Receiver Site 1983
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Receiver Site 1983
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Transmitter Site 1987
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NAVCOMMSTA Diego Garcia plaque
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NAVCOMMSTA Diego Garcia plaque
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NAVCOMMSTA Diego Garcia plaque
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NAVCOMMSTA Diego Garcia plaque

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ATCU Diego Garcia patch
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NAVCOMMSTA Diego Garcia patch
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NAVCOMMSTA Diego Garcia patch
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NAVCOMMSTA Diego Garcia patch

From Naval Facilities Engineering Command History 1965-74, Chapter 10 - link

The Navy's communications facility on the atoll of Diego Garcia was a major Command project during the 1970s. Before the Diego Garcia facility was established, the Indian Ocean had been a blacked-out area in the Navy's worldwide communications network. Construction of the Diego Garcia facility was undertaken to remedy this situation. The facility was built primarily by personnel of the Naval Construction Force under a bilateral agreement between the united Kingdom and the United States. What of the atoll itself?

Diego Garcia is 12,000 miles from the nearest United States port. Even within the geography of the Indian Ocean it is isolated. Before construction began, the nearest airfield was located at the British base at Gan, 400 miles to the north. The nearest commercial port is Colombo, 960 nautical miles distant.176 The atoll is part of the British Indian Ocean Territory (BlOT), formed in 1965 from territory formally belonging to Mauritius and the Seychelles Islands. The atoll is one of fifty-two which make up the Chagos Archipelago which spreads over an area of 10,000 square miles. The Chagos Archipelago is located in the heart of the Indian Ocean, south of India and between the African continent and Indonesia.

Diego Garcia is a narrow coral atoll having a land area of about eleven square miles, which nearly encloses a lagoon. It is shaped roughly like a "V", which stretches thirty-seven miles from tip to tip, with an opening to the north-northwest. Shallow reefs surround the atoll on the ocean side as well as within the lagoon. Most of the aggregate used in the construction effort was blasted from the outer reefs, then crushed to required size.

Diego Garcia was discovered approximately 400 years ago by the Portuguese. It subsequently fell under French control and in 1814 it passed to the British. In 1974 it was part of the British Indian Ocean Territory. In the past, the atoll's major industry was copra. In addition, there was a phosphate mine and the atoll further served as a coaling station.

In December 1966, the United Kingdom and the United States signed a bilateral agreement constituted by the Exchange of Notes dated 30 December 1966 (BlOT Agreement 1966), which made the islands of the British Indian Ocean Territory available for the defense purposes of both governments as need arose. On 24 October 1972 a supplementary agreement was signed by the two governments concerning the construction of a limited United States Naval Communications Facility on Diego Garcia (Diego Garcia Agreement 1972). The purpose of this facility was to provide a link in United States defense communications and to furnish improved communications support in the Indian Ocean for ships and aircraft owned or operated by or in behalf of either government. FOllowing Department of Defense approval of the plan, the first two increments of the project were submitted to Congress, and were approved and subsequently funded in the fiscal year 1971 and 1972 Military Construction Appropriation Acts. Construction was to be accomplished by the united States, utilizing units of the Naval Construction Force.

The base on Diego Garcia was initially planned as an austere communications station with all necessary supporting facilities including an airstrip. The project was originally intended to be completed within three years, however, this deadline was later extended a year to July 1975. Pursuant to the Diego Garcia agreement of 1972, supplementary arrangements were also made between the Royal Navy and the United States Navy for the joint operation of the communications facility. Consequently, both the British and American flags would fly over the facility and the United Kingdom would assist in manning it.l77

The actual construction presented several problems to those who would do the building. One of the most critical problems on Diego Garcia was that of obtaining good fill material. Vast amounts of fill were needed for the foundations of all horizontal and vertical structures. In addition, good material was required for aggregate for the concrete work done on the atoll. Due to the limited amount of developable land on the atoll, future expansion would require that marginal lands be filled and made buildable. These marginal lands included marshy lowlands, borrow pits and shallow portions of the lagoon.178

There were three sources of fill material on the atoll: (1) borrow excavation, (2) the coral shelf that surrounded the atoll, and (3) dredged material. The first two sources were the least desirable because borrow pits made additional land areas unusable and mining of the coral shelf was both costly and difficult. Dredging offered the best method of obtaining fill material and aggregate in terms of quantity and quality. It was recommended that whenever feasible all the dredged material be deposited ashore. This amount should be sufficient to provide fill for all projects planned on Diego Garcia. Where feasible the dredged material was stockpiled and/or put in areas of future potential use.

