REPAIR SHORELINE REVETMENT, BACK OF BOQ 8 & 9, U.S. NAVY SUPPORT FACILITY – DIEGO GARCIA, B.I.O.T.

This Design-Build project located in Diego Garcia (DG) included the repair of the existing revetment and restoration to 700 linear feet of shoreline in order to protect threatened infrastructure and nearby buildings as a result of wave activity without proper slope protection.

In order to appreciate the challenges encountered throughout the project, we must first recognize the geographic remoteness of DG.  Diego Garcia is a narrow atoll, one of the 52 islands in the Chagos Archipelago, which extends over an area of 25,900 square kilometers.  The coral atoll is horseshoe-shaped with an opening approximately 6.4km wide where the lagoon transitions into the Indian Ocean.  The land distance from tip-to-tip of the atoll is roughly 60km, while the total land area is about 2,720 hectares.

The project in its entirety was critical to the continued operations of the U.S. Navy Support Facility (NSF) in DG.  The design was provided by Winzler & Kelly Consulting Engineers in close coordination with our local staff in DG and was accepted by the Navy with very minor comments.   Repairs included replacing the existing rubble-mound revetment with an engineered revetment consisting of Class A armor stones, Class B underlayer stones & geotextile fabric, and stabilizing portions of existing shoreline corridor with backfilling and re-vegetation.

The mobilization of all equipment and rock revetment materials proved to be the most time consuming of all work activities.  It took about 5 months to deliver the rocks to DG from Mauritius over a span of 4 separate trips.  Prior survey of the quarry location in Mauritius was conducted and samples of revetment materials were produced in accordance with the design.  Our supplier in Mauritius produced the required materials ahead of time, prior to the arrival of the Tug and Barge.  Coordination details with the Ports in both Mauritius and Diego Garcia were conducted and finalized one day prior to the arrival of the shipments respectively.  Actual installation took approximately 3½ months to complete.

Despite the lack of available resources to complete this type of construction in DG, Black Construction Corporation (BCC) overcame a number of obstacles and fostered the following practices to ensure the project was completed on time, within budget and with very limited disruption to nearby residents occupying the surrounding facility:

1)    Lack of resources – BCC chartered a US flag tug and barge vessel to haul underlayer and armor stone for the project.  There was a total of 4 barge loads (26,000+ metric tons) of revetment material procured in Mauritius.

2)    Limited staging area – BCC constantly hauled revetment materials on-site as crews installed the rocks.

3)    Equipment breakdown – Due to heavy equipment involved with the placement of the armor rocks, constant equipment breakdown was inevitable.  Replacement parts were on-hand in anticipation of equipment failure.  This became a critical/essential part of the planning process.

4)    Hazardous working environment – Scheduled work close to the water was coordinated with the ocean tide.  Work schedules were modified in order to commence during low tide.  Environmental controls were strictly adhered to.

5)    Long-lead Items – Shipment of rocks (4 barge loads) took approximately 120 days from Mauritius to complete and required a ‘round the clock, 24 hour operation during loading in Mauritius and unloading in DG respectively.

There were no recordable safety violations and no lost time was incurred during the performance of this contract!

The award is a significant achievement and awarded only to those companies which have demonstrated a corporate safety posture throughout the life of their contract.