AAI conducted a variety of design and project management tasks for PB Energy Storage Services, Inc., of Houston, Texas, related to the design and construction of a large underground gas storage complex located near the city of Zhuhai, China, southwest of Hong Kong. The facility included two storage caverns, each having a volume of approximately 200,000 m3 and located 100 to 200 m deep, depending upon the relative vapor pressure of the propane and butane products to be stored. The design included a sophisticated network of access shafts and connecting drifts to support the unique requirements of gas storage containment. The caverns were constructed in fractured granite next to the sea with slope access for construction and shaft access for post-construction operation. During the design phase, AAI evaluated the rock mass classification and ground support requirements and conducted numerical modeling analyses of overall cavern stability, alternative opening profile shapes and appropriate pillar widths. AAI played a key role in the design process by providing advice to PB Energy regarding common excavation and support practices and evaluating the viability of detailed construction plans. Throughout the construction phase, AAI provided senior personnel on-site to oversee construction activities and ensure long-term cavern stability by verifying that proper excavation and ground support methods were employed and by monitoring changing ground conditions and modifying support plans as needed during construction. The total project duration was about 3 years (2004–2007).