M. H. Marshall's General Report: February 24, 1931

Churchill River Power Company’s Development
Island Falls, Churchill River.

This is the detailed engineering report on the Island Falls power development. It is based on the sixty-one weekly reports made during the construction period (June, 1929 to August, 1930) by Resident Inspecting Engineer, M. H. Marshall. It was made available to us by Tom Kaminski of Saskatchewan Watershed Authority. Although the content is the same, our format is slightly different from the original, and the appendices have been omitted.

  • General
  • Location and Accessibility
  • Power for Construction Purposes
  • Reach of river developed
  • Water supply
  • Possibilities of Storage
  • Description of Site
  • Plan of development
  • General
  • Transportation
  • Construction Camp
  • Construction Plant Layout
  • Order of Construction
  • Coffer Dams
  • Excavation for Foundations
  • Power House
  • Main Dam and Spillway
  • South Bulwark
  • Substructure
  • Superstructure
  • Installation
  • Turbines
  • Alternators
  • Transformers
  • Switching Equipment
  • High and Low Tension Busses
  • Miscellaneous Equipment
  • Auxiliary Units
  • Heating, etc.
  • Dam
  • Spillway


File 4732.
Calgary, Alberta February 24,1931



Churchill River Power Company’ Development,
Island Falls, Churchill river, Saskatchewan.


M. H. Marshall. M.E.I.C. Resident Insp. Engineer.


The Island Falls power development on the Churchill river has been constructed by the Churchill River Power Company– a subsidiary of Hudson Bay Mining and Smelting Company, to supply power for use in the mines at Flin Flon where extensive low grade coppersulphide deposits are in course of development, and also to supply powerto the Sherritt-Gordon mine at Cold Lake for a similar purpose.

The metalliferous mining development of northern Manitoba and in part, of northern Saskatchewan, is of comparatively recent growth. Prior to the year 1910 some prospecting had been done in the area north of The Pas which is known as The Pas mineral belt, but no actual development had taken place. The success attending gold mining operations in northern Ontario served as an impetus to further exploration work which lead to the discovery of copper ore deposits on Schist and Flin Flon lakes in the year 1915 and active development was started at the Mandy property on Schist lake in 1917. The opening of this mine revealed a high grade copper sulphide deposit which was worked successfully until the year 1919. During the war years the price of copper rose to approximately twenty-seven cents per pound on the New York market, as against an average price of fourteen cents per pound and it was possible to freight ore from the Mandy mine to The Pas, ship by rail to the smelter at Trail, B.C., pay smelter charges and still show a substantial profit.

The decline in metal prices immediately after the war made this procedure no longer profitable, as most of the high grade ore had been worked out, and the mine was closed down towards the end of the year 1919. During the period of development about 6¾ million pounds of copper were recovered which yielded an average price of twenty-two cents per pound.

The results obtained at this mine drew attention to the possibilities of the district, and were largely responsible for the efforts now being made to open up large bodies of low grade ore of a similar mineralogical composition.

The Flin Flon mine is situated on the boundary line between the provinces of Manitoba and Saskatchewan at approximately 54°45 'north latitude and was discovered about the year 1915. The location is roughly about four miles north and west of the Mandy mine previously referred to. The property had changed hands several times before it was finally offered to the Whitney interests, who secured an option in 1925 and at once proceeded to make a careful investigation of its possibilities. The previous owners had put down 35,000 feet of test holes by means of the diamond drill and a body of low grade ore which was estimated at 16,000,000 tons had been located, but development had been retarded on account of the fact that no successful means of treating this class of ore had as yet been worked out.

During the years 1926-27 experimental work was carried out at the mine with a view to finding a satisfactory method of treatment and the results obtained were sufficiently encouraging to warrant the purchase of the property and the start of an active programme of development. It was realized that a considerable amount of power would be needed for running the mine and metallurgical plants and all the known possibilities for developing hydro-electric power were investigated, a site finally been selected at Island Falls on the Churchill river.

The Hudson Bay Mining and Smelting Company was formed and arrangements made for the construction of a railway from The Pas to Flin Flon and also for the construction of a hydro-electric plant at Island Falls.

The Sherritt-Gordon mine is situated at Cold Lake about forty miles northeast of Flin Flon. A branch line had been built to the mine from Cranberry Portage on the Flin Flon Railway and this property is rapidly approaching the production stage. Hydro-electric power from Island Falls plant is now being used at this mine and the town of Sheridan, a block of 5,000 H.P. having been contracted for.

Location and Accessibility.

The Island Falls power plant is located on Churchill river at a point approximately sixty miles north and west of the mine at Flin Flon in north latitude 55°32'and thirteen miles west of the boundary between the provinces of Manitoba and Saskatchewan.

A preliminary investigation of the site had been made in the year 1927 and active survey work was started in July, 1928, when arrangements were completed with the Fraser-Brace Engineering Company of Montreal to design the plant and act as agents in constructing it. A contract was also made at that time with Lang & Ross of Sault Ste. Marie to build the transmission line and a telephone line between the plant and Flin Flon. The power site is in an isolated position and before any steps could be taken to start construction operations, it was obvious that a system of transportation would have to be provided that would be suitable for handling the large amount of material. Machinery and supplies needed for construction purposes. This class of traffic is best handled during the winter months when the lakes are frozen over and large tractor trains can be employed, but it was first necessary to move in about 500 tons of camp equipment and supplies in order to make a start with the work, proceed with the construction of the camp and provide means for handling the heavy equipment.

No road existed in the area between the mine and the power site, and it was therefore necessary to at once start on a programme of road construction, with docking facilities at the end of each lake and also the building of a fleet of scows for water transportation. Fordson tractors and teams were used on the portages to transfer shipments. The summer route above described necessitated the construction of nineteen miles of graded road, twelve timber docks and ten scows, with terminal facilities at each end of the line. Five camps were built at the heads of the main lakes and communication maintained by telephone. The distance between terminal points on the route is seventy-two miles.

