landfills and methane gas

so many nights I drive north on buelah st  and see the 20' tall blue flame,  so close to the road hidden mostly by the pine trees . It's such a small landfil yet every night  it appears  . I'm sure its safe since theres a fairfax elementary school not more than 7 or 800 feet on other side of the road . how much gas does this landfill produce?  I see at the county landfill all the gas is piped for reuse . Do private landfills not required to do so? Closed landfills like the one on Loisdale Rd. not produce methane? How do they determine when it's safe to build car dealerships  or shopping centers  or wegmans  on top of landfills?