The Salton Sea Species Conservation Habitat Project is a large-scale environmental restoration initiative addressing critical issues surrounding California’s largest lake. The Salton Sea, a landlocked saltwater lake 250 feet below sea level, has been shrinking due to reduced inflows and increased evaporation, exposing the lakebed and causing environmental and health concerns.

The California Department of Water Resources (DWR) led this initiative after extensive studies, selecting Knight Piésold (KP) and Kiewit Infrastructure West Co. (Kiewit) as the EPC team. Key issues include hypersaline water conditions (currently 50% saltier than the Pacific Ocean and projected to reach 300 g/L within 15 years), disrupted food chains affecting local and migratory birds, and elevated asthma rates among Imperial Valley residents.

The project addressed these challenges, including creating a sustainable ecosystem that:

• Counters hypersaline water conditions that have become inhospitable to aquatic species,
  
• Restores lost terrestrial and aquatic habitats for local and migratory bird species,
  
• Reduces airborne particulates released from exposed lakebed sediments, and
  
• Mitigates health risks for Imperial Valley residents with improved air quality.
  

The team successfully completed the project, meeting or exceeding all prescribed performance criteria and client expectations. The project provides over 4,000 acres of terrestrial and aquatic habitats, covering an area twice the combined size of downtown Vancouver and Stanley Park.

The Salton Sea has been shrinking due to water conservation efforts and restrictions on water delivery from the Colorado River reducing inflow to help maintain pre-existing surface area and salinity. The KP-Kiewit team designed man-made shallow habitat ponds to restore lost aquatic and terrestrial habitats, targeting salinity levels between 20 g/L and 40 g/L.

The innovative gravity flow design uses a specialized diversion structure with a labyrinth weir to control water levels to effectively divert fresh water from the New River. Flows cascade through the mixing channels, then sedimentation ponds before flowing into the habitat ponds – more robust and cost-effective than the original pumping concept.

Saline water from the Salton Sea is pumped to the mixing channels, and fresh and saline flows are mixed through a diffuser system to achieve the desired salinity. Key technical challenges include construction on lakebed sediments in a high seismic area, subaqueous berm construction, and structures installed in a highly saline environment.

The team developed over 17 miles of earthen berms on exposed lakebed sediments and an offshore pump station, accessed by a mile-long causeway, using specialized construction methods and seepage mitigation designs.

The team balanced seismic design requirements with cost-effectiveness, while integrating climate change adaptability in the design to protect both the habitat ponds and upstream agricultural lands from increased flooding risks.

The project has successfully created over 4,000 acres of aquatic and terrestrial habitats, where endangered species are now flourishing, migratory birds have returned in greater numbers, fish populations are recovering, and native vegetation is thriving once again. This proof-of-concept project has resulted in a toolbox of cost-effective construction methods that will be carried forward through future restoration projects. Ongoing expansion projects will add an additional 7,800 acres of habitat.