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on time and in a satisfactory manner.

To consider more specifically the different types of tunnel struc-
tures described in the paper: The express tracks in Sections 8 and 9,
between 53d and 79th Streets, were in a tunnel very nearly equivalent
to a standard double-track railway tunnel, driven for the most part in
solid rock, and lined with a concrete arch. It is generally believed by
American tunnel engineers — certainly by the writer — that the top head-
ing and bench method is the cheapest and best for tunnels of this type,
and that, where timbering is necessary, segmental timber fills the bill.

Examples of the successful use of segmental timbering in tunnels
through all kinds of ground are so frequent that it is hardly worth
while to refer to them; but one recent instance refutes Mr. Moulton's
condemnation so emphatically that it deserves mention. A double-
track railroad tunnel was driven by the Northern Pacific Railroad
near Tacoma, Wash., in 1912 and 1913, through heavy clay and sand



DISCUSSION ON SUBWAY TUXNEL WORK 407

wet enough in places to have "a tendency to flow around the breast Mr.
boards into the heading".* This tunnel was excavated behind a roof
shield, and was timbered with segmental sets of 12 by 12-in. timbers,
placed on 2-ft. centers, and lagged on the outside. Each set consisted
of eleven segments. The lining proved entirely stable, and required
less than 20 ft. b. m. per cu. yd. of material removed.

To return to Sections 8 and 9 : it seems certain that, where a tunnel
can be driven safely without timber, it is not good engineering to
timber it. Segmental timber can be placed in short stretches as the
excavation progresses, or after the excavation is completed if it seems
necessary, and when placed it offers no obstacle to the construction of
the permanent arch ring. Square-set timbering, on the other hand,
must be placed as the excavation is removed, regardless of the char-
acter of the rock; it must fill the entire volume excavated, and con-
sequently it will interfere to the greatest conceivable degree with the
arch centering and the building of the arch itself.

A further objection to square-set timbering is this: the Lexington
Avenue tunnels were driven so close to the surface that, even where
the borings showed good rock, there was a likelihood of cutting a
fissure filled with running ground and extending to some point below
the roof line of the tunnel. Now if it is supposed that a bottom head-
ing misses the fissure and that the next lift reaches it, the bottom will
be neatly stoped out from under, and a run will be started that will
stop when the soft ground gives out or the tunnel fills up. For an
example, refer to the accident that occurred in driving the Mont d'Or
Tunnel, under the River Bief Rouge, in 1912. This danger can be
avoided by a top heading properly timbered to secure the roof. If
necessary, the use of compressed air can be resorted to, as was done at
56th and 57th Streets.

Sections 10 and 11, between 79th and 106th Streets, included two
general types of construction. The stretch from 79th to 98th Street
was for the most part a double-deck tunnel, two tracks wide, with a
steel lower story supporting a concrete arch roof. The rock, as Mr.
Werbin states, "was fairly good, and very little timbering was used".
The arguments just cited, bearing on the proper construction methods
for Sections 8 and 9, consequently apply with equal force here. Cer-
tainly, the conditions and methods of excavation illustrated by Figs.
11 and 13 are as nearly ideal as the most grasping contractor could
desire.

From 9Sth Street to the end of Section 11, the tunnel varied in
cross-section, but was characterized by a flat roof supported by steel
bents on 5-ft. centers, with rows of columns between the tracks. This
is a type of construction to which segmental timbering is entirely

* Engineering Record, February 7th and 27th, 1915.



408 DISCUSSION ON SUBWAY TUNNEL WORK

tmsuited, and ordinary timbering methods can be used to advantage
only if the rock is so solid that it will sustain itself without support
over a flat roof at least as wide as a one-track structure. The con-
tractor, nevertheless, attempted to continue the plan that had been
successful on other parts of the work, and kept his air shovel working
until unsoxind rock north of 100th Street stopped him. A heavy and
elaborate system of timbering failed to prevent large over-breakage in
the roof. It was considered cheaper to take down loose rock above the
roof line than to hold it in place, and at one point 12 ft. of rock were
removed. Large quantities of excess concrete and dry packing were
required.

