Fen Management Handbook - Scottish Natural Heritage

7.2.3 Disposing of excavated material
Excavated material is best disposed of on site, where it can be used to consolidate
existing tracks or bunds, or used as a source material for nearby fen creation
projects. It is likely to contain plant materials such as seed and rhizomes, fungi,
mosses and bacteria, possibly even invertebrates. Nutrient enriched silt and other
scrapings must be removed to a sufficient distance to prevent leachates (nutrients
and toxins) seeping back into the fen. Material to be disposed off-site should
be tested for contaminants to ensure it is safe to use as topsoil for improving
agricultural land or other similar purpose. Finding a suitable use nearby can
eliminate or reduce the significant cost of disposing of such waste.
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Disposing of excavated sediment
Piles of excavated sediment and dead plant material can generate
nutrients or oxidised leachates which can inhibit some plants or
encourage other undesirable ones. This can be a particular problem
with sediments rich in reduced forms of iron which will oxidise to oxides
and hydroxides of iron as well as dilute sulphuric acid to produce an
ochreous leachate.
At Cors Geirch on the Lleyn Peninsula in Gwynedd, the material
removed to create a large turf pond was used as topsoil on a nearby
landfill site.
At Minsmere in Suffolk, the rejuvenation of a reedbed was achieved by
scraping off the top 30 cm of accumulated litter and surface peat with a
360 degree excavator; the material was placed in windrows and left to rot.
7.2.4 Revegetation
The type of fen that will develop following excavation will depend in part on the
seed bank, the living rhizomes of plants left in the substrate and the conditions
created. At many sites where the water level has been raised or the surface
lowered, vegetation has been allowed to develop without further intervention other
than grazing and mowing. Buried seeds often germinate readily when exposed to
the air and some may survive many hundreds of years in anaerobic conditions.
At Dry Rigg Quarry in North Yorkshire, mares-tail (Hippuris vulgaris) and
bog pondweed (Potamogeton polygonifolius) appeared from an area
where fen peat had been buried under quarry spoil for many decades.
Although it cannot be proved that the seeds were not imported from
elsewhere, such as on the feet of waterfowl it is possible that the seeds
were present.
To a lesser extent, adjoining fens or sites in close proximity and with hydrological
connectivity will contribute viable fragments to assist the re-establishment of fen
vegetation. Deliberate introduction of species to excavated areas has had mixed
success. Planting out specific fen plants as plugs into turf ponds may be successful
where competition from established vegetation is absent or low, but is unlikely to
be successful in standing water as the plants are likely to float to the surface and
be lost. Planting is best carried out in spring to allow establishment through the
summer before wave action from winter flooding can dislodge the plants. Section
8: Fen Creation offers more advice on this subject.