Fences for friends: managing water, pollution, and amphibians in construction sites

Whether amphibian and reptile fencing are required as a precautionary and good practice measure, or as part of higher-level protection under specific development licence requirements, your onsite pollution prevention strategies will need to be tailored to the relevant site conditions.

To fence or not to fence…

Most construction sites are legally required to plan and implement amphibian and reptile protection mitigation strategies for the duration of their project. These are often implemented using physical barriers to movement, known as amphibian, newt, or reptile fencing.

Fencing may be used on a variety of project sites, such as residential developments, to larger projects such as landfill, quarries, or power stations. It’s also commonly found on linear projects such as pipeline corridors and road building projects due to the nature of their intersecting habitats.

However, fencing and water don’t mix well

One site condition that often presents a challenge in terms of management is the presence of water, and often what to do when an excess is present on, or adjacent to site. The installation of what can be kilometres of an impermeable barrier to water can exacerbate issues with onsite water management. Potential knock-on impacts include excess dirty water in working areas which can result in delays and additional cost.

Therefore, it’s critical that the design of mitigation and site water management is considered simultaneously, and during the early stages of project planning, and certainly before work on site commences.

The key challenges

So, what are the key water management challenges associated with temporary and permanent amphibian and reptile fencing?

• Water permeable ditch crossings may be required which must last the duration of the project or have sufficient longevity for permanent projects with minimal maintenance.

• Pooling of water onsite with no way to drain offsite.

• Control of sediment and soil degradation/erosion.

• Fencing may be required to withstand water pressures during heavy rainfall periods.

So, what do we recommend?

Every site is different and therefore we always recommend that the water management plan be discussed at the design stage of the amphibian and reptile mitigation. Despite the differences, here are some solutions that can be considered:

Water course crossings

1. Dependent on the species to be protected onsite, and the nature of the watercourse, restricting movement may be required while allowing the flow of water. The Flow history should be obtained, and crossings designed based on peak flows.

2. Permanent or higher flows may require a more robust fence using welded wire mesh made from stainless steel. High strength posts driven deeper into the ground may be required to counter high water pressures.

Precipitation and the pooling of water

1. Investigate soil types and conditions before mitigation design to identify potential problem areas.

2. Drainage channels within the site can be used to direct excess offsite, provided adequate silt protection measures are installed. These could be temporary V channels cut into the earth or more permanent drainage such as French drains.

3. Where excess silt is present, this may require dedicated treatment systems (see advice in tips to manage water).

4. The discharge locations should be made up of small hole stainless steel wire mesh between two upright posts.

Maintenance strategy

1. Weather, soil, and hydrological conditions are likely to impact a site, and where mitigation is in place, changing seasons may bring new challenges with regards to maintaining your sites integrity. A maintenance strategy should include regular audits of fence integrity and will likely require a greater number of visits during the wetter months of the year.

2. Other seasonal strategies may include clearing of debris from ditch crossings and openings – likely most prevalent during autumn when leaves are known to clog up watercourses and drainage.

3. A response procedure with a fencing contractor should be established to respond to any failures.

It’s complex, but we can help

The amphibian and reptile species found across the UK are subject to one of three different levels of legal protection, each with varying status within national policies. If you have any questions on this subject and/or would like to know about how we can support your project, please get in touch with Simon Knott at, simon.knott@naturallycompliant.com.