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CIVIL ENGINEERING PROBLEMS IN THE CONSTRUCTION OF I

A GUGGENHEIM-PROCESS NITHATE PLANT ON THE PAMPA OF CHILE

A Thesis Submitted to the Faculty
of
Michigan State College
of

Agriculture and Applied Science

by
John Sterling Lang
Candidate for Degree

of
Civil Engineer

June, 1952

7;?

4.91.0 «

‘ES

THE

rl'uny’? ElleAm I414
.. r. . 4 .»q

INTRODUCTION

For any construction project there must be a back-
ground of study and work which leads to the adoption of
that particular project at the site it is finally to be
found. Each project has its own peculiar problems which
must be studied and handled in the manner best suited to
the conditions. I

. Locating a plant for the production of sodium
nitrate by the Guggenheim-Process necessitates the prov—
ing of an area of suffidgent extent of mineable ore to
warrant the erection of a plant of such magnitude, picking
the most advantageous site within this area for the erec-
tion of the structures, and a study of sources of power,
water and materials, and the problem of transportation.
Besides these main items, there are numerous other con—
siderations which must be treated before the actual con-
struction of the plant can be started.

All construction jobs are alike in being a series
of problems of using the best available means to the re-
quired end, although each type of job differs from others

Of the same type as prevailing circumstances dictate. Each

1021.“ l

-2-
day's work is distinct from the preceding, and minor diffi—
culties are always being encountered which call for solution
based on previous experience, or which call for ingenuity.

This paper will deal with all the phases of this sub-
ject in which the Civil Engineer is interested and has an
active part; and may prove a valuable reference not only as to

methods but more especially as to procedure.

General Description of the Nitrate Pampg

The nitrate pampa of Chile is a plain, as the word
denotes, but not the waving-grass type Which seems to be the
popular conception of a ”pampa", being in reality a barren,
desolate expanse of undulating desert. On its surface, there
is absolutely no natural vegetation nor’animal life, due main-
ly to the high salt content of the ground and the lack of
water. The innumerable small hills and hogbacks are hardly
appreciable in the monotony of grayish color given the sandy,
rocky surface in the brilliant sunlight.

The narrow strip of land occupied by the nitrate-bear-
ing ore lies between the Coastal Range on the west, and the
foothills of the Cordillera on the east, extending roughly
from Arica on the north to Chanaral on the south. The aver-
age width being approximately 15 miles and the length 500

miles,‘ith an average elevation of 4000 feet above sea level.

 

aunurfpf .3.- .. b7 .,

 

-5-

The Coastal Range rises precipitously from the Ocean,
access to the pampa being gained by'making a zig-zag route
along the face of the mountains, a steep ascent up a canyon,
or by a combination of the two.

Rainfall as a factor against which precautions must
be taken is non-existent. There are no recording stations
because, practically speaking, there is nothing to record.
Throughout the year, there are perhaps half a dozen showers
which are very light and of only a few minutes' duration, and
one which lasts several hours, and that is all. It is a
factor not considered in design of buildings, roads, or connect-
-ing units. When enough rain falls to slightly dampen the
ground, the surface color changes to a dark brown, which is a
great relief to the eyes.

Fogs frequently find their way up the canyons at night,
and at times last several hours of the morning, giving a cool
freshness to the air, though lowering visibility. However, as
the sun rises, the fog rapidly disperses, leaving the usual
clear air with a few clouds at the horizon.

As the sun approaches the zenith, its brilliance and
glare become more pronounced; the heat waves lengthen and burn
as the strong west winds of the afternoon blow with increasing

intensity. The evening and morning breezes are very gentle as

 

.‘wr. .Lpl‘.

-4—

a rule and change direction late in the day, as they are always
found blowing toward the Ocean in the morning. Combining the
location of the pampa with the range of temperature between
night and day may give the explanation of the shifting of
wind direction. Occasionally on winter nights (winter being
from June to September), the temperature falls to the freezing
point, and at midday in summer, rises to 90 degrees Fahrenheit
in the shade, with variations as the seasons change, although
the nights are always cool, which seems to be a blessed trait
of all deserts.

This, then, is the setting for the construction of the
huge plants as now designed for the production of sodium nitrate
by the process perfected under the direction of the*Guggenheim

Brothers.

    
  
  

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-5-

Government Trigggulatigg

The Chilean Government has done very careful work
in the establishment of a triangulation system which now
almost completely covers every section of the country.
The survey parties, consisting of highly trained and
very competent men, equipped with the finest types of in-
struments and apparatus, have produced results which have
been proved equal to that of the U. S. Coast and Geodetic
Surveys in exactness.

The method consisted of starting from the ends of
a Base Line, turning angles to desired points, going from
these points to others ahead, and so on to another Base
Line of known length and the angles balanced thereto. In
the northern part of the country, the Base Lines have been
located on the pampa because longer stretches of Open level
country are here available than along the coast to the
west, or in the foothills to the east. Exact measurement
is taken between the end points of the Line, and the lati-
tude and Longitude of each determined by astronomical ob—
servations. Exact levels are run from mean sea-level, and
the length of the Base corrected to sea—level. Each of
these steps, as well as each angle turned, is repeated,

checked, and rechecked.

-7-

The network of Primary Triangulation Stations
was run from one Base to another with distances between
Stations varying from 55 to 40 kilometers, as determined
by the t0pography, and the whole system carefully bal-
anced.‘

.The number of hours which could be utilized every
day for such field work is, of necessity, small. The
afternoons are counted useless because of the force of
the wind and the dazzling heat waves which make accurate
work at this time of day impossible. Even a few hours
after sunrise, visibility decreases with the increase
in glare, and an object at any appreciable distance is
carried from side to side as the breeze shifts the heat
waves. Accurate work is done, therefore, only the first
few hours immediately after sunrise. Foggy mornings
_eliminate the entire day shnce, by the time the fog dis-
perses, the heat has risen, and with it the other elements
which make accuracy impossible.

On the pampa the topography is quite ideal for tri-
angulation work, with its absence of vegetation of any
description, and the hills which make perfect stations
for observation. Lack of rain and unstable footing

eliminates other sources of discomfort to most field

parties.

-3-

At times, no more than an hour a day is available
for the actual triangulation work, which means that everyb
thing must be placed in readiness before sunrise so that
advantage may be taken of every minute of the brief period,
starting as soon as visibility will permit.

Having the Primary Stations established, the Govern-
ment has continued the work with a system of Secondary and
also Tertiary Stations, in those sections where the possible
need for more numerous points has warranted. Therefore,
today, an extremely comprehensive system of land-survey

references is to be encountered.

0re—body;Locations -Government

The story of the discovery and first uses of nitrate
as an aid to agriculture and an element of explosives,
dates back to the sixteenth century, and is involved with
traditions and legends, and so will not be treated here.
Let it, then, suffice to say that the discovery was made
at the northern end of Chile as the map shows this country
today, and that the first export of nitrate was made from
the Port of Iquique, consigned to England in 1820.