Certain constraints also limited the nature and location of construction on the atoll. Not only was the amount of developable land on Diego Garcia limited, but much of the better land was not available due to the presence of various clearance requirements related either to safety or to operational factors. One of these operational factors concerned the communications installation itself. In order to assure minimum interference between high frequency transmitter and receiver, there had to be a separation distance of fifteen miles between the two. The receiver station was to be located five miles frm the airfield, five miles from the primary power plant, one mile from the cantonment area and three miles from the light industrial areas.179

Air safety also put constraints on construction. The Air Installations Compatible Use Zone (AICUZ) was intended to define an area where land uses which were incompatible with air operations would be excluded. The Air Installations Compatible Use Zone was derived from two elements, noise and crash potential. Noise contours and crash potential areas were delineated for Diego Garcia. The Air Installations Compatible Use Zone could contain such compatible uses as outdoor recreation, industrial facilities, warehousing and petroleum storage. Airfield safety requirements made it necessary to restrict all construction within 750 feet of the runway center line. Beyond that line facilities could be constructed which did not penetrate a 7.:1 slope. It is also necessary that zones 3,000 feet beyond the end of the runway be free from obstruction.

Another constraint on building was the 600 foot clearance zone that had to be maintained around the Radar Wind sending building, which was located approximately 1,500 feet west of the Air Operations building.

Water was also a limiting factor. Due to the critical water supply situation, several areas were designated as "water zones." No construction was allowed in these areas in order to insure an adequate supply of well-water to support the needs of the personnel on the island.

There was also a necessity for the safe storage of explosives. Since no inhabited structures could be built within the Explosives Safety Quantity Distance (ESQD) arcs generated by stored explosives, the safety zones imposed a rather extensive limitation on developable land.(180)

The final limitation on development concerned the boundaries of the areas allotted to each of the two contracting powers. In accordance with the agreement between the united States and British governments, the united States could use the west side of the atoll up to latitude 7024'30" S on the east side of the atoll. (181) On 23 January 1971, a nine man reconnaissance party from Naval Mobile Construction Battalion 40 landed on Diego Garcia to confirm planning information and to initiate a preliminary survey of the beach landing areas. Subsequently, during early March 1971, a fifty man landing party arrived at Diego Garcia aboard the USS Vernon County (LST 1161). This party comprised personnel of Naval Mobile Construction Battalion 40, Amphibious Construction Battalion 2, Amphibious Forces Pacific Underwater Demolition Team, Construction Battalions Atlantic, and Air Transportable Communications Unit 4. Men from these units marked underwater obstructions, installed temporary navigational aids and cleared beach areas in preparation for an over the beach landing of additional personnel. On 20 March 1971, an advance party of 160 men arrived and during the following month the main body of Naval Mobile Construction Battalion 40 landed. The battalion's main assignment was the construction of a temporary Seabee camp, construction of water and electrical distribution systems, completion of a camp dining hall, laundry, refrigeration and material storage facilities, and construction of a temporary industrial site and a 3,500 foot interim airstrip. Prior to the completion of the airstrip on 15 July 1971, all personnel, equipment and supplies had to be landed on the beach by LST and Mike boat.

In October and November 1971, Detachment "Chagos" of Naval Mobile Construction Battalion 71 and the whole of Naval Mobile Construction Battalion 1 arrived. Their arrival marked the beginning of large scale military construction on Diego Garcia. Naval Mobile Construction Battalion 1 devoted its major effort to erecting the receiver and transmitter buildings. Other projects undertaken included the placing of the base course for the permanent runway, taxiway and parking apron, operation of a precast yard and block plant, and construction of the 5,000 foot POL lagoon causeway. Detachment "Chagos'" construction efforts were located at the permanent industrial site and consisted of four permanent structures, the largest of which was the cold storage and general warehouse. During this period civil service personnel from the Naval Electronics System Command were also deployed to Diego Garcia to provide electronic equipment installation support in conjunction with the construction of the transmitter and receiver buildings. (182)

In July 1972, Naval Mobile Construction Battalion 62 relieved Naval Mobile Construction Battalion 1. The men of the new battalion concentrated on the construction of the transmitter and receiver buildings. They also paved the airfield and continued work at both the cantonment and the industrial sites. On 25 December 1972, the first Air Force C-l41 jet transport landed on 6,000 feet of completed permanent runway (with the Bob Hope Christmas Show Troupe). The concrete work on the full 8,000 foot permanent runway with adjoining taxiway and parking apron was completed by March 1973. Following completion of the runway, a weekly C-l4l Military Airlift Command flight was initiated between Diego Garcia and Utapao, Thailand.

