MWH recently celebrated the completion of the east train on the Pima County Ina Road Water Reclamation Facility, where we are currently providing construction management-at-risk services. The $227 million project includes the expansion of the primary and secondary treatment facilities from 37.5 to 50 mgd. MWH is self-performing approximately $45 million of the work, including seven miles of underground yard piping and all process piping and equipment for the new and renovated facilities.
MWH had to work through several important stages before the east train was successfully completed; all while keeping the existing plant operational. Extensive collaboration between MWH, the plant’s operation staff, designer and the Owner’s project manager was crucial in reaching theses set goals. Throughout this past year, the project team completed hundreds of Maintenance of Plant Operations plan (MOPO), including setting a 35-ft-long, 8-ft-diameter influent screw pump at the headwork’s facility, the tie-in of new blowers into the existing blower header, numerous midnight shifts to complete electrical transfers to new gear, the design and installation of a temporary polymer feed system, and a temporary heat sink to provide powerhouse cooling.
The integration of the new east train into the existing plant required three full plant shutdowns to make the necessary tie-ins, each requiring a separate MOPO, a walkthrough and several dry runs. For example, in April 2012, the team coordinated a 12-hour shutdown of the entire plant to install two 10-ft x 10-ft concrete junction structures over the existing effluent pipeline, allowing flow to the new west chlorine contact basin.
Temporary work was also developed and implemented by MWH to facilitate the transition from an existing process train to a new one. Project crews tested the new plant and tank drain pump station, and effectively accomplished biological seeding and startup of the east plant facilities. After the team worked through numerous impacts as a result of inaccurate as-builts, that included a 30-in RAS line reroute days prior to the startup, a few minor SCADA anomalies, and the commissioning and startup of equipment, the required 100-hour operational test on the east plant reached completion. The primary and secondary treatment facilities were successfully turned over to Pima County’s staff to operate.
In addition to the planned work, the team successfully overcame severe weather conditions that included monsoon rains, which flooded the chemical feed facility just weeks prior to the scheduled startup of the east train.
With the successful startup of the east train, the west train process flow was shut down with a custom fabricated steel bulkhead designed by MWH, which now allows for remaining construction and tie-ins of the west plant. The anticipated project completion is slated for October 2013.