Nitrate lands were sold outright at first, but as
the value of the product became recognized through world
demand, the lands, or rather the mining rights, were

leased on a basis of square kilometers of area and with

-9-

the only stipulation that the boundary must be continuous.
As the nitrate-producing industry grew and the sales rose,
it became evident to the Government that the choicest
areas only were being leased and the greatest share of
the land left in a miserable state, besides a large reve-
nue being lost to the country. It was therefore decided
that mining rights should be leased in accordance with
the expected output as determined by the grade of the ore
and the size of the ore-body in an area. The system of
sampling the lands changed in manner a number of times
until the present system was evolved.

The prospecting is now done by the Government.
Sample pits are sunk at intervals of 400 meters over the
entire territory and where the ore-body'proves good,
other pits are sunk at 200 meter intervals, and for a
still more accurate estimate, at 100 meter intervals.
These pits are tied-in to the triangulation system for
recording and plotting on maps, and the assays of the
rock give the thickness and grade of the ore body. From
this data the estimate is made of the possible output.

With the foregoing information at hand, the Govern-
ment sells mining rights to any section of land desired,
after advertising for bids, and selling to the highest

bidder.

-10-

Under the hand-mining methods of production, a cut—
off of 15% nitrate in the ore is accepted as the limit of
workable ore, and therefore the larger percentage of the
nitrate ground is left untouched. With the mechanical
mining methods employed under the GuggenheimeProcess of
production, a 7% cut-off is used, thereby mining out the
larger percentage of the ground, in an almost continuous

cut, which allows more efficient and larger scale Operation.

gipeable Areas - Frigate Surveyg

The present law by which only the Government may
locate and sink sample pits, is of recent origin, and
therefore does not embrace numerous lands held under
previous rulings. These small holdings are of very
irregular shape, since they consist only of the high
grade ore which runs above 15%. These irregular scattered
parcels do not conform to mechanical mining methods, and
therefore all the area is united inside long straight
boundary lines. In the instance of the latest plant built,
"Oficina Pedro de Valdivia", special permission was ob-
tained by the Anglo-Chilean Consolidated Nitrate Company,
to sink all additional pits necessary for completely cover-

ing the squaredaup area, the sampling to be check by the

-11-
Government.

The Company sent out field parties for the purpose
of completing the system of pits, plotting all new and
old pits on a tepographical map of the whole area, and
sampling all pits for a check on previous work and for
estimating the possible output to determine the feasi—
bility of the area for the construction of a fifty mill-
ion dollar plant.

To this end, data must first be obtained from the
Government Engineering Department which give descriptions
of the triangulation stations in that section and of the
sample pits tested. Tepographical maps of parts of the
area may be available, but it has been found more practi—
cal to ignore them and make an independent survey, using
only the established government points and bench marks.

A chain traverse is therefore run from one triangulation
station to another, along a route best adapted for the
location of instrument points for topographical surveying,
and elevations are established on the instrument points
by running circuits of closed levels. All the work is
checked and balanced, and the t0pography taken from the
established points for mapping on one-meter contour inter-
vals. At the same time that the topographical notes are
being taken, sights are also taken to each existing sample

pit. Where an additional instrument point is needed, it

-12-
may be located by a stadia "shot" for both distance and
elevation. The one-meter contour interval is sufficiently
small to give the desired information as to general sur—
face topography, as is not so small but that a consider—
able area may be covered every day with a party of two or
three rodmen.

The sinking and sampling of the test pits is purely
the mining engineer's work and will not be detailed here.
In outline, the work consists of stripping the loose layer
of dirt off from the rock, which is drilled and blasted
in successive steps of approximately three feet depth,
down to such a depth that nitrate-bearing rock is no long-
er encountered. A completed pit is three feet in diameter
more or less, and extends down to a depth of from three to
ten or twelve meters. Drilling is necessarily done by
hand, since the transportation of air compressors and hose
and drills has not as yet proved economical. The drill
holes are loaded with explosive, shot, cleaned out, and
the operation continued. The presence of nitrate is
tested by chipping particles of the rock onto a lighted
wick and noting the burning or sparkling which takes
place. The rock is classified as it appears along the
face of the pit, and samples are tested in a laboratory
to determine the exact percentage of the nitrate, since

the wick tests gives only an estimate. An area of in-

 

 

 

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locating the plant on ground which otherwise would be
mined is out of the question. Although it would be
' possible to place the permanent town on such ground, it
would be very undesirable as it would necessitate small
units being completed, while miniNg and the essential
blasting was being done, before other units could be
completed. Hence the need for finding a suitable site
on barren ground.

The ore is tranSported from the various sections
of the mine to the plant at the primary crushers, in
flat bottom gondola-type cars of 55 ton capacity, 6 to
9 cars in a convoy, moved by electric locomotives. The
motive power is derived from a diesel engine power house
and fed through trolleys on the main lines, the locomotives
running from storage batteries on the branch lines along
which the cars are loaded. The plant should be situated
as near as possible to the center of gravity of the ore
body, or perhaps slightly downgrade from the center of
gravity, and at an elevation which will cause no excessive
gradient to be overcome on the ore-train route to the
crushers. This latter point of gradient is not of prime

importance since the grade can be lowered by laying out a

-15-
longer, more circuitous route, but the matter of distance
is Of great importance in economical Operation, and there-
fore, the center of gravity is the goal aimed at, rather
than giving preference to the tOpographical features.

The suitability of the foundation materials for
hearing the structures to be placed upon them is of vital
importance to any projected building program. That the'
material under the loose covering of sand and stone is
rock, does not detract from the care with which it must be
examined because Of its seamy structure and high percent-
age of various soluble salts. Therefore, prospecting is
done in the areas considered suitable from other view-
points for a plant-site by sinking test pits in the same
manner, but deeper than those sunk by the Mine Department
for ore. In prospecting for good foundation material for
the Oficina Pedro de Valdivia, pits were sunk in some in-
stances to a depth of 15 meters and a salt content too
great for the support Of the buildings still encountered,
and the work discontinued because the accumulation of
gases became too strong. And so, one by one, the pro-
posed areas were discarded in favor of the present site,
which was finally accepted more through necessity than its

being ideally situated, with reference to the ore body.

-15-
It stands well down from the center of gravity and on hard,
almost granite-like rock, of low salt content. The matter
of the soluble salt content is of utmost importance because
of the amount of spill and leakage of water and solutions
which is bound to occur, and the effect this would have on
the crumbling and settlement Of the foundations. Earth-
quakes, though quite frequent, are of only slight force, but
must be considered in the design of structures and foundations.
The most important single factor in the Operation
of the plant is the disposal of the tailings, or waste mater-
ial, known as "Ripio'. It is taken from the leaching vats
by clamshell buckets operated from movable cantilever brid—
ges which span the vats from one side, and dumped into cars,
run alongside and hauled out on the disposal track loop.
This waste material, being wet, is of equal tonnage with the
dry are delivered at the crushers from the mine, and runs
from 200 to 600 thousand tons per month, depending On the
rate at which the plant is Operating. A saving of only one
cent per ton will aggregate a considerable amount over even
a short period of time, and great stress is consequently
given to economical disposal. It is desired that there be
an area adjacent to a location fOr the vets, and sloping
away from it, so that by keeping the upper surface level for

economical haulage, the face Of the dump will be high and long,

-17-

and the need for track shifting will not be continuous, and
the haulage distance will not increase in direct proportion
to the amount dumped.

