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Source: U.S. Environmental Protection Agency.

Source: U.S. Environmental Protection Agency.

A high score for one migration route can be more than offset by low scores for other migration routes. Averaging the route scores creates a bias against sites with only one hazard, even though that hazard may pose an extreme threat to human health and the environment.

The EPA provides quality assurance and quality control for each HRS score to ensure that site evaluations are performed on a consistent basis. HRS scores range from 0 to 100, with a score of 100 representing the most hazardous sites. Generally, HRS scores of 28.5 or higher will place a site on the NPL. Occasional exceptions have been made in this priority ranking to meet the CERCLA requirement that a site designated as top priority by a state be included on the NPL.

When the EPA places a hazardous waste site on the NPL, it also issues a summary description of the site and its threat to human health and the environment. Some typical examples are in EPA files, and in Wentz's book (1989).

(This discussion follows C.A. Wentz, Hazardous Waste Management, McGraw-Hill, pp 392-403, 1989.)

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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