We often see ecologists/landowners suggesting the creation of new ponds in respect to BNG projects. The costs however can be considerable in certain circumstances and the number of BNG units created surprisingly not as great as one would imagine. However if the appeal of creating water landscape features is the prime objective BNG can be a useful way to fund this. We recommend advice for both aspects at the earliest stage of planning the project.
Ideally for a BNG-funded pond an environmental team of ecologists, hydrologists, water experts and engineers, planners and landscape designers together with Statutory Metric surveyors, BNG selling agents and planning solicitors is needed to advise on pond and BNG Habitat Bank creation projects.
If considering a pond creation the following checklist may help:
- Planning permission will usually be needed to create a new pond as excavation works usually are involved.
- Is there enough water from the stream, spring, land drains or a borehole to supply the ponds?
- Does it need to be certified by someone for insurance purposes?
- Are there flood prevention measures?
- Habitat Survey – Environmental Audit may be required.
- Any Listed Building Impact.
- Ecological Impact: Great Crested Newts survey, dormice, bat roost, breeding birds, reptiles or badgers, etc may be needed.
- Clean Water – Source water may require testing for flow and quality.
- Flood Risk assessment may be needed.
- Is site within SSSI and SAC impact risk zones?
- Visual impact assessment maybe needed.
- Environmental Impact Assessment maybe needed.
- Drainage Issues – tests and a completed assessment may be required.
- Expert input potentially required for drainage and construction from a water expert, hydrologist, , wastewater expert and engineer.
- Can require input from consultees such as Natural England, Environmental Agency, Conservation Officer etc.
- Potential change of use – agriculture to residential / natural swimming can sometimes be questioned.
- Abstraction of more than 20 cubic metres of water per day will require an ‘abstraction licence’ from the Environment Agency.
- Check the volume of a large pond. A volume of 25,000m3 or more behind an embankment will require Panel Engineer input and design as it will fall under the ‘Reservoirs Act’.
- Test the soil for water-retaining suitability.
- Consider making enhancements to the landscape to help improve flood resilience. A series of scrapes and swales in the area downhill of a large pond could help.
- Excess water could be diverted into this area (by means of an auxiliary spillway) to create wetland areas during a flood event. As these areas fill with water they will attenuate the discharge. They will also provide a different type of habitat which could also improve biodiversity.
- Careful selection of native aquatic and moisture-loving plants is vital to maximise biodiversity and to ensure that the water bodies do not become overgrown.
- Future maintenance – Access for a small excavator/dumper and weed-harvesting machine (such as a ‘Truxor’) could be needed.
- Consider a suitable lining solution such as EPDM if the soil proves to be unsuitable.
- Consider quality, quantity and consistency of the soil.
- Nutrient in the form of nitrate and phosphorus will be a cause of algae growth. If adjoining land drains through field drains that are cut when constructing the pond and not diverted algae blooms will be a possibility.
- Using a ‘bypass interceptor’ to capture potential hydrocarbons and oils from road run-off may be needed.
- Define the most appropriate water source and configure to fill/top-up the pond as required.
- Question whether there will be enough water available during the driest months when there is minimal rainfall and maximum evaporation.
- Gradient – 1:3 maximum (currently too steep). Ensure structure retains water by either compacting a core in the dams with a sheepsfoot roller or waterproofing with a suitable lining membrane such as EPDM if the soil is unsuitable. Enable controlled filling from a suitable water source (and discharge at the opposite end with a separate overflow outlet).
- A silt trap, or series of silt traps (they will look like small ponds), may be required in-line upstream of a large pond so that suspended solids can be captured before they reach the pond. Note that some solids and silts will inevitably pass through the silt traps. The silt traps will need regular maintenance to dig out accumulated deposits.
Install a control system (could be a ‘hatch’ or ‘penstock’) so that water can be diverted around the pond if required – a typical instance when this is required may be because of the threat of flooding/pollution.
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