In-Situ Decommissioning (ISD) is the permanent entombment of a facility that contains residual radiological and/or chemical contamination.  The ISD approach is a cost-effective alternative to both demolition and complete removal of the structure and its content (including the cost of transport and disposal). In addition, the effective use of ISD reduces human health and safety risks while helping to attain sustainability goals through the reduction of greenhouse gas (GHG) emissions, petroleum consumption and waste generation.  Not all contaminated structures can be decommissioned using ISD; candidate sites must meet strict criteria. Where the superstructure is removed, ISD often means in situ disposal.