Did you know?
Sediment runoff rates from construction sites can be up to 20 times greater than agricultural sediment loss rates and 1000-2000 greater than those of forested lands.1
Soils serve as habitat for a diverse range of organisms such as plants, worms, insects, arthropods, bacteria, fungi, protozoa, and nematodes. The “soil food web” decomposes organic matter, stores and cycles nutrients, maintains soil structure and stability and filters pollutants.
Soils
Soils are essential for the production of food, timber, medicines, fibers and other raw materials. Healthy soils allow rainwater to penetrate, preventing excess runoff, sedimentation, erosion and flooding. Soils also help clean, store and recharge ground water. By storing water and slowing the delivery of water to plants, healthy soils play a significant role in vegetation health as well.
Water and air pollutants are removed or transformed into less harmful materials in the soil. For example, clay soil particles and soil organic matter can attract and hold chemicals present in water infiltrating the soil. In addition, soil accommodates microbes that break down or convert pollutants into more benign substances.
Current Soil Practices
Compaction, which is caused by the use of heavy machinery during construction, degrades soil structure and reduces infiltration rates,2 which increases the runoff volume and flooding potential.3 Compaction also reduces spaces for oxygen and water in the soil, making it difficult to plant or restore vegetation. Compressed soil reduces root growth and access to water and nutrients.
Disturbing and removing vegetation, which commonly occurs during site development, can damage soil structure and increase erosion and sedimentation. Plants need adequate amounts of soil to be healthy. Also, disturbed soils can release into the atmosphere significant amounts of organic carbon previously sequestered in the soil.4
Removing topsoil before or during construction destroys soil horizons and hinders reestablishment of healthy soils. It also disturbs soil structure and profile on-site even if the original topsoil is returned to the site after construction or fill material is imported from an off-site location to serve as topsoil. When soil is harvested and imported from a second site, the impact is doubled. Importing soil from an outside source may also introduce weeds or undesirable vegetation to the site.
Contaminated soils can result from the use of pesticides and substances containing heavy metals at industrial sites. Soil pollutants may harm soil biota that provide critical nutrient cycling and decomposition services.5
Examples of Sustainable Soil Practices
Preserve and protect healthy soils by identifying areas of healthy soils, retaining topsoil, preventing erosion and sedimentation, minimizing grading, compaction and soil disturbance and avoiding vegetation removal and disturbance.
Improve health of degraded soils through soil restoration, reuse and rehabilitation to achieve conditions similar to regional reference soil.
Reduce waste during maintenance especially by recovering yard trimmings for composting. Compost reduces the need for fertilizers by supplying nutrients in a slow-release manner. It also holds more rainwater onsite, decreases runoff and provides increased soil moisture and filtering capacity.