Mountain View (in the area nearest the bay) is a former landfill.

http://www.mountainview.gov/depts/pw/landfill.asp

I only mean to point out that although it may not be "allowed in the present," these problems last a lot longer than it takes for humans to move in to the area, or write new laws.

The misnamed Shoreline Amphitheater and the golf course are built on the old landfill site.

Events early in Shoreline's history had a problem with the lawn catching fire due to the uncontrolled seepage of methane from under the lawn (as a decay biproduct). Sort of the "everybody-hold-up-your-lighter-for-mood" effect, but uncontrolled.