Operating solenoids using Arduino

I want to use an Arduino to 'fire' a soleniod pair. The two windings operate one armature with an 'over centre' spring in a "push me - pull you" configuration. They are normally fired by a couple of passing contact (momentary) switches. They operate on 16 to 20 volts DC, but I don't know the current they draw, which I would guess to be about 2A for less than one second. Obviously, both solenoids would not be fired at the same time! I may also need to use an electrolytic across the power supply to get enough 'punch' into the coil.

Any suggestions as to the feasability of this?

See Arduino Playground - SolenoidTutorial. If it is acceptable to connect Arduino ground to the -ve side of the solenoid supply voltage, you can omit the opto isolator and the 1k pullup resistor, and use a logic-level mosfet driven from an Arduino pin through a 150 ohm resistor.