Low Impact Development Manual for Michigan - OSEH - University ...

e. Add six inches compost or other media and till
up to eight inches for minor compaction. (Six
inches of compost equates to 18.5 cubic yards
per 1,000 square feet of soil.)
f. Add 10 inches compost or other amendment and
till up to 20 inches for major compaction. 10
inches of compost equates to approx. 30.9 cubic
yard per 1,000 square feet.
g. Compost can be amended with bulking agents,
such as aged crumb rubber from used tires,
or wood chips. This can be a cost-effective
alternative that reuses waste materials while
increasing permeability of the soil.
Stormwater Functions and
Calculations
Volume and peak rate reduction
Restored soils result in increased infiltration, decreased
volume of runoff, and significantly delayed runoff.
Soil restoration will lower runoff volume and peak rates
by lowering the runoff coefficient (i.e., curve number).
Designers can receive credit based on areas (acres)
complying with the requirements of these BMPs. These
areas can be assigned a curve number (CN) reflecting a
“good” condition instead of “fair” as required for other
disturbed pervious areas. Chapter 9 and Worksheets 3
and 4 show how to calculate the runoff credit for this
BMP.
Water quality improvement
Although either organic or inorganic materials may be
used as soil media, only organic matter can improve
water quality by increasing the nutrient holding
capacity of soils. Soils rich in organic matter contain
microorganisms that immobilize or degrade pollutants.
See Chapter 9 for information on how to calculate the
volume of runoff that needs treatment for water quality
improvement.
Organic materials that include fecal matter or animal
renderings should not be used where water may infiltrate
though the soil and carry nutrients, primarily phosphorus,
to surface waters (Hunt and Lord, 2006).
Maintenance
Soil restoration may need to be repeated over time, due
to compaction by use and/or settling. Taking soil core
samples will help to determine the degree of soil compaction
and if additional media application is necessary.
Winter Considerations
Since soil restoration is performed in conjunction with
plantings, this BMP should be undertaken in spring or
autumn and during dry weather, so that plantings can
establish.
Cost
Cost information has been compiled by Cahill Associates
and reflects 2007 conditions:
• Tilling costs range from $800/acre to $1,000/acre
• Compost costs range from $860/acre to $1,000/
acre. Costs of other soil media would vary greatly
depending on their individual material costs and the
amounts used.
LID Manual for Michigan – Chapter 7 Page 286