The winter route follows a chain of small lakes form the north end of Mari lake and is sixty-eight miles between terminal points. There is a maximum grade of four per cent against northbound traffic, and about twenty-five miles of road were cleared and graded ready for icing before the winter set in. Small camps were set up at various points along the line and provided with telephones. Freighting of the 35,000 tons of plant, material and supplies necessary for the construction of the plant was in the main carried on during the winter months and operations were conducted on a regular schedule. Each train consisted of one “Linn” tractor, six large sleighs and a caboose. The average load per train was seventy-seven tons although load up to 120 tons have been hauled. The running time for the round trip varied from thirty-six to forty hours.

Power for Construction Purposes

A large amount of power is required for construction purposes on a job of the size of the Island Falls development and as steam and gasoline units could be used only to a minor extent owing to the high cost of transporting fuel, the only alternative was to find a suitable site where hydro-electric energy could be generated. The contractors were fortunate to locate a site suitable for this purpose at Spruce Falls at a point where Swan river enters Sisipuk lake. There is a natural fall of twenty-five feet at this site and a timber power dam was constructed which provided a working head of approximately forty feet. The site of this temporary development is about thirteen miles northeast of the Island Falls site and a 26,400 volt transmission line was built to convey power to the works. A telephone line was also installed.

The power-house was of frame construction and provided space for two small units, complementary equipment, switch-room and office, in addition to which two dwelling were provided for the operating staff. The generating machinery consisted of two 1,250 H.P. vertical water wheels with propeller type runners, coupled direct to 1,000KV-A, 600 volt, 3 phase, 60 cycle generators with direct connected exciters. Water was conveyed to the wheels by two wood stave pipes of 7’.0 diameter and length of ninety feet. The transformer bank consisted of three 667 KV-A units, 600 to 6,600/26,400 volts, placed apart from the power-house and protected by a lightening arrester and 100 amp. fuses. At Island Falls there was a sub-station, transformer bank and two motor-generator sets which supplied current for the electric locomotives.

Work on the temporary power plant commenced October 4, 1928; operation commenced March 20, 1929, and was continued without interruption to June 5, 1930, when the plant was closed down.

During the period of operation this plant supplied 4,698,000 KW. H. of electrical energy for construction purposes, at an average cost of 4.35 cents per KW.H.

Reach of River Developed.

The stretch of river affected by the Island Falls development extends from Big Eddy Falls, where the power plant is located, to Mussena Falls, a distance of approximately thirteen miles. Between these points the river channel is interspersed with numerous large and small islands, and the shoreline broken by extensive bays.

The falls to which the name Island properly applies are situated about two miles upstream from the power plant, where a large island takes up a considerable part of the river channel; above these falls are the Assiski and Mukoman rapids.

The total drop from Mussena Falls to Big Eddy Falls is approximately sixty feet. At normal high water there may still be a small fall at Mussena which would, however, disappear during flood periods.

The selection of an economical power site involved a considerable amount of engineering study and several sites were investigated, including the White Mud site on the Nelson river. The development of this site was, however, found to be too costly for the amount of power required and attention was directed to the Churchill river where several power sites were known to exist. Surveys were made and a site was eventually chosen at Big Eddy Falls, as this afforded the best chance of an economical development. At this point the river is confined to two narrow channels separated by a small island of rock, and the fall is concentrated in one pitch of about fifteen feet with high, rocky banks on each side. A spillway channel was also found which could be used to discharge the main flow of the river to Sandy Bay, an arm of the Churchill river. This bay joins the river about two miles below the power plant and by discharging into it, the likelihood of an abnormal rise in the tail water is obviated.

Water supply

The northern part of the province of Saskatchewan is covered by several large lake systems and innumerable small lakes, swamps and muskegs, most of which are interconnected and in the are under consideration drain by means of the Churchill river and its tributaries into Hudson Bay. The presence of these lakes tends to retard the run-off, thereby effecting a natural regulation of the river; and the numerous falls and rapids along its course make it a very valuable stream for water power purposes. The river proper has its origin in Churchill lake in northwest Saskatchewan but the headwaters of some of the tributaries are in the province of Alberta. The general course of the river in Saskatchewan is between the 55th and 56th parallels of latitude and the total fall from Churchill lake to Island Falls power site is approximately 450 feet, with the descent well concentrated in the falls and rapids previously referred to.

The drainage basin above the power site covers a area of approximately 70,000 square miles, with annual precipitation of from fifteen to twenty inches; and the run-off for the year ending September, 1929, was estimated at 10,500,000 acre-feet.

No continuous measurements of the river flow had been taken prior to the commencement of construction surveys at Island Falls, but gauge reading have been taken regularly since July, 1928, and a number of measurements were made. The minimum flow recorded since that date occurred in May, 1929, when the flow fell to 10,000 c.f.s. and the maximum flow recorded was 35,700 c.f.s which occurred in June, 1930. There is reason to believe that this maximum has been greatly exceeded in past years as the high water-mark, which is clearly defined, is several feet higher than the maximum water level at the time of measurement, so that the peak flow may have reached 100,000 c.f.s. This probability has been taken in to consideration in the design of the plant and ample spillway capacity is provided to take care of similar flood conditions. The matter of using the large lakes in the Churchill basin as storage reservoirs has been given some study and it would be possible to secure artificial control of these lakes at a reasonable cost by constructing dams at the outlets, which are narrow, with rock bottoms. Reindeer lake, Lac la Ronge and the Churchill group of lakes could be controlled at reasonable cost and would make a large storage available for future developments.

Possibilities of Storage.

Site. Approx. Area Tributary Drainage Area Possible storage per foot depth on W.S.
Reindeer lake 2300 sq. mi. 23,000 sq. mi. 1,472,000 ac.ft. 64 B.C.F.
Ile à la Crosse lake 185 sq. mi. 29,000 sq. mi. 118,400 ac.ft. 5.15 B.C.F.
Lac La Ronge 505 sq. mi. 5,700 sq. mi. 323,200 ac.ft. 13.9 B.C.F.
Churchill Group 1000 sq. mi. 29,300 sq. mi. 642,800 ac.ft. 28 B.C.F.

