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AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852

TRANSACTIONS

Paper No. 1170

THE WATER SUPPLY OF THE EL PASO AND SOUTHWESTERN RAILWAY FROM CARRIZOZO
TO SANTA ROSA, N. MEX.[A]

BY J.L. CAMPBELL, M. AM. SOC. C.E.

WITH DISCUSSION BY MESSRS G.E.P. SMITH, KENNETH ALLAN, and J.L.
CAMPBELL.




_Location_.--The El Paso and Southwestern Railway traverses the arid
country west of the 100th Meridian in New Mexico, Texas, and Arizona, as
shown on the map, Fig. 1. The water supply herein described serves that
division of this road lying between Carrizozo and Santa Rosa, a distance
of 128 miles.

_Rainfall_.--The average annual precipitation is 9.84 in. The year 1909
was exceptionally dry, with a rainfall of less than 5 in.

_Original Water Supply_.--East and west of El Paso, for distances of 270
miles in each direction, the railway crosses no streams, and the supply
was obtained from wells ranging from 100 to 1,100 ft. in depth. On the
division served by the new supply, this well-water is of very bad
quality, as shown in Table 1.

After the most thorough practicable treatment, these waters were still
so bad that they caused violent foaming, low steam pressure, hard
scaling, rapid destruction of boiler tubes, high coal and water
consumption, extraordinary engine failures and repairs, small engine
mileage, low train tonnage, excessive overtime, and a demoralized train
service.


[Footnote A: Presented at the meeting of May 4th, 1910.]


TABLE 1.

----------------------------------------------------------------
            |  Incrusting solids, in  |  Non-incrusting solids,
  Station.  |    grains per gallon.   |   in grains per gallon.
----------------------------------------------------------------
Carrizozo   |           31            |             7
Ancho       |           14            |            14
Gallinas    |           91            |             8
Varney      |          180            |            14
Duran       |          127            |            55
Tony        |          115            |            11
Pastura     |          141            |             6
Pintado     |           81            |             9
Santa Rosa  |          140            |            29
----------------------------------------------------------------


_New Water Supply_.--The writer was directed to find, if possible, a
supply of good water, and his efforts proved successful. The pure water
now in use has eliminated the adverse conditions before mentioned; has
improved the _esprit de corps_ of the train service; and, in a short
time, the reduction in operating expenses will liquidate the first cost
of the new supply.

This supply is taken from the South Fork of Bonito Creek, which flows
down the eastern slope of White Mountain. The latter is 12,000 ft. high,
and is 16 miles south of Carrizozo (Fig. 1). The watershed is a granite
and porphyry formation, heavily timbered, and the stream is fed by snow
and rain. This combination yields an excellent water, carrying on an
average 6.05 grains of incrusting and O.95 grains of non-incrusting
solids per gallon. The North Fork of the creek carries 16.60 and 2.40
grains, respectively. Below the junction of these forks, the water
contains 10.48 grains of incrusting and 1.57 grains of non-incrusting
solids per gallon; and a branch pipe line takes water from the creek
during intervals in dry years when the daily flow of the South Fork is
less than the consumption.

_The Water Plant_.--The water is taken to and along the railway in pipe
lines. The system includes 116 miles of wood pipe, 19 miles of iron
pipe, one 422,000,000-gal. storage reservoir, four 2,500,000-gal.
service reservoirs, two pumping plants in duplicate, and accessories of
valves, stand-pipes, etc.

From a small concrete dam across the creek at an elevation of 7,728 ft.,
the pipe line drops down the narrow valley eastward, 5-1/2 miles, to an
elevation of 6,980 ft, where it turns abruptly north, rising in 1 mile
to a table-land, 7,215 ft. above sea level, across which it continues
northward 5 miles to the storage reservoir, which is on the north edge
of this elevated country. Hereafter, this reservoir will be called the
Nogal Reservoir, from the old mining village of Nogal lying 1-1/2 miles
to the north and 600 ft. below it. From this reservoir, the line drops
abruptly to the Carrizozo plain, and crosses the latter northward to
Coyote, at Mile 156, on the railway, at an elevation of 5,810 ft.,
passing, on the way, 6 miles east of Carrizozo, to which a branch pipe
runs, Carrizozo being 5,430 ft. above sea level. There is a
2,500,000-gal. reservoir at Coyote, and a similar one at Carrizozo.


[Illustration: FIG 1. MAP OF LINES OF EL PASO & SOUTHWESTERN SYSTEM]


This describes the gravity section of the line which brings the water
from the mountain stream to the railway. From Nogal Reservoir to the
latter, the capacity of the pipe is equal to the future daily
requirements; from the source of supply to the reservoir, the pipe has
twice as great a capacity, thereby storing surplus water. This section
is 32 miles long, with a 6-mile branch line.

The second, or pumping section, extends eastward along the railway,
rising from an elevation of 5,810 ft. at Coyote to 6,750 ft. on the Corona
summit, which is the water-shed line between the Rio Grande on the west
and the Rio Pecos on the east. At Coyote a pumping station lifts the
water to Luna Reservoir and the pumps at Mile 171, and the latter lift
it to the reservoir on Corona summit at Mile 192-1/2. This section is
36-1/2 miles long.

The third, or gravity section, extends from the reservoir on the Corona
summit to the Rio Pecos at Mile 272, dropping from an elevation of 6,750
to 4,570 ft. in 80 miles. The pipe line extends to Pastura, 58-1/2 miles
from Corona, as shown on Plate V.

Where the pipe line passes a water tank on the railway, a 4-in. branch
pipe is carried to the bottom of the tank and up to the top, where it is
capped by an automatic valve. A gate-valve is placed in the branch pipe
at its junction with the pipe line.

There are regulating, relief, check, blow-off, and air-valves,
air-chambers, and open stand-pipes on the line, too numerous to mention
in detail. They are designed to keep the wood pipe full, regulate flow,
prevent accumulation of pressure and water-hammer, and remove sediment.

_Water Pipe_.--A study of the profile developed a system of hydraulic
grades, pipe diameters, and open stand-pipes limiting the pressure to
130 lb. per sq. in., except on 19 miles of the pump main between Coyote
and Corona where the estimated maximum pressure is 310 lb.

Investigation justified the assumption that wood pipe under a pressure
of 130 lb. would give satisfactory service for 25 years, on which basis
it would be less expensive than cast iron, and therefore it was used.
Cast iron was considered preferable to steel for pressures not exceeding
310 lb. on account of its greater durability.

