For Wall Street bankers and investors prospecting for municipal-bond deals at a conference in Texas, Michael Phemister promised them a gusher. The vice president for treasury management at DFW International Airport said he’s planning to sell between $10 billion and $11 billion in bonds over the next five to seven years to add capacity to an airport that serves one of the fastest-growing areas of the nation. “Our airfield is in pretty good shape, but we’re out of gates again,” Phemister said at a bond buyer conference in Dallas.