The reservoir was created by the Bureau of Reclamation and is part of the Contra Costa Water District infrastructure.
The park's swimming lagoon is a man-made feature separate from the main reservoir body.
The site contains remnants of indigenous habitats that are actively managed for local flora and fauna protection.
The park serves as a gateway to Black Diamond Mines Regional Preserve via connecting regional trails.
During the summer, the swimming lagoon is subject to closure if blue-green algae blooms are detected by regional water quality testing.
Contra Loma Regional Park is a 780-acre facility centered around an 80-acre reservoir originally constructed for local water storage. The park features a designated swim lagoon with sandy beaches, operated seasonally under lifeguard supervision. It provides a network of multipurpose trails suitable for hiking, cycling, and equestrian use, connecting into the larger East Bay Regional Park District trail system. Anglers utilize the reservoir for bass, trout, catfish, and bluegill fishing, though boat restrictions apply. The landscape consists primarily of rolling grasslands and oak woodlands characteristic of the East Bay hills. Picnic areas are dispersed throughout the park, offering both shaded spots and open lawn areas. Wildlife observation is common, with frequent sightings of red-tailed hawks, eagles, and wild turkeys. It serves as a regional recreational hub for the Antioch and Pittsburg communities.
The view from the top of the ridge overlooking the reservoir and the sprawling Antioch valley.
Check the East Bay Regional Park District website for current water quality alerts before planning a swim day.
Wear high-traction hiking boots if planning to venture onto the peripheral fire roads, as they can be steep and loose.
Bring binoculars for birding, especially near the dam area where raptors frequently perch.
Do not attempt to swim in the main reservoir, as it is strictly prohibited for water quality and safety reasons.
The swim lagoon is open only during the warmer spring and summer months; access to the park itself remains open year-round.
Dogs must be leashed in developed areas and under voice control in open space areas; stay on designated trails to prevent habitat damage.
