To complete land restoration, topsoil must be emplaced,
without over-compaction, and vegetation cover established
to prevent surface erosion. Until continuous vegetation cover
is established, storm-water runoff must be managed and
treated to prevent sediment discharge from the site. Mine
and landfill sites can both be restored for pastoral farming or
in some cases forestry has been established. Amenities such
as parks and golf courses are also good uses for restored
land. Hamilton Gardens, an internationally recognised garden destination, is the site of an old Hamilton city landfill
that was used up until the 1970s. A site in Auckland, near Mt
Wellington, that was New Zealand’s largest aggregate
quarry, has been restored for urban housing. The 1100 ha
suburb of Stonefields is expected to house about 6000
people. Meanwhile at the nearby former Greenmount
Landfill site, which finally closed in 2016, it is proposed to
form a 54 ha park that will include areas of native forest, dog
exercise areas, children’s play grounds, and walking and
cycling tracks.
Refuse Anthropic Soils are likely to contain significant
volumes of waste material which, as it biodegrades, may
subside or emit methane (CH 4 ) gas. The potential for subsidence limits the use of such sites for buildings or other
intensive developments. However, former landfills are often
used to provide welcome parkland or greenspace as cities
over-take their former rubbish dumps.
Methane emissions are a potential hazard associated with
Refuse Anthropic Soil. Being heavier than the ambient air,
methane may accumulate in nearby low-lying areas such as
house basements where it becomes an explosion hazard.
Methane is also a potent greenhouse gas so allowing it to
escape to the atmosphere is not desirable. Thus it is best to
engineer the site to instal an impermeable cap and a methane
collection system so the methane can be collected. Where
there is sufficient volume generated, the methane can be used
as a valuable source of natural gas for heating or electricity
generation. Where volumes are low the methane is often
‘flared off’ (burned) as it is less damaging to emit the
combustion products (CO 2 and H 2 O) to the atmosphere than
the methane (which has a higher, though shorter lived,
warming potential than CO 2 ).
At many Refuse Anthropic Soil sites there is also
potential for leachate to contain toxic substances. At modern
engineered landfills, the base of the site will have been
sealed prior to infilling and leachate collection and treatment
systems must be included. However, at older sites of former
rubbish dumps it is likely that no such provisions are in
place. In some sites where leachate has been recognised as a
problem, it has been decided to excavate the whole site and
remove contaminated materials to a contained and managed
landfill. If potential for leachate is a concern, monitoring
wells around the margins of the site can provide information
on the extent and form of any contamination. Pumping
wells, to remove the leachate and draw surrounding
groundwater back towards the site, may be effective. For
example, research at a former rubbish dump near the Gisborne coast showed that pumping of shallow groundwater
adjacent to the ‘dump’, to prevent leachate escape, had
drawn sea water back into the site.
3.7.3 Moving Soil Materials and Ecosystems
Fill Anthropic Soils can be designed to provide appropriate
soil properties for future uses, for example, by designing
appropriate plant rooting depth, water-holding capacity,
drainage, and fertility. Where good design and implementation have been employed, such as at well restored mine
sites, the resulting soils may have no limitations for future
use and could be used for intensive food production or urban
development. The relocation of soil material must be carefully managed to prevent adverse impacts on the soil due to
inappropriate soil mixing, storage conditions, or mode of
placement. If Fill Anthropic Soils are not well designed or
installed, problems may occur. A common problem is
over-compaction where clay materials have been emplaced
with heavy machinery, at high water contents. The resulting
dense, massive, material is often impermeable to water and
inaccessible to plant roots. Thus increased runoff will occur
and the soil will provide a poor substrate for establishment
of vegetation.
Where fill soil materials are used (for example, for land
restoration, urban amenity, or ecosystem design), unless the
fill is derived from surplus material from another site, it has
to be mined from somewhere. The management of Anthropic Soils should weigh the effects of mining at the source as
well as the use at the site of relocation. A potentially powerful means of analysing the net consequences of relocation
is to estimate and compare soil ecosystem functions before
and after relocation and balance the loss of functions at the
mined site against the gain of functions at the relocation site.
The relocation of soil material may affect soil properties
that are considered valuable. Original soil profiles are often
mixed during excavation, transport, and relocation. For
example, soil-water movement is altered by mixing, bulking,
compaction, and by changes in soil biological, and soil organic matter, processes. Relocation may also lead to the
incorporation of foreign materials, such as bricks, concrete
or other human-made materials, weeds, and pests.
Where the original area hosts a native ecosystem then
care must be taken to restore not just the soils but also the
native biota. Some restoration may seek to relocate, not just
the soils but whole below-and-above-ground ecosystems.
