Geoscience Reference
In-Depth Information
F
IG. 68
Careful stripping of topsoil and subsoil with excavator and dumper truck before gravel extraction at Shep-
perton, Middlesex, and their replacement at the receptor site. (Photograph B.N.K.D.)
One way of reducing the effects of methane on the overlying vegetation is to in-
troduce a layer of compacted clay over the refuse as a seal, which will tend to drive
the gas out to the boundary. This, too, can have drawbacks as it may affect trees on the
boundary. (More serious effects occur if there are nearby buildings into which the gas
can migrate). Alternatively, plastic venting pipes can be laid, rather like field drains,
which duct the gas passively out to the edges of the field and allow it to disperse into
the atmosphere. In some cases it is possible to pump the methane out and flare it off
or use it as a fuel for local heating or electricity generation.
Problems associated with reclamation of landfill sites, particularly those con-
cerned with landfill gas emissions, were studied at the Joint Agricultural Restoration
Experiment at Bush Farm, Upminster, Essex. This was one of a series of experiments
to study the reclamation of sand and gravel workings under the direction of a group of
advisers drawn from the Department of Environment, Ministry of Agriculture Fisher-
ies and Food, and Sand and Gravel Association.
The initial objective here was to examine the feasibility of high grade restoration
using alternative methods of soil handling. The opportunity was taken to compare
the relative advantages of directly transferring soil from one area to another, with the
more traditional use of stockpiles. In each case, standard earthscrapers for reinstat-
ing soils in the conventional way were also compared with excavators and dumper
trucks as in the previous example. The site of 8.2 ha was divided into four areas of
roughly equal width. Each quarter was stripped in turn, quarried, infilled with indus-
