COUNTY OF AVON ACT 1982
INQUIRY NOTE
General Doints
I
1. Section 33 of the County of Avon Act 1982 (referred to herein
as "the
Act"; a copy of s.33 is attached) requires the consent of the
Council for
operations which inter alia descend to a depth exceeding 5
metres below
the natural surface level .of the ground.
2. This covers the sinking of boreholes, piling operations, and
the excavation
of basements and car park areas below 5 metres.
3. Due to the provisions of section 33(3) of the Act, any
application for a
consent is made by the contractor who will be undertaking the
work.
4. The Environment Agency (EA) is regularly consulted by the
Council on
applications under the Act on an informal basis. It is not a
statutoty
consultee under the Act.
The Drocess in this case
5. The proposed method of drilling boreholes, excavation and
piling for the
Scheme has been under consideration for a number of years.
Specialist
contractors carried out investigations in December 1998, October
1999
and April 2001.
6. Applications under the Act were made by these
consultants to the Council
for exploratory boreholes in January 2001 and May 2002. Consents
were
issued in March 2001 and June 2002 respectively.
7. The potential impacts on the hot springs and the need for
consent under
the Act were examined in the planning application supporting
material.
The ES (Vol 7.1, Pt IV, page 24, para 3.3) noted the need to
obtain a
consent under s.33 of the Act.
8. The ES (CD Vol 7.1, Pt 1, paragraph 3.44, page 25, and
Pt IV, pages 19
to 30) contains a detailed assessment of the potential for
effects on the
hot springs due to the construction of the Scheme. The
conclusions were
as follows:
'3.45 Artesian water and thermal artesian water were not
encountered
within 51 m of the ground surface and the risk of encountering
artesian
or thermal water during the construction of the 10 m deep
basement for
the proposed Southgate Centre is low.
3.46 There may be the possibility of artesian or thermal
artesian water
entering a pile bore or the basement excavation through a
structural
discontinuity within the bedrock strata that has not been
encountered in
the site investigation and that may only become apparent during
the
piling operations or bulk excavation for the basement
construction. In
order to recognise the possibility of such an occurrence, the
attached
Method Statement details the measures to be taken should
artesian water
be encountered during the basement construction operations
to
safeguard the stability of the excavation and to control and
eliminate the
flow of artesian or thermal artesian water."
9. A precautionary approach has therefore been taken to the
issue of the
thermal waters. Although no evidence existed that the springs
would be
harmed by the Scheme, a Method Statement was developed to
protect
thermal water should, contrary to expectations, it was
encountered.
10. In addition (see CD 5.1, Tab 1 page 13-14), it was
anticipated that
notwithstanding the conclusions in the ES quoted above,
additional work
would improve confidence that any risks to the movement of
thermal
water supplying the hot springs would be acceptably low.
11. It was also noted that "given the scale of the proposed
development, and
the depth of the proposed excavation and secant wall, a
precautionary
approach will still need to be maintained throughout, and
construction
method statements would need to be agreed with the developer
prior to
the issuing of such a license". This was echoed by the EA in
its
consultation response (CDS.1 Tab 2, page 3).
12. By the time of the report to the Council's Development
Control Committee
on 5 June 2003, 8 additional boreholes had been applied for
and
consented under the Act, and had been drilled. These were
drilled to a
depth of 40 metres, well below the level of any piling or
excavation
required in order to implement the Scheme. In one borehole
artesian
water was found at a depth of 40 metres, but it was not thermal
water.
13. Chemical analysis of the results was undertaken, but the
results had not
become available (see CD 5.1 tab 4, page 22) by S June 2003.
The
Council's expert consultant, Dr Gallois, received the results of
the
additional borehole tests on 27 May 2003, and by 5 June 2003
had
reviewed the contents. He advised that the chemical tests might
clarify
matters further (CD 5.1 tab 5, pages 4-5).
14. The chemical tests indicated that the water in the
boreholes was not the
same water as in the King's Spring or other thermal sources in
the area.
There was on that basis no indication that thermal water was
crossing the
site in a horizontal band or via a vertical fault. This provided
a secure
technical basis to move to more detailed negotiations. No
objection to
the likely impacts of the Scheme has been received from Dr
Gallois or the
EA.
15. CGNU's lead consultant on this topic is Beattie
Watkinson, consulting
engineers, engaged to co-ordinate the negotiation and consents
under
the Act. In order to take matters forward on the basis of the
technical
work referred to above, they appointed Keller Ltd, an
international
company which specialises in the design and construction of
ground
engineering solutions. Keller has prepared a series of method
statements
on the basis of the work undertaken.
16. The first method statement was submitted in draft to the
Council on 15
March 2005. This dealt with the installation of CFA (Continuous
Flight
Augur) piling on the proposed Bus Station site. The Council
provided
comments on 6 April 2005, including comments from Dr
Gallois.
17. The method statement was amended in accordance with
those
comments, and reissued on 14 April 2005. On 27 April 2005 a
meeting
was held between the Council, Dr Gallois and the EA at
which the method
statement was agreed, subject to a few comments from Dr
Gallois.
Those comments have now been incorporated and the method
statement
has been sent to the Council for final review.
18. The method statement will be incorporated into the CFA
piling tender
documentation for the proposed Bus Station, and will be
formally
submitted without amendment by the successful contractor for
the
contract.
19. The Bus Station method statement will form the
template for the other
method statements for the purposes of the Act consents. The
Council is
aware of this, as a r e ' ~Gr allois and the EA, and
subject to the details of
the remainder of the site, there is general acceptance of the
way forward.
20. At present, the outline proposals for dealing with the issue
of the hot
springs, which were agreed as part of the planning process are
being
refined for the submission of the remaining method statements.
Detailed
work has already taken place on the specification of the piling
and the
grouting for the construction of the basement levels.
21. It is anticipated that the remaining method statements will
be all but
finalised and agreed within the next few months. There may be a
need
for residual testirig to take place once some of the existing
buildings on
the site have been demolished, but in the light of the
significant amount
of assessment work, no major changes are expected.
22. Once the contractor is appointed, applications under the Act
will be made
on the basis of the Bus Station methodology and, elsewhere on
the site,
that method with suitable variations.
23. As a result, there is no indication from the EA or
the Council, both of
which have been fully consulted, that the consent procedure
under the
Act is likely to provide any impediment to the implementation of
the
Scheme.
19th May 2005
