Page 38 - Green Builder March-April 2016 Issue

CREDIT: NEW BRUNSWICK DEPT. OF AGRICULTURE

Fix-It. Vetch and clover are good choices for cover crops, as they fix nitrogen in the soil.

dimensionally and chemically stable. Sand and gravel improve in their roots, stems or leaves. The plants are usually harvested once
infiltration and are good materials to layer under rain gardens and they have done their job.
other stormwater infrastructure, but by themselves they will not
correct the drainage issues with clay soils. 3. BROWNFIELD SITES

Biological amendments improve the diversity and number of soil If your project involves redeveloping a brownfield site, the possible
organisms. Typical amendments include mycorrhiza, a symbiotic presence of contaminants could affect stormwater infrastructure,
fungus that colonizes plant roots, and compost teas, which inoculate especially if the features rely on infiltration. These features must be
soil with microorganisms. “Macrofauna” such as earthworms provide designed carefully, so contaminants in the soil are not mobilized,
a number of benefits, including improved pore structure and which could increase the risk of groundwater contamination.
detoxification of contaminants.
Any lot that’s being redeveloped could house contaminants in the
Chemical amendments, also known as fertilizers, are used to soil, so it’s a good idea to take the following steps before designing
change soil pH or add missing nutrients, but in general, they are green infrastructure or other landscaping.
the least effective type of amendment and can have unintended
consequences. They can also run off the landscape and end up in Learn the history of the lot. Contact previous property owners and
waterways, especially if over applied. Chemical amendments should
be used only after other methods have been tried. Just Add Worms. When adding earthworms to soil, they need to be
“planted” several inches below the surface. They also need organic
Mulch. Anything added on top of the soil layer can be called mulch, matter for a food source.
and common mulching materials include peat moss, leaves, wood
chips, bark, compost, rice hulls and straw, and synthetic materials
such as sheet plastic and geotextiles. Mulch protects soil, keeping it
cool and moist and stimulating biological activity. A layer of mulch
can also help soils recover from mild compaction or prevent further
compaction.

Cover crops. Planting a cover crop such as oats, clover or alfalfa
is a good strategy for improving the soil before installing a rain
garden or other stormwater feature. Cover crops can add organic
matter, stimulate biological activity, inhibit weeds and protect the
soil from erosion and moisture loss. Cover crops can be sown in the
fall or summer.

Bioremediation. Taking advantage of organisms’ natural process
to repair soil is called bioremediation. Plants, microorganisms
and/or soil amendments such as compost can all be used to digest
harmful chemicals and transform them into nontoxic byproducts.
Phytoremediation refers to the practice of using plants to take up
harmful chemicals from the soil and groundwater and storing them

36 GREEN BUILDER March/April 2016 www.greenbuildermedia.com