Beneficial re-use of dredged sediment

Sustainability is an increasingly important and essential topic for all in this modern age. River and marine engineering schemes, where waste may be generated, should involve a strong drive towards a zero to landfill strategy. In this week’s blog, Nikki Maley explores how dredged sediment can be used safely and productively, as well as economically.

It is a legal requirement to apply the waste hierarchy in order of preference: reduce, re-use, recycle/compost, energy recovery, disposal – when considering waste management.

So, with regards to schemes involving dredging operations how can the sediment be re-used safely, productively as well as economically? Firstly, we should ascertain whether the sediment is a ‘waste’.

What is waste?

A material is considered a ‘waste’ when the producer or holder discards it, intends to discard it, or is required to discard it. Reprofiling sediment within a watercourse may therefore not constitute generating waste, as the sediment is not technically being discarded. This could include creating internal high and low spots within the watercourse footprint to improve navigation or for habitat purposes i.e. islands.

When assessing whether a material is waste or not, discarding doesn’t simply mean throwing away or getting rid of something. Discarding also covers activities and operations such as recycling and recovery operations, which put waste material back to good use.

Where dredged sediment is required to be removed from the watercourse, discarded but re-used locally then waste regulations may apply.

Waste Hierarchy | JBA Consulting
Waste Hierarchy

What are the waste regulations?

A site-specific risk assessment should be undertaken to determine the most appropriate management techniques for the re-use of waste. This would involve obtaining a relevant number of sediment samples for a particular test suite, analysing and classifying to determine appropriate suitability based on the localised options available.

The Environmental Permitting Regulations identify an array of specific permits/exemptions to deposit, retain, treat or dispose of waste. For small-scale dredging campaigns the quickest and most economical method of re-using non-hazardous sediment locally is by registering a waste exemption or combination thereof, for example:

· D1- dredge to bank

· U1- use of waste in construction

· U10- spreading waste to benefit agricultural land

· U11- spreading waste to benefit non-agricultural land

For larger-scale projects involving greater tonnages, Standard Rules environmental permits (issued by the EA with specific conditions) can allow the use of mobile plant for landspreading activities resulting in benefits to agriculture or ecological improvement.

Benefits of dredged sediment

Dredged sediment can be very valuable for agricultural improvement as the finer fractions can contain high levels of organic matter, nitrogen, sulphur with useful levels of phosphorus, potassium and magnesium. Dredged sediment can be used to replace the need for artificial fertilisers and improve soil structure.

A benefit statement will be required to assess the potentially toxic elements and nutrient levels within the sediment and field soil system. If deemed suitable, then based on the pre and post cropping regime and existing soil structure, an appropriate spread depth will be determined to provide optimal benefit. Sediment can also be beneficially utilised for ecological and engineering purposes to improve a variety of local land conditions. A permit holder may gain approval for a scheme within 25 working days from the submission date.

An individual writing a benefit statement for the deployment application must have the appropriate technical expertise. The preferred qualification for operations resulting in agricultural benefit is training and certification on the BASIS Fertiliser Advisers Certification and Training Scheme (FACTS). FACTS is an independent non-statutory certification Scheme for advisers in plant nutrient management and has been the body responsible for setting standards, training and accrediting the Continuing Professional Development (CPD) of those providing nutrient management advice. The agricultural industry recognises the importance and benefit of qualified advice to promote farming systems that optimise crop nutrition and protect the quality of soil, water, air and farm biodiversity.

Localised beneficial re-use can therefore prove to be a great option for improving sustainability, supporting local agriculture/ecology, reducing programme length and significantly reducing costs associated with haulage and disposal.

Want to know more?

If you’d like to know more or need any help on a potential re-use project including the production of a benefit statement, please get in touch with Nikki Maley to discuss further.

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