This Seismic retrofit project involved removal of the top two feet of existing shell plate, complete existing structure and roof, and all roof appurtenances. A new shell ring was installed on top of the existing shell plates and a brand new external press-broke roof was installed (two-bay structure) along with supporting columns and an open structure halo support system. The Press-broke external rafter configuration provides robust structural support without internal rafters/structure obstructing the roof, inaccessible areas, and the tank interior, simplifying maintenance and extending lifespan.
New roof appurtenances were installed including a new center roof vent, a square roof entry hatch and a new 24×72 scaffolding roof hatch and new large roof platform with davit crane and safety tether points, a new baffle system and a new cathodic protection system.
The seismic retrofit also included new shell reinforcing plates encompassing the first and part of the second shell course accommodating all existing shell penetrations and existing anchor chair system.
There was also a seismic retrofit of the adjacent 1MG reservoir, but that retrofit included mostly foundation replacement and reinforcement and there was minimal steel work.
