Cull Canyon in Castro Valley: the award-winning swim lagoon, the silted-up reservoir and the trail to Chabot

For Castro Valley families, summer has long meant the sandy beach at Cull Canyon. The East Bay Regional Park District's recreation area sits a short drive north of Interstate 580 on Cull Canyon Road. Its main draw is a 1.5-acre swim lagoon with lawns, a bathhouse and plenty of shallow water for kids.

The lagoon, and when it reopens

The lagoon won the 1966 Governor's Design Award for Exceptional Distinction for Recreational Development in the landscape category. When it was built, crews added a secondary dam to create an inner swimming area with its own beach. That made the swim area's water level independent of the reservoir, so summer drawdowns didn't affect it. The park district says the swim complex is closed now and will reopen for the 2027 swim season.

The posted swim fees are $3 for ages 2 to 17, $5 for adults 18 to 61 and $3 for seniors 62 and older and people with disabilities. The kiosk is cashless. On weekends and holidays the facility fills up early, and once it is full no one else gets in that day. No dogs, alcohol, glass or portable barbecues are allowed in the lagoon area.

The reservoir that filled with silt

The lagoon was built inside Cull Creek Reservoir, created by a dam finished in 1963. Wikipedia, citing 2014 reporting, says 12,000 to 20,000 cubic yards of silt and debris washed in each year. By 2014 the water was only about 6 feet deep, the sediment caused a large fish kill in August 2013, and the dam had been judged seismically unsafe. Dredging was estimated at $16 million. County engineers proposed notching the weir instead, which would let water flow past and leave the sediment behind. The park district now says the reservoir no longer exists south of the swim area.

Picnics and the trail

Several picnic areas outside the swim complex can be reserved, and the park district strongly recommends reserving on weekends and holidays. Groups of 30 or more must reserve on any day. Cull Canyon is on the Chabot-to-Garin Regional Trail, part of the Bay Area Ridge Trail. The trail heads north six miles through East Bay Municipal Utility District land to EBMUD's Chabot staging area on Redwood Road, and you need an EBMUD hiking permit for that stretch. From there, the Willow View Trail leads into Anthony Chabot Regional Park. Parking is free.

Related: our Lake Chabot guide.