ENVIRONMENTAL MERITS OF COMBE DOWN
The Combe Down area is:
- Within the World Heritage Site of the City of Bath;
- Adjacent to the Cotswold Area of Outstanding Natural Beauty
(AONB);
- Within a conservation area, containing a number of Listed
buildings;
- Above a Grade 1 aquifer;
- A Site of Special Scientific Interest;
- A Special Area of Conservation;
- Of international importance for Greater and Lesser Horseshoe
bats;
- Of international geological importance partly due to the work
of William Smith.
An Environmental Statement was carried out for
the stabilisation scheme and was submitted to the Local Planning
Authority in December 2002. The Planning Application and
Environmental Statement can be seen at the Combe Down Stone Mines
Information Centre in Combe Down.
Due to the multitude of environmental issues, environmental
management is an essential part of the Project. The Project Team,
contractors and consultants operate environmental management plans
to all site works. Audits of the plans are regularly
undertaken.
Geology
Combe Down forms a plateau capped by Great Oolite limestones
between the valley of the River Avon and Horsecombe Vale. The
geology of the region is dominated by rocks of Middle and
Lower Jurassic age. The Great Oolite is the uppermost lithology.
This is underlain by the clays of the Fuller’s Earth Formation,
which in turn is underlain by limestones of the Inferior Oolite and
the Midford Sands of the Lias. The Great and Inferior Oolite
formations provide effective aquifers (rock in which water can be
stored and pass through) for public and private water supplies.
The Great Oolite stone, used for building purposes, formed over
146 million years ago when the area was underneath a deep tropical
sea on which the shells of ooliths were deposited. The ooliths
bonded together to form the distinctive rock known as oolitic
limestone or locally as ‘Bath Stone’. The Romans found that it was
easily worked and used it for important fortifications. During the
17th Century, small quarries were opened on the edge of the Combe
Down plateau, with major quarries being developed in the 18th
Century.
The British Geological Survey (BGS) worked with the Bath &
North East Somerset Council to ensure no adverse impact is
associated with the Project.
Geomorphology
The slopes of the Combe Down plateau are over-steepened as a
result of erosion by the River Avon and its tributaries. This has
led to land slippage on many of the slopes. Furthermore, softening
of the Fuller’s Earth clays has led to cambering of the overlying
strata, especially near the edge of the plateau. This has resulted
in stress fractures in the form of gulls, being a feature across
the plateau. Some of these features remain empty (or void), others
are filled with clay or rock fragments. Examples can be seen in
Springfield Quarry, off Entry Hill Rise, Bath.
Hydrology
The Combe Down Mines lie above a Grade 1 aquifer (rock in which
water can be stored and pass through, and which is then suitable
for use as drinking water) and a source protection zone on account
of the potable water supply.
Water movements on Combe Down are largely controlled by the
geology. Water percolates the permeable surface rocks of the Combe
Down plateau and emerges as springs on the valley sides above the
impermeable Fullers Earth.
The aquifer underneath Combe Down is split into 2 main parts.
The top part is made up of Great Oolite limestones with Fullers
Earth underneath. The lower part is made up of Inferior Oolite
limestones with Midford Sands. Water for public and private use is
extracted from the springs that issue at the base of these units,
in particular at the Prior Park, Whittaker and Tucking Mill
springs.
It is important that the stabilisation project does not affect
the quality or quantity of water emerging at these springs, and
that any changes in groundwater flow do not cause instability in
the slopes of the plateau.
Ecology
Combe Down and its surrounding area is of great value for nature
conservation with a wide variety of flora and fauna, including wild
populations of bats, deer and badgers. A significant
amount of land in Combe Down is designated as sites of special
nature conservation interest.
The stone mines are of particular significance comprising part
of the Combe Down and Bathampton Down Site of Special Scientific
Interest (SSSI) and forming part of the Bath and Bradford on Avon
Bats Special Area of Conservation (SAC).
The high conservation value of the nature conservation
designations makes ecology and the natural environment a key issue
which will be regarded throughout the project.