Wind direction is Of no importance in the choice
of the site itself, but is the main factor in determining the
relation of one unit to another. It is desired to keep the
crusher and vat-dust from blowing over the living quarters,
power house, electrical units, and other plant buildings. To
this end of locating the units, large scale accurate topographi—

cal maps are needed.

Preliminary Plantsite Surveys

The mine department, logically, does not spend time
taking tOpography Of the areas shown by the sample pits to be .
barren of ore, and so it falls to the Plant Construction de-
partment to extend the contours to cover the areas which appear
from actual observation of the land to be possible plant sites.
This work is done in the same manner as was that done by the
mine engineering staff -— running chain and stadia traverses
from the established triangulation stations, and running sys—
tems Of check levels to all the instrument points chosen. The
traverse lines are plotted on a large map having a scale of
1:5000, the triangulation stations shown, as well as the instru—

ment points with.their designations and elevations. On this

-18-
same map, the contour lines of the mine are traced for
the purpose of tying in with the new lines, and as a
check for discovering obvious errors.

The topography itself is taken from the points
established along the balanced traverse line. Zero read-
ings are first taken by sighting on another instrument
point on the traverse line and making all reading on the
horizontal verniers rather than using the magnetic read-
ings, because they can be read more quickly and accurate-
ly, and the magnetic readings are taken only from time to
time as checks on the bearings.

Excepting the instrument-man, the party was made
up of Chilenos, the note-keeper being the one who could
write the most legibly, and the three rodmen, among whom
there was one with some experience in the work, and who
was therefore commissioned to keep an eye on the others to
see that they learn as rapidly as possible to pick the
desired points at which to place the rod. It was found
practical to designate a color tOreach of the rodmen, and
the instrumentman to have a square of cloth of the same
colors. As each flag was waved, the rodman knew he was
to move to another point, place the rod and wait until his

color was waved again. Because of the monotony Of the

-19-
ground color, the entire surface at a distance appears
flattened out to a plain, and so stress had to be placed
on the rodmen picking the tOps of knolls and the lowest
points between them, banks and beds of old dry rivers, and
other irregularities in the surface. By correcting the
positions chosen by the rodmen when they were close to the
instrument, they soon learned which were the desired points,
and so could be trusted at a distance. of necessity, the
longer readings were taken in the morning while the air was
clearest, and drawing toward the instrument as the heat
waves and wind disturbed the air. A number of scattered
'points were recorded as far as 800 meters from the instrue
ment, but usually the outer edge Of points was not more
than 600 meters distant. Even with the inexperienced rod—
men, and with instrumentmen who may have done very little
topographical surveying, the parties averaged close to 400
points recorded daily, and with training a party has turned
in 800 points. With the party organized, the routine of
the instrumentmen became one of calling out figures in Span-
ish to his notekeeper, as: horizontal angle, distance,
(flag), vertical angle, and so on. The main difficulty
encountered, besides the inexperience Of the members of the

party, was from the wind in its shifting the heat waves and

-20-
thereby carrying an Object with it, and its force in the
later part Of the day, against which the instrumentmen

must be braced while reading the verniers.

Studies for Communication and Sources of Materials

 

The preliminary tOpographical maps were completed
as rapidly as possible with the field engineers aiding the
Office men in the evenings with the calculations Of the
recorded notes and plotting onto the map, co that the in-
formation might be available for use in conjunction with
the factors aforementioned in the determination Of the
plantsite.

At the same time that these studies are being made,
investigations are carried on to locate sources of sand and
gravel for use in the construction work, water for building
purposes and permanent use, and for transportation facili-
ties to and from the plant.

Sand was found in the dry river beds and on flats,
of good quality and properties, but only in quantity suffi-
cient merely to do the preliminary work, and not enough to
warrant the erection of a recovery plant. The same test
pits sunk for locating supporting foundation material for
the buildings, were also examined for concrete aggregate

qualifications. A location was chosen at a hill, 8 kilo-

MAX. 100 WW

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-21-
meters from the present plantsite, composed of rhyolite of
good hardness and only very slightly decomposed. The quarry
was here dug into the side of the hill by blasting out the
rock in steps and advancing the track as was required to
keep it against the face of the cut. The rock was hand
loaded into cars which were run to the bins and discharged.
Four jaw crushers capable of handling 100 tons of rock per
hour, were installed and used throughout the construction
work. The bulk of the sand was also produced at this same
point by passing the finer gravel through a pair of hori—
zontal rolls. The entire output was washed before sending
it to the concrete mixing plants, and the resulting material
was good hard, sharp sand and gravel, with a very low salt
content. At the height of the construction work, river
sand was brought in by trucks to keep the aggregate quantity
sufficient to supply the demands of the numerous jobs requir-
ing concrete at the same time.

Water first came to the property in a tank truck,
from the Oficina JosngranciscO Vergara, which is now a sub-
sidiary of the Lautaro Nitrate Company, Limited, at which
there is a pumping station supplied from the Rio Loa at a
distance of 22 kilometers. The first field Office was at
the "Las Bombas" station on the State Longitudinal Railway,

which runs from Iquique to Santiago, and is only 5 kilometers

-22-
from the present location of the Oficina Pedro de Valdivia.
The fresh water came to Las Bombas by tank car from a
junction point on the Railway at Baquedano, and the salt water
by pipe line from the Rio Loa. The original source of all
the water in this region is the Rio Loa, there being no ground
water, although this River always contains salt water only.
Its source is in the Andes Mountains and it cuts a deep gorge
through the nitrate pampa, picking up salt as it flows, and
has its outlet at the Pacific Ocean north of the port of
TOOOpilla, although it is rare that any Of the water finds
its way so far, due to the evaporation primarily, and now to
the amount drawn from it to supply the Oficinas in the pampa
through which it flows. Although the water must be distilled
for domestic use, it is suitable for concrete mixing, form
and road sprinkling, blasting, and sanitary lines, having a
salt content of only .5 to .6%. Arrangements were made, there-
fore, to pump the raw water from Las Bombas to the chosen
site Of the Oficina, and to this end, a pipe line was laid
connecting with the pumps at the railway station. Another,
a four inch line, was laid from the Oficina Vergara distilling
plant, to supply the necessary fresh water. Both of these
water lines terminated in temporary tanks placed on a hill
near the projected site, and served well, until the permanent

system was installed.

