Marin reservoir connection plan delayed by creek habitat concerns

The Marin Municipal Water District has paused a $10 million project to pump water from Phoenix Lake to Bon Tempe Reservoir over concerns that more could be done to mitigate the effect on creeks.

District staff hoped the board would approve the project at its meeting on Tuesday so that they can begin ordering materials, including 6,300 feet of 18-inch pipe needed for construction to begin this fall. The project has been identified as a quick way to increase water supply.

However, local environmentalists told the board they are worried the plan ignores the quality of habitat for steelhead trout, a federally listed threatened species, in Ross Creek and Corte Madera Creek. Phoenix Lake, the district’s smallest reservoir, is in the Corte Madera Creek Watershed.

“We believe that there could be a way to not only solve the need for emergency water and more water for human needs, but to also actually improve the habitat to Ross Creek, and make it better for the aquatic system and threatened steelhead there,” said Terri Thomas, board member of the Marin Conservation League.

Shaun Horne, director of watershed resources, said the state-required environmental analysis already addresses the concerns and the project has been tailored accordingly.

As such, the plan proposes that water can only be pumped between the reservoirs from Oct. 1 to Feb. 28 to minimize fishery disturbances. The plan also proposes that after pumping Phoenix Lake, the district would have to wait for it to rebound to 170 acre-feet before it could draw from it again. An acre-foot equals about 326,000 gallons.

“We wouldn’t expect to mitigate that any further than what’s been presented to you this evening,” Horne said Tuesday.

Phoenix Lake, constructed in 1905, is only drawn on during water shortages because it does not have a pumping and distribution system. Instead, employees have to spend four weeks setting up a pump station and pipes to transport Phoenix Lake water to the Bon Tempe treatment plant.

Building a new pump station and positioning a permanent connection between the two reservoirs is anticipated to yield approximately 260 acre-feet of water a year, improving drought resiliency, district officials say.

Staff said the environmental analysis concluded that the project would have a “less than significant impact” on the fishery.

Board member Jed Smith said he wanted a clearer understanding of what that means.

“Is it negative at all, and if so, what can we do about better protecting this important watershed?” Smith asked staff.

The primary concern was not so much about the volume of water, but the timing of pumping and how that affects creek flows, said Eric Ettlinger, district aquatic ecologist.

Adult steelhead migrate up and the young reside in the creek for a year or two before making their way to the ocean, Ettlinger said.

“There is concern that if you truncate the spring flows, the fish will have a harder time getting out to the ocean,” he said. “Pumping in the spring was more likely to have an impact on those spring flows.”

Having the pumping window end on Feb. 28 each year helps ease that concern, he said.

Horne said the practice of pumping water between the reservoirs is happening already, and that the project is about making the work more efficient.

“It’s kind of surprising that we don’t have this operational efficiency already built into this reservoir as a management solution,” Horne said. “So this project is really improving that and enhancing something we probably would have done a long time ago if we had the resources to do so.”

Board member Monty Schmitt said the project has highlighted something he was not aware of.

“We are in many ways treating Ross and Corte Madera creeks differently than we are treating Lagunitas Creek with respect to the restoration of coho and steelhead habitat, and the benefits that a living river provides both ecologically as well as to our communities,” he said.

Schmitt said he would like the project to include some aspect of restoration. He believes adding the environmental benefit could give the project an edge in winning additional grant funding, he said.

Ben Horenstein, general manager of the water district, said it would be more appropriate to come up with a project on creek stewardship independently of this project.

The board directed staff to meet with local environmental groups and federal and state fish agencies to review the project again.

Board president Ranjiv Khush said the pause is not so much about trying to rewrite the project proposal as it is about making sure everyone is informed.

“I think if we can establish a process here that promotes more trust between the different stakeholders, we will, I think, benefit in the long-term when we’re facing more difficult issues, much bigger questions,” Khush said.

Horenstein said staff plans to return to the board on the issue next month.