_Wood Pipe_.--Machine-made, spirally-wound, wood-stave pipe, made in
sections from 8 to 12 ft. long, with the exterior surface covered with a
heavy coat of asphalt, was selected in preference to unprotected,
continuous, stave pipe. The diameters were not so great as to require
the latter.

The first 40 miles of wood pipe was furnished by the Wykoff Wood Pipe
Company, of Elmira, N.Y., and the Michigan Pipe Company, of Bay City,
Mich., delivered the remaining 76 miles.

The pipe is wound with flat steel bands of from 14 to 18 gauge and from
1 to 2 in. wide. The machine winds at any desired pitch and tension. At
each end the spiral wind is doubled two turns, the second lying over the
first and developing a frictional resistance similar to that of a double
hitch of a rope around a post. The ends of the band are held by screw
nails or a forged clip, the latter being the better. It has two or three
spikes on the under side which seat into the stave, and two side lugs on
top which turn down over the band. The latter passes twice over the seat
on the clip, the first turn holding the clip to the stave, while the
second turn is held by the lugs which are hammered down over it. The end
of the band is then turned back over the clip and held down by a staple.

The staves are double-tongued and grooved and from 1-3/8 to 2 in. thick.
The smaller thickness is sufficient. The exterior face of the staves
should be turned concentric with the axis of the pipe and form a circle,
so that the band will have perfect contact with the wood.

The joints are formed by turning a chamber in one end of the pipe and a
tenon on the other, or both ends are turned to a true exterior circle
and driven into a wood or steel sleeve. The chamber and tenon were used
in this work.

Finally, each piece of pipe is covered with as much hot asphalt as it
will carry.

_Steel Bands_.--The specifications required bands of mild steel, of
60,000 lb. strength, with an elastic limit half as great. The winding was
spaced to limit the tension to 15,000 lb. per sq. in. If severe
water-hammer is present, the ordinary working stress should be
materially less than the latter, otherwise the spiral bands will stretch
enough to permit the water to spurt out between the staves. This was
determined to be true on 4,500 ft. of 12-in. pipe connecting the
Carrizozo Reservoir with a water column at the roundhouse there. In
pumping tests at the mills, attempts were made, at various times, to
burst the pipe, but they never succeeded. Before the elastic limit was
exceeded, the water was running out between the staves as fast as the
pump forced it in. On the following day, pipe thus tested would carry
the pressure for which it was designed without leaking. Except for
defects in the band, pipe of this kind will not burst in the service
for which it is properly designed. This is true, without exception, of
the 100,000 pieces of pipe in this service.

There has been some trouble with a number of the riveted splices on the
banding. Such a splice occurs for every spool of banding used. In every
case where one of these splices has pulled apart, the break was the
result of defective riveting, permitting the rivets to pull out. In no
case has a rivet been found sheared off, and even one good rivet appears
to be sufficient to prevent rupture. The explanation is found in the
high frictional resistance between the band and the pipe, which
distributes the weakness of a bad splice over several adjacent turns of
the band around the pipe. The band loosens a few turns only on either
side of a parted splice, generally not more than three. In no case has
any pipe been removed from the trench, repairs being made without
interruption to the flow of water.

It is desirable to substitute welding for the riveting of these splices.
The trouble is not present with the round band, the wrapped splice of
the latter giving practically 100% efficiency.

The flat band was chosen for this work because it is the more
effectively buried in and protected by the asphalt, and will not crush
the soft wood staves under high pressure. The longevity of either the
flat or the round steel band is dependent primarily on effective
protection against contact with corrosive elements. Wrought iron should
be used for this kind of service, and, for the same reason, for many
other purposes. Engineers and consumers should join in some
comprehensive and effective plan to bring back the old-time production
of high-grade wrought iron.

_Wood Staves_.--The staves of this pipe are of Michigan and Canadian
white pine. This pine cannot now be had of clear stuff or in long
lengths in large quantities; otherwise, it is unexcelled. Douglas fir
and yellow pine, coarser and harder woods, have the advantages of clear
lumber and long length. Cypress is not as plentiful, and redwood is
costly. The mill tests did not determine definitely the minimum degree
of seasoning necessary, and press of time compelled the acceptance of
some rather green lumber. Service tests do not show that there is any
abnormal leakage from pipe made of such lumber, and it could not now be
distinguished in the trench by such tests. Undoubtedly, however,
thorough air seasoning should be required.

_Bored Pipe_.--Owing to its small size, a part of the 3-1/2-in. pipe
was bored from the log. This was a mistake, for bored pipe has a rough
interior and a reduced capacity. The inspection and culling are
difficult and unsatisfactory, and imperfections readily apparent in a
stave frequently escape detection in bored pipe.

_Pipe Joints_.--The chamber and tenon of this pipe is an all-wood joint,
4 in. deep. An iron sleeve makes a better and stronger joint. It
compensates for any lack of initial tension in the banding over the
chamber of the wood joint, and secures full advantage of the swelling of
the wood. Cast iron is better than steel; it is more rigid, and its
granulated surface breaks up the smoothness of the wood surface swelling
against it. One objection to the cast-iron sleeve is that of cost, but
it adds 4 in. to the effective length of every section of pipe, as
compared with the wood joints. On the Pacific Coast, a banded wood-stave
sleeve is used with success.

_Coating_.--To preserve the banding from corrosion and the wood from
exterior decay, the pipe is thoroughly enveloped in refined asphalt
having a flow-point adjusted to the prevailing temperature during
shipment and laying. One grade can be used through a considerable range
of temperature. This coating endured a 2,000-mile shipment successfully.
Each piece was carefully inspected along the trench, and any break in
the coating was thoroughly painted with hot asphalt. Enough of the
latter came in barrels, with the pipe, from the factory.

The first 37 miles of this pipe has been in service for two years.
Recent inspections show the coating to be in excellent condition and the
steel underneath to be bright and clean. In some cases, where the
initial pressure and leaking between the staves of the dry pipe were
great, the escaping air and water lifted the coating into bubbles. At
some points where this lifting was great enough to rupture the asphalt,
and the soil is heavily charged with alkali, some corrosion has begun.

The integrity and impermeability of this asphalt coat are quite as vital
as constant saturation. This coating protects the entire pipe from
exterior contact with destructive agencies. With such effective exterior
protection, a constantly full pipe is not so imperative. In the exterior
protection of the wood, this coated pipe has quite an advantage over
continuous stave pipe.

