By Brigadier R.B. Muir, CBR, BSC, MICE, AMIMechE, AMIEE, AMIStructE
This article deals with the nuclear trials held at Christmas Island in 1958. The aim of the article is to describe the part played in these trials by the Army in general, the Royal Engineers in particular, and an attempt will be made to point the lessons learned. Over two-thirds of the military garrison on Christmas Island were Royal Engineers.
Extracted from the Royal Engineers Journal - March 1960. Part Two
PLANNING
Distribution of load. The bulk of the planning on preparatory engineer work required for each test was carried out on the island. There were two main reasons for this. The time factor was acute and, secondly, design was linked closely with local operational, scientific and topographical considerations. On the other hand as much as possible of detailed planning on longer term requirements, such as development of the base, was done in London. Members of the RE planning team from HQ Grapple visited the island as required, when agreement was reached with all concerned on the first key plan of a particular project. Back in England plans were then developed in consultation with the appropriate authorities, e.g. financial and medical. It was important to lay down check points at which partially developed plans were re-submitted to the island for a check on local implications. On two occasions the Army Task Group Commander, in his capacity as Chief Military Planner, flew to England for conferences at Air Ministry and Aldermaston, returning to the island in less than three weeks. Methods of communication between the Army Task Group Commander and his planning staffs at Air Ministry also included teleprinter conversations.
Priorities. Because time was at such a premium it was obviously essential to establish clearly defined priorities. The "desirable" had to be segregated ruthlessly from the "essential". The priority of any particular project could usually only be determined in consultation with the other services at Task Group Commander level.
Requirement investigation. Before planning began, it was necessary to ensure that the requirement was correctly defined by the user. This critical examination was usually conducted by asking the user "What do you want to do?" and not "What do you want?" The user will frequently have strong convictions on what he wants but unless a preliminary joint exercise is carried out on the lines suggested, the final product may be surprisingly disappointing from the user's point of view. This investigation should result not only in the requirement being met with the minimum effort, but also in a satisfied customer. Another factor often worth considering at this stage was the possibility of future development.
Planning plan. The planning plan was then formulated, and this included target dates for the various stages of planning and execution. There was sometimes a tendency to place undue emphasis on the projected date of start of a work on the ground. It is by no means certain that the job which starts first will finish first. The aim was to complete the job in time, with the least expenditure of resources.
Flexibility. During planning it was essential to maintain an element of flexibility. However much finality was achieved in the initial definition of the requirement, changes during planning were liable to be proposed by the planners as well as the users. Clearly a major consideration was the impact of a suggested change both on the date of completion, as well as on the efficiency of operation of the final product. Exceptionally, a relatively major change may be capable of being implemented with a very small additional effort which is out of all proportion to the value which will accrue. Generally, however, a change in plan as a result of second thoughts leads only to delay and frustration. A vital consideration always was the possible effect of a proposed change on the morale of hard-pressed planning staffs and on units executing the work. Obviously, changes which constituted refinements or frills were resisted strongly. The best is indeed the enemy of the good.
Rationalization. Considerable economy in time and effort was achieved by rationalization, as far as possible, of user requirements for such items as laboratories, decontamination facilities, offices and messes. This enabled the basic structure to be provided by using a standard design. Standardized timber trusses (24 ft span) and wall panel frames were manufactured locally in RE workshops, on mass production lines, using jigs. This reduced substantially the erection time as well as the number of skilled workmen required on a site. As an extension to this principle, specially designed standard hutting for personnel accommodation was prefabricated subsequently in the United Kingdom, and shipped to the island.
Work study. Within the limitations of the time available, work study techniques were employed to devise the best means of execution. Highly repetitive work, such as the erection of prefabricated hutting sections, was carried out in phased construction using locally trained specialist teams. Again, the assembly of steel shelters involved considerable welding of high workmanship. Time was saved, and the load on skilled tradesmen reduced, by centralizing this welding operation in RE workshops on a line production pattern. Simple alignment aids designed for the assembly of complicated plant and structures also saved much time.
