Secondary containment at Environment Agency permitted anaerobic digestion facilities

The Environment Agency (EA) has provided updates to its guidance and standard rules environmental permit sets for anaerobic digestion (AD) facilities. This introduces changes to the requirements for secondary containment for sites regulated under the Environmental Permitting Regulations. This briefing note provides an overview of the changes to assist operators in understanding how the changes affect their compliance obligations.

Standard rules

In December 2021, the existing set of standard rules environmental permits for AD facilities were replaced. Whereas the previous set of standard rules environmental permits stated that potentially polluting liquids should be provided with secondary containment ‘unless the operator has used other appropriate measures…’, the new standard rules environmental permit sets state that all tanks and containers must be provided with secondary containment complying with CIRIA 736 guidance.

Operators of standard rules permitted facilities were migrated to the new standard rules environmental permit sets as of 20th March 2022 and are required to comply with the conditions. As there is no flexibility in the conditions of the standard rules environmental permit sets, those sites not benefiting from secondary containment must:

• Install secondary containment;
• Vary their environmental permit to become a bespoke environmental permit; or
• Surrender their environmental permit.

Bespoke permitted facilities

The EA has concluded consultation on its proposed Appropriate Measures for the Biological Treatment of Waste guidance. Publication is expected soon despite being initially intended for late summer 2021.

Similar to the new standard rules environmental permit sets, the July 2020 draft guidance states that all liquid based waste and digestate must be stored in tanks provided with secondary containment complying with CIRIA 736 standards.

In its July 2021 consultation response document, the EA states:

‘…the requirement to ensure secondary containment to CIRIA 736 standards applies to new sites. Existing facilities… are unlikely to be designed and built to a CIRIA 736 specification. In such cases we expect operators to evaluate primary and secondary containment to ensure it is fit for purpose and use alternative means to achieve an equivalent standard. All sites must be assessed by a chartered engineer.’

Accordingly, all existing facilities will be required to review their containment arrangements to ensure that CIRIA 736 or an equivalent level of protection is provided.

Should you require support with undertaking a review of your containment arrangements, SLR can help. SLR was the lead author of the CIRIA 736 guidance and has chartered engineers experienced in undertaking reviews of containment arrangements.

SLR can:

• Review secondary containment arrangements;
• Risk assess alternative arrangements and equivalency to CIRIA 736 standards;
• Prepare environmental permit applications; and
• Provide compliance support and regulator liaison services;

If you require further advice, then please contact us.