The headpond created by the power dam and other works will have an area of possibly sixty square miles which in itself will provide a considerable amount of storage.


Description of Site.

The river cross section at the site of the plant is comparatively narrow, the overall length of the structure required to span it being 810 feet. The bed-rock, which is a reddish gneiss, is exposed to high-water mark in the river channel and above that elevation is overlain by a bed of brown clay. The rock is of a homogeneous character and very few fissures were found, so that a firm foundation was assured and grouting was unnecessary. At the north bank, however, some disintegrated rock was encountered and this had to be cleared away to the bedrock before concreting. The river channel is spanned by the main dam, which is make up of four sections comprising ice chutes, undersluices and spilldam sections and the north bulkhead dam, which connects with the north bank. The power-house, headworks extension and south bulwark are built entirely on the south bank, from which rock was also excavated to make the tail-race.

In the design of a power plant or other works, at a point remote from centres of distribution, it is necessary to consider the use of local material as far as possible in order to save freight and haulage charges, so that the presence of sound rock and clean gravel and sand beds near the site naturally suggested the use of concrete for the more important structures, and structural steel work was reduced to the minimum. The power-house was designed to eliminate all unnecessary space both to reduce the expense of hauling material as well as to cut down on rock excavation which would afterwards have to be replaced by concrete. A further saving was effected by designing the power-house as an integral part of the dam in place of building a separate structure.

Plan of Development.

The general layout of the development is shown on the plan which is appended and included the following structures:-

  1. A power-house constructed of concrete blocks and supported by a mass concrete substructure which contains the turbine intakes, wheel pits and draft tubes for three 14,000 horse-power main units and two 1,250 horse-power auxiliary units. Total initial development 44,500 H.P. Overall dimensions of power-house in plan 203 feet by 112 feet.
  2. Headworks for future extension, providing for three additional 14,000 H.P. units which will bring the total development to 86,500 H.P. Overall length of the extension 139 feet.
  3. Main dam, consisting of ice, undersluices and spill dam sections with shore connection. Overall length 468 feet.
    Ice chutes – Three stop log controlled openings 15 feet 6 inches wide.
    Undersluices – Four submerged outlets controlled by steel gates; each outlet is 24 feet high by 12 feet wide.
    Spill dam – Gravity type dam, with rollway formed with crest of compound curve section connected by tangents of varying lengths to reversed curve at bucket. The dam has thirteen stop log controlled openings each 15 feet 6 inches in width.
    N. shore connection – Mass concrete bulwark 65 feet in length provided with opening for fish ladder.
  4. South shore connection – Mass concrete bulwark with length of 497 feet, making connection from headworks extension to the south shore.
    The total overall length of these structures from shore to shore is 1,307 feet and the maximum height of the dam is approximately 90 feet.
  5. Spillway dam – The spillway dam which is located about one mile to the south of the main dam is a solid concrete structure, with two small earth dams at the east end.
    The dam is of gravity type with superimposed deck for operating purposes and control is by stop logs. Overall length of dam, excluding earth fills – 1,033 feet; width between abutments – 893 feet. Openings number forty-six with widths of 15 feet 6 inches. Rollways of mass concrete. Reversed 38° area of 15 feet radius connected by tangents of varying length.
    Deck is of tee beam construction with width of 18 feet between parapets.
  6. Maximum height of dam – 44 feet. Earth dams – Nine earth dams or levees were constructed along the margins of the headpond to prevent overflow. These dams were built with crests 10 feet wide and side slopes of 2:1 and 3:1. The maximum heights varied from 5 feet to 20 feet.



Preparations for the construction of the works comprising the development were started in July, 1928, but actual construction operations did not get under was until the spring of the following year owing to the large amount of preliminary work which had to be done.

An engineering party was first sent in and proceeded to make detailed surveys of the various dam sites. Camp sites were established along the transportation routes, logging operations started, roads cleared and graded, and a start was also made with the location and clearing of a the route for the transmission line.

While this work was proceeding, a small construction force had been sent to the power site. Temporary camp buildings were erected and the construction plant layout decided on. The transportation system was placed in operation as soon as the roads could be used and a total of 450 tons of material, equipment and supplies was delivered before the lakes froze over.


The transportation system which has already been referred to, was successfully operated throughout the construction period and in no case was the work delayed through failure to deliver material, equipment or supplies. The bulk of the tonnage was of necessity hauled in during the winter periods of 1928-29 and 1929-30, as the best time to do such work is when the lakes are frozen over, and trans-shipment of freight at the head of each lake is obviated. The summer route was operated during the months of June to October in each year and the winter route from December to May. The amount of material transported during the winter months was approximately 33,400 tons and during the summer months 1,600 tons for a total freight haul of 35,000 tons during the construction period.

Construction Camp.

During the initial stage of construction the accommodation provided for the staff and workmen was mainly tents and temporary buildings of a class that could be readily constructed from the material available at the site, but the housing and servicing of a force of eight hundred men called for buildings of a more permanent character and the winter of 1928-29 was spent in erecting the buildings forming the permanent construction camp. The buildings were constructed with vertical log walls with roofs and gables of sawn lumber, the roofs being covered with rubberoid. Members of the staff with families were provided with residences which were fitted with all modern conveniences and similar quarters were provided for the Resident Engineer of the Dominion Water Power and Hydrometric Bureau.

Particular attention was paid to the sanitation of the camp. A water supply was installed which gave an ample supply of water for domestic and fire protection purposes. Wash houses with hot and cold water were provided for the workmen and all latrines were fitted with automatic flushing tanks. Disposal of waste water was taken care of by installation of a complete sewerage system which discharged into a separate tank, from which the effluent was turned into the river at a point well below the camp.

