The Sacramento Regional County Sanitation District (Regional San) operates an existing wastewater treatment facility in Elk Grove, a suburb of Sacramento, California. The wastewater treatment plant processes the entire Sacramento region’s wastewater, serving more than 1.4 million people.

However in 2010, the state issued stringent environmental regulations that required the existing facility to significantly reduce effluent discharges into the Sacramento River. This called for various and significant upgrades to the wastewater treatment processes of the facility, which opened in 1982.

To meet these regulatory requirements, Regional San created the EchoWater Project, an estimated $1.6 billion multi-stage project involving various infrastructure and technological upgrades to the existing plant, including new infrastructure. In January 2016, Flatiron, in partnership with engineering firms Carollo and AECOM, were awarded a $40 million contract to construct a critical element of the overall EchoWater Project, a nitrifying sidestream treatment facility that will assist Regional San in meeting new federal and state permit effluent limits, particularly for ammonia discharges.

By nitrifying ammonia, Flatiron’s tertiary treatment facility will reduce high concentrations of ammonia generated through anaerobically digested biosolids. It will also produce nitrate-rich effluent that can be used for odor control at various locations in the facility’s footprint. A flow diversion structure will intercept flow and divert it to the new treatment system and a fine screening facility will remove debris.

An effluent pumping station will deliver the nitrate-rich effluent to other points in the system for additional processing. To ensure adequate alkalinity for separate biological treatment processes, a lime storage and feed facility will also be constructed. In addition, the new facility reduces the amount and variability of the ammonia load on a new biological nutrient removal system that is being constructed by another project contractor. 

Significantly improve treatment of wastewater

EchoWater initiative is among the largest public works projects in Sacramento’s history

Project will help ensure the sanitation district meets stringent environmental regulations and significantly reduce harmful discharges to the Sacramento River and other waterways

Sidestream treatment reduces ammonia concentrations generated through digested biosolids