Direct transfer of soils with the overlying vegetation can be
an important option for preserving habitats for rare and
endangered species and can save some costs and risks of
54
3 Anthropic Soils
without over-compaction, and vegetation cover established
to prevent surface erosion. Until continuous vegetation cover
is established, storm-water runoff must be managed and
treated to prevent sediment discharge from the site. Mine
and landfill sites can both be restored for pastoral farming or
in some cases forestry has been established. Amenities such
as parks and golf courses are also good uses for restored
land. Hamilton Gardens, an internationally recognised garden destination, is the site of an old Hamilton city landfill
that was used up until the 1970s. A site in Auckland, near Mt
Wellington, that was New Zealand’s largest aggregate
quarry, has been restored for urban housing. The 1100 ha
suburb of Stonefields is expected to house about 6000
people. Meanwhile at the nearby former Greenmount
Landfill site, which finally closed in 2016, it is proposed to
form a 54 ha park that will include areas of native forest, dog
exercise areas, children’s play grounds, and walking and
cycling tracks.
Refuse Anthropic Soils are likely to contain significant
volumes of waste material which, as it biodegrades, may
subside or emit methane (CH 4 ) gas. The potential for subsidence limits the use of such sites for buildings or other
intensive developments. However, former landfills are often
used to provide welcome parkland or greenspace as cities
over-take their former rubbish dumps.
Methane emissions are a potential hazard associated with
Refuse Anthropic Soil. Being heavier than the ambient air,
methane may accumulate in nearby low-lying areas such as
house basements where it becomes an explosion hazard.
Methane is also a potent greenhouse gas so allowing it to
escape to the atmosphere is not desirable. Thus it is best to
engineer the site to instal an impermeable cap and a methane
collection system so the methane can be collected. Where
there is sufficient volume generated, the methane can be used
as a valuable source of natural gas for heating or electricity
generation. Where volumes are low the methane is often
‘flared off’ (burned) as it is less damaging to emit the
combustion products (CO 2 and H 2 O) to the atmosphere than
the methane (which has a higher, though shorter lived,
warming potential than CO 2 ).
At many Refuse Anthropic Soil sites there is also
potential for leachate to contain toxic substances. At modern
engineered landfills, the base of the site will have been
sealed prior to infilling and leachate collection and treatment
systems must be included. However, at older sites of former
rubbish dumps it is likely that no such provisions are in
place. In some sites where leachate has been recognised as a
problem, it has been decided to excavate the whole site and
remove contaminated materials to a contained and managed
landfill. If potential for leachate is a concern, monitoring
wells around the margins of the site can provide information
on the extent and form of any contamination. Pumping
wells, to remove the leachate and draw surrounding
groundwater back towards the site, may be effective. For
example, research at a former rubbish dump near the Gisborne coast showed that pumping of shallow groundwater
adjacent to the ‘dump’, to prevent leachate escape, had
drawn sea water back into the site.
3.7.3 Moving Soil Materials and Ecosystems
Fill Anthropic Soils can be designed to provide appropriate
soil properties for future uses, for example, by designing
appropriate plant rooting depth, water-holding capacity,
drainage, and fertility. Where good design and implementation have been employed, such as at well restored mine
sites, the resulting soils may have no limitations for future
use and could be used for intensive food production or urban
development. The relocation of soil material must be carefully managed to prevent adverse impacts on the soil due to
inappropriate soil mixing, storage conditions, or mode of
placement. If Fill Anthropic Soils are not well designed or
installed, problems may occur. A common problem is
over-compaction where clay materials have been emplaced
with heavy machinery, at high water contents. The resulting
dense, massive, material is often impermeable to water and
inaccessible to plant roots. Thus increased runoff will occur
and the soil will provide a poor substrate for establishment
of vegetation.
Where fill soil materials are used (for example, for land
restoration, urban amenity, or ecosystem design), unless the
fill is derived from surplus material from another site, it has
to be mined from somewhere. The management of Anthropic Soils should weigh the effects of mining at the source as
well as the use at the site of relocation. A potentially powerful means of analysing the net consequences of relocation
is to estimate and compare soil ecosystem functions before
and after relocation and balance the loss of functions at the
mined site against the gain of functions at the relocation site.
The relocation of soil material may affect soil properties
that are considered valuable. Original soil profiles are often
mixed during excavation, transport, and relocation. For
example, soil-water movement is altered by mixing, bulking,
compaction, and by changes in soil biological, and soil organic matter, processes. Relocation may also lead to the
incorporation of foreign materials, such as bricks, concrete
or other human-made materials, weeds, and pests.
Where the original area hosts a native ecosystem then
care must be taken to restore not just the soils but also the
native biota. Some restoration may seek to relocate, not just
the soils but whole below-and-above-ground ecosystems.
Direct transfer of soils with the overlying vegetation can be
an important option for preserving habitats for rare and
endangered species and can save some costs and risks of
54
3 Anthropic Soils