BRIDGETON, Mo. (AP) The Missouri Department of Natural Resources is ordering the operator of a smoldering St. Louis County landfill to install three additional temperature monitors.The St. Louis Post-Dispatch (http://bit.ly/1dn0qZt ) reports that the DNR's Solid Waste Management Program director, Chris Nagel, wrote to Republic Services Inc. about concerns at Bridgeton Landfill.The landfill is dealing with two issues: a severe smell caused by the underground smoldering that is affecting nearby residents; and concerns about the fire's proximity to buried nuclear waste in an adjacent landfill.Nagel said recent data showed increased temperatures and carbon monoxide readings in the neck of the landfill. He said the monitors are needed to better track movement of the underground fire to see if it is moving in the direction of the buried nuclear material.Nagel wrote that the elevated readings indicate the smoldering fire "continues to progress toward and potentially impact the first row of gas interceptor wells and other landfill infrastructure."The stored nuclear waste is a federal Superfund site. The Environmental Protection Agency is still trying to determine the best way to remediate it.Nagel's letter requires Republic to immediately install three additional temperature probes along the east and west walls of the landfill neck."Any further delay in installation of these (probes) may result in conditions, including increased pressure and saturation of waste mass, which could complicate or prevent future installation and result in inadequate monitoring in this area," Nagel said.The requirement of additional temperature monitoring probes is among steps called for in a contingency plan submitted by Republic as required under a settlement with Missouri Attorney General Chris Koster. That plan has not been finalized.DNR wants more monitors at Bridgeton Landfill