Site organization. Detailed pre-planning of the organization of each work site was the only way of avoiding waiting time for either plant or labour, both of which were at a premium. The aim was to complete the setting out, and the optimum layout of initial stores, before working parties arrived on the site. Maximum use was made of mechanical aids during construction. RAF mobile platform equipment, which can be adjusted pneumatically, was invaluable for high building work. Realistic yardsticks of production were evolved, and this inspired a healthy competitive spirit between working parties. Safety precautions during construction were strictly enforced and, in spite of the intense activity, the accident rate was negligible.
TYPICAL ENGINEER TASKS
Roads. The foundation of the roads on Christmas Island is coral mud which, when laid and compacted at the optimum moisture content, sets into a very hard surface. Suitable deposits of this mud are fairly widespread in the inner lagoons of the island, but in winning it care had to be taken to avoid plant becoming bogged. For this reason, the usual method employed was a dragline excavator, as very rarely was the bearing capacity adequate to use Euclid scrapers. The bearing capacity of these coral mud roads reduced rapidly with a change in the moisture content. This could occur either as a result of intensive rain or a prolonged drought, either of which were liable to happen. Consequently corrugations and potholes developed with alarming rapidity, and the maintenance effort necessary to keep the roads at accept- able standards became quite prohibitive.
Bituminous surfacing. For this reason it was decided to embark on a bituminous surfacing programme of the main road network. The bituminous surface was laid to an average depth of 21 in and the mix selected was:-
Coarse aggregate (13- in) 28.2 per cent
Medium grade (J-. in) 28.2 per cent
Quarry rejects 11.7 per cent
Fines 23.4 per cent
Cement 2.5 per cent
Bitumen (60/70) 6 per cent
Because of the absence of frost action, it was unnecessary to lay a sealing surface on the binding course. The resultant surface wore extremely well and the edges of the carpet set very hard, and stood up well to the occasional vehicle which had to pull off the road. This was important as there were no kerbs or containing shoulders.
A limiting factor on the rate of laying was the production of aggregate. A batch of four 20-ton Parker crushers were located near the NE point, and coral stone was scooped from above the high-water mark and fed to these machines, using dozers and bucket excavators. An ad hoc quarry troop of one officer and eighty-three other ranks was formed under command of the field park squadron. It operated the following plant in addition to the crushers:-
19 RB 4
BK 50 2
8-yd scraper 1
D7 with winch 1
D4 with winch 1
Size II dozers 4
By introducing shift work, output finally reached the figure of 1,400 tons of crushed aggregate per day. This figure was just adequate to meet the requirement for roads, airfields and building construction works.
The bitumen mix was produced at a Starmix 40 plant located near the main airfield which required a working party of one officer and twenty-eight other ranks to operate. Subsidiary plant comprised one 19 RB, one Lorain, one Size II dozer, and two 1-cu yd dumpers. Owing to the high moisture content of the coral aggregate which was never less than 10 per cent, the output of the Starmix drier proved inadequate. This was increased to a satisfactory level by blowing compressed air into the drier and stepping up fuel consumption. Local modifications were also carried out on the control panel so as to avoid by mechanical means the possibility of error in operation. Shift work paid big dividends and, because of the advantages of continuous production, the output for two double shifts was more than twice the normal single shift figure.
Originally the operators for this plant were trained in England. Subsequently, training wvas carried out ab-initio on Christmas Island and on balance this system of training was preferable. Within a period of six weeks, teams to operate the different types of plant could be trained to adequate standards. In addition, a party of twenty-six other ranks was required to operate the bitumen heating tank farm in support of the Starmix 40. The plant for this consisted of nine bitumen kettles (1,000-gallon), three bowsers (1,000-gallon), one Jumbo crane, and one Matbro fork-lift truck. The bitumen was heated to 350° F in tar kettles, and the final mix produced at 300 to 330°F.
