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Dewatering Guidelines Have Major Implications for the Construction Industry

IntroductionConstruction companies looking to discharge water off site need to be more ‘water aware’ at the planning stage of projects or risk wasting both time and money. Under the Environment Agency’s Regulatory Policy Statement companies now must have a plan in place for disposing of water, distinguishing between excess water due to rainfall and water that results from construction processes.

Read on to find out more about the how The Environment Agency’s ‘Temporary Dewatering of Excavations to Surface Water’ statement will affect you….

Environmental GuidanceThe Environment Agency’s regulatory position statement (RPS) reaffirms that all contractors must have a Bespoke Permit to discharge anything other than clean water off site into the surrounding environment.

Given that most UK soils contain silts or clays, almost all construction projects could potentially generate unclean wastewater and so, will need plans to either treat the wastewater on-site, or find an alternative, and often more expensive, disposal route. Tankering or discharge to sewer are common alternative disposal methods, but both are costly and the sewer route requires prior approval from the local utility company.

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When Are Permits Necessary?Bespoke Discharge Permits have always been mandatory if the water being released is from land or groundwater that is known to be contaminated, or from any form of quarrying activity. However, outside of this, there have been some areas that were open to an individual’s interpretation. This is no longer the case, with the RPS providing specific directions for contractors on site.

The Discharge Must: • Be clean water. As an example, this could be clear

rainwater or infiltrated groundwater which has collected in the bottom of temporary excavations.

• Not result in water containing fine or coarse suspended solids, i.e. silty water, entering surface water.

• Not last more than three consecutive months. If the activity stops and then restarts at a later date, the clock continues from that point.

• Be made to surface water, such as rivers, streams 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 contaminated by oil, metals,

hydrocarbons, solvents, pesticides or any other form of polluting substance.

• Result in the spread of non-native invasive species, parasites or disease.

• Cause flooding from surface water.• Erode the banks or bed of the receiving

watercourse.• Contain concrete wash water, even after it has

been successfully treated.• Include site drainage from surface areas, such as

haul roads, storage or working areas.• Come from a site with naturally elevated

concentrations of substances which exceed environmental quality standards.

Before Work StartsAny construction work that companies predict will not meet the criteria outlined in the Environment Agency’s RPS (almost all projects), need to have a Bespoke Discharge Permit as an absolute necessity. This means that contractors are going to need to be more aware of the ramifications of their projects and be better placed within their own preparations before ever stepping foot on site.

Companies that require a permit, will now have to show, at the planning stage, that there are detailed plans in place to minimise the level of contaminants, such as silt, entering the excavation. They must be able to showcase their intent to reduce the level of water entering the excavation, no matter whether this is via rainfall, runoff, groundwater ingress or a high-water table, and then explain how any water collected on-site is to be safely discharged. In addition to this, they must ensure that discharge does not take place within 500m upstream of any Environmentally Sensitive Area.

On top of this, the latest statement necessitates that there are plans in place to ensure that programme machinery is not used in areas where pumping operations are to be carried out, preventing extreme solids loading caused by machinery movement. Finally, contractors must have considered the use of sustainable urban drainage methods, designed to manage the drainage of surface water in the urban environment.

Dewatering Guidelines

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IntroductionDewatering Guidelines

What Does This Mean?The implications for the UK construction industry are very significant. The Environment Agency’s statement means that contractors need to be better prepared than ever, forcing them to be more proactive in their thinking and planning around the management of excess waters on-site. • The procedure of obtaining a Bespoke Discharge

Permit can be both timely and costly, especially if one is urgently required on an active site, where work has had to stop due to rainfall.

• This process is not one to be rushed through and clear plans need to be set in place before any permits are granted.

• It is cost effective and time efficient to consider all potential issues before the work begins.

• Thinking about the best practical options for managing the wastewater on-site before the planning stage, and obtaining the relevant permits before the job begins, will allow the project to run smoothly, with no disruption.

As a collective, the construction industry will have to be more responsive to the notion of discharging water and in turn, become more educated on the subject.

Those in charge of sites will need to be able to distinguish between excess water due to rainfall and excess water which has been derived from any manner of construction processes. For example, just the simple task of washing down concrete lorries after they have been on-site, produces alkaline waste waters registering up to 13 pH, or the same as oven cleaner, which if released back into the natural watercourses untreated will damage ecosystems and kill aquatic life.

In addition to recognising the various types of excess water the RPS makes it imperative that decision-makers can determine the correct water treatment solution prior to pumping.

It also suggests that the use of low tech solutions when discharging to surface water, such as Floc Blocks, is riskier than ever, as the RPS now demands no carry over of any chemical dosing agents, such as flocculants or coagulants.

Dewatering Guidelines

Dewatering Guidelines

Planning is ParamountThe Environment Agency’s RPS effectively makes the preparation of a Site Water Management Plan prior to commencing work mandatory, no matter if a Bespoke Discharge Permit is required or not. For those sites that require a permit, a clear and well-thought-out plan is essential, not only to guarantee a permit is granted, but also to ensure the smooth running of a project once work commences.

In order to be granted a permit, contractors need to show the Environment Agency that they have developed a robust water management plan for the site.

The plan must:• Endeavour to minimise risk and the amount of

contaminated water generated by isolating clear surface and groundwater as far as possible from the construction activities.

• Isolate concrete wash water and any potentially oil contaminated water from the rest of the site.

• Estimate the amount of contaminated water that will be generated and put in place suitable methods for treating it.

• Include contingency plans to cover the scenarios that are unlikely, but still possible.

• Demonstrate adequate site operator training and awareness of the environmental issues associated with the risk of waterborne contamination.

• Document the procedures put in place and provide evidence of compliance regarding the water quality standards imposed by the Permit.

ConclusionThe update of the Environment Agency’s Regulatory Policy Statement is a welcome reinforcement that wastewater needs to be taken more seriously by construction companies and proves that it has never been more important to understand the control and management of surface water runoff and excess water. It also shows that with some preparation and efficient planning, it can be guaranteed that only clean water is released back into the natural environment.

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

Next StepsSiltbuster has been actively preparing the industry for this moment for a number of years through its inhouse training courses, which have been attended by over 5,000 delegates to date. It also provides technical support to those involved in infrastructure projects, including the preparation of Site Water Management Plans. Added to this, its equipment, whether hired or purchased, has been treating wastewater on constructions sites all over the world for almost 20 years. To make sure your project does not fall foul of the new guidelines, book a place on the ‘Prevention of Pollution on Construction Sites’ Siltbuster CPD accredited course. Alternatively to arrange a bespoke technical training day tailored to a specific site get in touch with Siltbuster by phone or via the website.

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