The writer believes that from 98th to 103d Street, square-set timber-
ing could have been used advantageously in the manner that Mr.
Moulton suggests, and that the contractor could have saved money by
using it. The cost, however, would probably have exceeded the higher
figure given by Mr. Moulton, namely, $5 per cu. yd., due partly to the
difficulty of organizing the job in New York City, but chiefly to the
fact that the volvmie of rock removed in drifts and cross-cuts would
have been much greater in proportion to the total volume than is the
case in mining. Mine slopes are comparatively high and narrow, but
these flat-roofed tvmnels were low and broad.

Mr. Israel V. Werbin,* Assoc. M. Am. See. C. E. (by letter). — Mr.

Moulton's discussion has perhaps set many to thinking of the possi-
bility of adapting mining methods to excavating tunnels for en-
gineering construction. The suggestions made by him are undoubtedly
interesting, but, as one who has been intimately connected with the
work described, the writer must take exception to his conclusion that
mining methods could have been used advantageously on certain parts
of the work.

Referring to the large double-deck tunnels, with a cross-section
approximately 40 ft. square, Mr. Moulton states:

"The work on these sections presents problems more nearly com-
parable to metal mining than those encountered anywhere else on
subway construction in New York City."

The mistake is made right at the start in assuming that there is
any similarity between metal mining and the work described in the
paper. There were several important factors connected with the
work in question which eliminated any possibility of using any of
the methods suggested by Mr. Moulton, and these were:

(1) That the work was done under narrow streets, in built-up
sections of the largest city in the world;

(2) That the tunnels were driven dangerously near the rock line;

• New York City.



Werbin



DISCUSSION ON SUBWAY TUNNEL WORK 409

(3) That the rock was known to be of a dangerous character; and Mr.

(4) That the problem was not merely one of making an excava- ^^ ^°'
tion, but of doing this so that there would be absolutely no
settlement of the street surface, and, most important of all,

of building a structure inside of the finished excavation.

Surely none of these problems is to be met in mining work, par-
ticularly if credence is to be given to the occasional newspaper reports
of large areas adjacent to mining operations settling, on account of
the work done beneath them.

Mr. Moidton criticizes the use of the top heading as being anti-
quated and expensive. This manner of attack is followed almost
everywhere in tunnel operations in America. This fact may not
perhaps make it the better method, but there were other important
considerations which made it the only practical method to use on
work of this kind.

The tim.nels in question were driven in connection with subway
work, and, from the point of view of economy of construction, it was
desirable to keep the structure as near to the street surface as possible.
The importance of this feature will be realized when it is noted that
the cost of the excavation in such work is approximately 50% of the
cost of the entire construction. It is also important, from the stand-
point of operation, for the railroad at the stations to be as near to
the street surface as practicable, so as to reduce to a minimum the
height of the stairs, and to dispense with the use of elevators.

When the first subway in New York was built, a portion on
upper Broadway was built in a deep tvmnel, and access to the stations
at 168th, 181st, and 191st Streets is obtained by using elevators.
Experience shows that with the large amount of traffic handled by the
city railroads, the use of elevators is not only an expensive feature
of operation, but is highly undesirable. For this reason, on the
new work in the double-deck tunnels on Lexington Avenue, the express
stations were placed immediately beneath the local tracks, so that
communication with the local stations could be had by short stairways
instead of elevators. In order to maintain reasonable grades, it was
necessary to keep the express tunnels a short distance below the local
tracks. If a bottom heading had been used, good rock (not requiring
any timbering) would have been encountered all along the line, except
for a stretch of about 200 ft. at 74th Street. There were, however,
several places along Lexington Avenue where old watercourses ran
across the line of the subway structure, and at these places the surface
of the rock was considerably below the roof line. The material
directly above the rock at these points was a fine quicksand or alluvial
earth, which, when encountered, was very difficult to hold and keep
from being washed into the excavation.



