Or Protective Action Guides is discussed here.
The 1 in 23 cancer risk is wrong. Assuming we're talking about mortality, then as I commented within the link:
"The “long term public exposure of 2,000 mrem…” is misleading. The recommendation is 2,000 mrem for first year and 500 mrem each year thereafter. The risk will depend on how long one remains in the area. The risk of death (per PAG which is from EPA(1999) and old) is 6E-4 per rem. So if one stayed in the area under maximum recommended guidelines for 10 years (cleaned up by then or one moves) one’s cancer mortality risk increase is only about 0.4%. Not 1 in 23, which equates to 4%."