Tucson’s oldest firehouse has become an example of how long-delayed capital projects can cost more than a spreadsheet can list. And in this case, officials say, it might be an actual pound of flesh. Fire Station No. 3 near Campbell Avenue and Broadway dates to the 1950s and has been retrofitted repeatedly in an attempt to extend its useful life. However, city officials say any more changes would be a waste of taxpayer dollars. A federal grant is paying for a study to determine whether the building is exposing firefighters to toxic levels of known carcinogens from the exhaust of fire trucks and rescue vehicles.