Hi,
I would do like this.
Configure two independet masters. One for the tank pump, one for the borehole pump. Assign both masters to normal stations.
Add a virtual (not equipped) station at the end of your irrigation programs. Assing only the borehole pump as master to this virtual station. The lenght of virtual station timing will act as a delayed run of your borehole pump. You can program any delay whatever you want within seconds to several hours range. Even this delay can be tuned according to the water consumptions of individual programs. I mean that shorter programs need less extra run of borehole pump.