410 DISCUSSION ox SUBWAY TUNNEL WORK

Mr. Under such conditions, the use of a bottom heading would have

been dangerous. The top heading had the advantage of acting in
the nature of an exploration tunnel, so that the contractor was prepared
in advance for the conditions with which he had to deal. When bad
ground was encountered, it was taken care of by timbering, with or
without lagging boards, as might be necessary; and, when the over-
lying material was once properly caught up and held, the element of
danger was practically removed. Assuming that under such conditions
the work was conducted with a bottom heading, it would mean that
a very expensive system of timbering would have been necessary every
time another lift was taken out, with the continuing possibility of the
danger and damage that such an operation would have involved.

It must be borne in mind that the structure for the local tracks
had been completed in advance of the express tunnel excavation, this
being necessary in order to maintain necessary progress in the work.
The loss of any material between the local structure and the express
tunnels, therefore, would involve damage to the completed local track
structure, in addition to settlement in the buildings at the street
surface. It might also be mentioned that the contractor was held
absolutely liable for all damage to buildings that resulted from his
operations, irrespective of the matter of negligence, so that a pro-
cedure which would reduce to a minimum the possibility of damage
might ultimately prove the most economical, even though some other
method might permit the removal of the excavation more economically.
When these matters are considered, the writer is sure that no mistake
was made in using a top heading.

Mr. Moulton claims that with the methods of timbering ordinarily
used in metal mining, it would be possible to work more nearly to
the pay line of the excavation. The writer fails to see how the method
of timbering can in any way affect the lines of excavation. This
matter is determined more or less by the character of the rock and
the way in which the strata lie. The writer believes that the men
engaged on such works as that described in the paper are fully as com-
petent as mining men to carry the excavation to approximate neat lines.
The method of cribbing up the entire excavation might serve to hold
some of the rock in the roof from falling down, but, as the writer
has tried to bring out in the paper, no attempt was made to hold up
such rock by timbering, the consensus of opinion being that the better
practice would be to remove all loose rock. This conclusion was
reached after careful study, there being little doubt that any timbering
that would have to be put in to hold such rock in place, would be
far more expensive than the additional cost of removing such excess
excavation. The rock along the work in question had two seams
running almost at right angles to each other, with the apex pointing
upward, so that the rock in the roof was more or less wedge-shaped,



DISCUSSION ON SUBWAY TUNNEL WOEK 411

with the bottom of the wedge downward. The very dangerous condition Mr.
is evident, and, when this rock persisted in working loose, even where ^^'''^'"■
timbering was placed, there was no doubt that it was good practice
to remove these large masses of loose rock rather than attempt to hold
them in place, where they would have been an ever-continuing menace
to the lives of the men working in the tunnel.

Mr. Moulton has criticized the segmental type of timbering as
being expensive. The answer to this is that the problem was not only
one of making an excavation, but also of building a structure inside
the completed excavation. The square-set system of timbering used
in mining, described by him, may be all right in a mine, but would
make the cost of the construction that had to follow the excavation
almost prohibitive. The subway structure could not have been erected
without shifting considerable timber, and no engineer engaged on
such work will deny that, once bad rock is caught up, it is very poor
and dangerous practice to disturb the timbering.

The almost universal use of the segmental set in bad ground
was prompted by the fact that, after it had been placed, the structure
could be built beneath it with very little moving of the timbering.
Another great advantage in the use of segmental timber in this work
was the fact that, almost throughout the work, water was encountered
in great quantities, and, by concreting between the timbers and grout-
ing, a temporary roof was made. The water was then concentrated
and led oS through the grout pipes, and in this way was prevented
from washing away the fresh concrete in the finished structure until
it had had a chance to set.

