A320 crew lost green hydraulic system fluid while holding for a gate with the parking brake set. The aircraft was towed to the gate due to loss of nose wheel steering.

Narrative

Landed normally after uneventful flight. During taxi-in; we held behind an aircraft while the taxiway was blocked by another aircraft pushing back. We were stopped; with the parking brake set; both engines running. We then received a Class I ECAM 'HYDR G RES LO LVL;' accompanied by a rapid drop in G hydraulic fluid level distinctly visible on the ECAM HYD page. We promptly accomplished ECAM actions and turned off the PTU and G hydraulic pump. We then informed Ground Control (ATC) that we were without steering and had to be towed in. ATC asked if we could move straight ahead to unblock the intersection (our location at the time); and we moved forward a few feet. I was not comfortable with moving the aircraft; however; and stopped. We were towed in from that point. Airport personnel responding to the potential spill informed us that there was a considerable amount of hydraulic fluid spilled on the taxiway. They later gathered information from both pilots at the gate. Tow-in was accomplished quickly and efficiently by ground personnel. Their response was excellent. Passengers were simply told (by me) that we would be towed to the gate from that point and reminded to remain seated until the sign was off. All I can say is that timing is everything. A few minutes earlier and we would have been in the air. Apart from never; this is just about the best time to lose a major system; on the ground; stopped; and close to our intended gate!