I spent about 90min driving to the junction of Fredrickson Ln and Contra Loma
Blvd where the regional preserve 
trailhead is located. It is
surprisingly popular,
and there was only one of about 20 spaces left for parking when I arrived just
after 9a, mid-week. It took about 35 min to make my way up and over a low
ridge into 
Lone Tree Valley,
then up past the old Star Mine 
quarry site to
the top of a spur trail off the Star Mine Trail. The Star Mine was one of the
last active coal mines in the area, among the very few coal mining districts
in California. The ore was of poor quality and the place was eventually
abandoned when richer ore was discovered north in Oregon. The highpoint of
Peak 919ft is found about 1/5mi north of where the spur road tops out, leading
me to park the bike and hoof it through tall grass to the highpoint, passing
along a narrow saddle enroute. Though this would mean another session of
sticker removal upon my return, the short hike proved an interesting one, the
final climb to the highpoint above the Star Mine involving some easy scrambling
and 
nice views from the 
rocky summit.
After returning to the bike (and removing a few annoying stickers), I headed
west down a 
single track trail that proved challenging due to its
roughness and lack of regular use. This returned me to 
dry Sand Creek
where I turned south to continue towards the second peak. I reached the
preserve boundary at the end of Lower Oil Canyon Trail. A sign on a
gate here indicated the land on the other side was in a landbank, not exactly
private property. After lifting the bike
over the gate I followed a series of little-used ranch roads up the mountain,
gaing about 600ft over the course of a mile and a half. I came across a second
gate about halfway up at the landbank boundary, this one closed by a simply
chain clasp sans lock. I startled 
a deer
resting on the road on the other side
as I opened the gate to pass through. After more riding, I reached a saddle
about 1/6mi SE of the summit at another gate. I 
parked the bike
here and hoofed
it cross-country the remaining distance to the summit along thin deer trails,
the last half through tall, dry grass. It was a nice view spot to take in the
Delta areas to 
the east, Mt. Diablo to 
the southwest, rolling
hills looking 
south. Upon returning to the bike I would spent about
20min pulling a far
larger quantity of stickers from my socks and shoes which had become painfully
inundated with the sharp objects over the short hiking stint. The return was
pretty much along the outbound route, with the exception that I bypassed the
first summit on the return. The most interesting find was a medium-sized
snake
I spied basking in the road after nearly running it over. I stopped to encourage
it to move out of the road before I continued back to the trailhead. The parking
lot was as full as when I had started out earlier, and it took only seconds
before the spot I left was occupied by another car. This is one popular
trailhead...