-25-

The last big problem to consider was the transporta-
tion of goods and materials to and from the coast, either
at Antofagasta or Tocopilla, and presented two distinct
methods: first, transportation on the Company's lines, or
second, transportation over the Government lines.

Apparently the most simple and logical solution to
the transportation question was to take advantage of the
proximity of the State Railway, only 5 kilometers distant
from the plant, to which the Railway would build a branch
line along the route laid out by the Nitrate Company, rather
than go to the expense of building a line of its own to con—
nect with its own railroad at the Oficina Maria Elena at a
distance of 40 kilometers. However, balancing the chances
of completing the connection by the date it would be needed
for operation in bringing in materials, freight charges,
and long time cost of Operation, it was decided better to
add the 40 kilometers to its own lines over which it has
control of cargo movements, and can more economically handle
shipments of the product from the two oficinas by dispatch-
ing it all from the same Port. Powerful electric locomotives
haul trains from the Port of Tocopilla along the face of the
canyon walls to the level of the nitrate pampa, and at a

junction station, steam locomotives replace the electric on

-24-
the remainder of the run to the oficinas further inland,
the main one being the Oficina Maria Elena, from which a
spur line goes on th the Oficina Vergara.

By matching up the tOpographical maps of the 40
kilometers between Maria Elena and Pedro de Valdivia, the
route of extension of the railroad was laid out so as to
miss as much as possible of the mineable ground, and still
conform to the topography for grades, maintaining one per—
cent as the maximum grade. The entire line from Tocopilla
to Pedro.de Valdivia has a 42 inch gage, as do all the bran—
ches and Spurs within the oficinas.

The road between the oficinas Maria Elena and Pedro
de Valdivia is laid out to parallel the railroad, more from
convenience than necessity, since the pampa can be travelled
by automobile in any direction, and with very little scraping
or'grading, becomes a fair road after the passage of a number
of cars. The usual practice in pampa road construction is to
mix river gravel with the natural surface dirt after crude oil
has been added to it, the result being a highway comparable
to the macadam roads in the United States, and cared for occas-

ionally scraping and adding oiled sand and gravel.

-25-
Final Plantsite Tgpograph11and Triangulation

More detailed, accurate information is desired
regarding the chosen plant area than that given by the one~
meter interval contour map with the scale of l:5000, for
purposes of making estimates of excavation, fill, and all
the details of design and construction. It is also desired
to establish a system of rectangular coordinates, having
one base parallel with the axis of the plant in order that
every point in the plant area will be designated as a posi-
tive "northing" and "casting", and that no other quantities
need enter the plans which might cause confusion in design,
field layout, or construction.

To this end, the existing tepographical map and
the ground itself is very carefully gone over to determine
possible sites for the various main units and their relative
locations to each other. With the main axis thus chosen, it
is drawn as a direction line on the map, and its deflection
from the true north, as given by the cobrdinates of the<3ov~
ernment triangulation stations, is scaled from the map, and
thenceforth this new direction is termed "Plant North". In
this case it was N. 15° - 47' E. of true North. Next, the
point of origin for the coordinate system was arbitrarily
chosen by marking a point on the map far enough to the west

and south of the plant site so as not to throw any of the

-26—
units out of the northeast quadrant, and this point lo—
cated with relation to the surrounding triangulation
stations by taking angle measurements to them, and chang-
ing the Government Coordinates of all the stations to
Plant Coordinates by systems of triangles -— a matter,
merely, of computations.

The "working map" for layout, design, and con-
struction purposes was to be put on cloth at a 1:500 scale,
showing contour intervals of one foot. It being decided
that the best manner of taking this final tOpography was
to layout a network of points on 400 foot intervals, a
line of stakes was run from a triangulation station, parallel
with the plant meridian, so that a point was fixed every 400
feet on even hundred-foot plant Northings. From this line
of points, cross lines were run to complete the network,
the points established on these EastAWest lines being located
on even hundred-foot "eastings", thus simplifying the work
of placing them on the map and plotting the data derived from
the succeeding stadia notes. The topography taken from each
of these established points was recorded more rapidly than
the former work, since the party had become more experienced
and were never far from the instrument, the longest rod read-
ing necessary being at only 280 feet from the instrument. The
elevation of each point was established by running circuits

of closed levels.

-27-

All plant work from this point to the end of con-
struction is based on foot and yard measurements to conform
with usual practice of estimates, design, and fabrication in
the "States", from which most of the personnel and materials
originate.

In preparation for the field layout of the actual
construction work, a system of reference points and bench
marks, advantageously placed, is essential to the progress
of construction with delays. A ZOOO-foot Base Line was there-
fore staked out in the direction of the Plant North-South
axis, on an almost level stretch of the ground. Wood stakes
cut from "two-byefours" were firmly set on line, and pieces
of paper tacked on the tOps to receive pencil markings of the
line of sight and measurements. This work was, of course, done
with the utmost care so that the exactness would be unquestion-
able, and angular measurements taken from the end points to
all visible triangulation sations for a re-check, and so the
length and location of the line established.

Although the position of the various units is not
definitely known at this time, it can be approximated sufficient-
1y to place reference points so they will not be disturbed at
the beginning of excavation and construction operations. A

point prOperly placed in this area was permanent until blasted

-27-

out with the rock, which is an advantage seldom to be had on
the average construction job in the United States. On this
work the loose dirt was removed from the rock into which a
.hole was then drilled from two to three feet, and a bolt
granted into the hole, the head of the bolt being flush with
the surface of the rock. Vhen the grout is set and the bolt
firmly held in place, a small punch-mark is made on the head.

The location of these reference points, later de-
signated as Plant Triangulation Points, is determined by
angular measurements with the end points of the Base Line,
as well as with each other. This small system of triangula-
tion stations serves as the foundation of all the field lays
out which is to follow when the actual construction is started.

Elevations are determined for each of the reference
points by running circuits of closed levels to include all of
them, and when the level notes and elevations are checked,
these points are then designated as Bench Marks. Since all
elevations used in the plant construction are well above 4600
feet, this amount was taken as the datum so that it would not
be necessary to be using a set of large numbers. An actual
elevation, then, of 4685.00 feet above sea level, would appear
in field books and on drawings, merely as 85.00 feet. The

same simplification followed the choice of the "origin" of

-23-
the rectangular system of coordinates.

With the completion of the one-foot contour map,
and the establishment of the system of plant triangulation
stations and bench marks, the field staff of the engineering
department is ready for the actual construction work to be

started.

Field Party Equipment

The equipment of the field parties for the work
here, from preliminary topography and triangulation to the
completion of the construction, was not much different from
what might be encountered on equivalent projects in the United
States.

The instruments used were the C. L. Berger and Sons
Engineers' Wye levels and Engineers' transits, twelve of each
being provided, and one transit for special work: a "Wild
Universal Theodolite and Tachometer", made by S. A. Henri
Wild, Heerbrugg, Switzerland. This latter instrument, read-
ing direct to one second of angle, was used especially for
the triangulation work and setting reference lines during
construction, and always given respectful care.

