An important aspect of natural gas pipelines is the Potential Impact Radius, or PIR. This is defined as:
“Potential impact radius (PIR) means the radius of a circle within which the potential failure of a pipeline could have significant impact on people or property”.
What does significant mean here? Well the actual definition is based on survivability:
“PIR is the distance beyond which a person standing outside in the vicinity of a pipeline rupture and fire would have a 99% chance of surviving”
The formula for PIR is pretty simple – it’s based on pipeline diameter and pressure:
PIR = 0.69 * (maop * d^2)^0.5
(here the “^” symbol means “raised to the power of). In English this is:
To determine PIR, start with diameter of the pipeline squared, times the maximum allowable operating pressure. Raise that the power of 0.5, multiply the result by 0.69, and there you go.
For the PennEast pipeline maop = 1480, and diameter = 36″.
This results in a PIR of 955. This means if the pipeline breaches at point X, everyone in a circle of 955′ radius (radius, not diameter!) of the pipeline will have less than 99% of surviving e.g. could die. Note that the we’re talking about an exponential equation, so it means as you get closer to the pipeline you have an exponentially worse chance of surviving. In the case of PennEast, at 500′ you would have little effective chance of surviving.
Fun fact: the model assumes no whether or geographical conditions, just a perfectly flat surface with no wind or other weather conditions. Wind and topography can have a major impact and means damage can occur significantly beyond the official PIR. See the top picture for the potential differences between PIR and actual impact radius.
Some fun facts:
My house is 180′ from the proposed route pipeline centerline. So me and my family are toast.
Hewitt Park – 800′ from center line.
Hunterdon County Library Southern Branch – 725′ from center line.
West Amwell Elementary – 1750′. So they’re good so long as the wind is not blowing to the North East that day.
Lowes Shopping Center in PA, near Lehigh River: the whole shopping center plus Route 33 falls within 900′.