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Know how to clear water off your site? Think again

Richard Coulton

New Environment Agency rules for clearing water off sites require contractors to act now to stay compliant, explains Siltbuster’s Richard Coulton.

This month the Environment Agency published a new Regulatory Policy Statement (RPS) entitled Temporary Dewatering of Excavations to Surface Water, which potentially has major implications for the disposal of water from sites.

The statement sets out the circumstances under which water can be discharged off site without the need of a Bespoke Discharge Permit from the Environment Agency.

It states that contractors need a bespoke permit if they want to discharge off site into the surrounding environment – be that to surface water, groundwater or coastal / estuaries waters – for anything other than clean water (ie uncontaminated surface runoff, rain or groundwater).

Dewatering guidance explained

In particular, the guidance states that:

The discharge must:

  • Be clean water, for example clear rainwater or infiltrated groundwater which has collected in the bottom of temporary excavations.
  • Not result in water containing fine or coarse suspended solids (silty water) entering surface water.
  • Not last more than three consecutive months (the activity may stop and restart but the clock does not restart); if the activity is likely to go over three consecutive months then a permit must be applied for.
  • Be made to surface water, such as a river, stream or the sea.
  • Have a method statement that minimises the risk of pollution.

The discharge must not:

  • Pollute surface water.
  • Contain any chemical dosing agents, flocculants or coagulants.
  • Be from a site which is contaminated by oil, metals, hydrocarbons, solvents or pesticides or other polluting substances.
  • Result in the spread of non-native invasive species, parasites or disease.
  • Cause flooding from surface water or erosion of the banks or bed of the receiving watercourse.
  • Contain concrete washwater even if it has been treated, or site drainage from surface areas such as haul roads, storage or working areas.
  • Be from a site with naturally elevated concentrations of substances which exceed environmental quality standards.

Before starting work on site, you must:

  • Plan how to minimise the level of contaminants such as silt entering the excavation, and how to dispose of water that enters the excavation.
  • Plan not to use machinery in excavations while dewatering is taking place.
  • Minimise water entering the excavation – for example from rainfall, runoff, groundwater ingress or high water table.
  • Consider using sustainable urban drainage construction methods.

Furthermore the discharge must not take place within 500 m upstream of an Environmentally Sensitive Area.

What does the RPS mean?

The implications for the construction Industry are significant.

Firstly, the management of excess waters on site can no longer be managed on a reactive basis – construction companies must now be proactive.

They must plan how to minimise the level of contaminants from entering excavations, and how to dispose of any waters entering excavations. They must ensure machinery and operatives will not be working in areas where pumping operations are being carried out. And they must plan the management of surface water runoff across the site.

Soils on most sites contain silts and clays, therefore the new guidance means water cannot simply be discharged off site.

Most projects are now faced with the challenge of either applying for a Bespoke Permit, with treatment on site, or finding an alternative (and potentially more expensive) disposal route. An example of the latter could be either tankering off site or discharging to a sewer, which requires the prior approval of the local utility company.

The RPS also effectively makes the preparation of a Site Water Management Plan before starting work mandatory for all sites, irrespective of whether a Bespoke Permit is required. For those sites that require a permit, the plan is essential.

The EA wants to see that the contractor has developed a robust water management plan for the site that:

  • Endeavours to minimise the risk and amount of contaminated water generated by isolating clear surface and groundwater as far as possible from the construction activities.
  • Isolates concrete washwater and potentially oil-contaminated water from the rest of the site.
  • Estimates the amount of contaminated water generated and puts in place suitable methods for treating it.
  • Includes contingency plans to cover ‘what if’ scenarios.
  • Demonstrates adequate site operator training and awareness of the environmental issues associated with the risk of waterborne contamination.
  • Documents the procedures in place and provides evidence of compliance with the water quality standards imposed by the Permit.

Get ahead of the game

It is widely known within the industry that obtaining environmental permits can take time and it can be very costly if plant and workers are stood down in the interim.

That’s why it is imperative that contractors at the planning stage think through the best practical options for managing waterborne pollutants on sites and, where applicable, apply for the Bespoke Permit well in advance.

At Siltbuster we have been preparing for this over the past few years through our in-house training courses, as well as giving technical support to those involved in major infrastructure projects.

Complying with these requirements clearly requires planning and a major increase in workload for engineering and environmental departments. It demands specialist knowledge of not only the proposed construction works but also the hydrology and appropriate methods of water treatment.

Dr Richard Coulton is CEO of Siltbuster

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