Asphalt and concrete contractor in Contra Costa County

Much of Contra Costa sits on clay soils that expand when wet and shrink as they dry. Over a wet winter and a hot, dry summer, that movement travels straight up to the surface.

You'll see it as cracking with no obvious traffic cause, often along the same lines year after year. The takeaway: keeping water out of the subgrade matters more here than almost anywhere else in the region, so crack sealing and good drainage belong near the top of your maintenance plan.

The usual fix for unstable ground is binding it with a lime or cement treatment. That's not always possible, and when it's ruled out, the usual answer goes with it.

At the Future Chrysler Dodge Jeep Ram dealership on Diamond Boulevard in Concord, the subgrade was unstable and chemical treatment wasn't an option. We replaced more than 66,000 SF of pavement and seal coated 57,000 SF after working out a field fix for the subgrade.

Hotter inland weather works both ways. The season for placing asphalt and seal coat opens earlier and runs later than on the coast, which gives you more flexibility in scheduling.

At the height of summer, though, a big unshaded parking lot gets hot enough to soften the binder. That's when rutting and shoving show up where vehicles turn and brake slowly, like dealership lots, drive-through lanes and retail entrances.

Contra Costa has plenty of big, flat, unshaded parking lots serving office parks, retail centers and auto dealerships along the I-680 and Highway 4 corridors.

Large flat lots drain poorly when the grades are marginal, so resurfacing them is as much about getting the grades right as it is about paving. Getting the slope right across the whole lot keeps a new surface from ponding in the same spots the old one did.