As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT CRUISE ALT FL340 APPROX 1 HOUR INTO FLIGHT, EICAS MESSAGE HYD 3 QTY LOW APPEARED. PULLED UP HYD PAGE ON MFD AND QTY WAS AT 16 PERCENT. ATC DECLARED EMERGENCY AFTER BEING NOTIFIED. LANDED WITHOUT INCIDENT. REMOVED AND REPLACED ACMP 3A IAW EMB 170 MM 29-12-01. NO LEAKS FOUND, OPS CHECK GOOD.