30 Sep 01
b. Erosion Control Layer.
(1) General. The erosion control layer of a cover system is designed to protect underlying cap
components from wind and water erosion. The erosion control layer is usually vegetated; however, an
armored surface may be applicable in some situations.
(2) Design Criteria--Vegetative Cover. Vegetation on the protective layer can resist wind and
water erosion, maximize evapotranspiration, and enhance aesthetics of the final cover system. The
selection of appropriate plant species is critical in establishing a vegetative cover. Grasses and low-
growing plants are most suitable and are available for most regions and climates. In contrast, trees,
shrubs, and other woody vegetation are usually unsuitable because their deep root systems can damage
the underlying layers, plug drainage layers, and inhibit visual inspection of the landfill surface. Planting
during the appropriate season can also be critical to successfully establishing a vegetative cover. It is
recommended that an expert in local vegetation be consulted for a specific seed mixture. In general, the
vegetation used at a site should meet the following requirements.
(a) Locally adapted perennial plants.
(b) Resistant to drought and temperature extremes.
(c) Roots that will not disrupt the drainage and low-permeability layer.
(d) Capable of thriving in low-nutrient soil with minimum nutrient addition.
(e) Sufficient plant density to minimize soil erosion to no more than 0.45 kg/m2 per year (2
tons/acre per year), calculated using the USDA Revised Universal Soil Loss Equation (RUSLE). A
higher erosion rate may be acceptable during the construction and vegetation establishment period.
Otherwise, temporary erosion protection should be provided until the final cover is well established.
Additional discussion on erosion control is covered in Paragraph B-4h, Cover Surface Runoff and
Erosion Control Requirements.
(f) Capable of surviving and functioning with little or no maintenance.
(3) Design Criteria--Armored Cover Alternative. An armored cover is used when a
vegetative cover is inappropriate as the erosion control layer of the cover system. This would occur in
climates that do not support vegetation or where other conditions, such as steep slopes, preclude the
use of vegetation. An armored cover is typically constructed with very coarse materials, such as
crushed rock or cobbles. However, concrete, asphaltic cement, or other recycled materials may also
be used. The armored component should meet the following requirements:
(a) Capable of remaining in place and minimizing erosion of underlying material during extreme