The use of the longitudinal beams mentioned in the paper was
not advocated so much on account of permitting any economy in
removing the excavation, but solely because, with such a system,
the posts directly under the sets did not have to be moved every
time an additional lift was taken out; and it afforded a good founda-
tion for the posts, irrespective of soil conditions. The beams and
posting, therefore, could be placed where they would offer the minimum
interference with the construction work that was to follow. The
Lexington Avenue work was the first in which the large longitudinal
beams were used to any extent, and the advantage of their use has
been so marked that this system is being adopted on much of the
more recent work.

Mr. Moulton has presented some data as to the estimated cost of
making the excavation if mining methods had been adopted. He
does not seem to have taken local conditions into consideration, and
if, to the prices he gives, he adds the cost incurred by the contractor
practically having no choice in the location and the number of shafts,
the high cost that must be paid in the city for labor, plant sites,
dumping privileges, superintendence and insurance costs, and the



412 DISCUSSION ON SUBWAY TUNNEL WORK

Mr. increased cost due to the drilling and blasting methods required in a
" '°' job of this kind, the total sum for doing the work would be found to
be higher than he apparently thinks it would be.

The writer is sure that, if Mr. Moulton had been familiar with
the conditions peculiar to this work, he would not have advocated
the use of square-set timbering, or conducting the excavation with
a bottom heading. It would seem to the writer that the only place
where such a method could have been considered would have been
in connection with the tunnels of 100th and 102d Streets, where the
spans were greater than 60 ft., provided very bad ground had been
encountered. The large I-beams to hold up the roof in this part of
the work were used by the contractor mainly so that he could continue
to utilize his air shovel, but, as stated in the paper, this method
of procedure was found to be very expensive, and of little advantage,
so that the use of the air shovel was abandoned and the mucking was
done by hand.

It was found possible to excavate the section for sufficient width
to permit the construction of one track of the structure at a time
without using any timbering whatever, except for occasional jwsting;
and, after the structure for this one track was completed and the
roof had been caught up, the excavation for the adjacent track was
made.

It would seem to the writer that the method followed was better
than to attempt to make the excavation wider and use timbering.
The only objection to the piecemeal method of construction was the
damage to the finished structure that resulted from carrying on the
blasting adjacent to it, but this could have been avoided had the
contractor taken proper precautions.

It might have been advantageous to use the methods suggested
by Mr. Moulton, provided the rock encountered would not have per-
mitted the excavation for one track with practically no timbering.



AMEEICAN SOCIETY OF CIVIL ENGINEEKS

INSTITUTED 1852



TRANSACTIONS



This Society is not responsible for any statement made or opinion expressed
in its publications.



Paper No. 1389

A METHOD OF DETERMINING

A REASONABLE SERVICE RATE

FOR MUNICIPALLY OWNED PUBLIC UTILITIES*

By J. B. LippiNCOTT, M. Am. Soc, C. E.



With Discussion by Messrs. Frank S. M. Harris, T. Kennard
Thomson, W. B. Yereance, Leonard C. Jordan, H. F. Clark,
Allen Hazen, W. G. Irving, H. A. Whitney, and J. B. Lippincott.



Synopsis.

The physical development of the Western States is far from com-
plete, and although the larger municipalities may be able to finance
utilities satisfactorily, in a manner commensurate with their needs,
the growth, particularly of the outlying districts and smaller towns,
will await largely the investment of private capital. In order to
advance, all commvmities must have light, transportation, telephone
service, water, etc. These utilities, whether privately or publicly
owned, are essential to development. In California, at present, exclu-
sive of steam railroads, 95% of the value of the public utilities is in
private ownership.

In addition to the advisability of the public administration of
both publicly and privately owned utilities being conducted on a
fair and reasonable basis, it is essential that this administration should
be such as will encourage the investment of private capital therein.
If the rates for service of publicly owned utilities are too low, and

* Presented at the me.eting of October 18th, 1916.



414 RATES OF MUNICIPALLY OWNED PUBLIC UTILITIES

deficits are made up from the general tax funds, such administration
is unfair to privately owned utilities, and will tend to discovirage the
investment of private funds therein, in States practicing this policy.
Of late, and at present, in California, voluntary investment in privately
owned utilities is awaiting the determination of public policy relative
thereto.

