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Landfill sites: How deep is the final soil cover over the cap or refuse?

Final soil cover is less than 2 feet thick:

Consider adding soil so that at least two feet of final cover exist over the cap, if one is present, or over the refuse if there is no cap. In most cases the law requires at least 2 feet of cover.

Trees, shrubs, and greasses grow poorly in cover with soil less than two feet thick. Without two feet of cover, this will be a very draughty site for which regular irrigation is recommended. Small-maturing trees that are tolerate drought are best suited for sites with less than two feet of soil.

Final soil cover is 2 to 4 feet thick:

Small- and medium-sized, drought-tolerant trees are best suited for sites with two- to four-foot-thick final cover. Occasional irrigation during extended drought will enhance growth and maintain healthy trees, especially during the establishment period.

Final soil cover is more than 4 feet thick:

A final cover of four feet or more of soil is the most desirable planting environment, but is very unusual for a landfill site. Many trees should thrive on this site, and there are few restrictions on plant selection other than those mentioned in tree selection for landscapes.