Deep Bury Underground Tank Top Modification

Project: Regulatory changes required that an existing underground tank system be upgraded with tank top to grade sump structure.

Challenge: The existing tank was buried at -30’. Slope/benching excavation in accordance with OSHA regulations was not feasible due to the proximity of adjacent multi-story buildings. Due to the restricted property size and access, excavation utilizing typical shoring with excavate/haul methods would have generated too much soil to stockpile on-site, or would cause a complete shutdown of facility operations by terminating access to the facility.

MJK Solution: MJK designed a caisson shoring method to minimize the area to be excavated, and simultaneously maintain access to the facility without endangering adjacent structures. MJK met with Cal-OSHA representatives to review the proposal and received approval for the method.

Through hand-excavation and the use of vacuum equipment, the soil was removed from within the caisson while pile-driving equipment was used to move the caisson deeper. With a risk of potentially driving the caisson through the underground tank, or potentially missing the critical tank-top area necessary for the upgrade, constant and precise measurements were taken throughout the driving operations to measure for depth, and deflection. Once the tank top area was reached, the upgrades were made, a sump to grade was installed, and the modifications approved by local regulatory agencies. Estimated cost savings to the client exceeded $250,000.00