Each piece of pipe goes directly from the winder to the asphalt rolls,
then to an adjacent saw-dust table, then back to the rolls, then to the
table again, and then to the dry finishing rolls at the opposite end of
the table. The coating thus consists of two layers of asphalt and two of
saw-dust. When the pipe leaves the finishing rolls, the coat is hard and
smooth and about 1 3/16 in. thick. This describes the coating as done at
Bay City, Mich.

At Elmira, N.Y., one application of asphalt and saw-dust only, without a
finishing dry roll, completed the work; but the band was run through a
bath of hot asphalt as it was wound, thus coating its underside also.
This initial treatment of the band on the Wykoff pipe is necessary
because the exterior of the stave is neither planed nor turned to a
circle. The exterior of the pipe forms a polygon, and the band is in
perfect contact only at the angles. The theory in regard to the Michigan
pipe is that the perfect contact of the band and the wood on the true
exterior circle excludes air from the under surface of the metal, and
prevents corrosion. Experience appears to justify this theory.

_Cast-iron Pipe_.--Beginning at the first pumping plant at Coyote, at
Mile 156, and running up to Mile 166, and again commencing at the Luna
pumps, at Mile 171, and extending up to Mile 179, the minimum pressure
on those portions of the pump main is more than the 130 lb. per sq. in.
allowed for wood pipe, and the final estimated maximum pressures run up
to 310 lb.

The selection of iron pipe for these pressures was, first, as between
steel and cast-iron; and, second, as between the lead joint of the
standard bell and spigot pipe and the machined iron joint of the
universal joint pipe. Again, the choice was as between lead and leadite
for the bell and spigot pipe.

Cast iron was selected because of the certainty of its long life, and
the bell and spigot pipe was selected on the basis of comparative costs
for pipe laid. The standard lead joint was chosen on the result of
tests. This cast-iron pumping main has a diameter of 12 in. throughout.

_Pipe Weights._--Makers of standard bell and spigot pipe urged the usual
heavy weights selected for municipal service and heavy water-hammer.
Three pressures, _viz_., 217, 260, and 304 lb., were used for the
division of pipe weights, on which the standard pipe-makers specified
shell thicknesses of 0.82, 0.89, and 0.97 in. Eliminating water-hammer
and adopting a working stress of 2,400 lb., the thicknesses are reduced
to 0.54, 0.65, and 0.76 in. To make the latter conform to the
specifications of the New England Water-Works Association, the pipe was
cast to 0.57, 0.65, and 0.77 in. The reduction in cost amounts to
$52,811.

By the provision of air-cushions, hereafter described, the writer's
anticipation of no water-hammer on the pumping main has been fully
realized.

The pipe was manufactured and inspected under the above-mentioned
specifications.

_Pipe Joints_.--There was a question about the reliability of the lead
joint at 300 lb. The writer had a section of 12-in. pipe, with standard
joints containing 22 lb. of lead, laid and tested to 500 lb. without
sign of failure or leakage. The joints were caulked down 3/16 in. below
the face of the bell. Of 8,700 joints thus made in the field, not one has
blown out or failed. A few weeped slightly on top, and they were made
permanently tight by additional caulking. The present maximum pressure
is 278 lb. These joints are the standard joints specified by the New
England Water-Works Association. It should be borne in mind that there
is no water-hammer on this line. In 8,700 joints, 198,000 lb. of lead and
3,200 lb. of oakum were used, or 22.76 and 0.37 lb. per joint.

Leadite was tested in competition with lead, but it leaked at 100 lb.
and failed under a sustained pressure of 300 lb. It is a friable
material, and cannot be caulked successfully. Its principal ingredient
appears to be sulphur. The failure was by slow creeping out of the
joints. It is melted and poured, but not caulked. It has attractive
features for low pressures and for lines not subject to movement or
heavy jarring.

_Air-Cushions_.--To prevent water-hammer on the pumping main, all pumps
are provided with large air-chambers. In addition, and as the special
feature for absorbing the shock of pumping under high pressure through a
pipe 21 miles long, a large air-chamber in the form of a closed steel
cylinder, 5 ft. in diameter and 15 ft. long, is mounted on the pumping
main outside of the pump-house. This cylinder is set on its side, in
concrete collars, directly over the pipe beneath, to which it is
connected by a 12-in. tee, in which a 12-in. gate-valve is set. The
cylinder is provided with a glass gauge, cocks, etc. It was designed for
a working pressure of 300 lb., and, at each pumping plant, it has proved
to be entirely air-and water-tight. As indicated by sensitive gauges on
the pump main, just beyond these large air-chambers, the latter absorb
all the water-hammer which gets beyond the air-chamber on the pumps.

_Air-Pumps_.--Each pumping plant is provided with four automatic
air-charging devices, connecting to all air-chambers of the pumps and to
the air-chamber on the pumping main. They are of the Nordberg type, and
have proved very efficient. They are operated only a part of the time;
otherwise, they accumulate too much air in the chambers.

_Air-Valves_.--On the entire line there are 144 automatic air-valves
made by the United States Metal Manufacturing Company, of Berwick, Pa.
They are working satisfactorily.

_Gate-Valves_.--In addition to the customary gate-and check-valves at
the reservoirs and pumping stations, gate-valves are located at
necessary points and elevations in the line to control the flow of water
and keep the pipe full, even to the extent of closing all such valves
tight and holding the line full without flow. This is for the purpose of
delivering through a full pipe any desired quantity of water less than
that required to keep the open pipe full. This, of course, is on account
of the wood pipe. As the differences of elevations are very great on the
gravity sections of the line, and as any one valve might inadvertently
become closed tight when other valves above would be open, the bursting
of the pipe under such conditions is prevented either by a pressure
relief valve attached to and immediately above the gate-valve, or by an
open stand-pipe erected on some suitable elevation between the valves.
This is more clearly shown on the profile, Plate V, of the ground line
and the hydraulic grades of the pipe line. An inspection of this profile
will show that these controlling valves are located so that, when
closed, the pressure against them does not rise above the maximum
pressure on the section above, due to the hydraulic grade of the line
when carrying its full capacity.

_Safety Valves_.--To prevent rupture of the pipe or injury to the pumps,
in case the pumping mains should become obstructed, a 6-in. pop safety
valve is mounted on the main just beyond the large air-chamber already
described. These valves are set to release at the maximum working
pressure of the pumps when the regular quantity of water is being
pumped, and they are piped to the adjacent reservoir, so that there is
no loss from them.