One 50—foot and one loo-foot Keufel and Esser "City

Engineers' Standard Tape", adjustable for temperature with

-29-
Spring balance, thermometer, and level, was used for
Base Line work and also in setting reference lines during
the construction period.

The remainder of the equipment for general use,
besides the Berger instruments, consisted of lOO—foot reeled,
steel tapes, and six—foot folding rules from the Lufkin Rule
Company; standard level rods and rods levels, some marked in
feet and tenths and some in feet and inches, for different
types of work; line rods of quarter-round wood, and hexagonal
steel, marked alternately in black and white, or red and white
bands; also the miscellaneous items as 8, 10, and 12—ounce
plumb-bobs, hatchets, 4, and 6-pound hammers for setting stakes,
colored lumber crayons, hand levels, stell squares, center
punches, and a few sawa, files, etc. All field notebooks were
of the Dietzgen Engineers' level, and transit, leather covered
series.

Wood and steel stakes were supplied by the carpenter
and machine shOps and sent as required. Canvas covers were
made up to protect the instruments from the dust of the job,

and so lengthen the time between cleaning.

The Workmen
To gather together 8000 experienced men to one place,

at one time, is a difficult task anywhere, and to organize that

-50-
number, of whom 50% are inexperienced in construction work,
and to complete that work satisfactorily with respect to
quality and time schedule is a far greater task, but one
that was accomplished in constructing the Oficina Pedro de
Valdivia.

The Chilean workmen who came to build this Oficina
were for the most part unskilled and inexperienced in any
branch of the construction work, with the possible exception
of excavation. Although some of the men had had previous
experience, as they proved, or were known from other projects
in the country, the majority had to be instructed in the work
from the start, and as the construction progressed, proved
their adeptness and capabilities in the various branches of
the work. The larger percentage seemed to have a leaning
toward things mechanical -— power tools, riveting hammer, air
drills, and the like. Adeptness was shown in the shOps, the
carpenter work, crane and shovel Operations, train crews,
and the engineers' field parties. As is the case everywhere,
the men worked willingly and well for leaders they respected,
or where personal benefit could be gained. There are always
the two extremes of "brilliant" and "dumb", which should not
be taken to find the average. On this project, the average
could well be taken by the improvement shown in the work of

8,000 as the construction progressed.

-51-

An example of inexperience might well be taken
from the party of a field engineer where each member, as
he started work, had to be taught his duties from the
fundamentals: that it is better to hold the tape level
in measuring; that a rod held for line or level readings
must be plump; that a contrast of colors is adVantageous
in taking a sight on an object; that the stake should not
be held with the tape to keep the measurement division on
the point; that a rear chainman should be to one side of
the line of sight; that the t0p of a stake should be moved
by tamping the ground rather than knocking the stake, and
all the other small and numerous details of the work. When
these points are explained and the reasons illustrated so
they are clearly understood, they rarely need to be repeat-
ed, an occasional reminder being sufficient, and each member
of the party takes a certain pride in his knowledge, and in
being able to do a thing better than some other member.
Some of these men, through instruction and practice when
time permitted became capable of doing simple level work, as
well as settingeup, taking sight, and giving line with the
transit. This is one extreme, of course, the other being
those men who are exasperatingly slow to comprehend even after
repeated explanations, but the average proved reliably accur-

ate workers.

-52-

Desigpgand Location of the Units

 

The work of designing the various units was done
partly in the Company‘s New York office, and partly in the
field office at the plantsite in Chile. This division of
the work was based on the time necessary to send plans back
and forth, the source of materials, experimentation being
done at the Marih Elena plant, and the best means to expedite
the progress.

The New York Office took.charge of the main plant—
production units for which the structural steel and equip-
ment would be fabricated in the United States, or which
might best be ordered through that office. These units in-
cluded the primary and secondary crushing plants, screening
plant, and rejects bin, the reinforced concrete leaching vats,
crystallizing and centrifuge plants, Diesel power house, elec-
tric transformer banks, and all the connecting piping, cables,
trenches, and belt conveyors and motors.

The Chile office had charge then of the entire water
supply system, the warehouse and shop buildings, all living
quarters, the graining and tagging plant and the grained
nitrate storage yard, the sanitary system, and all connecting
pipes, cables and conveyors. The structural steel for the

warehouse and shOps buildings was available from closed

-55-
oficinas on the Pampa where similar buildings had previous-
ly been in service. Also available was a quantity of mis—
cellaneous structural steel, to which was added new steel
sent from New York, and this combined for the erection of
the graining and bagging plants as fabricated in the machine
shop of the Plant.

Road and track layouts were also made in the New
York office to serve the units designed there, although
most of this work was done in the Field office for the
entire Oficina. Fills were made with the rock from the exca-
vation, except for the very slight fills for which the loose
surface dirt proved satisfactory. Underpasses, and small
bridges spanning trenches, were also designed in the Chile
office.

The extension of the electric power line from the
Oficina Maria Elena power house, and connecting with the
Chile Exploration Company's line running from their power
house at Tocopilla to the copper mine at Chuquicamata, were
also laid out by the Field office.

The water supply system consisted of a dam and pump-
ing station at the Rio Loa, some 45 kilometers distant from
the Oficina, a pipe line to the booster station at the Ofic-
ina Vergara, at which point some of the water was sent through

the distilling plant, and on to the storage tanks placed on

 

-54-
a hill in the plant area of the Oficina Pedro de Valdivia.
The storage tanks have a capacity for 9000 cubic meters of
salt water, and 4000 cubic meters of fresh water, besides
an elevated tank erected for additional pressure for flush-
ing, and for fire protection. From the tanks, pipe lines
were run through the plant and townsites as required for
solutions, cooling, domestic, and sanitary purposes.

The dam at the Rio Loa was the most interesting unit
of the water supply system, and although small, rather in—
geniously designed. The water stream is neither large nor
rapid, being only 150 feet wide, and of only 5—foot average
depth, with soft sandysclay bed. It was required to raise
the surface of the river only a few feet in order to give a
constant flow through the intake tubes to the settling basin
and to the pumps. A churn—drill rig was used for driving 40—
pound rails as piles, at two foot centers, across the face
of the dam, leaving a projection of four feet. Against the
upstream face of the piles, cement in sacks was stacked to
form the main wall. The Spillway was made by a rock fill,l
covered with fitted concrete slabs to prevent scouring, and
was regulated by a pair of lift—gates operated from an over—
head frame supported at each side on concrete walls. From

the intake tubes, laid horixontally just below the surface of

-55-
the river, the water was led through an open ditch to a
concrete settling basin fitted with cleanout, flood gates,
and screening grids. The water was pumped from the basin,
over the river bank, and on to the distillation plant and
booster station at the Oficina Vergara.

