Caldwell Solids Handling and Digester - Caldwell, Idaho 

JC Constructors built a new 60’ diameter by 35’ tall digester with control building as part of Caldwell’s 8.5 mgd treatment process.  The project required demoliton of the existing control building, pump station with wetwell, and two digesters as well as extensive piping underlying these structures.  To allow the plant to maintain full operation during demolition and throughout the project, JCC devised a distinct phasing plan for both temporary piping and electrical connections.  A key component of the phasing plan was allowing the existing system to continue operating as new construction progressed.  JCC devised an innovative solution by lowering the footing on the new control building wall that was immediately adjacent to the existing control building; JCC provided an engineering design for the change that ultimately reduced the construction duration and lowered the overall project costs.

The 3,700 sf control building required two 100 gpm chopper scum pumps, three 75 gpm progressive cavity pumps, three grinders, all with mechanical piping, valves, and equipment.  While installing the new buried pipe, JCC’s understanding of the overall piping network based on as-built drawings allowed them to simultaneously work on multiple piping systems.  Constructing the 35’ tall digester wall provided two distinct challenges from its uncharacteristically tall height and its steep floor slope.  To overcome these challenges, JCC selected wall form and roof shoring systems that met the specifications, kept the project on schedule, and allowed the structure to pass field tests.  The project also included a methane gas storage membrane with a burner and reuse system to provide methane to operator occupied buildings onsite.  Total construction cost was $7.1 million.