Chevron Platforms Hazel, Hilda, Hope and Heidi (known as 4-H Platforms) located in the California State waters offshore Santa Barbara Channel were decommissioned and removed from the ocean floor under a single dismantling and removal contract during the spring and summer of 1996. A unique aspect of this abandonment project was the use of explosives to sever the platform legs a few feet below the level of ocean floor, a first for California waters. The paper first provides an overview of decommissioning plan development based on California State Lands Commission (CSLC), other State and Federal regulatory framework, available crane barge lift capacity both onsite and offloading sites, the weather window on the use of heavy marine equipment during migratory patterns offshore California. Then, technical aspects of decommissioning of wells, removal and transportation of the platform topsides, deck and jacket components are discussed. Details of use of explosives for conductors and pilings removal, abandonment of pipelines and power cables and site restoration are also presented.
Platform Hazel with 25 wells was installed in 1958 and was located in 96 feet water depth. The Platform Hazel jacket was of "gravity structure" with large caisson bases filled with sand and cement with no anchor piles. Platform was floated to the site using these caissons and used as anchor points for the structure after jetting 18 feet into the sea floor and filled with sand and cement (Figure 1). Platform Hilda with 29 wells was installed in 1960 in a water depth of 106 feet. Platform Hope with 46 wells and Platform Heidi with 31 wells were installed in 1965. The Platform Hope was located in a water depth of 137 feet and the Platform Heidi was located in a water depth of 126 feet.