The island of Guam is an unincorporated American territory in the Western Pacific Ocean. The island, located between Papua New Guinea and Japan directly north of Australia, is the largest island in Micronesia. The Guam Waterworks Authority (GWA) operates five sewage treatment plants and is currently undergoing a series of works to improve the WWTP. Michaels Corporation, based in Wisconsin, is the drilling contractor for the project.

Extension of Guam’s wastewater treatment plants

The aim of the project is to extend the deep ocean outfalls that discharge wastewater from Guam’s two largest treatment plants.

The Northern District WWTP outfall is planned to be 548.6 m long. The outfall will terminate at a depth of 42.6 m. The end of the outfall will have a 121.92 m diffuser after the pipe daylights onto the ocean floor. The Agana WWTP outfall is planned to be 640 m in length and will terminate in 82.3 m of water.

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The original drilling at the Agana WWTP was halted when the remotely operated underwater vehicle found a metal object in the drill path which the divers suspected may have been an unexploded ordnance. Guam was the only American-held island in the region before WWII. The island was occupied by the Japanese in December 1941 until the Battle of Guam in 1944 resulted in the Allies recapturing the territory. WWII military occupation and warfare left millions of pounds of unexploded munitions and explosives in the region. Some of these munitions were fired but failed to detonate, while other ordnance was abandoned after conflict ended. Unexploded bombs, artillery shells, grenades and bullets are still found routinely. These munitions slowly degrade into the environment and can detonate if disturbed. The divers were former Navy divers who investigated and in this case were fortunate that the object was not dangerous. A challenging project

The project has encountered a number of challenges. The contractor started with the installation of the Northern District outfall. During installation of the product pipe into the completed borehole, operations had to be abandoned at 75 per cent complete because the pipe became lodged in the bore hole. The pipe was then completely removed from the hole. Due to various installation difficulties the company decided to switch from push reaming to pull reaming to complete the outfall extension.

The company then moved to the Agana WWTP extension because of Environmental Protection Agency deadlines. During the Agana installation a 54 inch reamer was lost down the hole, which the contractor had to drill around. The company also began using cable which snapped and snared in the hole. The contractor was forced to remove the tangled ball of cable before proceeding.

Once completed, the works will ensure higher environmental standards for Guam’s wastewater treatment plants and the island’s beautiful beaches.