Sentence:  A <WSD>tree well</WSD> is a great solution to a problem that often arises during excavation of a building, driveway, or road site. When excavated soil is carelessly mounded around the base of a tree, the tree gradually suffocates. Removing this soil from around the trunk and dry-stacking a <WSD>tree well</WSD> to retain the soil at a safe distance can save a tree's life. 
Meaning of the word marked with <WSD> tags:  A structure designed to protect the base and roots of a tree, typically used in an urban setting.