Del Valle Regional Park is a part of the East Bay Regional Park District (EBRPD) in an unincorporated region of Alameda County, California, 10 miles (16 km) south of the city of Livermore. The park covers 4,316 acres (~17.47 km2., ~6.74 sq. mi.).
The park largely surrounds Lake Del Valle, an artificial reservoir made in 1968 by damming Arroyo Valle, a small river. The lake provides a source of recreation for visitors including swimming, fishing, and boating. There are lifeguards present at designated swimming areas.
The park also offers 28 miles (~45.1 km) of hiking, horseback, and bicycle trails, in addition to 150 camping sites. It is the eastern gate for the Ohlone Wilderness Trail, which leads to Sunol and Mission Peak Regional Parks.
The park, like many East Bay Regional Parks, has numerous trails. One trail, the East Shore Trail, leads from the Arroyo Road staging area to a ridge above Del Valle, and then follows the lake for several miles toward the boat launch. The Sailor Camp Trail leads to the Ohlone Wilderness Trail, and an unnamed trail leads to Mendenhall Road. Most of the trails climb hills around the lake; most, however, stay between 500 to 1,500 feet (150 to 460 m) in elevation.
The park can be approached from Del Valle Park Road (via Mines Road) or Arroyo Road, where the parking meter is often broken. Del Valle Road connects to the southern end of the park, while Arroyo Road connects to the northern staging area.
You can reach the Arroyo staging area along a narrow footpath which connects to Sycamore Grove Park and the general LARPD (Livermore Area Recreation and Park District) trail network.