Marshall test results were satisfactory over a wide range of bitumen contents as will be seen from the following table.
Specified Average test results
Stability < 1,800 lb (Marshall) 2,600 lb
Flow > 0.16 in (Marshall) 0.11 in
Density 125 lb/cu ft 130 lb/cu ft
The bitumen mix was conveyed to the Barber-Greene layers by tipper trucks and no difficulty was experienced in transporting the mix for distances as far as 30 miles. The numbers required to operate a Barber-Greene were sixteen men per shift including two surveyors. The subsidiary plant comprised one stand-by Barber-Greene, two tandem road rollers, one Fordson tractor, one bowser (1,000-gallon) for pre-spray, and one water truck. Accurate grading of the formation was essential in order to avoid an extravagant use of asphalt. After the formation was graded and consolidated, the base was sprayed with MC1 at a temperature of 170 to 190°F before laying began. Asphalt mixes have a tendency to drag and extra shovel men were required to scatter asphalt over the laid surfaces in front of the Barber-Greene to fill the voids. The surface was laid in two strips of 12 ft width by BarberGreene layers, with a minimum of a 6 ft wide berm on either side. The temperature of the mix during laying was 250 to 300°F and rolling was carried out at 175 to 190°F. The rate of laying per machine averaged three-quarters to one mile of single strip per day.
Airfields. There were two main requirements:-
(a) To increase the surfaced hard standings at the main airfield from approximately 100,000 ft super to 1 million ft super.
(b) To construct an entirely new airfield on virgin ground at the SE corner capable of taking Valiants.
Clearly the laying of bituminous surfaced hard standings called for a higher degree of accuracy than for laying roads, but little difficulty was experienced in bringing the operators up to the required standard of accuracy. The most satisfactory sequence of rolling, and in fact the only way of avoiding camber, was to roll from the inside outwards. Wooden blocks were surveyed to guide levels at approximately 30 ft intervals. In rolling the outside edge it was important to ensure that the temperature of the mix did not drop to below 170°F before final rolling, otherwise there was a tendency for the edges to break off.
For the new airfield a bituminous surfaced strip was required of 2,000 yds in length, and 100 ft in width, with a minimum of 50 ft hard shoulders on either side. By using lagoon mud which was won entirely from below the water table, the chemical setting action produced CBR values of the order of seventy. In spite of interruptions to the work caused by the tests, the earth work for this new air-strip was completed by one plant troop within three months. Asphalt surfacing was laid at a minimum thickness of 3s in, the main purpose being to seal the base against rain and to provide a surface resistant to wear. Marshall tests on the bituminous mix were made at least four times daily.
Concrete work. Coral aggregate produced by the island quarry was used for all quality concrete work which was graded as follows:-
Grade I not less than 3,500 psi after twenty-eight days
Grade II not less than 2,500 psi after twenty-eight days
Grade III not less than 1,500 psi after twenty-eight days
Natural coral sand was generally clean and reasonably sharp. The crushed aggregate was quite porous and the cement water ratio averaged about 0.55. Plums were used in mass concrete work to economize in cement and crushed aggregate. Deposits of natural gravel were located above the high water mark. This gravel was fairly well graded and was used for low grade mass concrete. Concrete was laid at times at a rate of 40 cu yds/day in two shifts. Metal formwork of unit construction was widely used. It was extremely adaptable, easy to erect with unskilled labour, and well suited to high precision work.
A major requirement was the construction of an anchorage complex from which balloons could be flown for carrying out tests of the smaller weapons. These anchorages were heavily reinforced and varied in strength from 15 tons to over 40 tons. The surfaces of each anchorage block had to be flush with the asphalt surface, in order to ensure that movement of winch lorries on the site was not impeded. Excavations were required to a depth of 5 ft, and, with a water table at a depth of 2 ft, pumping arrangements were necessary to ensure that concrete was laid in the dry. A central weigh batching plant was set up to deal with the considerable quantities of concrete required, and dry mixes were supplied in dumpers to each site, where the correct quantity of water was added in the mixer. High quality control was imposed by means of a concrete laboratory set up on the site. Strength of test cubes reached over 4,000 psi at fourteen days. Elaborate earthing of these anchorages was an obvious requirement. The final megger tests on the copper strip earthing gave an average reading of 0.73 ohms which was well within the permissible maximum of 7 ohms.
