Many contaminated brownfield sites sit unused for decades because the cost of cleaning them to safe standards is more than the land would be worth after redevelopment, in the process becoming involuntary parks as they grow over. However, redevelopment has become more common in the first decade of the 21st century, as developable land has become less available in highly populated areas, and brownfields contribute to environmental stigma which can delay redevelopment. Also, the methods of studying contaminated land have become more sophisticated and costly.
Some states and localities have spent considerable money assessing the contamination on local brownfield sites, to quantify the cleanup costs in an effort to move the redevelopment process forward. Therefore, federal and state programs have been developed to help developers interested in cleaning up brownfield sites and restoring them to practical uses.
In the process of cleaning contaminated brownfield sites, previously unknown underground storage tanks, buried drums or buried railroad tank cars containing wastes are sometimes encountered. Unexpected circumstances increase the cost for study and clean-up. As a result, the cleanup work may be delayed or stopped entirely. To avoid unexpected contamination and increased costs, many developers insist that a site be thoroughly investigated (via a Phase II Site Investigation or Remedial Investigation) prior to commencing remedial cleanup activities.