Hospital accommodation with ten beds was provided and was in charge of a residential medical officer who was responsible for the health of the camp. All drinking water was chlorinated and daily tests were made by the medical officer, who also gave inoculations to those desiring them.

The precautions taken to safeguard the health of the men were very effective and no cases of infectious or contagious disease occurred during the life of the camp.

The construction of the camp was completed by the spring of 1929, by which time fifty buildings of various classes had been erected.

Construction Plant Layout.

All heavy material and equipment was delivered at Sandy Bay where it was unloaded on to flat cars by means of a derrick and distributed to points where it was either to be stored or used. Over four miles of standard gauge track was laid for ease in handling material and disposing of surplus rock and earth from excavations. The equipment used consisted of side tip wagons hauled by electric locomotives, of which four 20-ton and five 8-ton were provided. Two small gasoline locomotives were also used for part of the time at places where no current was available. Cement was stored in seven sheds 40 feet by 100 feet and lime in smaller shed 40 feet by 50 feet, these sheds being located near the receiving dock and connected by a spur to the railway. Sand was brought from the pit in scows and unloaded by a clam shell bucket into storage bins from which cars were loaded by gravity.

The mixing and crushing plant was contained in one structure placed on the south bank of the river; rock from excavation was delivered by cars to a jaw crusher situated in the upper floor and dropped after the first crushing into a cone crusher which reduced it to size of coarse aggregate; the sand was screened out and used for making building blocks and other purposes. Coarse aggregate fell by gravity into a mine skip and was raised by an inclined cableway to the upper storage bins from which it was fed to the measuring box at the mixer. Sand was dumped on screens above the storage hoppers, which arrested all large stones and was then passed down to the measuring box, which was placed alongside the box containing coarse aggregate. Cement was added and the operation of a lever dumped the dry material into the mixer where a predetermined amount of water was run in. Two 1-yard mixers were used and the wet concrete was dumped into a hopper, from whence it was loaded into steel concrete wagons and conveyed to the job; distribution on the job was effected by means of concrete towers and chutes.

Lumbering operations during the winter months furnished a good supply of logs, and two saw-mills were in operation converting these into boards and small dimensioned timbers, of which a large amount was required for form work and construction of buildings.

A well equipped machine shop was established to take care of plant repairs and work of a similar nature. An electrical shop, blacksmiths and tool dressing shop, and welding plant were also provided.

Steel for reinforcement was handled in a yard near the camp where specially designed rigs had been set up for bending steel to any required shape, and bars from one-quarter to one an one-half inches diameter could be dealt with.

The extensive use of compressed air for rock drilling and other purposes necessitated the installation of a compressor plant which was equipped with two 600 cu. ft. belt driven machines and a smaller direct connected machine used for a spare. Two portable gas driven compressors were also used in places remote from the air line. Three type 450 electrical shovels were used for earth and rock excavation. They were found to be well adapted for this work, being easily convertible for use as a crane, dragline or other purposes and one outstanding advantage was the possibility of using them under very low temperature conditions when steam operated machines could not have been used. In places where shovels could not be used, work was handled by 15-ton stiff leg or by derricks and rock boxes. These machines were also used for general handling of construction material.

Order of Construction.

Actual construction operations started in the spring of 1929 with the building of a coffer dam to enclose the area to be excavated for the tail-race and also a coffer dam across the south channel of the river at the side of the undersluices.

Excavation for the power-house substructure and headworks extension was also put in hand and completed by August 15th, as this work could be carried out in the dry. Preparations were made for pouring concrete as soon as this could be done and a start was made at Units 1 and 2 on June 18th, when the floors of the draft tubes were poured. Units 3 and 4 were proceeded with as soon as the bottoms were ready, also the Auxiliary units.

A block making plant had been in operation in May and June, during which time 155,000 concrete blocks 16 by 8 by inches had been prepared for use in building the superstructure. Work on this part of the power-house was put in hand on August 12th and the main walls were completed October 15th; roofing steel was immediately placed and the structure was enclosed by the end of November. By the close of the year 1929 the contractors had made excellent progress with the work; the power-house substructure and the main part of the superstructure had been completed and enclosed and the work of installing the turbines and generating plant was underway. The concrete work on the undersluice section and part of the spill dam had been completed and the headworks extension was also completed. Work at the spillway dam “A” had progressed to a point where the excavation was completed, side dams built and the rock formation below the dam practically cleared and ready for concreting in the following spring. Earth dam “C” had been completed and dam “90” partly completed, while the transmission line was 40 per cent completed.

During the winter of 1929-30 outdoor work was confined to lumbering and clearing around the headpond and construction of a railway to dam A; but excellent progress was made with the pouring of floors in the power-house and other interior work, also with the installation of turbines and power-house equipment.

The main coffer dam in front of the undersluices was demolished early in February, 1930, and gates placed in position. A few days later the downstream cofferdam was demolished and the river turned back into the south channel by way of the sluices, which enabled a start to be made with the north channel closure.

By the end of the winter the interior construction work in the power-house had been practically completed, installation of machinery was well advanced and deliveries of material and equipment had finished. Good progress had also been made with the electrical installation and some equipment installed.

The closure of the north channel was successfully accomplished early in April, when the construction of the spill dam and north bulwark was immediately started and brought to completion by the middle of July, the work of damming the river being thus brought to a satisfactory conclusion.

While this work was proceeding, work on turbine and generator installation had been speeded up and the power line was advancing steadily. The tail-race coffer dam was demolished on May 17th and water admitted to No. 1 Unit, Units 2 and 3 being ready soon after. The construction load was taken over by No. 1 Unit on June 8th and the temporary power plant shut down on June 12th, four months earlier than had been expected, power now being supplied to the mine at Flin Flon.

Work on the earth dams and dam “A” had proceeded steadily throughout the summer, and the whole of the works were completed and taken over on August 28, 1930.