Covered storage. A number of EDD sheds were built to provide covered storage and workshop facilities. The construction of one shed (150 ft by 50 ft) with aluminium sheet cladding and concrete floor absorbed one troop for six weeks. These sheds had previously been in use in England, and erection difficulties were increased by distortion in the steel framework as a result of damage during dismantling and in transit. A Bellman hangar of more than double the area (16,800 ft sup) with portal frame steelwork was completed by one troop in ten weeks.
As an experiment, Conder prefabricated steel framework was imported from England. This proved to be economical and extremely adaptable. This type of shed was capable of erection in about a quarter of the time required for EDD sheds. This was an important consideration since over 100,000 ft super of covered accommodation had to be completed within a space of six months.
Laboratories. The various laboratories required were quite complex, and had to be air conditioned to strict tolerance limits. These were built either in standard local prefabricated hutting or in pre-cast concrete block construction. An elaborate piped water system was usually required to provide both fresh and distilled water at a variety of controlled temperatures. The use of flexible plastic piping greatly reduced the plumbing effort involved. A laboratory of about 2,000 ft super was completed by twenty men in seven weeks, and in all about 50,000 ft super of laboratory facilities were provided within nine months.
Hutted Camp. A major project for base development was the erection of a hutted camp to house approximately 3,000 all ranks. Ancillaries included an air conditioned operating theatre, hospital wards and an open-air cinema. In building the tiered amphitheatre for the cinema, empty cement drums, filled with sand and stacked end-on in rows one above the other, proved a cheap and effective method of making retaining walls. Messes and cookhouses were built mainly of local prefabricated hutting. Because huts for sleeping accommodation to replace tents were necessarily on a lower priority, there was time to provide these in hutting prefabricated in the UK. The Junior Ranks Club which consisted of a restaurant, tavern and Junior NCOs Club, was basically a Conder storage shed adapted by local design. JRC buildings aggregating 150,000 ft super were ready for occupation within eight weeks from the start of work.
Communal mess buildings were built in the form of an open square overlooking the beach, and sleeping accommodation was sited to take full advantage of the prevailing wind. The two churches in the main camp were rebuilt largely by volunteer labour. Their walls were of coral stone taken direct from the beach and, combined with glass-louvred windows, the resultant appearance was most effective. Recreational facilities were provided by laying bituminous surfaces for hockey pitches, tennis courts and basket-ball pitches. Because the ground was so flat, and peak periods of rainfall so intense, drainage was a major consideration. Elaborate and extensive soak pits were constructed. Particularly low lying areas were avoided entirely for building. With heavy rainfall interspersed at times with long periods of drought, appearances could be most misleading, particularly when differences in level amounting to one or two feet could be critical. It was thus important to record accurately areas of flooding as these occurred, and diagnose the cause.
Miscellaneous tasks. Steel latticed masts. The erection of a number of steel latticed masts (averaging 150 ft in height) was another feature of test preparations. One of their uses was in connexion with the provision of closed television circuit facilities between the test area and central control. As was the case for a number of tasks, sappers had to be trained ab initio. There was never any shortage of volunteers for unusual jobs. One sapper who had developed into a highly skilled erector was asked why he had volunteered. He replied "I always did have a fear of heights, and I decided now is my chance."
