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EchoWater Resource Recovery Facility

Sacramento Regional County Sanitation District (Sac Sewer)
Elk Grove, California

Project Overview

Using advanced treatment and tertiary treatment, the facilitymeets nutrient limits and recycled water requirements while providing a drought-resistant source of recycled water for agricultural use.

Sacramento Regional County Sanitation District (Sac Sewer) owns and operates a 181-mgd wastewater treatment facility that serves more than 1.6 million people in the region. In 2010, the Central Valley Regional Water Quality Board issued a new wastewater discharge permit for the plant that called for much stricter limits on ammonia, nitrogen, biochemical oxygen demand (BOD), total suspended solids, and total coliform levels. In effect, the plant would now have to comply with Title 22 permit limits when discharging treated effluent to the Sacramento River.

To meet these stringent requirements, Sac Sewer created the EchoWater Project, a massively complex,10-year, $1.735 billion treatment facility upgrade program, for which Carollo Engineers completed planning, design, and engineering services during construction for five of the projects.

Carollo designed the following five projects:

  • 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 million gallons per day (mgd). The FEQ project required excavating 1.2 million 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 that’s 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 $309 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 filtration design also allows for a future conversion to ozone and biologically active carbon (BAC) filtration, while also looking to a potential future need for advanced treatment and greater water reuse.
  • Heavy Equipment Maintenance Building (HEMB)
    To make room for the new TTF, the plant’s existing HEMB had to be demolished and relocated. The new HEMB consisted of a CMU building to house maintenance facilities for the plant’s harvest crew equipment, a breakroom, storage, offices, and bathrooms. Maintenance amenities included compressed air, a welding fume hood, drop connections for liquids (oils, water, air), and a shade structure to store equipment out of the elements. The entire site was gated with secure access.

Now complete, the EchoWater Resource Recovery Facility (formerly the Sacrament Regional Wastewater Treatment Plant) is already the second largest treatment plant of its kind in the nation and is on its way to becoming one of the country’s largest agricultural water recycling facilities. Beginning in early 2027, much of the plant’s treated effluent will provide irrigation and ecological restoration water across Sacramento County as part of the Harvest Water Program. Carollo is part of a joint venture team providing capital program management services for Harvest Water.

Despite the complexity of the project, the large number of stakeholders involved, extensive permitting coordination, and a multitude of subconsultants and subcontractors, the projects were completed on time and on budget —a testimony to Carollo’s ability to manage a large-scale planning and design efforts that benefit the client, the community, and the environment.

Results and Highlights

Completed on-time and under budget

Treated water meets stringent nutrient limits and recycled water requirements

Drought-resistant source of water

Second-largest treatment plant of its kind in the United States

Project Awards and Accolades

2024 Outstanding Civil Engineering Achievement Honor Award


2023 Project of the Year (Tertiary Treatment Facilities Project)

APWA Sacramento Chapter

2023-2024 Large Plant of the Year

California Water Environment Association (CWEA)

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