RSK Biocensus Technical Director and Aquatic Ecology Lead Dr Peter Walker draws on case study experience to illustrate the benefits of planning ahead

Aquatic ecology might not be the first thing than springs to mind in considering large rail infrastructure projects but factoring in this habitat at the start of project planning offers considerable benefits – informing impact assessments and mitigation and, crucially, avoiding costly delays.

During my time as an aquatic ecological consultant, I have worked in every type of UK freshwater (and marine) environment and several locations abroad. This includes rivers and streams, canals and ditches, ponds, lakes, reservoirs, estuaries and intertidal areas and coastal and offshore waters.

A notable number of these projects involved the rail industry. These ranged from small-scale repair works on culverts to monitoring sea defence improvements or large-scale baseline ecology data gathering for larger infrastructure projects such as Rail Central or HS2 to help inform impact assessments and mitigation.

I am committed to applying this experience to identify key considerations with respect to aquatic ecology which may help with future rail project planning and avoid unnecessary delays, reduce the risk of falling foul of the law and, hopefully, help protect and conserve our diverse and valuable aquatic habitats and the organisms residing within them.

From the offset, it is important to understand the relevant legislation. Some species and habitats are protected by the Wildlife and Countryside Act or the Conservation of Habitats and Species Regulations. The Salmon and Freshwater Fisheries Act makes it an offence to disturb or damage spawning areas or spawning fish and the Eels (England and Wales) Regulations are in place to help this species complete its life cycle by improving opportunities for eels to navigate through river systems and preventing them being entrained into water abstractions.

The Water Framework Directive is likely to require a detailed assessment if any proposed activities might cause a deterioration in (or prevent future improvements to) water quality, habitat quality or connectivity or adversely affect species within a watercourse. This includes aquatic invertebrates, fish aquatic plants and diatoms for example. If you’re unsure as to whether your proposed works / activities may impact aquatic life, you should consult an (aquatic) ecology specialist early in the process, much the same as you would for terrestrial ecology considerations such as bats, badgers or great crested newts.

With rail projects, more often than not it is linear waterbodies such as streams, rivers and ditches that are affected. However, stillwaters such as ponds, lakes and reservoirs should be considered if they are close to and could potentially be affected by works. Similarly estuaries and coastal areas require consideration.

In addition to the habitats, it’s often necessary to consider individual species or groups of species, the potential impacts on them and the mitigation that can be employed. Some species that are specifically protected include white-clawed crayfish, freshwater pearl mussel and, in some waterbodies, fish species such as Atlantic salmon or lampreys. It’s also important to understand whether invasive non-native species are present and if the proposed activities at a given site have potential to result in the spread of those species away from the works location, which would be an offence.

So what sort of activities might require aquatic ecology surveys, advice or mitigation? Essentially anything that may affect the physical, chemical or biological components of an aquatic (freshwater, estuarine/brackish or marine (salt water)) environment.

This might include:

  • Physical alterations to a waterbody, watercourse or it’s banks (e.g. Installation of bridge footings, retaining walls, sheet pilings or other in-river structures).
  • Replacing or altering/repairing existing in-river structures (e.g. Culverts or bridges).
  • Temporary or permanent dewatering.
  • Temporary or permanent channel diversions.
  • Undertaking works within a channel, including works to the underside of bridges or culverts which require access from within the channel.
  • Undertaking works which could affect water quality, disturb bankside or in-channel sediment, cause noise or vibrations or artificially illuminate the aquatic environment.
  • Actual pollution incidents (e.g. Fuel or chemical spills, runoff or sewage discharges / leaks).

I’ve highlighted a couple of case studies to illustrate the importance of considering all waterbody types and sizes and of consulting relevant specialists early.

Case study – the honeycomb worm

Works were being undertaken to repair and improve sea defences which protect a railway line running along the coast. The planned works involved large plant and machinery accessing the seashore. RSK aquatic ecologists undertook a Phase 1 habitat survey which identified the presence of Sabellaria sp. (honeycomb worm) colonies at various locations which were at risk of damage from plant operating along the shore.

Sabellaria reefs are protected and so RSK prepared a method statement for the client which enabled works to progress while minimising the risk to the colonies. Monthly monitoring was undertaken to ensure that the works were being undertaken in accordance with the method statement and weren’t causing harm to the Sabellaria colonies.

Case study – fish rescue

As part of ongoing works to create construction storage areas and compounds a moderate-sized pond was being dewatered prior to infilling. The client was not aware of any fish in the pond and had not consulted an aquatic ecologist. During the dewatering process several fish were observed, and all works had to be stopped until a team of aquatic ecologists could be called to the site to undertake a fish rescue and translocation. This took over a week as a receptor pond had to be found for the rescued fish to be released into. The delay to works had additional knock-on effects for other works, affecting other schedules and costing the client time and money.

The case studies highlight that waterbody size can often incorrectly be seen as an indicator of whether or not aquatic ecology is an important consideration. In fact aquatic life, including fish, can be found in very small, very shallow waterbodies, sometimes in just a few centimetres water depth. Furthermore, consulting aquatic ecologists early in the process can save considerable time and money.

The take home messages here are:

  1. Polluting watercourses is an offence.
  2. Causing harm or disturbance to aquatic species or habitats can be an offence.
  3. Size of watercourse / waterbody doesn’t necessarily affect the likelihood of sensitive features or species being present.
  4. If you are planning works at a site that has aquatic features present (including ponds, lakes, streams, rivers, estuaries, the coast etc) and your works have potential to affect those features or organisms within them you should get advice from an experienced aquatic ecologist.
  5. Speak to the relevant specialists early in the project/works planning process to avoid delays once works commence.

Dr Peter Walker is a chartered environmentalist, technical director and aquatic ecology lead at RSK Biocensus. He is also chairman of the Institute of Fisheries Management West Midlands Branch and has held positions at leading academic institutions and rivers trusts.