What was found
(CAN) FLIGHT 178, CREW REPORTED "A" SYSTEM HYDRAULIC PRESSURE AND QTY WENT TO ZERO ON TAXI INTO YYC. LOW PRESSURE WARNING LIGHT ILLUMINATED FOR APPROXIMATELY 90 SECONDS - CREW SELECTED "A"' PUMPS OFF AND SHUTDOWN BOTH ENGINES. AIRCRAFT TOWED TO THE GATE. MAINTENANCE INSPECTION REVEALED THE NR 1 GROUND SPOILER ACTUATOR CASING WAS CRACKED AND LEAKING. MAINTENANCE REPLACED THE ACTUATOR, SYSTEM GROUND CHECKED SERVICEABLE - NO LEAKS AND RETURNED TO SERVICE WITH NO FURTHER INCIDENTS TO REPORT.