How we are regulating Hafod Landfill, Wrexham

Why does Hafod landfill site smell?

Landfill operations will always have periodic odours but this should not be a sustained event.  There are two main sources of odours at a landfill site:

• The waste as it is deposited can produce an odour like a household dustbin.
• Gases produced by the degradation of the waste over time.

When waste is disposed of at the site it is done in phases (known as cells).  Once a cell is full of waste it is capped off (sealed) with an impermeable covering. This prevents rainwater getting into the cell and aids the collection of the landfill gas which is produced when the waste starts to break down. 

Landfill gas typically contains methane (approximately 65%) and carbon dioxide (35%) which are not odorous gases. There will typically be a range of other compounds at relatively low concentrations within the landfill gas known as trace gases. These trace gases can contain substances which cause landfill gas to be odorous, such as hydrogen sulphide (H2S).  Hydrogen Sulphide is a trace gas that can cause the 'rotten eggs' smell, it can be smelt at much lower concentrations than the levels that can cause harm. Any gases will have undergone significant dilution by the time they are smelt within the local proximity, and it is very unlikely to impact human health.

Landfill gas odours can be the result of several factors: some of these may be a result of management failures, others are the result of planned and necessary works such as the installation of new gas extraction infrastructure.

Why does the odour come and go?

Odours are the result of complex interactions within the site.  Whether they can be smelt off-site, and where they will be smelt, is often a result of local weather conditions.  If you notice the smell one day but not the next this could be because of a change in temperature, wind speed or direction or a change in atmospheric pressure.  For example, gasses will always move toward an area of lower pressure, as a result we are more likely to experience odours when the atmospheric pressure is low or falling. Similarly, on colder or still days the odours are not dispersed as quickly which means we are more likely to experience odours. 

How do you regulate off-site odour from the landfill?

The permit includes a condition that requires the operator to prevent odour off site or, where that is not possible, to keep it to a minimum.  The operator will describe how it will achieve this in a document called an Odour Management Plan (OMP).  The OMP must be kept up to date and each revision is assessed by our officers to ensure it covers all the key areas of operations in relation to odour management. Officers assess compliance with the odour condition by:

• Verifying the presence, type and intensity of odour in the vicinity of a permitted site,
• Identifying whether the site is the likely source of the odour, and if proven, going on site to determine the causes of any odours and whether the operator is taking appropriate measures to control the odour.

Officers carry out odour investigations (including off-site odour assessments) in accordance with our guidance and by reference to published odour management guidance.

Odour intensity describes the strength of the odour as perceived by an individual officer. We record odour intensity using a scale of 0 to 6, where 0 = no odour, 3 = distinct odour and 6 = extremely strong odour. A permit breach will only be recorded where:

• Odour due to activities on the site at a level likely to cause pollution outside the site boundary is substantiated by an officer, and
• The operator is not taking all appropriate measures to control that odour.

If the operator is taking appropriate measures, then no breach of the permit has occurred, even if there is some odour. We would expect the operator to identify appropriate measures in its OMP, but we may require additional measures if serious odour pollution occurs.

The operator is informed about any odour reports we receive that relate to the site, but we do not release personal data, so they cannot identify individual reporters. The operator is expected to respond to reports of odour in accordance with its OMP for the site, and to advise us of any resulting changes to operations.

Is the smell harmful to health?

Whenever people are concerned about their personal health, they should visit their General Practitioner (GP) or contact NHS Direct on 111 or Home - NHS Wales

How we assess compliance

It is our role to assess compliance with the permits and to take appropriate regulatory action if we identify any breaches.  We do so by reference to our enforcement and prosecutions policy, and with appropriate regard to the Regulators' Code.

Our regulatory team assess compliance with the permit conditions at Hafod Landfill in several ways including site inspection, audit, off-site odour assessments, and review of reports and monitoring data.

We charge all permit-holders subsistence fees, which cover the cost of these routine regulatory activities. Subsistence fees do not cover provision of a constant officer presence on any permitted site.

A Compliance Assessment Report (CAR) is used to record the findings of our site inspections, audits and monitoring activities, reviews of monitoring and other data/reports. We use our guidance on assessing and scoring environmental permit compliance to score permit breaches in accordance with our Compliance Classification Scheme (CCS). The risk category and score we give a non-compliance reflects the potential impact it could have if it were not addressed promptly and adequately. The only exception is for non-compliances relating to amenity conditions - odour, dust, noise and pests. We categorise the risk and score these according to their actual (rather than potential) impact. There are 4 risk categories of non-compliance. Each risk category is scored. The scores are accumulated during the compliance year. Further information about how we score permit breaches, and how this impacts on the sites annual subsistence fees is set out in our guidance on our charging schemes. 

When is the site due to complete operations and close permanently?

Waste was first taken on 23/08/06. However, the development commenced on 07/04/00 when work began on the building out accessways, concrete bases etc. 

Therefore, North Wales Minerals and Waste Planning Service consider the end of landfill would be 07/04/55, being 55 years from the commencement of the development.