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water can be safely removed and subsequently disposed of correctly.

POLLUTION RISKS REMAIN Our initial assessment with clients

- even on-site regulated under COMAH or EPR - have frequently shown that where a containment valve has been retrofitted into below- ground drainage systems, significant pollution risks still remain as a result of valve closure.

Some companies may have little

idea of the drainage pathways on their site, and the potential pathways to the environment. All too often, companies retrofit a valve without having any technical evidence to demonstrate how it will hold water pollution safely on-site in an emergency.

A well-maintained and fully- functioning valve is not, in itself, evidence that polluted surface water will be contained on a site if there is heavy rainfall or a fire incident. Will it work effectively alongside bunds or other above and/or below ground flood protection measures?

Without this knowledge, how can companies understand the wider implications of containment system operation when predicting an emergency event, especially when there could also be unexpected flow into the drainage system?

OVERLOADED The drainage system could become

overloaded, and the backed-up flows could simply bypass the containment device either by other below-ground flow paths or as overland flood water. Any shortcomings in the containment system could lead to a damaging off- site pollution incident.

Under current planning guidelines, the suitability of a new development is assessed using a system that compares flood risk vulnerability against its compatibility with a flood zone. The National Planning Policy Framework (NPPF) states that for any “installations requiring hazardous substances consent” such as COMAH and EPR sites, their vulnerability classification would be “highly vulnerable”.

Indicative Pollution & Flooding 2D Overland Flowpath Mapping

Even if a site is not directly adjacent to a watercourse, the flood risks may still be significant. Most people are familiar with high-profile flooding events from rivers as a result of prolonged periods of extreme rainfall. However, there are many other sources of flood risk that are easily overlooked, but can have just as serious implications. These sources include surface water, tidal, groundwater, infrastructure failure, such as a dam or canal breach and fire water.

SEEK EXPERT KNOWLEDGE A robust flood risk assessment

provided by suitably-qualified experts will identify all sources of flood risk, along with potential flow paths into and out of a site. A Hazard & Operability (HAZOP) study may also be an appropriate methodology to support an evidence-based understanding of the combined water pollution and flood risks, especially for COMAH or EPR sites.

This would place planning restrictions on such development on the grounds of flood risk in two of the three “Flood Zone” classifications. But this applies only to new developments and many existing sites are unlikely to have been built according to these guidelines.

So when considering existing “highly vulnerable” sites, it’s a fair assumption that a great many of them are located in a flood zone that is not appropriate to their vulnerability, with the residual flood risks largely not understood.

As part of this process, using hydraulic modelling can be invaluable. It can accurately map the surface water pathways on and off a site as well as assessing and validating the effectiveness of the drainage system design.

Hydro Consultancy has developed this 2D-modelling technique, a pioneering approach that requires an uncommon mix of flood risk and pollution containment expertise. It can provide an effective method to test the efficiency of containment systems – and provide reliable evidence for regulators and Environmental Management System documentation.

As government funding is cut back, environmental authorities are being forced to relinquish their advisory role and are increasingly enforcing regulations through prosecution. Seeking expert help to reassess and provide evidence of a site’s compliance with water pollution containment is, perhaps, more important than ever before.

Even for those operators who are already fully familiar with their responsibilities, a comprehensive review could be both timely and highly advisable.

FIRE-FIGHTING WATER It is particularly important for

sites that store or use hazardous or polluting substances to take steps to ensure they do not escape into the environment on or off a site. Even for sites which would not obviously be at risk, flooding or fire fighting water could still be a concern. For example a fire at a waste recycling facility could lead to environmental pollution if fire fighting water is not contained on-site.

The introduction of the revised COMAH regulations on 1st June 2015 has provided a timely opportunity for regulated sites to fully review their environmental risks and ensure both their business and the surrounding environment are fully protected. TOMORROW’S FM | 29

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