_Check-Valves_.--Check-valves are placed in the pumping main to prevent
the backward flow of water. There is one near the pumps, and one at the
upper end and outside of the reservoir into which the main discharges.

_Blow-Off Valves_.--These valves are located in all material valleys or
depressions.

_Stand-Pipes_.--Between the gate-valves, at certain points where the
maximum hydraulic grade is not more than 60 ft. above the surface of the
ground, open stand-pipes are erected. If the grade line is too high,
relief-valves are used, as stated. Also at two points, where a steep
grade ends near the ground surface and is followed by a flatter grade,
stand-pipes are erected.

These stand-pipes are of 6-in. iron pipe standing in a special casting
in the pipe line and enclosed in a concrete base. They are, of course,
open at the top, and vary in height from 15 to 60 ft., depending on the
elevation of the hydraulic grade. They have given some checks on the
position of this grade during the velocity measurements hereinafter
described. Their locations are shown on the profile, Plate V.

_Nogal Reservoir_.--Nogal Reservoir is the storage unit of the system,
and is on the north edge of a table-land, 1,700 ft. above the railway, on
the Carrizozo plain, 15 miles away. It is 11-1/2 miles from the head of
the pipe on Bonito Creek.

This reservoir is a natural basin or bowl, 1/2 mile in diameter across
the top, 1/4 mile on the bottom, and 36 ft. deep. A level line, 1,500 ft.
long, drawn from its bottom, comes out to grade on the north declivity
of the table-land. On this level line an open cut was made and the
outlet pipe laid. The cut was then closed by a dam.

The supply pipe from Bonito Creek delivers water into the basin over the
top of its southern rim, the water, as it leaves the pipe, flowing over
a standard weir, without end contractions, into a stone gutter. A
by-pass pipe, with suitable valves, passes around the western side of
the basin and connects to the outlet pipe.

This comparatively small amount of work equipped a very good natural
reservoir with a capacity of 422,000,000 gal., which can be increased to
1,000,000,000 gal. by embankments across low places in the rim.

_Service Reservoirs_.--At Coyote, an artificial service reservoir, 100
by 200 ft. on the bottom, with slopes of 1-1/2 on 1 and a total depth of
15 ft., serves as an equalizer of the flow to and away from the pumps
at that point. The pump-house is built alongside this reservoir. The
delivery pipe from the Nogal Reservoir runs directly to the pumps, but
has a tee-branch, 50 ft. long, into the Coyote Reservoir. This branch
passes through a valve chamber between the pump-house and the reservoir.
In this chamber there are controlling valves and an automatic overflow.
This overflow is provided against the contingency of a full reservoir
and idle pumps. If the pipe line is delivering water faster than the
pumps discharge it, the surplus goes into the reservoir. This
arrangement is self-acting and controlling. There is a similar
arrangement at the Luna pumping plant, also at the Carrizozo service
reservoir, and at the regulating reservoir on the Corona summit.

Each of the four service reservoirs is of the same size, and lined with
4 in. of 1:2:4 concrete. At Luna and Corona the concrete is reinforced
with 3/8-in. round rods spaced 12 in. from center to center, both ways.
This reinforcement should have been used in all the work.

_Pumping Plants_.--The pumps at Coyote and Luna are Nordberg duplex,
cross-compound, condensing, crank-and-fly-wheel machines, with 6-in.
plungers, traveling 600 ft. per min. at full normal speed, and designed
to work against 300 lb. per sq. in. They have a guaranteed efficiency of
135,000,000 ft-lb. per 1000 lb. of steam at 150 lb. and superheated 75
degrees.

The boilers are 125-h.p., Sterling, water-tube, with Foster
superheaters, and 33-in. stacks, 100 ft. high.

Each plant is in complete duplicate pump and boiler units, only one set
working at a time.

The pump building is a substantial concrete, brick, and steel structure,
50 by 80 ft. in plan, with a fire-wall, with two steel doors dividing
the floor space into an engine-room 50 by 50 ft., and a boiler-room 50
by 30 ft. A concrete coal-bin adjoins the exterior boiler-room door.
Coal is delivered directly from the car to the bin.

The plant is lighted by a small, but very complete, engine and dynamo on
one base and run by steam from the Sterling boilers.

The two plants are exactly alike throughout.

_Reservoir Leakage_.--The Nogal Reservoir basin is covered with from 2
to 5 ft. of good clay, except where it is punctured by a dike, or washed
down to the underlying sandstone by a few gullies. These punctures or
washes were covered or filled with clay from 1 to 4 ft. deep. During the
first season the leakage, above the 6-ft. contour, was at the rate of 2
in. per day.

As the water fell, due to leakage, evaporation, and use, a herd of from
300 to 400 cattle were worked around the shore line. This reduced the
leakage to 3/8 in. below 8 ft., and to nothing below 6 ft., above the
outlet. As the flow line rises higher each season, the puddling will be
continued to the top. The leakage at 12 ft. above the outlet, or 17 ft.
above the bottom, is still approximately 1 in. per day. The total
puddling, to date, covering two seasons, is equivalent to 11,150 days'
work of one cow, and covers an area of 1,500,000 sq. ft.

The clay packed densely, the final hoof marks being not more than 1/4
in. deep and remaining distinct under the water around the shore line
for one year. Apparently, the reservoir will finally become water-tight
at all elevations.

The soil in which the four service reservoirs on the railway are built
proved to be about the worst for such work. In its natural state on the
prairie, after the excavation for the reservoir was completed, it
filtered water at the rate of 3 ft. per day. Tamping and puddling still
left a filtration of 12 in. per day, with a tendency to increase. Enough
water filtered through the concrete to produce settlement and cracks.
Finally, the concrete was water-proofed with two coats of soap, two of
alum, and one of asphalt. This has made all the reservoirs water-tight.
Elaterite, an asphalt paint made by the Elaterite Paint and
Manufacturing Company, of Des Moines, Iowa, was used successfully on the
Luna Reservoir. This paint is applied cold, and preliminary tests showed
it to be quite efficient.

The analysis of the soil is as follows:


Loss on ignition                 3.35
Silica                          56.36
Oxide of iron                    2.93
Oxide of aluminum                8.97
Calcium oxide                   15.95
Magnesium oxide                  0.98
Oxides of sodium and potassium   0.47
Carbonic acid                   11.35
Sulphuric acid                   0.11
Chlorine                         0.04
Manganese                      Traces
                               ------
                               100.51
Insoluble matter, 64.50 per cent.


