4.2.1 Applications & Limitations

Amending soils to establish a minimum soil quality and depth is not the same as preservation of naturally occurring soil and vegetation. However, establishing a minimum soil quality and depth will provide improved onsite management of stormwater flow and water quality.

Soil organic matter can be attained through numerous materials such as compost, composted woody material, biosolids, forest product residuals, or other locally available materials deemed suitable for this application. It is important that the materials used be appropriate and beneficial to the plant cover to be established. Likewise, it is important that imported topsoils improve soil conditions and do not have an excessive percent of clay fines.

This BMP can be considered applicable for all pervious areas, except for on till soils with slopes greater than 33 percent.

Additional applications and limitations for this BMP include:
  • Amended soils can be included in designs for dispersion BMPs to improve dispersal and absorption of stormwater flows and help satisfy Ecology’s Core Element requirements for flow control and runoff treatment. See Section 4.3: Dispersion, for guidelines on designing dispersion BMPs.
  • Creates a medium for healthy plant growth, reducing the need for fertilizers and pesticides and peak summer irrigation needs (Chollak, n.d.).
  • Can improve overall site water quality performance by promoting infiltration; increasing cation exchange capacity, pollutant adsorption, and filtration; and buffering soil pH (USCC, 2005).

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