I thought I last heard that it was 45 minutes from the time of first detection
of the Pegasus Pipeline breach until the time that ExxonMobil activated their remotely controlled block valves that are 18 miles apart in the Pegasus Pipeline, a 20 inch ID line.
In evaluating an upper bound on the potential spill volumetric rate estimation for the Keystone XL Pipeline the first item of necessary consideration is the nominal hourly pumping rate that would be a maximum amount of potential spillage per hour while pipeline pumping operations continued after commencement of a spill until the time the pumping ceased.
Keystone XL Pipeline Nominal Capacity = 830,000 barrels per day * 42 gallons/barrel
= 3.5E+07 gallons per day * 1 cubic foot/7.54 gallons
= 4.6E+06 cubic feet per day
= 1.9 E+05 cubic feet per hour
Keystone XL Pipeline volumetric transfer rate = a cube of oil 57.5 feet high per hour
Such a volumetric transfer rate is the upper bound on the amount that could be spilled during the time interval from commencement of the pipeline breach to the time when pumping is ceased, assuming 100% of the volumetric transfer rate issues from the breach with no further transit of flow through the pipeline beyond the breach.
After pumping of the pipeline ceases another upper bound on the amount spilled after cessation of pumping would be the maximum volume that would be contained in the pipeline itself per unit pipeline length.
Keystone XL Pipeline Inside Diameter = 36 inches = 3.0 feet
Area of Keystone XL Pipeline Cross-section = PI *R*R = 3.14*1.5*1.5 = 7.1 square ft
Volume of full pipeline per 1000 ft = 7100 cubic ft (a cube 19 feet high) per 1000 ft
Volume of full pipeline per mile = 37500 cubic ft (a cube 33.5 feet high) per mile
Finally......
Velocity of oil traveling in the Keystone XL Pipeline = 1.9E+05 cubic ft/hr / 7.1 sq ft
= 2.7 E+04 ft/hr / 5280 ft/mile
= 5.1 miles per hr