_Pipe-Line Leakage_.--There is no measurable leakage from the iron
pipe. By thorough inspection and measurement at the end of two years,
leakage on the wood pipe, between Coyote and Bonito Creek, from the
11-and 12-in. pipe, was found to be as follows:


On 8.6 miles, 11-in. pipe, 146,600 gal. per day = 17,046 gal. per mile.
 " 4     "    12  "    "    14,829  "    "   "  =  3,702  "    "    "


The 7-1/2-in. pipe on this section appears to be leaking less than the
12-in. pipe. Inspection and measurement of it are to be made in a short
time.

There is no material leakage from the 10-and 16-in. pipe between Bonito
Creek and Nogal Reservoir, as determined by velocity and volumetric
measurements hereafter described. The greatest probable error in the
velocity measurements would not exceed 1/2 per cent. If such error
existed, and was all charged to leakage, it would amount to but 17,204
gal. per day, or 1,582 gal. per mile, out of a daily delivery of 3,784,000
gal.; but the measured discharge of the pipe, as determined by the
velocity, was 5.84 sec-ft., while the mean maximum volume of this water
over the weir at the end of the pipe is recorded by the weir as 5.88
sec-ft.

From Coyote, east along the railway, the wood pipe is remarkably tight.
The rate of leakage from it, as determined by 600 observations uniformly
distributed, was as follows:


11-in. pipe              = 120 gal. per mile per day.
8-1/2 and 7-1/2-in. pipe = 268  "    "    "   "   "


The maximum rate on 1 mile was 1,613 gal. The minimum found was zero.

The observations were made by uncovering a joint and measuring the
leakage therefrom for 10 min. A graduated glass measuring to drams was
used. The rate of leakage varied from 5 drops to 45 oz. in 10 min. Of
the joints uncovered 57% was found to be leaking. It is rather
remarkable that, in the large leakage of the 11-and 12-in. pipe between
Coyote and Bonito, only one out of every eight joints was leaking. This
indicates a physical defect in such joints. The largest leak found on
one joint was at the rate of 17[,?]280 gal. per day. Leakage between or
through the staves is not measurable, as it is not fast enough to come
away in drops unless there is some imperfection in the wood.

The insignificant leakage of 120 gal., stated above, is from the 11-in.
pipe in the pumping main between Coyote and Corona. The present maximum
working pressure on it is 100 lb. per sq. in. All the figures given
above include visible and invisible leakage, the latter being such as
does not appear on the surface. The visible leakage is but a small part
of the total.

_Stopping the Leaks_.--Generally, any ordinary leak is readily stopped
by pine wedges. Sometimes a loose joint requires individual bands bolted
around it. Bran or saw-dust is effective in stopping the small leaks
which cannot be reached by the wedges. The good effect of the latter is
likely to be destroyed by a rapid emptying of the pipe. If the water is
drawn out faster than the air can enter through the air-valves, heavy
vacuums are formed down long slopes, and the air forces its way in
through the joints and between the staves. The result is that the pipe
will frequently leak badly for some time after it is refilled, although
it may have been tight previously.

A full pipe and a steady pressure are highly desirable. This doubtless
accounts to some extent for the extreme tightness of the wood pipe in
the pumping main.

_Grade Lines_.--The hydraulic grade lines, shown on Plate V, were laid
as best fitting the controlling elevations. The various diameters of
pipe were determined by Darcy's general formula, with _C_ = 0.00033 for
wood and = 0.00066 for iron pipe, checking by Kutter's formula, with _n_
= 0.01 for wood and = 0.012 for iron. These coefficients were taken as
conservative and on the safe side, and such they proved to be. It was
desired that the line should carry not less than 5 sec-ft. to Nogal and
half as much beyond.

_Velocities_.--The pipe line from Bonito Creek to the Nogal Reservoir
affords excellent conditions for velocity and capacity measurements,
there being no distribution service from it. Beginning at the creek, it
consists of 12,700 ft. of 10-in. wood pipe, with a hydraulic grade of
0.03338, followed by 48,000 ft. of 16-in. wood pipe, with a hydraulic
grade of 0.0030625, ending on the south rim of the Nogal Reservoir.
There is an open stand-pipe where the two pipes and grades join.

When this section of the line was laid, the last car of 16-in. pipe was
late in arriving and, as it was desirable to get water into the
reservoir as soon as possible, 500 ft. of 10-in. pipe were laid in the
lower part of the 16-in. line, near the reservoir, as indicated on Fig.
2, which shows the hydraulic grades and the pipe diameters of this
section of the line.

When the first two velocity measurements, of March 10th and 31st, 1908,
described below, were made (after the line had been put into service on
February 20th, 1908), the 500 ft. of 10-in. pipe were still in the
16-in. line, and the hydraulic grade was defined by the solid line,
_ABCDE_, Fig. 2.

When the third measurement, of May 12th, 1909, also described below, was
made, the 10-in. pipe had been replaced by 16-in. pipe, and the
hydraulic grade was defined by the solid line, _ABE_.


[Illustration: FIG. 2.]


The dotted line, _AFE_, is the approximate theoretical position which
the grade, _ABCDE_, should have assumed when the 500 ft. of 10-in. pipe
were taken out of the 16-in. line. On the contrary, it took the position
of the grade line, _ABE_.

During the interval between March, 1908, and May, 1909, the water came
to overflow from the stand-pipe at _B_, when the line was running under
full pressure, indicating an increase of capacity in the 10-in. pipe
greater than a corresponding increase in the 16-in. The alignment of the
10-in. line, vertically and horizontally, is more regular and uniform
than the 16-in. line. The latter has many abrupt curves and bends,
vertically and horizontally. It crosses nine sharp ridges and dips under
as many deep arroyos. This introduces a fixed element of frictional
resistance which does not decrease with the increasing smoothness of
the interior surface of wood pipe, and probably accounts for the higher
resistance of the 16-in. line.

From Fig. 2 it appears that, while the 10-in. line had an initial
coefficient of roughness slightly greater than 0.009 and now equal to
it, the 16-in. line had one equal at first but now slightly less than
0.01.

The line from Bonito Creek to Nogal Reservoir was to have a capacity of
5 sec-ft. Referring to the profile, it was determined that for the
hydraulic grade of 33-1/3 ft. per 1000 ft., a 10-in. pipe was necessary,
and that a 16-in. pipe was required for the grade of 3 ft. per 1000 ft.

