This from Josh Boyajian:

The Lisle Woodridge FPD has placed an order with Pierce for another engine. Expected this winter. It will be a PUC Pumper on a Arrow XT cab.   1500 gpm pump with a 750 gallon tank. (will be the same as 511) This engine will be for 521 at station 2. the current 521 will be moved to station 5 as 551. And the e-one engine will become o.o.s.