One of the methods EPA uses to determine RMP inspection priorities is based on their use of the Wharton School’s Hazard Index, which is defined as
“the sum over all chemicals of log2 (maximum quantity of inventory on-site/threshold), or, alternatively, as the number of chemicals times log2 of the geometric mean of the maximum-to-threshold quantity ratio.”
EPA has defined a “High Risk” facility as one that has:
- RMP WCS population ≥ 100,000
- Any accident meeting RMP reporting criteria within last 5 years
- Hazard Index ≥ 25
So do you know your facility’s “Hazard Index”?
Here is how you can calculate your “hazard index” or you can download an EXCEL spreadsheet I built that does the calculation for you.
So to calculate your “Hazard Index” we do the following:
- For each chemical on the site over TQ, you calculate the ratio of the inventory on site to the TQ amount. So if you have 160,000 pounds of anhydrous ammonia and the TQ is 10,000 your ratio for that chemical is 16.
- Then for each chemical you calculate the base two logarithms of the ratio. For the NH3 example above this would be 4 because 2^4 = 16.
- You can calculate the base two log by taking the base ten log and dividing by the base ten log of 2. For this example the calc is log10(16)/log10(2) = 4.
- Add these logs up for all the chemicals on site. That’s your index.
Or you can just download this EXCEL Sheet and it will do the calculating for you! hazard index worksheet.xls