_Test No. 1_.--On March 10th, 1908, a quantity of bran was poured into
the upper end of the 10-in. pipe at _A_ (Fig. 2), and the time of its
appearance at the lower end of the 16-in. pipe at _E_ was noted. The
time was 3 hours and 50 min.

This gave:

Area   of 10-in. pipe =     0.5454 sq. ft.
  "    "  16 "    "   =     1.3960  "   "
Length "  10 "    "   = 13,200 ft.
  "    "  16 "    "   = 47,500  "
Time,                 = 13,800 sec.


Let _x_ = velocity of flow in 16-in. pipe, in feet per second, then 2.56
_x_ = velocity of flow in 10-in. pipe, in feet per second.

From which:


 13,200    47,500
------- + ------- = 13,800
2.56_x_     _x_

            _x_   = 3.805

    and 2.56_x_   = 9.740


The discharge is:


     For the 16-in. pipe, 1.396  x 3.805 = 5.31 cu. ft. per sec.;
and, for the 10-in. pipe, 0.5454 x 9.74  = 5.31 cu. ft. per sec.


The question arose as to whether or not the particles of bran in the
water traveled as fast as the water flowed. It was also desired to check
by observation the relative velocities in the two pipes, as above
deduced.

_Test No. 2_.--To determine these points, a second test was made, on
March 31st, 1908, twenty days after the first one. In this test, green
aniline, red potassium permanganate, and bran were used. An observer
was placed at the end of the 10-in. line at _B_ (Fig. 2), and, by
letting a small quantity of water run from a relief-valve there, he was
able to note the time of the appearance of the colors and the bran.

The green was started in the upper end of the 10-in. pipe, at _A_ (Fig.
2), at 8.30 A.M. It appeared at _B_ in 22 min., and at _E_ in 3 hours and
52 min.

The red was started at 8.45 A.M. It reached _B_ in 21-1/2 min., but it
was so faded that the time of its appearance at _E_ could not be noted
exactly.

The bran was started at 9.00 A.M. It reached _B_ in 22 min., and
appeared at _E_ in 3 hours and 51 min.

From the average of these figures, the velocities were:


In the 16-in. pipe, 3.792 ft. per sec.
 "  "  10 "     "   9.695  "   "   "


and the discharges were:


In the 10-in. pipe, 5.287 cu. ft. per sec.
 "  "  16 "     "   5.293  "   "   "   "


The application of the equation for equalized relative velocities, as in
the first test, gives:


Velocity in  16-in. pipe = 9.705
   "     "   10 "     "  = 3.791
Discharge of 16 "     "  = 5.292
   "      "  10 "     "  = 5.293


These last figures would check exactly, except for dropping figures in
the fourth decimal place.

The results of these two tests, considering that 20 days elapsed between
them, are in very close agreement, and establish the fact that bran is
an accurate medium of measurement.

_Test No 3_.--The 500 ft. of 10-in. pipe in the 16-in. line near the
reservoir (Fig. 2) were replaced by 16-in. pipe in the summer of 1908.

On May 12th, 1909, green aniline was started through the pipe at _A_ at
11.00 A.M., 11.30 A.M., and 12.00 P.M. In each case it appeared at _E_ in
3 hours and 31 min. This time is 20 min. less than that observed in the
tests of the previous year, and is due to the removal of the 10-in. pipe
from the 16-in. line and to the increasing smoothness of the interior
surface of the pipe.

The relative velocities and discharges under the third test, using the
nomenclature of the first and correcting the lengths of pipe on account
of the removal of the 10-in. pipe near the reservoir, are:


48,000  +     12,700
-----      --------- = 12,660
 _x_         2.56_x_

                 _x_ =  4.183

         and 2.56_x_ = 10.708


and the discharges are:


From the 10-in. pipe = 5.840 cu. ft. per sec.
  "   "  16 "    "   = 5.839  "   "   "   "


_Coefficients_.--On May 12th, 1909, the 10-in. line was working on a
grade of 0.03338, and, with _n_ = 0.009, _C_ should have been 131. It
was actually 138, making _n_ = 0.00866. The 16-in. line was working on a
grade of 0.0030625, and, with _n_ = 0.009, _C_ should have been 145. It
was actually 141, making _n_ = 0.0092.

Referring to the estimated hydraulic grade between Coyote and Corona
(Plate V), the coefficients, 0.01 and 0.012, were used for wood and
iron, respectively, on which basis, the maximum pressure at Coyote was
expected to be 304 lb. and, at Luna, 310 lb. per sq. in. The actual
maximum at Coyote, with pumps at full normal speed, was 270 lb., and, at
Luna, 278 lb., indicating that the values of the coefficients taken were
too high. This checks with the tests between Bonito and Nogal.

Of course, the iron pipe will increase in roughness, and, in time the
pumping pressure will approach the calculated amount. The interior of
the iron pipe now has a smooth coat of asphalt.

_Pipe Breakage_.--The breakage or damage to the wood pipe in shipment
occurred on the ends, the tenons being most exposed to injury from
shifting in the cars. The damage due to the shipment and handling of the
Elmira pipe was 1% and one-half as much for the Bay City pipe. Less than
6 pieces out of 100,000 laid have had to be removed from the trench.

The iron pipe came from Chattanooga, and was badly handled in transit.
Much of it was transferred en route, and 6% was broken when received.
The breaks were generally cracks of the spigot end. Of this broken pipe,
practically all was cut and laid. The average cut was about 16 in. from
the spigot end of 533 pieces. This cut pipe has caused no trouble in the
trench.

At least 27 pieces of cracked pipe got past the field inspectors and
into the trench. This cracked pipe began blowing out at a pressure of 50
lb., and continued until the full normal pumping pressure was reached,
when the breaks suddenly ceased. These pipes were broken out at the rate
of 1 or 2 per day, with an occasional day between breaks. A 24-hour
work-train service was maintained. The pipe gang soon became skilled,
and could put in a new section of pipe in from 4 to 6 hours. Each break
generally caused an interruption of about 6 hours to the pumps on the
section where it occurred. The best record was 3 hours and 50 min. from
the stopping to the starting of the pumps. This strenuous life lasted 30
days. Most of these breaks were in or near the middle of the pipe.
Evidently, the field inspectors were not expecting cracks in that
locality. An inspection usually indicated that the pipe had been struck
by the bell of another one in the vicinity of the break.

