DALY CITY -- In the roughly 100,000 years since a finger of the Pacific Ocean helped deposit great mounds of sand in Daly City, most of the formations have been paved over with a web of roads and clumps of homes.
But a tiny section of those natural sand dunes remains untouched in the hills above the parallel strips of houses on either side of Bonnie Street.
The unassuming hunk of sand, spotted with bushes and an endangered species of flowering plant, is at the heart of what is expected to be a pitched battle between residents, environmentalists and developers.
The owners of the less-than-one-acre slice of dunes have proposed subdividing the land into lots for eight homes, along with roads and infrastructure. They call it a reasonable and safe use of the property
But residents, still rattled by a recent mudslide in the area, fear the sandy slopes are unstable and more development would put them and their homes in danger.
Also, environmental watchdogs say the dunes are among the last bits of habitat for the San Francisco Lessingia, a plant on the federal endangered species list since 1997.
The tension is growing, even though the proposal has not yet been the subject of a single vote. If it advances, the project would be have to go through public hearings and get City Council approval. However, even if the subdivision idea fails, a second possible project is in the works. A school adjacent to the dunes, which may be looking to expand, has penned an agreement giving it first crack at purchasing the dune land.
The landowners, who are heirs of the Callan family, a large property holder in San Mateo County, submitted their housing proposal to the city for the Hillside Park Court development in the fall of 2011.
Under the proposal, the homes would sit on the dunes a couple hundred feet southwest of the hillside where a city water pipe burst open on Nov. 13, causing a massive mudslide.
Plans have been stalled because the city had some questions and suggestions that the owners haven't addressed, officials said.
In addition to the homes, the owners are pursuing development on a second front through moves to sell the property to the private, prekindergarten-to-eighth-grade Hilldale School.
The 100-student campus off Florence Street is considering buying the land in order to expand, but has not made a final decision to do so, co-owner John Sittner of Pinnacle Schools said.
"We've had some discussions," Sittner said. "But I don't know where things are going."
Whether developers build homes or school buildings, the construction will destroy the dunes, said San Bruno Mountain Watch Executive Director Ken McIntire.
On a recent day, McIntire and Mountain Watch volunteer Del Schembari hiked through the area and pointed out patches of Lessingia, which has daisy-like yellow flowers.
"This is the world population of this plant," McIntire said, adding some patches also grow in San Francisco's Presidio park.
The group is trying to buy the land and is lobbying city leaders to protect it. So far, they said, they haven't had much of a response. But Mountain Watch representatives have met with Daly City Councilman David Canepa and he seemed receptive, McIntire said.
Canepa said he can't comment specifically on the proposed development, but said the city should do whatever it can to preserve open space in the already densely populated town of more than 101,000.
Residents who live below the hills are nervous about any development on the sandy slopes. They said heavy rains, an earthquake or another big leak could send buildings and sandy dirt tumbling down on them.
Besides, they said, the land should be protected as part of the larger preserve around San Bruno Mountain.
"The land is not stable," said Arturo Romero, 64, a retired postal worker whose home was narrowly missed by the recent flow of mud. "We are very lucky the mudslide went on the other side."
A representative for the owners said a decision on the land's future is expected to come within the next three to four months. The property is "not a geologic hazard" and building there would be reasonable, despite concerns about the Lessingia, said Terry Sedik, who represents the landowners.
"We've had a study done. We understand where (Lessingia) is and what the requirements are," he said. "Whatever happens there will be compliance with federal law on the plants."
Contact Joshua Melvin at 650-348-4335. Follow him at Twitter.com/melvinreport.