Q356. How far back in the past do we answer questions about the facility? How do we handle unknown information when the site was owned by someone prior?

A356. Waste quantities should be estimated at the opening of the landfill or 1960, whichever is more recent. The rule provides a series of three options to back-calculate disposal quantities, including using the first known annual disposal quantity for historical years for which data are not available. Default DOC values are also provided. There are no other inputs that need to be historically estimated.