Coffer dams

A considerable amount of coffer dam construction was needed to close off the river channels at the site of the power-house and dam. The cribs were constructed of logs fastened together by drift pins, and were divided into compartments about five feet square. The bottoms of the cribs were shaped to fit the rock in the river bottom and were launched from timbers projecting over the river, after which they were floated into place and loaded with loose rock. The upstream face of the coffer dam was sheeted and joints covered with one inch by four inch which were fastened by divers, who also stopped any leaks that showed up. Upon completion of the sheeting, a clay banquette was placed on the water side and leakage was reduced to proportions easily handled by the pumping equipment installed.

The general arrangement of coffer dams used is shown on a plan attached as an appendix to the report.

The construction and demolition of coffer dams was carried out as follows:-

Coffer dam No. 1. – West end of south channel.
Commenced May, 1929; finished July 13, 1929; demolished February 8, 1930.

Coffer dam No. 2. – South channel wing.
Commenced May, 1929; finished July 13, 1929; demolished February 17, 1930.

Coffer dam No. 4. - East end of south channel.
Commenced July 13, 1929; finished August 17, 1929; demolished February 17, 1930.

Coffer dams Nos. 1 and 4 completed the closure of the south channel, which was unwatered August 17, 1929, and water was passed by the undersluice February 17, 1930.

Coffer dam No. 3. – Tail-race.
Commenced May, 1929; finished July 28, 1929; demolished May 17, 1930.

This coffer dam was used to enclose the area occupied by the tail-race, only part of which was flooded. Two 12 by 12 inch and one 10 by 10 inch belt driven centrifugal pumps were used to unwater the coffer dam, but the small pump was later moved to the south channel as it was not needed after the pool had been lowered.

Coffer dam No. 5. – West end of north channel.
Commenced February 15, 1930; finished April 5, 1930; not removed.

Coffer dam No. 6. – East end of north channel.
Commenced March 31st, finished April 12th, 1930.

The last two dams were used to close off the north channel which was unwatered April 15, 1930. The upstream dam was left in place, but the small dam on the downstream side was washed out when water flowed over the spill dam. Demolition of the coffer dams was effected by burrowing into the rock fill and filling the pockets with dynamite, which was exploded by electricity. Before the charge was fired, the pond behind the dam was filled and the gates were opened, so that the dam was submerged and no damage was caused by flying material.

The total amount of coffer dam constructed was 17,500 cubic yards, of which 12,100 cubic yards was removed, the average charge of dynamite used being 1¼ lbs. per cubic yard of dam.

Excavation for Foundations


Excavation for the power-house was started in May, 1929, and completed by the end of August of the same year except for finishing the slope in front of the intakes, which was left until later.

The upper strata of clay was first removed by electric shovel and hand labour, loaded into side tip cars of five cubic yards’ capacity and then wasted. As soon as the rock was exposed, drilling crews were started and the rock was blasted, loaded onto cars and carried to the crushing plant where it was broken up for coarse aggregate, and rock dust for use in making concrete building blocks. Drilling was carried out with hack hammers driven by compressed air, which was fed by lines running from the main compressor station and in some cased by portable compressors mounted on trucks. Excavation was carried down to the grades shown on the plan and as soon as bottom was reached the surface of the rock was cleaned by means of a hose and wire brushes, and by air jet in places otherwise inaccessible. All seams and fissures were drilled into and grouted with cement. The power-house and all dams were provided with a complete system of under-draining to carry off seepage water; weep holes were drilled into the rock and drained into wood-box culverts from which pipe drains were led to the face of the dam.

The excavation of the pit was stepped up from the auxiliary units to the headworks extension in order to allow concreting to proceed as soon as a section had been bottomed and passed by the engineers, each section consisting of the space occupied by one unit.

Very little seepage water was encountered in the pit, the only water occurring in any volume being that from run-off, which was easily handled by small hand pumps.

Excavation of the tail-race was started in May, 1929, and was continued intermittently until November when the whole are had been excavated to grade.

Main Dam and Spillway.

The main dam is situated directly to the north of the power-house and closes off the former river-bed, the structure being divided into four sections as previously noted. Actual excavation for this part of the work was commenced August 10, 1929, and the area inside the south channel coffer dam was bottomed by the end of September, which allowed a 63-foot section of the spill dam to be constructed. The site of the north bulwark was stripped before winter set in, when operations were deferred until the spring. Excavation for the spill dam across the north channel was started April 10, 1930, and finished about the middle of May. A small area of disintegrated rock was found under the bulwark site and this was removed until bedrock was reached.

South Bulwark.

This bulwark or wing dam is situated on the south bank and roughly parallels the course of the river. It connects with the power dam at the south end of the headworks extension and runs along a rocky ridge for about 500 feet until elevation 130 is reached. The dam site was covered with a bed of clay which was removed by drag line until the rock was exposed, when the surface was cleaned up by hand labour. Operations were conducted at intervals and the excavation period extended from May-September, 1929, finally being completed in May, 1930.



The power-house is designed as an integral part of the main dam and not as a separate unit. The substructure is of mass concrete and contains the headworks, intakes, scroll cases, turbine pits and draught tubes, no steelwork being used in the design of these structures, except for reinforcement purposes and gate guides.

The area approximately 201 feet by 140 feet and sufficient space is provided for three main units and two auxiliary units. Headworks have also been provided for three additional main units to be installed at such time as the demand for power warrants the increased expenditure. The headworks extension occupies an area of 141 feet by 70 feet. Each of the main units is served by two intakes with a gate area of 19.5 feet by 15 feet; the scroll case is of the spiral type designed for a constant velocity of 8.48 feet per second, based on a flow of 2,595 c.f.s.

The auxiliary units have one intake each, with a gate area of 9 feet by 8.5 feet. The draught tubes of the main units are of the “Moody” spreading type with central hydraucones, which are designed to eliminate vibratory effects by preventing cavitation and formation of vortices, thereby increasing the efficiency of the turbines. Semi-steel supporting vanes are set around the draught tube bell for supporting the superimposed weights of concrete and machinery.

