The need for the substation is crucial,” Xcel spokesman Mark Stutz indicated in an e-mail. “We have been looking at a potential substation for more than a decade, due to annual growth in the Silverthorne area of 3 to 4 percent a year.

The fire started at the Watson substation, on Weil Avenue near River Des Peres and Watson Road. Shrewsbury Fire Chief William Fox said an Ameren employee quickly put out the fire using a hand-held extinguisher.