We have our papers just published as a twin articles in the Journal of Great Lakes Research 34(4), December 2008. The authors are John B. Braden, Laura O. Taylor, DooHwan Won, Nicole Mays, Allegra Cangelosi, and Arianto A. Patunru.
This first paper (p. 631-48) measures the economic benefits of remediating the Buffalo River, New York. It finds values equivalent to between 6-14 percent of property values, depending on the methods and areas. In other words, the pollution in Buffalo River has reduced the value of houses in the surrounding area up to 14 percent their values without pollution. (As a note, the idea of hedonics approach is to measure the value of a non-market good using a market good -- house or property in this case-- as a surrogate price revealer). Full remediation will potentially increase the value of the area as high as 14 percent of the current level. Finally you can read this as saying that the community members' willingness to pay for cleaner river there is as high as 14 percent of what they pay for their houses.
The second paper (p. 649-60) applies similar techniques to the Sheboygan River in Wisconsin. The numbers found are equivalent to 8-10 percent of property values.
Note: JGLR is a cross-disciplinary journal devoted to researches related to issues and problems of the Great Lakes (lakes spanned across Canada and America). Other papers talk about things like epidemiological aspects, engineering, etc.