Project Background

Since 2004, the District has had a vision for major WWTP improvements as shown by a Site Master Plan provided by Carollo Engineers. This plan notes the existing conditions at the time, including treatment deficiencies; and expands upon future needs with alternative treatment layouts, including consideration of recycled water. Not much came of this plan except for the implementation of constructing the Maintenance and Laboratory facilities. 

In 2020, staff began noticing more consistent consequences of an aging WWTP, particularly regarding the ungrounded electrical system, with blown fuses and damaged equipment. While there were electrical equipment upgrades in 2009, these were limited in scope. Notably in 2013, it was determined a specialized bullet resistant divider wall was required to be installed in the operations room to protect operators from the potential arc flash explosion.

As part of the process for developing the electrical project, Staff became aware of both the intricacies and inefficiencies of energy use at the WWTP. In September of 2021, MSD enrolled in the SoCalREN (SCR) program and began to explore energy cost saving opportunities through energy efficiency. In March of 2022, SCR identified the aeration basin blowers and ammonia controls as having high saving opportunities.

In 2021‐2022 (finalized January of 2023), the District received two technical memorandums (TMs) as part of an Enhanced Recycle Water Study from Carollo Engineers. One TM was a Condition Assessment (TM3) of our wastewater treatment plant (WWTP) and the other was a Cost for Rehabilitation and 30‐Year Operations (TM5) also referred to as the “Mini Masterplan”. While both TMs show the WWTP is in fair working order, the key takeaways are many treatment processes are past their useful life, none more critical than the electrical infrastructure, and substantial capital investment is needed.

Additionally, the plant lacks preliminary and primary treatment technologies; and SCADA instrumentation typically found at other similar treatment facilities. Lastly, it was suggested further studies were required to adequately determine the condition of the concrete as well as seismic risk to the WTTP processes and buildings.

In 2023 and 2024, the District suffered significant damage and operational hardship to severe wet weather events. This included multiple treatment processes failures, particularly at the headworks. Notably, the wet well flooded with 6 feet of raw sewage. The WWTP experiences high peak wet weather flows, treating over 7.5 MGD in extreme cases.

In December of 2024, the District received a Seismic Risk Assessment and Evaluation of the WWTP from Buehler Engineering. The key takeaways from this study show the in‐ground treatment process structures, such as the aeration basins and clarifiers, require replacement or extensive remediation; and the existing above ground buildings can continue operating, but structural retrofits are recommended.

With these planning studies, as well as staff experiences over the years, District Staff have come to the understanding that the WWTP requires substantial improvements to increase its longevity, energy/process efficiency, safety, and resiliency. The studies show the District should take action to address the aging WWTP sooner than later. Without a substantial investment in the WWTP, the District will take great risks to the treatment process, and by extension, its Mission.