The head-gates are of the fixed roller type, with concrete loading and operation is affected by hoists coupled to a motor-driven line shaft, wire rope being used for hoisting. The hoists are equipped so that the gates can be lowered quickly in case of emergency. The gates run in steel guides grouted into the structure and bed on a planed steel sill. Each gate is furnished with a water seal consisting of a rubber hose held in place by a spring brass clip which is screwed to the face plate, and holes are provided in the bottom girder of the gate to break any vacuum that may occur when the gate is being lifted.

Trash gates are provided in front of each head-gate to act as strainers, and emergency gates are also provided. These gates are handled by means of a 40-ton gantry crane installed in the gatehouse.

The tail-race outlets are provided with stop logs built of steel and timber which are handled by an 8-ton chain hoist suspended from a traveling gantry.

Provision is made in the substructure for pipe tunnels, ventilating ducts and passages giving access to the turbine pits; and the pump-room for the water supply system is also located in the basement, below the auxiliary units, part of which is also used for a machine shop.

Air locks are provided for each unit to allow of inspection of the turbine gates and runners, the water in the scroll cases being forced out by compressed air. Expansion joints, extending through the width of the substructure were left between each unit, leakage through the joints being prevented as far as possible by 12 inch copper strips of 16 ounce weight, bent in the form of a “V” with wings on it; and all vertical construction joints under water pressure were similarly protected.

The first concrete in the substructure was poured June 18, 1929, when the floors of the draught tubes of Unit 1 and the Auxiliary Units were placed and the work was then carried on continuously until the whole of the sub-structure and headworks extension was completed by October 26th, with the exception of grouting around machines and floor finish which was done after the machinery had been erected.


The power-house superstructure as at present built is 200 feet by 112 feet in plan and has a volumetric content of 1,400,000 cubic feet with provision for a future extension of approximately the same size. The building is divided into three bays, consisting of generator room, transformer room and switch rooms; and gatehouse. Provision is made in the transformer bay for a control room, battery room, oil storage and offices. The exterior walls and number of the partition walls are built of concrete blocks 16 by 8 by 8 inches, of which 155,000 were made at the site in the spring of 1929.

These blocks were made of rock dust and cement in the proportions of 5:1 and two block making machines and steam curing sheds were installed in connection with this work. The windows are double, wood sash was used throughout, and wooden doors are also provided for the main entrances and offices. Steel fireproof doors on rollers are installed between the generator and transformer bays, and the circuit breaker rooms are also provided with fireproof doors which can be raised or lowered.

The walls enclosing the transformer room were built of reinforced concrete, and the floors were also reinforced and given a hard surface finish, to which two coats of paint were afterward applied.

The lower part of the switch bay is partitioned off with hy-rib partitions coated with cement plaster, a separate compartment being used for each bank of circuit breakers, with access to the transformer bus, which is placed immediately over the transformer room. The high tension bus room is on the top floor of the building and is divided by transite partitions around the disconnecting switches and curtain walls between the high tension busses.

The roof is the ordinary pitch and felt type over 1½ inch rock cork insulation, resting on corrugated asbestos transite, and is carried by steel purlins supported by steel trusses or I beams which in turn rest of the concrete block walls.

Construction of the exterior walls was commenced August 12, 1929, and completed October 15. The building was totally enclosed by the end of November, by which time a temporary steam heating system had been installed, and work on the interior walls and floors could be proceeded with. The interior work was carried on throughout the winter and the work on the superstructure was practically completed by the following spring.

All walls were primed and given two coats of white paint, with dark green finish to five feet about floor line. Doors and windows were painted a dark lead colour and steel and ironwork dark red.



Three units were installed, designed for operation under heads from 52 to 60 feet, each with a normal rated capacity of 14,000 H.P. when operating under a head of 56 feet, at a speed of 163.6 revolutions per minute.

The turbines are of the vertical shaft, single runner type, direct connected to conventional vertical shaft two bearing generator, with thrust bearing located above stator. The runner is of cast steel of the Moody diagonal flow propeller type, with six vanes; and the guide bearing is of the lignum vitae water lubricated type, non-adjustable, the shaft being fitted with cast steel sleeves where it passes through the guide bearing and stuffing box. Operation is effected by cast iron serve motors supported by the pit liner, and connected to the operating ring which is supported by the head cover. The operating mechanism is protected during the opening and closing strokes by bronze shearing pins which will break in the event of a foreign object being caught between two guide vanes when closing or between the back of a guide vane and a casing stay vane when opening. A hand control mechanism is also provided. The governor actuator is of the “Woodward” type design arranged to use oil as the pressure medium and equipped with electrical motor-driven centrifugal mechanism. The actuator is located on the generator floor adjacent to the generators.

Each unit is equipped with an individual interconnected pressure system which includes an oil pump, accumulator tank and sump tank, and two air compressors with tank to supply air to the accumulator tanks and air lock are provided.


The generators are of the revolving field vertical shaft type rated at 12,000 KV.A, 3-phase 60 cycles with a speed of 163.6 r.p.m. and power factor 90 per cent. Current is generated at 6,600 volts and excitation provided by a 100 KW. 250-volt main exciter and a 2.5 KW. pilot exciter, both of which are direct connected. A 100 KW. 250-volt station exciter is also installed. Each generator is direct connected to the low tension side of the transformer bank.


Three banks of main transformers and one spare are provided, also one bank of transformers for the auxiliary units. The main transformers are of the oil filled water cooled type rated 4,000 KV.A, 1-phase 60 cycles, 6,600/110,000 volts D/Y with grounded neutral. Taps for 112,750, 107,250, 104,500, 101,750 volts and full capacity are provided.

The auxiliary transformer bank consists of three 667 KV.A 1-phase 60 cycles, 660/6,600 volts D/D oil insulated, self-cooled transformers with grounded neutral. All the main transformers are mounted on steel trucks and can be readily moved as required.

