Before TACO, contaminated soil would be removed or the soil and groundwater would be treated to reduce the amount of chemicals as much as possible. This was a rather conservative approach that did not allow much flexibility or input from the site owners, and could require more work than was really necessary to make the site safe for future uses. Under TACO, the site owner decides what approaches are best, and the remediation can be adjusted for the specific site. By taking into account site-specific information, the remediation can cost less and the land may be used again sooner. The owner has more control and involvement in the cleanup process, and the remediation still protects human health.
Risk is the probability or likelihood of something undesirable happening.
In environmental terms, risk is the probability of soil and groundwater contamination causing human injury or illness. There are three components to environmental risk. Controlling any one of these factors can either reduce or eliminate the risk. The ultimate goal of TACO is to reduce environmental risk to humans by managing one or more of these components. If an exposure route can be limited or cut off, then the health risk from the contamination is also limited.