Fuel storage. In the tank farm adjacent to the port there was a requirement for storage tanks of 3,000 barrel capacity. These were of bolted steel sections, three stories high, and totally enclosed. Local modifications were required to draw off moisture condensate. A tank, including foundations and erection, could be completed in nine weeks with a working party of eighteen. Pipes were laid from the wharf side so that fuel could be pumped direct from lighters. With a view to reducing the number of bowsers, the advisability of laying a pipeline from the tank farm to the main airfield was investigated, but the amounts consumed, although considerable, did not justify the cost and effort involved. A smaller tank farm was provided at the main airfield.
Port maintenance. Both coast erosion and anti-silting measures had to be implemented at the port. In conjunction with Admiralty Civil Engineers, the behaviour of currents and drift were investigated over a period by observing the movements of a variety of coloured stones placed at selected points along the beaches. As a short term measure, groynes, to counteract silting of the channel into the port, were built by using a series of wire gabions. The material was square mesh reinforcement which was bent and spot welded to form rectangular baskets. These baskets were then placed in the required position on the beach, secured with pickets, and filled with coral stone. Groynes of this nature can be just as effective as pile-driven groynes, they are very much quicker to produce, and require no plant or skilled labour on the site.
Cold storage. Two 50-ton cold stores were erected in the port area in order to economize in refrigeration space afloat, thus reducing shipping requirements. Each had a standby refrigeration unit and efficiency was increased by housing the whole installation inside a structure built up from standard local prefabricated hutting units. One 50 cold store could be completed by twelve men within nine weeks.
Utilities. Power. As scientific and base facilities built up so the requirement for power and light increased greatly. A new power station of eight 300 kW diesel generating units was built at the main camp. In the test area alone, nearly a hundred generating stations had to be set up and operated at different localities. In rear areas, the number of separate power stations was reduced by rationalization, to economize in manpower and running costs. Because of the distances involved, it was decided to change over from low tension to high tension distribution, and a start was made on this project towards the end of the year. At the main airfield planning was completed for an underground high tension ring main. The high rate of corrosion, and earthing as a result of salt in suspension in the air, resulted in a heavy maintenance commitment on electrical distribution lines. In order to keep resultant interference with user supplies to a minimum, it was important to sectionalize circuits to permit local isolation of faulty areas. Stand-by sets were provided at vital points to serve the operating theatre, the airfield control tower and laboratories which required continuous operation.
Water. The source of indigenous water on Christmas Island is shallow wells scooped to about eight feet in depth. These were covered over to reduce growth of algae and losses from evaporation. The fresh water layer lies on the top of the salt water table and in places was only a few inches in depth. The depth of the salt water table was influenced by tidal movement. It was thus vital to control rigidly the rate of pumping, otherwise the fresh water layer will become contaminated and may remain so for months on end. At peak strength the Task Force consumed approximately half a million gallons of water a week, the bulk of which was pumped to the user through a piped distribution system. Ground water sources were supplemented by vapour compression distillation plants since there was a scientific requirement for this type of water. The salinity of the fresh water sources averaged fifty parts per million, which was well within accepted standards. It can be recalled that the salinity of the Tobruk wells, used by the besieged garrison during the last war, was of the order of 1,500 parts per million. During the year, as an insurance against drought, the principal source of ground water for the main camp was duplicated, by providing an entirely new water point outside the sphere of influence of the original source.
Sewage. Initially, sanitation requirements were provided in the form of elsan type chemical closets. The effluent was conveyed in special vehicles for disposal by pumping out to sea. As part of the hutted camp development, a water borne sewage system was installed. Because the ground is so flat, the sewage had to be pumped under pressure. This required the construction of a number of totally enclosed collecting and pumping stations in reinforced concrete. Sewage was discharged direct into the sea from an outfall built over the reef at about three miles from the main camp. The use of treated asbestos piping for main and subsidiary sewers greatly reduced the effort involved. Piping was laid at an average depth of 3 ft. Garbage was burned and buried at a disposal area several miles downwind of the main camp. Operation of this area tied up completely one dragline excavator and one dozer. Flies and insects were kept very much under control by both air and ground spraying of insecticides.
Part three next week.
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