Sacramento completes $1.7 billion EchoWater project

Credit: Sacramento Regional County Sanitation District.

The Sacramento region can expect to see big changes related to how wastewater is treated and reused with the completion of the Sacramento Regional County Sanitation District’s (Regional San) $1.7 billion, decade-long plant expansion. Named the EchoWater Project, the extensive upgrade was completed in spring 2023 — on schedule and under budget.

The result is a safe and reliable supply of treated water for discharge to the Sacramento River, which will also be used for recycled water purposes such as irrigating local agriculture and supporting habitat conservation land.

Regional San says the expansion project was among the largest public works projects in the Sacramento region’s history.

Regional San owns and operates the regional wastewater conveyance system and the Sacramento Regional Wastewater Treatment Plant, which is located near Elk Grove, California. The treatment plant is the second largest of its kind in the nation and treats an average of 135 million gallons of wastewater each day from 1.6 million people throughout Sacramento County and West Sacramento.

“Our upgraded treatment process now removes 99 percent of ammonia and 89 percent of nitrogen from the wastewater,” said Regional San General Manager Christoph Dobson. “The result is cleaner water for discharge to the Sacramento-San Joaquin Delta and a drought-resistant, recycled water source for our Harvest Water project, one of the largest ag water recycling projects in California’s history.”

The EchoWater Project began in 2010 when the Central Valley Regional Water Quality Control Board issued new treatment requirements in Regional San’s wastewater discharge permit. The Board took that action to improve water quality and help alleviate ecological problems in the Delta. To ensure effectiveness and cost efficiency, Regional San tested many possible treatment strategies to achieve the new permit requirements. A specific strategy was selected, engineering designs were completed, and construction began. The massive upgrade consisted of 22 individual projects that together used 41,350 tons of steel and more than 225,000 cubic yards of concrete.

The centerpiece of the upgrade was the Biological Nutrient Removal (BNR) Project—the heart of the new treatment process. BNR is a sprawling complex, roughly equivalent in size to 18 football fields, and is responsible for removing 99 percent of ammonia and 89 percent of nitrogen, addressing concerns about possible impacts downstream.

Making the project even more monumental, it came in on schedule and under budget. The original estimate projected costs to be as much as $2.1 billion. Regional San’s commitment to the success of the project and being fiscally responsible helped keep the final cost to about $1.7 billion — drastically reducing the impact to customers’ rates. The project was also awarded nearly $1.4 billion in low-interest financing from the state’s Clean Water State Revolving Fund, which saved ratepayers more than a half-billion dollars in interest costs.

Carollo provided planning, design and engineering services during construction for the project.

“The EchoWater Project was massive in both scale and complexity,” said Carollo Senior Vice President Scott Parker. “The project’s successful completion on schedule and within budget is a testament to outstanding collaboration among project partners and is an extraordinary public works achievement with beneficial results for the community and the environment.” Carollo led the design effort for the following aspects of the project:

  • Flow Equalization (FEQ): The $122 million FEQ project added 110 million gallons (MG) of storage to the plant’s existing emergency storage basins to reduce peak flows to 330 mgd. The FEQ project required excavating 1,200,000 cubic yards of soil and completing two major pumping stations, concrete lining of the basins, a washdown system, large fill/drain piping, and major effluent control structures.
  • Return Activated Sludge Pumping (RAS): The $25 million RAS project replaced 48 return activated sludge pumps (210 mgd total capacity) designed to deliver higher flow and head conditions required by the new biological nutrient removal (BNR) process. The RAS project also included replacement of aboveground piping, valves, and flow meters; rehabilitation of pump cans and underground piping; and improvements to the existing mixed liquor channel.
  • Nitrifying Sidestream Treatment (NST): The $42 million NST process utilizes nitrifying sequencing batch reactors to oxidize ammonia in the solids treatment system supernatant and produce nitrate-rich effluent which is injected upstream in the collection system for odor control, offsetting chemical costs for the plant. NST includes influent and effluent pumping and lime addition.
  • Tertiary Treatment Facilities (TTF): The $310 million TTF project provides filtration and enhanced disinfection of secondary effluent to a level equivalent to California Title 22 requirements for tertiary disinfected recycled water to support unrestricted reuse. Tertiary facilities include a 330 mgd filter influent pump station, 217 mgd of granular media filters, backwash equalization and treatment, chemical feed systems, covered disinfection contact basins, new plant recycled water pumping systems and a new area control center.

The facility was renamed the EchoWater Resource Recovery Facility. Learn more at

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