The third Detachment "Chagos," composed of 180 men from Naval Mobile Construction Battalion 133, arrived in November 1972. It continued work on the air operations and radar wind buildings, the sewage lagoon, and bachelor officer and enlisted quarters. During December 1972, personnel of the Naval Communication Station Pre-establishment Detachment began to arrive. Their task was to prepare for the acceptance of equipment and facilities as they were turned over for operations and maintenance. In February 1973, the first group of Royal Navy personnel arrived to join the Naval Communication Station Pre-establishment Detachment. This group officially relieved Air Transportable Communications Unit 4 of its duty of providing off-island communications support to all units on the atoll. Finally on 20 March 1973, exactly two years after construction began, the Naval Communications Station, Diego Garcia, was officially establishment.

During March, Naval Mobile Construction Battalion 74 relieved Naval Mobile Construction Battalion 62 and subsequently continued work on various projects, giving special attention to runway lighting and the work at both the industrial and cantonment sites. During June 1973, there was another unit change, when Detachment "Chagos" of Naval Mobile Construction Battalion 10 relieved Detachment "Chagos" of Naval Mobile Construction Battalion 133.(183) The second construction increment slated for the Naval Communication Station, Diego Garcia was the provision of a ship channel and turning basin in the lagoon. This construction was awarded as an international contract to a construction firm from Taiwan. Construction began in August 1973 and would take two years to complete.

Most of the station's facilities were built in the cantonment area, located at the northern most tip of the atoll. The station's personnel were quartered and supported here. This area was designed as a walking/bicycling community, hence auto and truck traffic was strictly limited. Community support facilities included a gym, bowling alley, chapel, medical facility, Navy exchange, swimming pool, All Hands Club, and playing fields and courts. Additional planned facilities included an Armed Forces radio and television station, chapel addition, hobby shop, special services issue office, theater, library and education center. A Chief Petty Officers Club, Officers Club, snack bar and recreation area were also eventually to be built.184

The administration building was also located in the cantonment area. It was located thus because this location was readily accessible to personnel being supported and to the administrative personnel who worked there. An addition to this building was planned. A fire station was also sited in the cantonment area. Generally a location central to the developed area would have been preferred. However, since Diego Garcia was long and narrow and and since most of the facilities which were considered to be life safety hazards were concentrated in the Cantonment Area, a site there was deemed most suitable for a fire station.

The second major area of construction was the airfield and its supporting activities. It was located about midway down the length of the western side of the atoll. Revised requirements called for the extension of the original 8,000 foot runway to 12,000 feet. In order to avoid expansion into the ocean or lagoon, 3,000 feet were added to the southeast end and 1,000 feet to the northwest end of the runway. A 1,000 foot overrun was required at each end of the lengthened runway. An additional requirement called for an increase in the size of the parking aprons by 89,750 square yards so that taxiways and runway turnarounds might be built. The following new airport support facilities were also deemed necessary: an air transportation hangar, operations building expansion, airfield transit storage, an aircraft washrack and a crash fire station.

The public works area (formerly the industrial area) was located approximately five miles south of the airfield and its supporting facilities. Supply support for the atoll was centralized at this point. As the permanent facilities on the atoll began to take shape, certain geography related problems began to manifest themselves. All automotive and construction equipment on the atoll operated under very adverse environmental conditions. Experience showed maintenance demands to be extreme and vehicle downtime high. Accordingly, vehicular travel was limited as much as possible. The land use plan incorporated this rationale through designation of the northwest tip of the island for the cantonment area and the establishment of a new supply support point near it. The location of warehouses in the public works area made it necessary to move 90 percent of all supplies a total of twenty miles (airfield to warehouse plus warehouse to cantonment area). This was a particularly bad practice for cold storage items.

The Navy's POL storage requirement was 480,000 barrels in support of both ship and aircraft needs. The Air Force required an additional 160,000 barrels of storage. The POL site was located between the warehouse area and the Seabee construction support area . The original construction plan had the POL tanks located on a fill area adjacent to the causeway. A new site was required for the following reasons: (1) the old site would require use of critical fill material needed for other planned facilities, (2) the need to expand airfield facilities into the area along the causeways, (3) and the preference of POL operators to locate the storage tanks at a less exposed site. A new site was selected north of the airfield. It had the advantage of being located near the causeway/fuel pier and airfield operations area. One disadvantage was that a borrow pit was being used on the site. It would have to be filled and the area regraded before construction of the fuel tanks could begin.