There were several features in the design of the
building foundations and the superstructures, not encount-
ered generally. The one particular feature was the pro-
tection against damage from earthquake shocks. Insomuch as
there have been no recording instruments in service on the
pampa, the actual force of the shocks could only be estimated,
basing the conclusions on observed results of the shocks at
_the Oficina Maria Elena and old structures of other oficinas
in the pampa. The foundation bearing material being rock of
homogeneous structure with no significant faults or cracks,
it was assumed that the force be uniform in the sub—soil, and
design was based on theory that the force of the shocks would
be dissipated through the structural steel of the super—struct—
ure of steel framework buildings.

In conforming with the assumptions, the free-standing
column footings were specified to be firmly tied to the rock
against sliding, either by setting the footings in solid pock-

ets cut into the rock, or dowelling with reinforcing bars

-57-
grouted into drill holes. Bearing walls were likewise
tied and anchored to the rock, and the normal amount of
reinforcing steel increased 1% against earthquake shock,
this latter factor being held in all reinforced concrete
design throughout the job. The structural steel of the
taller, and the heavily loaded buildings, were designed
with stronger members, gusset plates, and diagonal braces,
than would otherwise have been employed, and the factors
of safety increased in both concrete and steel.

In the case of the Leaching Vets, a novel design
was used. These vats consist of a line of five double
batteries of reinforced concrete tanks, set end to end;
each battery being 526 feet long by 114 feet wise and 19
feet deep, with a partition wall across the center. The
walls and floors are reinforced concrete, supported as a
unit on a series of hour-glass and truncated pyramidal
footings, which were tied to the rock as before described,
and on which a thin steel plate of a size equal to each
separate footing was placed when the concrete was poured.
The upper surfaces of the plates were oiled and similar
plates placed on the first so that the entire vat, when
completed, rests on the steel plates with the film of oil
between them, which would allow horizontal eqrthquake

thrust to be dissipated in sliding the whole massive unit,

~58-

rather than in destructively cracking it.

The crushing and screening plants, as a unit, were
located at a slight angle with the plant axis, to conform
most economically with the contours, with especial reference
to the construction of the yards for the loaded and empty
mine ore-cars as to the amount of excavation and fill necessary.

The "Workmen's Townsite" was likewise placed at an
angle to conform with the tOpography for water supply and sew-
age disposal, and still maintain a uniform plan of layout.
The living quarters were all designed in blocks having con-
crete walls reinforced with wire mesh, corrugated sheet iron
roofs supported on two-bybfour inch hips, rafters, and purlins,
the floors of matched lumber, and small enclosed patios at
the rear of each.

The "American Camp" was located on the north slope
of a hill at the north of the plant, and just to the west of
the Native Townsite. These houses were of similar construction
to the blocks of native quarters, so designed with their ardhed
porches, square windoWs, green trim and roofs against the
white walls, to give a very attractive appearance, both in—

dividually and collectively.

-59-

Actual Construction - the Plan and Start

Correct planning and scheduling of the construction
work is the most important factor in the coordination and
continuous flow of the operations. Therefore, the quanti-
ties of excavation, fill, and concrete for each unit are
studied, as well as the relative time each must be completed
for steel erection and operation.

Until such time as permanent units could be complet-
ed, it was necessary at the start to provide for temporary
field offices, living quarters, transportation, compressed
air, and concrete mixing. Headquarters were first made at
"Las Bombas", the station on the "State Longitudinal Rail-
way", to which point lumber, piping, cement, and other mater-
ials were sent. Unoccupied bunk houses were made the living
quarters, and the five kilometers to the Oficina site were
made by motor truck twice a day until temporary shacks
could be built at the job. All temporary buildings through-
out the period of construction were erected of corrugated
sheet iron on wood framework.

Excavation started with stripping, drilling, blast—
ing, and mucking-out, of the townsite sewer trenches and
the railroad cut necessary to bring the track from Maria
Elena into the plant Operations. A11 excavation was done by

hand—drilling, and fuse-blasting, up to the time that the

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-40—
electric power line was brought in and portable air-com-
pressors provided. The workmen's townsite layout was
begun at this point, as well as the permanent warehouse
and plant tracks. Excavating gangs followed the layout
parties as fast as facilities were provided for housing
more men.

Layout of concrete mixing plants and material
handling equipment is a major consideration at the be-
ginning of all construction work anywhere. On this pro-
ject the mixing plants were located near the centers of
gravity of the quantity of concrete which each plant could
provide, and as best situated to conform with the contin—
uity of the work and the means of transportation.

Three concrete plants were erected; one prin—
cipally for the townsites, located between the two and
slightly uphill from them, thus making the loaded truck
haulage on a level- or down—grade. The others were placed
in the plant prOper; one of them to take care, primarily,
of the leaching vats, which was the largest single unit in
concrete needs, requiring 41,000 cubic yards for its com-
pletion; the other plant to provide for the numerous small-
er jobs, and so located that it might remain in service even
after the plant was operating. Either mixing plant, how-

ever, could supply concrete to any part of the plant, and

-41-
at times both were used to supply the same job simultaneously.

Each mixing plant was designed to be built of time
bers and heavy planking and consisted of three bins, 240
cubic yard capacity —— two for the coarse aggregate and one
for sand, and a compartment for holding 50 cubic yards of
cement. A11 fed through volume— or weighing-heppers at the
bottom, to a skip which was hauled by cable up an inclined
track to be dumped into the drums of the two one-cubic-yard
Ransome mixers which fed directly to the special tilt-bodies
on the transporting trucks. The quarry cars supplied the
aggregate bins from a deck track, and the cement was brought
in from the stock yard at the side of the mixing plant on a
push cart. Mixing time throughout the job was kept at from
fortysfive second to one minute.

In conjunction with the mixing plants a concrete
testing laboratory was provided for regulating the mixes.
Sieve analyses were made at the quarry and checks run from
the aggregate bins at the plant. Water-cement ratio con-
crete was used throughout the construction work and necessita—
ted continuous tests for salt content, slump, grading, and
strength in compression and tension. The concrete salt con-
tent varied between 1.5% to 2.1% for the 121,000 cubic
yards poured, and was so regulated that a very acceptable

uniformity resulted in the concrete. The water—cement ratio

-42-
held was 6.75 for 2500 pounds, and 7.50 for 2000 pounds of
concrete, the tests showing that the average ran well above
the required limits. Most of the cement was received from
plants in Belgium and Norway, with some sent from the south
of Chile during the final period.

A material—yard site was chosen to the northwest of
the plant, on a flat section of the pampa. This yard was
used for the purpose of uncrating and storing all materials
as they arrived, and holding them until needed at the plant,
and a customs officer was stationed here for making the
necessary inepections. Structural steel trusses and columns
and heavy equipment was here assembled and sorted for erection
on the job.