The rates for service of a publicly owTied utility should be fi_xed
in the same manner as that for one privately owned, that is, it should
be based on operation, plus depreciation, plus reasonable interest on
value. Any surplus resulting from such administration should be
deposited in the public treasury of the city to the credit of the
general tax fund.



Public utilities are the framework on which the commonwealth is
developed. All classes of citizens desire ready access to transportation,
light, water, power, and telephones, in order to develop their com-
munities economically. Excluding steam railways, 95% in value of
the public utilities of California are privately owned. Statistical
tables (Tables 1 and 2) show that not more than 10% of the State of
California (after omitting the area of the desert lands south of Owens
Lake) is developed as to density of population, and about 20% as to
value. The wealth per capita is high. It must be borne in mind that
the growth of a community, and its attendant wealth, are largely de-
pendent on public utilities; and the investment of private capital in
these enterprises should be fostered and encouraged with a view to
the further growth of the State. A new and undeveloped State, such
as California, manifestly cannot publicly build all its utilities.

There has been difficulty in obtaining the data on the relative value
of municipally and privately O'mied utilities in California. That of
the privately owned utilities for 1912 is taken from the report of the
State Railroad Commission. This covered all the privately owned
utilities, with the exception of the steam railroads, which have not been
pro-rated for the diilerent States. The best information on the munic-
ipally owned utilities is found in the report of the California State
Controller for 1914. This report gives statistics relating to the munic-
ipal utilities in the State. For some of them, however, the values
were not stated, and some were incomplete, as in the case of the Los
Angeles Water Department, where the aqueduct was omitted. To



RATES OF :\1UNICIPALLY OWNED PUBLIC UTILITIES
3 000 000



! 500 000



415



^1 500 000















/




RATE OF INCREASE

IN POPULATION

IN THE STATE OF CALIFORNIA.




c














J.


/














r


?








A


y^










/






_^


)


1/














200 000 300 000 400 000 500 000

Value in Dollars per Square Slile.

Fig. 2.



416



KATES OF MUNICIPALLY OWNED PUBLIC UTILITIES



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Zn



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12!



KATES OF MUNICIPALLY OWNED PUBLIC UTILITIES



417



TABLE 2. — Relative Value of Publicly and Privately Owned
Utilities in California in 1912.
Total population of incoriiorated cities in California = 2 340 242.
Publicly Owned Utilities.



Class of utilities.


33 i

■° s

5 a


Population
of cities
reported.


Value of
plants in

cities
reported.


I'opulation
of cities
owning

plants with
no value
reported.


p
o

o
o.


5; 3 4/

111

■■5*3


Water


81
14

1
6


1 033 410

109 819

6 000

978 137


$58 633 904
1 884 709


85 936
3 700


1 119 346
113 519

6000
978 127


$67 770 000
1 950 OiX)


Electric


Gas


42 000




4 091 440




4 091 440








Total


$73 853 440





Privately Owned Utilities.



Class of utilities.



Number
of plants.



Value.



Total values.



Street railways

Water

Gas and electric companies

Telephone and telegraph

Wharfinger warehouse com-
panies



30
238
113

81



$454 892 593
204 000 917
525 677 587
253 357 061

7 391 338



Publicly owned..
Privately owned. .



$73 853 440
1 445 319 496



Ratio of public to private 5.1
per cent.



Total .



$1 445 319 4%



cover this latter item, $26 000 000 is added here. The values for the
cities omitted are interpolated by computing the average value per
capita for all the cities given and applying this figure to the population
of the cities omitted. The Controller's report makes no mention of the
San Francisco City Railways. These results are tabulated. Excluding
the steam railroads, the value of municipally owned utilities is only
5.1% of those privately owned.

There is, of late, in the United States, a decided trend toward pub-
lic ownership of public utilities, especially by municipalities. In Cali-



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