All pipes were lifted from the car carefully and laid down at the trench
along the track in a single movement by a logging crane, and were not
broken in such handling.

Three breaks only have been reported as due to defective metal or
casting. No break of a sound shell of full thickness has been found.

_Trenching_.--Deep frosts are unknown in this section. The pipe was laid
so that the top was about 1 ft. below the surface of the ground. The
trenching was a simple matter. Part of the work between Bonito and the
railway on the Carrizozo plain was done by Buckeye ditchers. All other
ditching was done by a railroad plow followed by pick and shovel, or by
the two latter tools only. The ditcher could open 2,000 ft. of trench per
day, but averaged about 500. The plow and 35 men could open 3,500 ft. A
chain about 6 ft. long separated the end of the plow beam and the double
tree. In this way the trench was plowed to the bottom. Two mules, two
men, and a scraper could back-fill 3,500 ft. per day.

_Pipe Laying_.--Between Bonito and the railway, one gang of ten men
could lay 4,000 ft. of 12-in. pipe per day. The average was much less,
owing to a variety of causes. At the end, the railway company added to
the contractor's force, and laid the last 10 miles of pipe in 7 days,
there being a half dozen separate gangs at work.

Along the railway, the day's record on wood pipe was 4,000 ft. of 11-in.,
6,200 ft. of 7-1/2-in. and 8345 ft. of 3-1/2-in, pipe laid by a gang of
eight men after the pipe was distributed along the trench. These eight
men, of whom five were Americans, laid 76 miles of pipe, and became
expert. Their operation was like the working of a clock.

On the 12-in. iron pipe, the regular day's work was 96 joints, or 1,152
ft. of pipe laid and caulked. The record was 1,644 ft. Two gangs laid
101,300 lin. ft. in 60 days. Such a gang consisted of 1 foreman, 1
inspector, 8 caulkers, 4 yarners, 1 melter, 1 pourer, 1 helper, and 10
men putting pipe into the trench.

_Cost Data_.--The pipe from Bonito to the railway was laid by contract.
The price was 18 cents per lin. ft. laid and back-filled from the
railway to the Nogal Reservoir, and 28 cents from Nogal to Bonito. In
addition, 50 cents per ton per mile was paid for hauling pipe, and extra
compensation for setting valves. From Coyote, east along the railway,
the work was done by the railway company under the writer's direction.

The total cost of laying 384,300 ft. of wood pipe, from 11 to 3-1/2 in.
in diameter, was $18,156.77, or 4.72 cents per ft., divided as follows:


Ditching       $0.0249
Laying          0.0113
Back-filling    0.0110
               -------
    Total      $0.0472


This includes unloading from the cars. Train service cost 1/3 cent per
ft. additional.

The pipe gang, including back-filling, consisted of 1 foreman, at $100
per month, one assistant foreman at $75, and about 30 Mexicans at $1 per
day. The rates were the same in the ditching gang. The plow team cost $6
per day.

Including all general expense, the cost does not exceed 6 cents per lin.
ft.

The cost of laying 101,300 ft. of 12-in. cast-iron pipe was $23826.67, or
23.5 cents per ft., divided as follows:


Ditching       $0.0249
Laying          0.1180
Back-filling    0.0110
Lead            0.0790
Oakum           0.0014
               -------
    Total      $0.2343


This includes train service and unloading pipe, but nothing for tools.
The foreman and inspector received $100 per month, the caulkers, $3;
pourer, $3; melter, $2.50; 2 pipe-men, $2, and laborers, $1 per day.
Professional caulkers wanted $5 per day. Carpenters, blacksmiths, and
boiler-makers made good caulkers; their work is standing perfectly under
a 275-lb. service.

The cost of the pumping plants complete per horse-power is as follows:


Pumps      $79.00
Boilers     18.70
Building    41.70
           ------
  Total   $139.40 per h.p.


The approximate cost per million gallons of storage capacity is as
follows:


Nogal Storage Reservoir  $103.00
Carrizozo Service  "    3,040.00
Coyote      "      "    2,880.00
Luna        "      "    3,480.00
Corona      "      "    2,720.00


To cover general expense, 3% should be added to all the costs above
given. The costs per foot of pipe-laying include the setting of all
specials, valves, and stand-pipes. The difference of cost in laying
11-in. and 3-1/2-in. wood pipe is not nearly as great as the difference
in diameter or the total quantity laid on record days. While the record
is 4,000 ft. and 8,345 ft., the 76 miles of pipe of all diameters were
laid in a total time, including all delays, of 223 days, or an average
of only 1723 ft. per day. The cost of the 11-in. pipe is covered by 7
cents per ft. The pipe was laid by a single gang as fast as it was
received from the factory.

The reduction from 7 to 3-1/2 in. at Mile 230 (Plate V) is on account of
delivering water to the Santa Fé's new transcontinental low-grade line
which crosses the El Paso and Southwestern Railway at Vaughn, and has a
division point there. On its adjacent divisions, the Santa Fé had the
same trouble with local waters which compelled the El Paso and
Southwestern to find a better supply. The Bonito water is conducted to
and used at points 160 miles from its origin on Bonito Creek.




DISCUSSION


G.E.P. SMITH, ASSOC. M. AM. SOC. C.E. (by letter).--The author has done
great service to the West in demonstrating the practicability of
transporting small water supplies to great distances.

Close association with the desert is required to appreciate fully its
waterless condition. For most of the year there are no living waters on
the surface. As a rule, ground-waters are concentrated beneath very
limited areas of valley land. The great masses of valley fill in some
places are underdrained to great depths and in other places are so
compacted and cemented as to be impervious. Wells sometimes are driven
from 1,000 to 2,000 ft., without securing any supply at all. Moreover,
desert ground-waters are often exceedingly hard or alkaline, and,
therefore, are unfit for many uses.

In going to the high mountains for a supply, the author has struck a
principle of wide application. In many of the mountains of the Southwest
there are springs and small streams of excellent water. Often, as in the
case discussed, very little storage is required. These streams, however,
are absorbed or disappear before reaching even the mouths of the cañons,
and the problem has been to convey the water to distant cities and
mining camps at reasonable cost. There are several cities in Arizona now
possessing pumped water supplies, which have possible gravity supplies
of superior quality. The writer believes that ultimately the gravity
supplies will replace the pumping plants.

In the Bonita pipe line, wood-stave pipe was used for the gravity
sections. In other localities, where the grade of the line is very
uniform, as would be the case down a typical clinoplain, cement pipe is
deserving of consideration. It would cost no more than wood stave, would
be more durable, and, furthermore, it need have no greater leakage. Its
cost, however, increases rapidly when built to withstand high pressures.