Portable air compressors were available from nearby
non—operating oficinas and used first for drilling at the
warehouse hill until larger stationary electric-powered com-
pressors were set up on a slope adjoining the drilling op-
erations. The portable units were then used for working
small, scattered jobs. Drill sharpening machines were
temporarily placed near the warehouse site, and an old oil-
burning steam shovel was sent from Maria Elena to aid in
casting the blasted rock at the warehouse hill. This latter
machine was soon replaced by a 5/4-yard Diesel shovel as-

sembled at the station "Las Bombas".

—45-

Permanent houses for the workmen were concreted,
roofed, and completed as rapidly as possible to accommodate
the increasing number of men arriving for the construction.
Portable mixers were used for all concrete work until the
permanent plants could be erected. A more suitable head-
quarters thmn that first adopted was located near the site
of the permanent office and a small staff colony consisting
of office, mess hall, and living quarters was erected, the
original shacks being used for time offices, first—aid rooms,etc.

For moving the excavated rock and bringing in materi—
als, railroad tracks were immediately laid out, and as far as
practical, conforming with the permanent positions. A tempor-
ary garage for servicing the numerous cars and trucks to be
needed, a small machine shop, and tools for cutting and bend-
ing reinforcing steel, were built. As is true of any job,
the start appeared hOpelessly confused and tangled, but was
soon straightened out to the "ordered confusion" of any

rapidly progressing construction.

Supervisigpggnd Inspection
It was planned, of course, to place in responsible
positions only those men whose qualifications best fitted them
for successful organization, COOperation, judgment, and train-

ing of men. That the personnel was well chosen is best exem-

-44-

plified by the fact that this huge plant was in productive
Operation less than eighteen months after the start of ex-
cavation. That there were very few delays of any nature is
a credit to the efficiency of the designing departments,
material and equipment expediting, and the management of
all the construction departments, separately and collectively.

The architect, the owner, the general contractor,
the sub-contractors, and the superintendents and inspectors
of each, could all be found on this project combined under
the one Company. This condition automatically eliminated
the possibility of monetary gain to any of the branches
through dishonest, unsound, and often unsafe, methods of
building, use of materials, or adjustment of figures. There
are numerous "tricks" in construction work which may be termed
"petty thievery", which leads to expenses for delays and re-
pairs, and others which.ae very dangerous and may even be
classed as criminal offences since they may lead to fail-
ures in a structure, costing the lives of many peeple, be—
sides temporarily paralyzing operation. Among these "tricks"
might be mentioned such as reducing the cement content in
concrete mixing, placing concrete in uncleaned forms, bad
seating of beams, improper placing of reinforcing steel,
cutting down on the thickness of floor slabs, using inferior

grades of bricks, omitting bolts and rivets, poor caulking

-45-
and joining of pipe sections, and all the petty offenses
of poor construction.

The superintendent of each department had to in-
struct his assistants in their duties and to see that the
work was done correctly, but the final responsibility for
all work as completed was placed with the field engineering
department.

This placing of responsibility seemed soundly based
beCause each member of that department for the prOper exe-
cution of his duties, should have more general as well as
detailed information about his section than any other one
person on the job. Because he does the field layout for
all departments and installations, as well as inspecting and
checking them, the field engineer must be thoroughly familiar
with the work and able to give the information always to be

expected from him.

Eield Layogt'
VFor purposes of field layout, the entire Oficina
was divided into sections, or division of the work, such that
each could be handled by one engineer, and this turned over
to him with the responsibility for the correct executions of
the plans. On his work, then, the field engineer combined

the duties of inspector, construction foreman, assistant

. —46—
superintendent, and the usual problems of general layout,
working such hours as the job required, very often until
midnight and some times all night.

As soon as approved plans were received for the
layout of units, the location of the plant triangulation
stations was examined, and where necessary were relocated
at new positions where they would remain undisturbed. The
areas were than staked out for excavation. The first crews
hand-stripped the loose dirt covering the rock and cast, or
moved it in wheelbarrows to the tracks along which it was
carried to predetermined disposal points, most of it going
into the fill for the Ripio tracks. The greater percentage
of blasted rock also went to this samd fill for the Ripio
Loop. With the rock surface cleaned off, crews came in for
drilling to the depths designated by the engineer.

Electric power was available soon after excavating
Operations had started and permitted more compressors to be
operated, large electric blasts shot off, and the Operation
of 5-yard.electric shovels in casting or loading the broken
rock. With this added equipment in service, the work rapid—
ly spread to include the entire plant.

After experimentation, water-paint was used for
marking boundaries and depths of cuts on rock surfaces, and

proved very satisfactory. Green was the color used through-

-47-
out by the engineers for all their markings, and other de-
partments used other colors, so_that there would be no con-
fusion over the various markings, nor to whom they referred.

As the rock loading progressed in a cut, the tracks
were thrown over to the face so that the shovel booms would
reach the cars. With the advance, it was necessary for the
engineer to check the excavation to see that too much was
not being taken from the bottom nor sides of the cut. An
excavation line is generally placed at eighteen inches from
the outside formwork for a wall on any job where the bank
will stand. However, in this rook, the face was figured
closer, and the concrete poured against the rock face where
the saving in concrete did not offset the cost of formdng,
stripping, and backfill. The rock usually broke so irregular—
ly that formwork was seldom continuous along the face of any
cut, unless the rock happened to break wide.

When the area was cleared sufficiently, reference
points were accurately placed at locations which best suited
the conditions, and were set in a manner similar to the
triangulation points: bolts grouted into drill—holes, the
exact point being punched on the head when the bolt was solid.
Pencil markings on clean rock was servicible for a short time
only, since the rock surface would flake and chip under the

forces of expansion and contraction due to the wide range of

.43-
temperature between night and day. These reference points
were placed on lines which would prove Of the most value
to the job, as P.I.'s or P.C.'s for tracks and roads; col—
umn centers for buildings; center line for trenches; and
street intersections for the townsites.
Following the main, rough cut, details such as
column footings, motor foundations, etc. were staked out
and all loose or cracked rock cleaned away. The outlines
were then more carefully painted, and each checked for
elevation and to see that the bearing surface was leveled
up, and if not set in a pocket, that holes were drilled and
anchor rods grouted in them.
The carpenters came close behind the excavators,

for placing the batter-boards as located by the engineer to
clear the formwork to follow. An inverted T was first set
up and the ends of the cross bar weighted with rock tO hold
it firmly in place, the upright braced, and the ribbon nailed
to the uprights at a level given by the engineer. Batter—
boards are always a discouraging problem in the layout engin-

eer's work, due to the numerous factors by which they may
be shifted or destroyed, and make in themselves sufficient
reason for the establishment of a number of reference points.
There are Opportunities for error by mistakes and misinter-

pretation at every step of the work, and so it rests with

-49-
the engineer to be particularly accurate, and he has the
training and mechanical instruments with which to do it.
On this job, the probabilities that errors of one depart—
ment would be checked by another were so very slight that
more than usual dependence rested on the work of the
engineer, besides increasing his normal duties on construc-
tion work. He was here obliged to check the location and
dimensions of all formwork, the placing Of reinforcing
steel, the setting Of templates, marked the center of each
anchor bolt individually for boring the holes in the tem-
plates, the placing Of the bolts for location and projectiOn,
setting of all sleeves, conduits, miscellaneous iron, and
the bracing of all parts Of the formwork to receive con-
crete. NO concrete was poured without a written release
from the engineer stating that all details of that particular
form had been checked and was in readiness.

