In looking for something else, I came across the jobs bulletin board of the American Bar Association. The available positions can be narrowed to just environmental jobs. There appear to be primarily law firm and other commercial openings listed. Looks like a very useful resource, with one exception - some of the listings appear to require member log-in/password (though basic info such as job title and employer/location will often appear/be available even without log-in).
Here's link to website, for those interested - click the link and then enter "environmental" in the search box: