Subject to extremely harsh environments, it is important that sulfur pits receive the proper maintenance and repair in order to maintain structural integrity and extend their service life.
A sulfur pit in California had previously undergone a repair with the installation of a steel liner. However, the repair proved inefficient, and Structural Preservation Systems (SPS) was contracted to develop a long-term repair strategy that involved the installation of a concrete structural liner within the pit, commonly referred to as a "pit within a pit" repair.

SPS teams began by conducting a condition survey to determine the current status of the pit. A second contractor removed the sulfur pit's lid, and SPS removed the hardened sulfur, coils and steel liner within the pit. The removal of the steel liner revealed significant damage to the sulfur pit walls; and, in some areas, the wall had deteriorated completely. In addition to the visual inspection, SPS crews conducted an acoustic impact survey in order to detect subsurface voids and/or delaminations within the sulfur pit. Using wet rotary diamond core drilling techniques, concrete cores were extracted for testing. (The subsequent holes were filled with a shrinkage-compensating repair mortar.) The information gathered from the condition survey was then submitted to SPS' Engineering Services Division in order to develop the most effective repair strategy, taking into account the sulfur pit's aggressive environment.

The repair strategy included the installation of a new concrete floor. For the sulfur pit's walls, all cracks were routed, cleaned and chinked with lead wool. Reinforcing anchors were drilled and installed, and a 12-inch thick concrete wall was constructed within the 16-foot by 23-foot by 6-foot pit. Constructed of a sulfate resistant cementitious repair material designed to handle the aggressive environment of a sulfur pit, the material for the concrete wall was mixed on-site to ensure quality control.

During the project planning and implementation, SPS addressed several unique challenges.  Special coordination with the material supplier of the concrete floor was vital in order to develop the proper formula that would withstand the sulfur pit's harsh environment. Additionally, because the owner wanted to have the option to expand the sulfur pit in the future, SPS had to make provisions when designing the repair to allow for the possibility of expansion. Despite the challenges, SPS completed the repair project within the tight two-week timeframe during a planned shutdown, and the owner was very pleased with the results.