Civil Engineering Reference
In-Depth Information
changes are refl ected in a revised plan. Ensure that
revised copies are sent to all plan holders and that old
versions are destroyed.
13.4
Containing water run-off
The environmental impact of contaminated water run-
ning off from the location of a fi re into the surrounding
land and water courses can be signifi cant. Water used
for fi re fi ghting is always contaminated with the effl uent
from fi re and often contains other contamination as a
direct result of a fi re. For example, a fi re in a cold stor-
age depot may result in quantities of food stuffs degrad-
ing and presenting signifi cant biological hazards.
In order to minimise the risks of environmen-
tal damage as a result of fi re it is necessary to ensure
that the site of any potential incident has suffi cient
emergency containment systems, emergency materials
and equipment, arrangements for waste management
and consideration has been given to the preplanning of
fi re fi ghting strategies and run-off management.
Figure 13.6
Boom used to catch overfl ow from bunded
area
Sacrifi cial areas
- the use of sacrifi cial areas
involves the routing of fi rewater run-off to a designated,
remote area, which is provided to allow infi ltration of any
contaminant and to prevent run-off from the site. The
contaminant is often contained within a layer of perme-
able soil or other similar material and should be prevented
from dispersing into other strata or ground water by an
impermeable lining system which should be capable of
containing both vertical and horizontal seepage.
The sacrifi cial area may also be used for other
purposes, such as car parking or as a sports ground.
Storm water drainage serving the area must be capable
of being shut off quickly and effectively in the event of
an emergency incident. After use, if the area has been
contaminated, the permeable material can be excavated
and removed for disposal. Sacrifi cial areas can also be
used for controlling storm water run-off from the site,
which helps in the management of fl ooding and pollution
from surface run-off.
Bunding of vehicle parking and other impermeable
surfaces
- impermeable yards, roads and parking areas
can be converted to temporary lagoons using sandbags,
suitably excavated soil or sand from emergency
stockpiles to form perimeter bunds. Permanently installed
bunding, in the form of either a low kerb or roll-over bunds
around suitable impermeable areas, the entire site, or just
the sensitive area, is a better option. In the event of an
incident, all drain inlets, such as gullies, within the area,
must be sealed to prevent the escape of the pollutant.
Catch pits and trenches
- pits or trenches may
be used where other methods have failed or no other
method is available. Their use should be considered
carefully due to the risk of ground water contamination. If
possible, a liner should be employed, particularly in areas
of high ground water vulnerability, although the effect of
13.4.1
Emergency containment systems
Although permanent containment facilities should be
provided at many sites, for example at sites that come
under the COMAH Regulations, there may be circum-
stances where a spillage cannot be dealt with by such
facilities, for example if it occurs outside a bunded area.
A bund is a purpose-built dam around an area
where a spillage is likely to occur. Typically bunds can be
seen around oil storage tanks. In the event of a spill, for
whatever reason, the hazardous substance is contained
within the bunded area.
In some cases, particularly at smaller sites, contain-
ing contaminated fi rewater run-off will be considered to
be impracticable because of cost and space consider-
ations. In such cases, temporary containment systems
or pollution control materials are available and should be
used to minimise the environmental impact of fi rewater
run-off.
However, if reliance is placed on these secondary
measures, consideration of some other form of local
containment may be necessary to provide suffi cient time
to prepare them. Their use and location must be clearly
marked in the pollution incident response plan and
indicated on site with durable signs explaining their use.
There are a variety of emergency containment
measures that may be used including:
➤
Sacrifi cial areas
➤
Bunding of vehicle parking and other hard standings
➤
Pits and trenches
➤
Portable tanks, overdrums and tankers.
