A group of scientific experts employed by the state to review policy related to the Sacramento-San Joaquin Delta is asking for a refined analysis of the possible impacts of the twin tunnels conveyance plan.

The California Department of Water Resources (DWR) in July released a revised environmental analysis of its proposed “California WaterFix,” which would install three intakes on the Sacramento River and dual tunnels to convey water 30 miles around the Delta to the state and federal pumping plants.

The project is the successor to the 2006 Bay-Delta Conservation Plan, which was revamped in April 2015. In addition to the WaterFix, restoration activities were released as the “California Eco Restore” program.

The environmental impact report/environmental impact statement [EIR/EIS] said “the need for the action is derived from the multiple, and sometimes conflicting, challenges currently faced within the Delta,” including risks to water supply reliability, water quality and the aquatic ecosystem.

“DWR’s fundamental purpose in proposing the proposed project is to make physical and operational improvements to the SWP/CVP system in the Delta necessary to restore and protect ecosystem health, water supplies of the SWP and CVP south of the Delta, and water quality within a stable regulatory framework, consistent with statutory and contractual obligations,” DWR’s environmental review said.

The purpose of the tunnels is to create a dual conveyance system in which some of the water now exported by the SWP and CVP would be tunneled directly to the pumps while the rest would continue it flow through the Delta. Under the current system the existing Delta channels are used to convey all the water to the export pumps located in the South Delta.

The Delta Independent Science Board (ISB) said the EIR “contains a wealth of information but lacks completeness and clarity in applying science to far-reaching policy decisions.” The group noted that “the effects of California WaterFix extend beyond water conveyance to habitat restoration and levee maintenance” and that consequently “these interdependent issues … warrant an environmental impact assessment that is more comprehensive and comprehensible …”

The ISB consists of 10 scientists who advise the state on proper adaptive management of the Delta.

In a statement, Cassandra Enos-Nobriga, program manager for DWR, said the department “is grateful for the Independent Science Board review of the California WaterFix/Bay Delta Conservation Plan [EIR] and that the scientists’ comments “will help ensure the state’s approach to protecting the Sacramento-San Joaquin Delta uses the best possible scientific methods, coordination and inquiry.”

“The ISB’s specific comments on various resource chapters of the [EIR] will enhance analysis of the proposed project by DWR and the U.S. Bureau of Reclamation and improve the final environmental impact documents,” Enos-Nobriga said.

She noted that “while the ISB reviewers state that they would like to see greater detail on a ‘landscape’ level, an EIR/EIS does not call for such an analysis. The state, however, is working to improve its landscape-level understanding of resource management. Similarly, efforts are underway to better articulate how the California EcoRestore program will be properly and effectively coordinated with other restoration programs.”

DWR and the Bureau of Reclamation are targeting completion of a final EIR/EIS in mid-2016.