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Avoid creating a "bathtub" effect where isolated areas of coarser soils or loamy sands are surrounded by fine soils or clay. The design engineer and landscape architect should review both subsoil and topsoil materials for compatibility of compactness and texture in planting areas of the LID Practice. Methods, such as soil amendment and preparing a larger planting bed, may be required to prevent discontinuous soil layers. In bioretention practices with a loamy sand soil media placed in clay soil textures, an underdrain is necessary.
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Topsoil must be capable of sustaining vigorous plant growth and to be free from subsoil, roots, vegetation, debris, toxic materials and stone over 50 mm diameter. Specify that topsoil sample must be provided to the consultant for testing and analysis including herbicide or atrazine content. All topsoil supplied must conform to a sample provided. Minimum topsoil depth is 150 mm for turf areas and ranging to 1.25 m for perennials, shrubs and trees.
Topsoil must be capable of sustaining vigorous plant growth and to be free from subsoil, roots, vegetation, debris, toxic materials and stone over 50 mm diameter. Specify that topsoil sample must be provided to the consultant for testing and analysis including herbicide or atrazine content. All topsoil supplied must conform to a sample provided. Minimum topsoil depth is 150 mm for turf areas and ranging to 1.25 m for perennials, shrubs and trees.
[[category: materials]]
[[category: materials]]