The proposal by the Tulare Lake Drainage District calls for building an 1,800-acre evaporation pond to capture agricultural runoff in the Tulare Basin and dedicating 3.6 acres of farmland as mitigation habitat.
The district says the huge pond would allow irrigation and continued farming of 18,000 acres of land now marred with salty groundwater.
Evaporation ponds are used to dispose of agricultural drainage laced with crop-killing salt and other metals. The district, located in Kings and Kern counties, already operates three drainage ponds totaling 3,165 acres and has about 500 acres of set-aside mitigation habitat.
In a comment letter, the California Department of Fish and Wildlife said it was concerned that selenium-laced drainage could impact threatened and endangered species in the area, as well as nesting shorebirds. The agency asked for a full environmental review of the proposed pond.
The department's regional manager Jeffrey Single said the district didn't clearly identify the area where the drainage would come from, so it's impossible to tell how poisonous to birds it could be. And, Single said, the 3.6 acres the district had promised to preserve for wildlife was insufficient.
Single also said it's unclear why a new, large evaporation pond is needed when the existing ponds do not appear to be filled to capacity during peak irrigation season.
The district is supposed to maintain a two-foot depth in existing ponds, so birds do not wade in the shallow selenium-laced water, but it has routinely failed to keep water at that level, Single said.
Tulare Lake Drainage District manager Gary Rose could not be reached for comment.
Tulare Lake was historically the largest freshwater lake west of the Mississippi River, and the basin continues to be known for its large patches of wetlands and bird habitat.
Agricultural runoff in the basin has in the past been found to have extremely high levels of selenium and to cause deformities in bird embryos. Officials have tried to reduce the impact on species by providing other habitat areas and managing the ponds to discourage birds from wading and nesting.
The issue has been studied since the 1980s, when millions of migratory birds were born deformed after nesting at Kesterson National Wildlife Refuge in Merced County, where selenium-laced agricultural runoff was sent.
There are currently 4,800 acres of agricultural evaporation ponds in the San Joaquin Valley.
Several state and local agencies must still review the new proposal before it moves ahead, and the Central Valley Regional Water Quality Control Board must issue a waste discharge permit.