After screening proposals to expand water storage capacity, the Marin Municipal Water District has narrowed its options.

But expansion of the Soulajule reservoir — the district’s star prospect — is drawing mounting opposition from neighboring ranchers who fear that their multigenerational homes and ranches will be engulfed by the new footprint created by the larger dam.

As discussed to date, the proposal would elevate the dam by 39 feet, expanding the reservoir by 530 acres, meaning some existing agricultural land would be under water.

“When you consider the relative cost of this project, please know that by raising the Soulajule dam by 39 feet, you will cause us irreparable loss,” Carol Dolcini, a West Marin rancher, told district officials at a board meeting Tuesday.

“The people of Marin need reliable and resilient and affordable water supply that can withstand extended drought,” she said. “MMWD should be able to achieve this without destroying neighboring communities. Please do not continue to push this destructive plan.”

The shortlist of projects, narrowed from 11, also includes expansion of Kent Lake and a proposal to create a new reservoir in the area of upper Nicasio, staff said.

For comparison purposes, each proposal called for an increased storage capacity of 20,000 acre feet of water, said Paul Sellier, the district’s water resources manager.

At that size expansion, Kent Lake would need to be raised 37 feet. That would enlarge the footprint by 180 acres.

The creation of a new dam in the area of upper Nicasio would call for construction of a 103-foot dam with a 310-acre footprint.

“At this point, it’s a white paper exercise so that we can compare what the impacts are,” Sellier said.

“The next steps are to refine them, right-sizing each to see if there is a natural breaking point where less inundation and less impact could be achieved.”“Is there an option where there are no impacts to structures? We need to take a close look at that and understand how we minimize impacts,” Sellier said.

The discussion was an update on the district’s water supply roadmap, approved last year, that set the stage for the district to significantly increase water supply for the first time since the 1980s.

The plan seeks to add another 12,000 to 20,000 acre-feet of annual supply by 2035.

The district serves 191,000 residents in central and southern Marin. Its seven reservoirs make up about 75% of the district’s water supply. The reservoirs can hold up to about 80,000 acre-feet of water, about a two-year supply. An acre-foot is about 326,000 gallons of water.

The water supply roadmap estimated the agency would need at least 8,500 acre-feet of additional water per year to weather a severe four-year drought.

So far, a project at Soulajule appears to be the most viable because it is the lowest cost at $291 million and has the fewest construction hurdles, staff said.

The Kent Lake project is estimated at $613 million, in part because construction would be limited to three months out of the year because of presence of the protected northern spotted owl, among other challenges.

The upper Nicasio project would also inundate agricultural properties and require water to be transferred from Soulajule or the existing Nicasio reservoir to fill.

It is expected to cost about $606 million.

Other projects previously considered would either be be too complicated, too costly, or both, such as a proposal to raise the Alpine Lake dam 75 feet for $1.29 billion.

All estimates account only for construction, which board member Monty Schmitt said wasn’t a fair representation of the expense.

Schmitt said some of these projects that would inundate private property require the district to purchase land and structures.

He wanted to know what those costs were, too, he said.

Board member Larry Russell said he believes all proposals are out of reach and the district should stop the exercise, and instead, look into upping investments in conservation and desalination as means to boost water supply.

“Pie in the sky is pie in the sky,” Russell said.

“You have to look at this cold-heartedly from a pure engineering feasibility standpoint, and you know, there’s just better places to spend the money. It’s as simple as that to my mind.”

Larkspur resident Ed Jameson said he agreed with Russell.

“Cut to the quick. None of these projects make sense and no more should be spent evaluating them, and as he suggested desal looks cheap,” Jameson told the board.

Russell also said that considering the Soulajule expansion “is just unnecessarily riling up the folks that live there.”

Maria Ghisletta, one of the Hicks Valley ranchers near the Soulajule dam, said “many of us are frustrated, fearful, angry. Honestly, emotions run the gamut.”

Ben Horenstein, general manager of the district, said these are big, complex projects that will require difficult conversations.

He said that while staff gets deeper into analysis, they will also be considering other options for water recycling and desalination.

Horenstein said continuing the study is a worthwhile exercise to understand the options.

Board member Matt Samson agreed, saying he’s excited to see the study develop.

Board chair Ranjiv Khush said the last significant water supply infrastructure in Marin was built about 50 years ago, but most was constructed more than 100 years ago.

“I ask what are we going to leave for people that are going to be here a hundred years from now if we don’t have the courage to explore really difficult, challenging, expensive questions,” Khush said.

“So I feel strongly that we should continue this analysis until we have all the data on the table, including impacts on community members, including price tags, including the possibilities of external funding, so that we can make decisions that are defensible, not emotional and not well-founded,” Khush said.

“I also believe it would be very irresponsible to stop this process at this stage and I am encouraged that staff is not going to consider that option,” he said.