Increasing public pressure to keep our waterways clean, and higher financial penalties for offenders means it’s never been more important to understand your responsibilities during the construction phase of your development. Each project will have its own unique challenges, Naturally Compliant Director Simon Knott shares his top tips to successful onsite surface water management, regardless of your projects scale.
What is a Pollution Prevention Plan?
A Pollution Prevention Plan (PPP) that complies with local regulations will be a comprehensive strategy that minimises or prevents the release of pollutants into the natural environment. It involves assessing pollution sources, setting prevention goals, implementing strategies to prevent pollution at its source, complying with regulations, monitoring progress, and engaging stakeholders. PPPs aim to create a sustainable and responsible approach to reducing environmental impact caused by human activities.
Plan for success
As with most things on a construction site, successfully planning how to manage onsite water requires plenty of thought before breaking ground. A good plan will include the following steps and therefore address your statutory obligations.
1. Know what and where the onsite and near-site water receptors are.
The terminology may change but the themes remain the same. Surface waters are defined as watercourses, rivers, streams, estuaries, lakes and canals. If pollutants from your site reach any of these you are at risk of being fined, so it’s important to know where they are in relation to your scope of works.
2. Keep non-site water away from your construction activities.
This will obviously vary massively depending on the nature of the site, but isolating your activities from any pre-construction surface flows should be included in your plan. These can include impermeable bunds, upslope cut off drains, or a mixture of the two. However, the water you stop moving over your site will need to go somewhere, so plan to move the water across your site in a way that it remains uncontaminated. Tying your pre-construction drainage into existing watercourses is one way of achieving this, provided the pre con drainage is isolated from your “dirty” construction water and all statutory paperwork and commitments are observed.
3. Keep clean water clean
Contaminated, or polluted water needs to be treated onsite prior to being released back into the natural water environment. Typical contamination includes excess silt, but can also include chemicals used on site etc. If there is uncontaminated water on your site, try and keep it that way (see next steps?).
Broadly speaking, reducing the volume of contaminated water reduces the associated costs of treating it.
4. Utilise multiple discharge points and keep them as far away as is practical from the natural water environment.
In the UK, it rains, a lot! This means that even though you have installed measures to stop water flowing onto your site, it’s very likely that the project will have to treat any additional water that falls onto it. Where possible, its preferable to install multiple discharge points to treat surface flow close to the pollution source. This means you are treating smaller volumes at each location and discharging the treated water over a larger area.
As mentioned above, surface waters or the natural water environment are your receptors, try to discharge your treated water as far as possible from these to reduce the risk of pollution and/or contamination. If this isn’t possible, robust treatment measures will be required.
5. Slow silt laden site water down
Reducing kinetic energy in silt laden waters allows sediments to settle more effectively. This is commonly achieved through check dams and settlement ponds within your treatment systems. Shallow ponds are more efficient at removing sediment from water than deeper ponds, it’s therefore important to understand the difference between attenuating water for flood prevention and using settlement ponds to treat silt laden water.
6. Over compensate and maintain
It’s better to overestimate the volume of water a treatment system will need to deal with as it gives the system a better chance to cope with any unexpectedly large downpours or other climatic variables, such as significant snow melt or precipitation falling on baked earth which can lead to an initial increase in surface flow.
The treatment systems are there to remove pollutants and can become overwhelmed, so it’s critical to maintain the systems so they remain effective.
Finally, managing water comes with a cost, be it the area required for gravity treatment, the cost of pumps and treatment equipment, or the cost to your programme to attain the necessary consents. Recognising these costs in the tender process gives the project the best chance of staying complaint.
Naturally Compliant has a strong track record of developing water management and pollution prevention plans to meet the needs of a variety of projects. For more information on successful water management planning, please contact Simon Knott at, simon.knott@naturallycompliant.com.