Photo by: Jesse Ruiz, CVWD Multimedia Specialist

CVWD Goes One Year Without an SSO

Roni Gehlke, Editor, Clean Water Magazine, Announcements

For the first time in its 103-year history, the Coachella Valley Water District has gone one year without a sewer system overflow (SSO). While there isn’t one reason why the District would have reached such a milestone, its staff has been working on minimizing issues that have caused SSOs in the past.

“There were years we came close, going nine to 10 months without an SSO, to achieving a year without an SSO but fell short,” said Juan Martinez, CVWD’s collection system supervisor. “This exceptional accomplishment has been achieved through attention to detail by disciplined professionals who perform thorough preventative maintenance, system repairs, emergency response, training, and provide exceptional customer service.”

A staff of 20 within the collections division oversees a little over 1,164 miles of wastewater collection pipelines for 96,932 customers. Formed in 1918, CVWD has grown into a multifaceted agency that delivers irrigation, non-potable and potable water, collects and recycles wastewater, provides regional stormwater protection, replenishes the groundwater basin, and promotes water conservation.

CVWD’s sanitary collection systems convey to one of five treatment plants owned and operated by the District. Each of those facilities offers different treatment options, ranging from mechanically aerated, concrete-lined ponds (oxidation basins), to a treatment facility consisting of a mechanically aerated, synthetic-lined pond (aeration basin) that each provide a secondary level of wastewater treatment.

The three other plants include a facility with mechanically aerated lagoons and a Biolac® activated sludge treatment plant, a system treatment plant employing extended air and tertiary methods, and the largest plant in the District’s system — an activated sludge treatment facility that provides for secondary and tertiary treatment of domestic, municipal wastewater including septage waste from two separate septage receiving facilities.

Over the past couple of years, the collections team, in collaboration with the CVWD sanitation engineers, planned, designed, and installed a bypass discharge manifold on two major 18-inch sewer force mains.

“The manifold now allows the Collections team to bypass or redirect flows during an emergency or a high flow situation,” Martinez said. “The manifold bypass protocol has reduced the risk of an SSO.”

Martinez also said that the District’s wastewater treatment plants are routinely inspected and maintained by wastewater treatment operators, mechanical technicians, electricians, and telemetry teams in an effort to ensure optimized operations. One of the plants also recently went through a headworks contingency plan upgrade which included implementing a Corrective Action Plan to help eliminate the possibility of a future single point of failure by providing a series of multi-layered and independent operational redundancies.

Martinez explained that the costs of SSOs depend on the size, damage caused, mitigation response, and repairs needed. Historically, they have ranged from a few thousand dollars to the tens of thousands, in addition to potential fines from regulatory enforcement agencies.

“Adding additional preventative maintenance, testing, and a reinforcement of the standard operating procedures will serve to provide significant operational optimization benefits and reduce the risk of an overflow/SSO,” he said. “Concurrently, staff is performing comprehensive assessments of the Headworks facility at two of the plants to ensure similar protocols and multi-layer redundancies are in place to protect those facilities.”

In retrospect, over the two years prior, CVWD experienced four SSOs in 2019, with three of those due to material failures of air-vacs serving the sewer force main or a segment of pipe becoming offset in the gravity system. The fourth incident was due to heavy flowing and rapid floods from a rainstorm.

In 2020 there were two SSOs resulting from a pipe becoming offset in the gravity system, causing a blockage. The other was due to an electrical/communications failure at one of the wastewater treatment facilities, which led to the Corrective Action Plan to optimize operations and create multiple layers of redundancy.

“I am extremely proud of the entire Sanitation Branch of Operations and Maintenance for achieving this amazing accomplishment,” said Dan Charlton, CVWD’s assistant general manager. “I am especially proud of the Collections division as their resilience, emergency response training, diligence, and the daily proactive regiment has been instrumental in this accomplishment and laid the foundation for continued optimization in the future.”