Erosion - Mining and the Environment: From Ore to Metal - page 790

TABLE 20.1
Example Revegetation Practice and Maintenance Plan (US EPA 1999)
Revegetation Plan
● Systematic sample collection and analysis of topsoil, subsoil and overburden materials is to be conducted to determine the type and amount of soil
amendments necessary to maintain vegetation growth.
● Topsoil placement and seeding is to occur no later than the fi rst period of favourable planting after backfi lling and grading. Backfi lled areas prepared for
seeding during adverse climatic conditions are to be seeded with an appropriate temporary cover until permanent cover is established (a cover of small
grain, grasses, or legumes can be installed until a permanent cover is established).
● Disturbed areas are to be seeded in such a manner as to stabilize the surface and establish a diverse, effective and permanent vegetation cover, prefer-
ably with a native seasonal variety or species that support the approved post-mining land use.
● Re-graded areas are to be disced (tillage using disk rippers) prior to application of fertilizer, lime and seed mixture. Fertilizer mixture is to be applied as
determined necessary by soil sample analyses. Treatment to neutralize soil acidity is to be performed by adding agricultural grade lime at a rate deter-
mined by soil tests. Neutralizers are to be applied immediately after regrading. A minimum pH of 5.5 is to be maintained.
● Mulch is applied to promote germination, control erosion, increase moisture retention, insulate against solar heat and supply additional organic matter.
Straw, hay, or wood fi bre mulch are to be applied in an amount in the order of 2.5 to 6.25 tonnes/hectare. Small cereal grains can be used in lieu of
mulch (small grains absorb moisture and act as a soil stabilizer and protective cover until a suitable growing season occurs that will allow permanent
revegetation to establish).
● Conventional equipment and methods are to be used, such as broadcast spreaders, hay blowers, hydroseeders, discs, cyclone spreaders, grain drills, or
hand broadcasting methods. Excess compaction is to be prevented by using only tracked equipment. Rubber tyred vehicles are to be kept off recon-
structed seedbeds.
Maintenance
● Vegetative cover is to be inspected regularly. Areas are to be checked and maintained until permanent cover is satisfactory. Bare spots are to be
reseeded, and nutrients added to improve growth and coverage. Areas that are damaged due to abnormal weather conditions or pests are to be
repaired.
● Unwanted rills and gullies are to be repaired with soil material. If necessary, the area is to be scarifi ed and (in severe cases) back-bladed before reseeding
and mulching.
● Revegetation success is to be determined by systematic sampling, typically at a minimum sampling rate of 1% of the area. Aerial photography can be
used to determine success (typically at the 1% level-or higher if necessary). Standard of Success (SOS) for revegetation is based on percent of existing
ground cover or achievement of vegetation growth adequate to control erosion.
● Periodic mowing is to be performed to allow grasses and legumes a greater chance of growth and survival. Plants are not to be grazed or harvested
until well-established.
● Previously seeded areas are to be reseeded as necessary, or on an annual basis, until covered with an adequate vegetal cover to prevent accelerated
erosion. Areas where herbaceous cover is bare or sparsely covered after 6 to 12 months are to be re-limed and/or re-fertilized as necessary to
promote vegetative growth, then reseeded and mulched.
Controlling Exit Runoff and Sediment Load
A silt fence or sediment i lter is relatively simple to install and is a down-gradient barrier
intended to intercept sheet l ow runoff and settle out sediment upslope while allowing
runoff to i lter through. A silt fence or sediment i lter can be used to control exit runoff
and sediment load from small disturbed areas. For larger areas a series of i lters may need
to be installed at appropriate intervals ( Figure 20.10 ). A silt fence works particularly well
in conjunction with an existing vegetative buffer strip running across a slope - the vegeta-
tion cover helps dissipate the energy of runoff, while silt fences collect sediment. However,