Additional public works shops and stores were to be provided through conversion of existing general warehousing and cold storage facilities located in the public works area. The warehousing function was to be consolidated in the new supply support area. The expansion of the existing power plant by two additional 1,200 kilowatt generators was proposed. In order to retain the necessary separation for noise, access and fire safety between the existing public works office and the power plant, the natural expansion direction was to the south. However, two fuel tanks had been built in this area. These tanks would have to be relocated prior to the construction of the power plant extensions.

Since the primary function at Diego Garcia was initially communications support, the communications facilities were the most completely developed. The locations of the receiver and transmitter areas were for all practical purposes fixed by the existence of permanent buildings and antennas. An addition to the receiver building (located in the cantonment area) was the only expansion of communications functions planned during 1975.185

Waterfront facilities were built in the cantonment area. By 1975 these temporary facilities were judged inadequate for both offloading and maintaining the boats which were the only means of moving cargo from ship to shore. Even if a pier were to be built, boats would still be required for movement of cargo. A permanent facility which would allow efficient offloading of the boats was a necessity. In order to maintain the boats properly, a complete maintenance facility was required. The maintenance facility was to include previsions for removing boats from the water for overhaul and returning the boats to the water afterward.186

Additional modifications planned for the waterfront area included a small boat pool and a pier. The small boat pool was to be located at the causeway and would contain facilities for lifting boats out of the water, a boathouse, moorings for all small boats and a crane for loading and offloading cargo. The pier was to be T-shaped and would extend out into the lagoon from the end of the existing causeway. (187)

A fleet recreation area was considered necessary to accommodate the large number of fleet personnel who might be on shore at various times. All personnel support facilities in the cantonment area were designed for the support of the permanent party. They were not large enough to support additional transient fleet personnel. Because of this, a fleet recreation facility located away from the permanent cantonment recreation was to be provided. Other presently planned facilities include a hardstand for the vehicles of the Marine Amphibious Unit (to be located near the causeway), and short-term training facilities for Marine personnel. (188)

By 1975 permanent electrical power generating facilities had been constructed on the atoll. These facilities included the main power plant, three standby power plants and a regulating vault. The main power plant located in the public works area, was composed of four 1,200 KW generators which generated power at 41,160 volts. It was proposed to add two additional 1,200 KW generators to this plant. The standby generators were located respectively at the transmitter station, the receiving station, and at "c" building. The regulating vault was located at the air operations building.

Two barge-mounted desalinization units furnished the atoll's water supply. The planned permanent facility, which was to be located within the main power plant building, included two 60,000 GPD capacity units designed to operate on heat recovered from the main power plant generating units. A subsequent study for alternate solutions for the water supply indicated that a groundwater source utilizing the electrodialysis method for water treatment was best suited for Diego Garcia. (189). Electrodialysis units were to be installed at the various centers of water demand. The plan to install the desalinization units in the power house was consequently discarded and the space set aside for them was used in subsequent expansion of power generating facilities.

Sewage disposal on Diego Garcia was rather simple and straightforward: Sewage from the cantonment area was pumped to a large sewage lagoon which had an ocean outlet. Sewage from all other facilities was handled by small septic tanks with leaching fields. No expansion to any of these systems was expected.

As the Naval Communication Station, Diego Garcia was still a developing facility at the end of 1974, especially as regards its total final mission, many changes and additions can be expected in construction planned for it in the future.

176 "Project Reindeer Station, Diego Garcia: Deployment Information" (undated briefing), from Mr. W. J. Vacca, NAVFAC Construction, Code 051PJ, pp. 1-2. 
177 "Deployment Information: Diego Garcia," p. 3. 
178 Master Plan for US Naval Support Facility, Diego Garcia (Feb 1975), p. B-3. 
179 Master Plan: Diego Garcia, p. B-3. 
180 Master Plan: Diego Garcia, p. B-5 
181 Ibid.. 
182 "Deployment Information: Diego Garcia," pp. 3-9. 
183 "Deployment Information: Diego Garcia," pp. 3-4. 
184 Master Plan: Diego Garcia, p. C-3. 
185 Master Plan: Diego Garcia, pp. C- 8--C-9. 188 Interim training facilities or Marine personnel . 
186 Master Plan: Diego Garcia, pp. C-8--C-9. 
187 Ibid., p. C-9 
188 Ibid. 
189 Ltr from COMPACNAVFAC of 13 Jul 1973 (09F:mm serial 4603).