The proposed restoration of three quarries in Cambridgeshire is potentially a very interesting (and unusual) case where mineral extraction followed by restoration using inert waste should enable wet grassland to be created, safeguarding the long-term potential of the “best and most versatile” (BMV) agricultural soils present.
Restoration / Priority Habitats
Cambridgeshire County Council
Block Fen / Langwood Fen Masterplan SPD
Located adjacent to the Ouse Washes SPA, the Aggregate Industries/Mick George site at Block Fen will deliver 480ha of wet grassland over 40 years to benefit rare breeding birds such as black-tailed godwit and snipe. Importantly, the site will also have large bodies for storing water and relieving the pressure of summer flooding on the Ouse Washes. Making the fertile fenland soils wet will safeguard them from erosion, should the land be required for agriculture in the future. Underneath it all around 21 million tonnes of inert waste will be safely stored.
Cambridgeshire County Council has produced the Block Fen / Langwood Fen Master Plan, a Supplementary Planning Document (SPD) which details the extraction and restoration proposals at Block Fen and provides land use planning for the wider Earith / Mepal area.
A trial area of lowland wet grassland was created at Witcham Meadlands Quarry in 2008 with operators Mick George and Aggregate Industries working in partnership with the RSPB.
Following gravel extraction, inert fill and clay capping, the stockpiled subsoil and topsoil were replaced to bring the finished site level back to the original field level. A grass seed mix suitable for wet grassland was sown, with good germination being achieved. Specialist machinery created Dutch polder-style surface furrows as well as shallow scrapes, and water control infrastructure (including dipwells) was installed to monitor water levels.
The 10ha of habitat restoration has provided a valuable opportunity to refine the methodology including using more accurate methods to level soils and minimising compaction of the subsoil. The vegetation structure continues to develop and grazing was introduced in 2010. Invertebrate populations are monitored and should develop as the wetland becomes established (Block Fen / Langwood Fen Masterplan SPD, July 2011 (pg. 28)) similar restoration was also successfully trialled on a pilot project at nearby Manea Ouse Washes. This has seen the creation of 12ha of wet grassland on former arable land, and is currently used for grazing pasture whilst maintaining the long-term potential of the Best and Most Versatile (BMV) soils.