The use of bran for determining velocities is of interest. The results
are in close accord with those obtained from the weir measurements. In
the measurement of ground-water velocities by means of salts in
solution, it is found that the velocities of different filaments of
waters are extremely variable, and a quart of salt solution, after
moving forward a few feet, is widely dispersed. It would be of value to
know to what extent the bran was distributed during its 4-hour journey
through the pipe line, and during how many minutes it was being
discharged at the lower end of the line. Was the first appearance, or
the average time of appearance, accepted for computing the velocity of
flow?

KENNETH ALLEN, M. AM. SOC. C.E. (by letter).--From its lightness,
toughness, flexibility, and the facility with which it can be laid, wood
pipe has manifest advantages for use in inaccessible places and where
handling is difficult; loss in transportation is almost negligible, it
will stand much unequal settlement without cracking, and ordinary leaks
are easily repaired.

The coating of the bands is of such great importance that it should be
inspected very thoroughly, in order to remedy defects before the
back-filling is done. The writer has found Durable Metal Coating an
excellent preservative. Bands coated with this preparation were buried
in a salt marsh, and, after a year, the metal was found intact and the
coating fresh and elastic. This coating, however, does not adhere very
firmly to a smooth metal surface, so that, with careless handling,
patches may become rubbed or torn off.

There is no advantage in coating the surface of the pipe. To prevent
decay, such pipe should carry water under pressure or be laid in a
saturated soil, so that the wood of which it is made will always be
saturated, and coating the wood may interfere with this. Under these
conditions the life of such pipe is not known, but it is evidently very
great. Large quantities of wood pipe have been removed from trenches in
Boston, New York City. Philadelphia, Baltimore, and elsewhere, usually
in perfectly sound condition. It was commonly made of logs of spruce,
yellow pine, or oak, from 12 to 18 ft. long, 12 to 24 in. in diameter,
and with a bore from 3 to 6 in. in diameter. Some 6-in. pipe taken up in
Philadelphia had an external diameter of 30 in. The ends were usually
bound with wrought-iron collars, and adjacent lengths were connected by
an iron thimble driven into the end of each piece.

A few years ago the writer took up more than 2000 ft. of wood pipe of
this kind, which had been laid in saturated soil about a century
earlier. It was of Southern pine logs, about 16 in. in diameter, 14-1/2
ft. long, and had a 5-in. bore. Joints were made with tapering cast-iron
ferrules 9 in. long, and connections to smaller service pipes were made
with similar but smaller ferrules of cast brass. The wood was apparently
as sound as when it was first laid.

The use of flat iron for wrapping or banding pipe is believed to be
wrong in principle. Round iron furnishes the requisite strength with the
least exposure to corrosion, and ensures a more perfect contact with the
wood.

In a 42-in. stave pipe laid by the writer for the Water Department of
Atlantic City, N.J., the lumber used was Washington fir, cypress having
been found difficult to procure in sufficient quantity, and redwood
being more costly and no better. In this, his experience coincided with
that of the author. Cedar was considered, but could not be obtained in
sufficient lengths or quantity, and long-leaf pine which would have
passed the somewhat rigid specifications would have been difficult to
secure. It is believed, however, that there is a field at least for
long-leaf pine for such construction. Washington fir was found admirable
in every respect, and was moderate in cost at that time.

The bands were bent in the field, and, after heating in an oven for
about 3 min., were dipped in bunches of five into a kettle of melted
mineral rubber at a temperature of about 400° Fahr., and then hung up
for the coating to harden. This took place rapidly, as the work was done
in winter. If the band were wound spirally, the coating would have to be
done in the shop, but field coating is preferable, as it avoids injury
to the coating during transportation.

An advantage of wood pipe for conveying water is its low coefficient of
friction. The results obtained by the author (_n_ = 0.00866 to 0.0092)
appear to be very low as compared with determinations made for
wood-stave pipe. Kutter's coefficient for the latter varies from 0.0096
in the case of the 30-in. pipe at Denver,[B] to from 0.012 to 0.015 as
determined by Messrs. Marx, Wing, and Hoskins for the 72-in. pipe of the
Pioneer Power Plant of Ogden.[C] Probably 0.011 would be a fairly safe
figure to use in designing new work.


[Illustration: FIG. 3. DETAILS OF OLD WOOD PIPE.]


J.L. CAMPBELL, M. AM. SOC. C.E. (by letter).--Referring to Mr. Smith's
question about the velocity measurements by bran, the first appearance
of the bran and the colors was taken because the intervals of time given
thereby were in close accord among themselves and with the weir
measurements. The time from the first trace of bran or color until final
disappearance varied between 15 and 20 min. Bran in abundance or
pronounced color showed in 2 min. after the first appearance, while the
disappearance or fading was noticeable after a period of from 7 to 10
min. It required 2-1/2 min. to get the bran or colors into the intake at
the head of the line and leave the water clear.


[Footnote B: _Transactions_, Am. Soc. C.E., Vol. XXXVI, p. 26.]

[Footnote C: _Journal_, New England Water Works Assoc., Vol. XXII, p.
279.]


Mr. Allen refers to the bored wood pipe laid many years ago in Eastern
cities. The writer's experience indicates that a bored pipe will not
deliver as much water as a planed stave pipe, on account of the greater
interior roughness of the former.

Referring to the profile, the 8-1/2-in. pipe between Corona and Duran
had a theoretical capacity of 744,000 gal. per day. A recent test showed
it to be delivering water at the rate of 759,000 gal. per day.

The 3-1/2-in. pipe between Vaughn and Pastura had a theoretical capacity
of 84 000 gal. per day. It delivers only 65,000 gal. per day. There are
5 miles of bored pipe on the upper end of this section. Pressure
gaugings show a hydraulic gradient in excess of the theoretical on the
bored pipe, whereas the stave pipe on the lower end carries the 65,000
gal. on a flatter gradient than the theoretical one.

Experience on this pipe line indicates that _n_ = 0.009, in Kutter's
formula, closely approximates the capacity of planed wood stave pipes of
8 to 16 in. in diameter. The writer favors the use of 0.01 as
conservative and economical.

With equal exposure to corrosion, the round band is undoubtedly the
better, but the flat band has the advantage of being completely buried
in the protective coat of the particular kind of wood pipe under
consideration.