Our members fly all types of model aircraft. We have specific locations where we can fly Control Line and Radio Control aircraft.
The Concord Model Engineers have two Control Line circles on the Western end of Hillcrest Park in Concord, near Acro Associates (toward the left side of the park area on the map).
We fly Electric R/C and gliders at the Lime Ridge, a public open space. The area where we fly is accessible by going to the end of Court Lane in Concord.
concordmodelengineers.org 
My name is Lucas Hundley, and I fly with a number of you guys out at court lane from time to time. I’ve recently had to register my models as we all have using the FAA’s online system. One of the new requirements I’ve noticed is notification of any airports within 5 miles.
I looked this up, this means we need to be calling Buchanan tower at 1-925-685-5743. The manager there is Charles Deavers, though we can speak with anyone there. They’ve requested we notify them at least a day in advance of activity at Court Lane, so if you’re headed out there on Sat/Sun, best to contact them on Friday and explain your intentions and approximate time.
Kind of lame I realize, but these are the new rules. Perhaps over time we can work out a blanket understanding with them and they can just assume we’ll be active at that site every weekend at least.
Now that the runway was removed from Hillcrest, are you going to start flying gas RC at lime ridge?
@Dirk, some of us do fly RC at Lime Ridge, parking at the end of Court Lane.
Generally, we fly late Sunday afternoon. Email me at chuckhhill@aol.com and I’ll add you to my mailing list.
Since the area at Hillcrest Park for flying line control has been destroyed, is there any place I can go to fly my line control planes ?
Aeronuts have a field in Alameda, near the Oakland Airport.