Environmental Engineering Reference
In-Depth Information
tides that are best for breaching, or they can be
environmental, such as making sure land is
'sterilized' before the spring and early summer
bird breeding season.
One of the absolutely critical considerations
in any construction exercise, but one that brings
its own unique issues for those undertaking rea-
lignments, is health and safety. The building in of
health and safety considerations as part of the
project planning is a legal requirement [e.g. The
Construction (Design & Management) Regula-
tions 2007, or CDM 2007), and on realignments
the sort of considerations that are relevant include:
. Building in health and safety requirements into
the scheme's morphological design. This can in-
cludemaking sure that there are safe access routes
for plant into and out of the site. Larger sites may
need to be divided into discrete sections or 'cells'
so that not all the breaching has to be done in one
go (i.e. in one tidal window).
. Timing the breach construction to be carried out
on a neap tide (so that flow speeds through the
breach will be at their lowest). This needs to be
planned with a clear understanding of how much
excavation can be undertaken in the low-tide win-
dow. For the final stage breaching at the Wallasea
North Bank site, a 330-m length of sea wall
material was removed at three breach locations
during a single 7-hour tidal window, and this is
thought to be about the maximum that can be
achieved safely. The amount of work required on
the final breach can be minimized by slowly strip-
ping down the walls, as the tide levels drop from
a spring to a neap tide.
. Ensuring that all workers have appropriate
Personal Protective Equipment (PPE) such as life-
jackets as well as having stand-by plant that is not
required but can be brought into service if there
are any problems with the plant being used.
. Safe methods of working, such as pinning open
the digger doors during breaching to allow drivers
to exit easily, and deployment of trained shoreline
support staff who have throw lines and other
equipment in the event of any problems.
. A clear project management structure with one
leading project manager to ensure that there is no
mixing of messages to the plant operators.
. Major coastal defence earthworks - 3 months
per km.
. Placement of dredgedmaterial - 4months in two
tranches over the winter (November/December
and February/March).
. Settlement, consolidation and vegetation of
walls - 12 months ideally but can be accelerated
by engineering.
. Breaching of the sea walls - 2 weeks in two
separate tranches between the top of spring tide
and bottom of neap tide.
. Post-breach monitoring - 5 years to validate
hydrodynamic predictions and assess attainment
of compensation targets.
In viewing the whole project plan, one of the
critical potential obstacles or 'pinch points' that
is largely outwith project management control is
the response of local people and politicians. This
aspect can be mitigated by adopting comprehen-
sive and early consultations with a wide range
of groups and individuals including the general
public, statutory authorities, specialist interest
groups and estuary users (ComCoast 2007). Not
only is this very important for communicating the
need for, and rationale of, the project it also en-
sures that interested parties (especially locals) feel
involved in the process and can lead to extra
components being included in the scheme design
(e.g. a recreational area inside the site and signage
on the new sea walls). This process is also valuable
for informing the Consent and EIA process by
enabling key issues to be highlighted.
Undertaking the Construction Work
For the most part the construction work for re-
alignment requires the same plant and approach as
would be expected for any typical infrastructure
development. The amount and type of plant will
clearly be influenced by the location, scale and
timescales of the work and, as described above,
there needs to be a clear timetable of events to
achieve the required tasks and meet important
deadlines. Deadlines can include engineering
ones, such as ensuring that all land works are
completed in time for the smaller midsummer
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