Table A-6. Oil Residence Index (ORI) look-up matrix based on exposure (columns) and substrate type (rows)

Substrate VE E SE SP P VP
rock 1 1 1 2 3 3
man-made, impermeable 1 1 1 2 2 2
boulder 2 3 5 4 4 4
cobble 2 3 5 4 4 4
pebble 2 3 5 4 4 4
sand w/ pebble, cobble, or boulder 1 2 3 4 5 5
sand w/o pebble, cobble, or boulder 2 2 3 3 4 4
mud 999* 999* 999* 3 3 3
organics/vegetation 999* 999* 999* 5 5 5
man-made, permeable 2 2 3 3 5 5

* 999 is equivalent to NULL in the database