Special attention was given to the setting of an-
chor bolts for the structural steel buildings, so that de-
lays might be avoided later in the steel erection. For
all bolts, one template was placed with its under surface
at the elevation of the rough concrete, thus maintaining
the spacing of the bolts at the most inportant point, and

also serving for an unmistakable guide in pouring the

~50-
concrete. For bolts with projections of more than one foot,
and some were as much as four feet, another template was
placed just under the nut Of the bolt and supported on two
legs from the lower board, and the whole firmly tied from
rocking by diagonal braces to the form. Slight differences
in projection were taken up by turning the nut, thus rais-
ing or lowering the bolt as required. All bolts were later
checked again, after placing the concrete and stripping the
templates.

Base plates for the steel columns were received
separately from the steel itself, and each was set on the
bolts, brought to perfect level at the correct elevation,
and grouted in place. The unit was then ready for the
steel erection.

The value of accurate work on the foundations of
any job cannot be over-estimated in the saving of time and
labor on the job as a whole. The construction of anything
is made unnecessarily difficult throughout by a few in-
accuracies or careless mistakes at the start. It has been
said that a layout engineer's work is two-thirds done by
the time the foundations are complete.- This statement
seems well founded on fact when consideration is given to
the trying period Of excavation, especially of soft, mucky
ground, in which everything seem to be shifting out of position,

and the dependence Of the rest of the structure on the foundations.

-51-
It is rarely possible to have too many reference points and
line sights, and more Often appears that there are too few,
because of the many ways in which points may become lost,
dug out, or otherwise destroyed or obliterated so as to be-
come useless.

The pouring Of the concrete for trenches, founda—
tions, and all work below ground floor levels, was done
principally by dumping from the trucks into floor hOppers,
from which it was wheeled to the forms in concrete buggies
on wide runways; although sometimes it was dumped into mor-
tar boxes, shovelled into wheelbarrows, and so taken to the
forms. However, this latter method was rare, and used only
when the buggies were all in use on other parts of the work,
or when the job was so isolated or small not to warrant
building the heavier runways for accommodating buggies.

Floors above ground level, and walls and roofs, for
the main units, were concreted by the use of buckets in steel
towers, being hoisted up and discharging into chutes leading
to floor hOppers and on to the buggies. Wood towers were
erected for some units, and used for raising materials as well
as concrete. For other units ramps were built, and.the tnggies
or wheelbarrows pulled them up by hand to the forms, while for
pours Of small yardage high above the ground level, the con-

tainers were hoisted on a cable suspended from an outrigger.

 

-52-
the various types Of placing—methods being adOpted to best
fit the needs of the individual job.

There was not much of the work of such similarity
that form—panels could be designed for repeated use, except
for concreting the leaching vats, trench walls, and the liv—
ing quarters Of both the American and Workmen's Townsite.
Lumber was very rapidly used up in having to tear the sections
apart after each pouring, in the unnecessary amount of cuts
which the carpenters seemed determined to make in each piece,
and the wasteful manner in which the stripping of the forms
from the concrete was done.

The installations of all equipment, motor bases,
tanks, drives, tile and finished concrete floors, and the
innumerable miscellaneous items, were all required to be
checked by the engineer. Steel columns were plumbed by
instrument ahead of rivetting, and everything checked as
erected. The magnitude of the steel erection was such that
three locomotive cranes were in constant use, and the
electric shovels pressed into service as they could be re-
leased from excavatiOn and equipped with drag-booms for use

8.8 cranes o

-55-
Revigions and Alterations

There was, of course, frequent revisions to the plans,
as is to be expected even on one small unit, following the
checking Of details. However, very few changes from the origi-
nally approved plans were received which were of more than
minor importance to the smooth running of construction. Al-
most without exception, a revision was received by the field
before that section Of the work had advanced any appreciable
degree, so close were the designing offices kept in touch
with the field Operations. A few delays in some units were
suffered, but those cases were exceptional and unavoidable.

Future extension has been provided for in the present
construction by building the units large enough to accommodate
added equipment, the foundations for which have been installed.
At such time as production may be increased, there remains only
the placing Of the equipment. The eXperience derived from the
erection and Operation of the Oficina Maria Elena has been the
factor which has minimized alterations in the new Oficina.
Experiments will be continued in the future, but the basic in-
stallations will doubtlessly remain as they stand at the pres—

ent.

-54-

Job Progress Repprts

 

The progress reports Of the construction work are
taken principally from the data included in the diaries
and monthly cubication reports of each engineer. The com-
pilation Of this data, arranged with the separate charge
numbers for each type of work for each unit, gives the main
office a check on the status Of the job with reference to
unit costs, material dispatching, and general progress.

In making up his report, each engineer took cross
section Of his area and plotted the notes against the sur-
face as given by the accurate topographical map, and com—
puted the volume of excavation and fill done that month.
Formwork was measured when placed, as was all work which
might be buried at the time the report was to be made.

Formwork was given in square feet of actual con-
tact surface, concrete, excavation, fill, backfill, masonry
walls, and grout were in cubic yards, tracks, roads surfaced,"
and pipe were in lineal feet, while reinforcing steel was
in tons, and guniting in square yards. Besides these items,
an estimate of the percentage Of each type or class Of work
was also given as completed to that date.

A daily entry was likewise made in a book, giving
significant dates, such as the start of excavation, concrete,

and steel erection; completion dates Of each class Of work;

-55-
and the movements of shovels, cranes, equipment, etc.
From a study of these data, the progress of the
construction could be determined at any time, comprising as
they did, all units of the actual erection work as set down

by the men most familiar with the details of the advance.

Qperation and Maintenance

As the construction was narrowing down, and the
units of the Plant preparing for operation, and the Mine
likewise organizing for production, the field engineers
were transferred to one department or the other when they
could be released. With the start of full Operation of the
plant, there remained only scattered odds and ends to be
cleaned up, that part of the work often termed as the “Dust-
pan jobs", which were finished under the direction of the
single remaining field party. And so the Construction Field
Engineering Department comes to a close, with its work well done.

Maintenance requires only occasional checking of the
tracks in the plant lines, minor alterations made from time to
time, and monthly measurements of the advance of the face of
the Ripio Disposal dump. An independent staff is not.needed
for this work, but is merged with the production where operat—
ing duties are of more importance than field engineering as

referred to construction.

-56..

The plant is Operating satisfactorily --

the work of the civil engineer is complete.

 

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