TEMPE (3TV/CBS 5) -- Tempe officials say a portion of the damaged Union Pacific Railroad bridge spanning Tempe Town Lake will be demolished Sunday morning. Surrounding homes and businesses will be evacuated as the demolition takes place.

During a press briefing Saturday, Assistant Tempe Fire Chief Andrea Glass said a 150-foot section, the most heavily damaged portion of the bridge on the south end of the structure, will be removed.  

The announcement comes a day after a pair of workers were exposed to hazardous chemicals as they were in the process of cleaning up train cars that had derailed in the accident.

The bridge was damaged after a Union Pacific train derailed and caught fire while crossing a bridge over Tempe Town Lake Wednesday.

Glass says on Sunday between 7 a.m. and 9 a.m., "small precision cutting charges placed in predesignated and precut locations around a section of the bridge to demolish and remove a small portion of the bridge."

The section is a 150-foot span on the southern end of the the lake between Tempe Town Lake and Rio Salado Road.