The Briones Regional Park is named after the Rancho Boca de la Canada del Pinole ("rancho at the mouth of Pinole Canyon") after Felipe Briones. After 120 years of histrionics this area was set aside as a regional park centered around the Bear Creek watershed. Cattle ranching is still very important in the area along with luxury homes. Briones Regional Park is over 6,116 acres and consists of open grasslands interspersed with deep oak forests, and is typical of the region.
The Reliez Valley Road staging area is a small parking lot off of that road that's located right about where the cities of Lafayette, Walnut Creek, and Pleasant Hill meet on the east side of Briones Regional Park. The Blue Oak trail immediately ascends west of the TH through an open forest of Coulter pines and typical California oak savannah. You will notice some nice homes to your right. You'll reach a water tower about 1/2 mile up after gaining a few hundred feet. The trail is fairly steep, but is in good condition as it's another one of these fire roads.
From the water tower you go down then up then down to Blue Oak's junction with the Blue Oak shortcut and a spur loop that heads northeast. Take the shortcut uphill to its junction with the Spengler trail. This section is fairly steep uphill, and the Spengler trail going up to the southwest is also steep. Take Spengler to a spur trail at the junction just below a fairly nasty spring due to the presence of cowpies. A LOT of cowpies. Go right at the junction .37 mile to the junction of the Table Top and Briones Crest trails. Continue west about 1/5 mile to some short spur trails leading to the top of Briones Peak. There are nice views to the west and north from the summit along with a bench just outside of a little climb-through gate.
Head back along the spur trail back to the Briones Crest trail, and go west to the Briones Road trail. It is wide open here with raptors soaring overhead with pocket gophers scurrying underneath. There are myriad gopher trails leading to numerous holes in the tall grass, and it is common to see the little rodents scampering across the trail. You eventually travel down to the Maricich Lagoons, and the lowest lagoon (actually glorified stock tanks) features an information sign explaining the area's significance to the California newts that are seen in winter and early spring. Turn east at the lagoon on the Spengler trail, and pass through a cattle gate. You soon travel under a dense canopy of California oak woodland down to the trail's junction with the Alhambra trail near a particularly nasty spring due to the presence of numerous cowpies.
The Spengler trail quickly ascends to its junction with the Diablo View trail before descending a steep slope back to the Blue Oak trail. There is a 4-way junction here. Go northeast on a trail that dead-ends in a neighborhood about a mile from the TH, due east on a spur trail that eventually reconnects with the Blue Oak trail, take the Blue Oak trail proper back to the junction w/ the spur trail, or continue up then down on the Spengler trail to the same junction.
Turn left (east) at this junction to travel, and travel along the portion of the trail you already enjoyed in order to return to the TH