF the present New York consumption. In
other words the prompt Introduction OF salt and
proper restrictions OF fresh water waste might savo
tho city the expenditure OF than half
the estimate recently made Tor extension OF tho
supply 1919 600 000) and establish n supplemental
department which time would result in very great
| sanitary, insurance and financial advantages
Respectfully yours,
! SAMUEL McELROY, Civil Engineer