A 70-acre site tucked back in the woods off Route 90 in Warren has been a thorn in the side of town officials, residents and the Maine Department of Environmental Protection for the better part of the past 20 years. On the property, about 27,000 tons of carpet-like material snakes through the abandoned lot like small mountain ranges. After a previous contract with a Massachusetts company — which trucked out much less material than anticipated — came to an end last year, the DEP is once again collecting proposals from bidders to remove however much material they can from the site. Proposals are due Sept.