Current and potential transformers are installed in steel shuttered compartments opposite the main transformers.

Switching Equipment.

The high tension oil circuit breakers connecting the main transformers to the high tension bus bars and outgoing lines are of the solenoid operated type, 125 volts, 3 pole, single throw, 400 amperes, 110,000 volts with automatic overload trip. The three individual poles of the breaker are entirely insulated from one another. The disconnecting switches which are located on the top floor of the power-house are of the 3 pole, single throw, gang operated type, 600 amperes, 110,000 volts, with hand lever operation.

The main and auxiliary switchboards, relays, rheostats and voltage regulators are mounted on panels placed in the control room, form which the operation of the station is directed by a complete signal system.

High Tension Busses.

A transfer bus is located on the floor adjoining the breaker compartments immediately above the main transformer room and the high tension busses are suspended from the roof trusses or carried by standard bushings along the roof of the gallery adjoining the switch compartments.

The high tension busses are made of 1½ inch diameter copper tubing and copper bars of various widths are used for low tension busses.

Miscellaneous Equipment.

Storage of oil used in the transformers is maintained by means of cylindrical horizontal tanks, seven of which are located in a gallery adjoining the transformer room, from which it is protected by a concrete wall. The tanks are filled by gravity from the gatehouse floor and circulation is effected by small centrifugal pumps. Part of the tanks are used for used oil which is mechanically filtered, retested and returned to storage. A gravity oil supply system is provided and the equipment is place in the breaker room adjoining the gatehouse.

The power-house is equipped with a ventilating system consisting of a motor-driven “Sirocco” fan located in the conduit gallery.

Fire protection and water for the cooling system is supplied by means of a pumping plant situated in the basement below the machine shop. Water is drawn direct from the river and is circulated by means of a series of centrifugal pumps. The domestic water supply is also controlled from this point, and after chlorination is pumped to the townsite through a 4-inch main.

A well equipped machine shop is installed on the main floor adjoining the auxiliary units and has been furnished with machines capable of handling ordinary repairs.

The battery room is located on a mezzanine floor between the gatehouse and the control room, and two small motor generator sets are used for charging the batteries.

Auxiliary Units.

The auxiliary units were used in the temporary power plant and are to be installed in the power-house as soon as weather conditions will allow of the machines being transported to the permanent location. These units consist of two vertical water-wheels rated at 1,250 H.P. each and are direct connected to 1,000 KV.A, 600 volt, 3-phase 60 cycle generators which supply current for station services. The transformer bank, which has been previously described, is located in the main transformer room, and the busses and switching equipment are placed in a small room near the transformer room.

Heating, etc.

The superstructure is heated by means of electric heaters which are attached to the walls of the various rooms, and louvres in the front wall of the generator room admit cool air to the underside of the generators whence it is circulated through the machine.

A 75-ton gantry crane is provided in the generator room for handling the heavy equipment and a 40-ton gantry crane is also installed in the gatehouse for handling trash racks, emergency gates and other purposes.


The main dam spans the river channel on the north side of the power-house and is provided with three ice chutes with stop log control, four large undersluices with submerged gates and a spillway section with thirteen openings fitted for stop log regulation. The guides for the stop logs are electrically heated to facilitate winter operation and a stop log machine is placed on the deck for placing or withdrawing the stop logs.

The undersluice gates are of the fixed roller type, loaded with concrete and raised or lowered by a 30-ton gantry crane with link connections to the gates.

The spill dam section consists of thirteen rollways separated by piers extending to the river level. The structure is of mass concrete and is massive in appearance. The crest of the rollways is formed of a compound curve section which is connected by tangents of varying lengths to a reversed curve at the bucket. The north shore connection is made by means of a mass concrete bulwark dam and the overall length of the combined structures from the power-house to the north bank is 468 feet.


The extension of the south end of the power-house is similar in design to the existing headworks at the power-house, but only the intakes have as yet been constructed. The south shore connection is an extension of these headworks and is a mass concrete bulwark dam 497 feet in length. The total length of the power dam from shore to shore is approximately one quarter of a mile.


Coarse aggregates for concrete were obtained by crushing rock from excavation and sand was brought from pits opened on the shores of Sandy Bay about three miles from the job.

The proportions used for mass concrete in dams and other heavy work without reinforcement were 1:2½:5 and for reinforced concrete in floors and walls 1:2:4. The mixing process was continued until a homogeneous mass of uniform colour and consistency was obtained, the minimum time allowed for the mixing process being 1½ minutes.

Cement was used to the extent of five or six bags per cubic yard according to the calls of concrete required and water was added in sufficient quantity to provide a workable mix.



The main spillway dam, designate as "A" dam, is a concrete structure with an overall length of approximately one thousand and thirteen feet and is situated at a point about one mile to the south and slightly to the east of the power dam. The structure spans a valley at a place where there is a dividing line between the drainage to the Churchill river, and to Sandy Bay into which the overflow will spill.

The dam is of the gravity type with a superimposed deck for operating purposes at elevation 130. The deck is carried on piers which divide the dam into forty-six weir sections, of which forty-three have crest elevations of 112 and three of elevation 114. Regulation is effected by means of stop logs, for the handling of which two stop log machines are installed. The machines are electrically operated and power is transmitted by a short line from the main plant. A compressor house has been constructed at the west end of the dam in which an electrically driven air compressor will be installed, and a four-inch air line has been placed for the full length of the deck to provide air for agitating the water in order to prevent freezing-in of the stop logs.

Two small earth dams, with riprap protection, have been built at the east end of the main dam to prevent the escape of water from the headpond. The area in front of the dam was excavated with a sloping bottom which dropped from elevation 115 to elevation 110 at the upstream face and the site of the dam was excavated to bedrock.

