For decades, visitors to Santa Margarita Lake have been able to boat across it, paddle through it, and fish from it. They just couldn’t jump in.
A new state law could change that as early as next summer, opening one of San Luis Obispo’s drinking-water reservoirs to swimming and other forms of body-contact recreation. But before the first swimmer hits the water, some residents are pushing the county to keep the lake off-limits.
Gov. Gavin Newsom signed Senate Bill 1253 on Aug. 31, removing a long-standing state restriction on body contact at Santa Margarita Lake and giving San Luis Obispo County the authority to consider allowing it.
The law takes effect Jan. 1, 2027, but it does not automatically open the reservoir to swimming. County officials estimate summer 2027 is the earliest that could happen, and several regulatory, financial, and operational questions remain unresolved.
“This is an exciting possibility for Santa Margarita Lake, but there is still a lot of work ahead of us,” Public Works Director John Diodati said in a statement. “Protecting drinking water and public safety will remain our first priorities.”
Santa Margarita Lake, also known as Salinas Reservoir, is part recreation area and part drinking-water infrastructure. Water stored behind the dam is transported through the Cuesta Tunnel and treated by the city of San Luis Obispo before reaching customers.
“California has historically restricted body contact in many reservoirs used as drinking-water supplies, reflecting limitations of earlier water-treatment technology,” the county stated in a press release. “Modern treatment systems, however, can safely treat water from reservoirs where body contact occurs. Nacimiento Lake and Lopez Lake both allow body contact while serving as drinking-water sources.”
The city’s existing treatment system uses processes that meet state and federal standards for treating water from reservoirs where body contact occurs, according to the county. Santa Margarita Lake, however, will still require specific approval from the State Water Resources Control Board’s Division of Drinking Water, along with additional water testing and reporting required under SB 1253.
State Sen. John Laird, who authored the county-sponsored legislation, said those advances make it possible to expand recreation without sacrificing water quality.
“Santa Margarita Lake is an incredible public resource, and advances in water treatment mean we can safely allow people to enjoy more of what the lake has to offer,” said Laird in a statement. “SB 1253 expands recreational opportunities for residents and visitors while maintaining the safeguards needed to protect our drinking water.”
But the prospect is already generating opposition.
Cal Poly student Oliver Tostado launched a petition following the bill’s signing asking the county to “stop, delay, restrict, and decline implementation” of swimming and expanded body-contact recreation.
“This is not a petition against people enjoying the outdoors,” the petition states. “It is a petition to protect Santa Margarita Lake from a change that we believe could create unnecessary environmental, financial, wildlife, and public-safety consequences.”
The petition calls for environmental and wildlife evaluations, a swimming- and boating-safety assessment, and a public accounting of potential costs before supervisors make a decision. It also raises questions about additional staffing, sanitation, and parking, among other things.
As of Sept. 9, the petition has garnered 343 signatures.
If supervisors ultimately authorize body contact, staff currently envision lower-impact recreation such as swimming, paddleboarding, windsurfing, and fishing activities involving body contact, such as float tubes or wading.
“This legislation gives us an opportunity to consider something our community has talked about for many years,” Supervisor Heather Moreno said, “but it is important that we do this thoughtfully and responsibly.” ∆
This article appears in Student Guide 2026.