Excavation of the approach was started in the spring of 1929, and electric shovel being used for this purpose; soil was run to the dump in five yard side tip wagons hauled by an electric locomotive. The excavation was practically completed by the fall of the year and the winter was spent in building a railway from the mixing plant to the dam site in preparation for spring work. Work was resumed in March, 1930, when the foundation was cleaned up and concreting of piers started in early April, being carried on without interruption until the end of August, when the dam was completed and placed in operation.


The spillway channel discharges into Sandy Bay and has a drop of approximately fifty feet between the dam and the point where it enters the bay. This channel was excavated by erosion caused by release of water from the dam, a wide and deep channel being formed by this means without cost to the company.

The spillway has a discharge capacity varying from 70,000 to 118,000 c.f.s according to the stage of the river, and provision is also made in the main dam for dealing with a large quantity of water in case of emergency, so that ample spillway capacity has been provided to take care of future floods.


At a number of places along the river bank the ground level dropped below the elevation at which it was proposed to maintain the headpond and earth dams were constructed at these points to stop loss of water from the pond. In all, a total of nine earth dams were constructed and a total of approximately 61,000 cubic yards of material was placed in these dams, in addition to which 13,700 cubic yards of rock protection placed on slopes.

The dams were carefully constructed of local material excavated from borrow pits, and were formed with an upstream slope of 3:1 and a downstream slope of 2:1 berms were made on the upstream slopes in places where the high dam was necessary. The clay from the borrow pits was brought to the site by side tip wagons running on timber trestles, and after dumping was spread by teams and fresnos, rolled and sprinkled. The layers were about one foot in depth and were placed so that the fill had an uphill grade from the water side. The smaller dams were constructed entirely by fresno work, small tractors and teams being used for the purpose.

The upstream face of all dams were paved with eighteen inches of riprap which was quarried from rock in the vicinity, and a toe fill of rock was also laid on the downstream side, with drainage ditches leading away from the dam.

Work on the dams was carried on intermittently during the construction period and all were completed by August 1, 1930.


The main transmission line to Flin Flon is 58.94 miles in length with 125 feet cleared right of way. The branch to Sherritt-Gordon mine is about forty-five miles in length and is of pole construction. The main line is carried on suspension type double circuit towers set in concrete foundations or grouted into rock, and is strung for two 3-phase circuits. A lightning arrester is provided at the power-house end of the line, located on the tail-race operating platform.


The amount of clearing done was not as great as would usually be required in a more settled area, and only the power site and the margin of the headpond within view of the power-house was cleared of timber. The total area cleared amounted to 829 acres but this does not include clearing for transmission line right of way, which was done under a separate contract.

The quantities of work comprised in the development exclusive of the transmission line are indicated in the following figures:-

Excavation and earth works 194,000 c.y.
Rock excavation 63,300 c.y.
Riprap 11,400 c.y.
Concrete 83,700 c.y.
Concrete blocks 134,800 pcs.
R. steel 1,130 tons.
Structural steel 200 tons.
Coffer dams 17,500 c.y.
Freight handled 35,000 tons.

From start to finish the whole of the work was completed in a little over two years, but actual construction of the permanent works was completed in sixteen months, and power was being supplied to the mine twelve months after the first ground was broken.

The cost of the development amounted to $6,238,073.32 and of the main transmission line $790,451.13 making a total cost of $7,028,524.45 (see attached sheets). The branch line to the Sherritt-Gordon mine was constructed by the mining corporation and is not included as part of the development.

Construction of the works was carried out by the Fraser-Brace Engineering Co. Ltd., of Montreal, who were also responsible for the general design.

M. H. Marshall, M.E.I.C.
Resident Inspecting Engineer.


Statement of Cost.

“A” Dam Concrete $297,322.81  
“A” Dam Earth 3,950.17  
“90” Dam Earth 1,421.15  
“C” Dam Earth 12,376.28  
“M” Dam Earth 42,215.03  
“D” Dam Earth 1,748.35  
“SF” Dam Earth 27,044.42  
“10” Dam Earth 898.36  
North Channel spillway & undersluices 391,304.51  
Dam south of power house 51,911.61


Unwatering power house site 137,517.60  
Power house substructure 610,255.14  
Power house superstructure 282,173.98  
Power house equipment 1,135,981.09  
Power house gates & guides 94,179.74  
Power house cranes 44,128.60  
Booms 2,269.09


Administrative buildings 24,384.64
Camp buildings 44,344.58  
Permanent buildings 59,483.00 128,212.22
Field administration & Superintendence 42,841.12  
Field engineering 42,515.45  
Contract engineering 30,614.02  
Miscellaneous field expenses 100,585.81  
Island Falls office expenses – Misc. 17,374.84  
Island Falls office administration 43,309.39  
Engineering fees – Fraser-Brace Engineering Co. 256,238.36  
Labor supply. 22.56  
Tool account. 14,319.46  
Temporary construction & maintenance 186,163.75  
Temporary water supply 20,292.87  
Stable account 23,177.14  
Camp & Kitchen operation [Cr.] 1,874.86  
Temporary power plant 165,355.72  
Clearing site & flooded area 33,373.08  
Excess cement 56,662.00


Contractors Equipment:    
Plant rental 103,998.32  
Plant installation & dismantling 114,790.61


Construction plant and equipment 309,616.23  
Equipment spares and supplies 59,417.94


Fire insurance 142,793.38  
Purchasing department expenses 7,510.31  
Owner’s representative expenses 87,850.34  
Government’s representative expenses 5,606.53  
Injuries & damages during construction 4,240.25  
Flooded area survey 17,173.00  
Interest earned during construction [Cr.] 884.17  
Miscellaneous credits [Cr.] 85,882.16  
Construction bonus 2,500.00  
Miscellaneous 13,223.84


Railroad (undistributed) 121,010.01  
Flin Flon to Island Falls 954,023.12




Island Falls site 33,717.98  
White Mud Falls site 37,964.49  
Lac La Ronge 4,475.17  
Reindeer lake 5,862.23  
Ile a la Crosse 2,779.29 84,799.16