Ty Llwyd Quarry Frequently Asked Questions

What types of waste are in the Quarry?

The types of waste believed to be deposited within the quarry include:

  • Baled jay cloths
  • Plastic reject pens
  • Clay
  • Flattened egg tins
  • General factory & canteen waste
  • Poly Chlorinated Biphenyls (PCBs)
  • Fabrics, paper, card soaked by solvents
  • Plastics
  • Various chemicals

Have Polycholrinated Biphenyls (PCBs) been detected in the samples Environmental Health have taken?

Yes, PCBs have been detected in leachate samples taken by Environmental Health. However, when Environmental Health took four samples of the water that was migrating off site during the recent prolonged wet weather in January 2023, no PCBs were detected in any of the four samples.

What is the purpose of the aeration chamber?

The aeration chamber was designed to take any leachate breakouts from the quarry and woodland site, as well as any groundwater that may be impacted by leachate and naturally agitate it to encourage some of the contaminants to turn into a vapour and therefore improve the quality of the water before it is returned to the ground.

Please note that the aeration chamber also takes a significant amount of clean, surface water from rainfall & from the Quarry cap drainage system. It may also take groundwater that is not impacted by leachate.

Is the aeration chamber working?

A. It appears to be working as planned. Pre and post aeration samples (the point at where the leachate enters the chamber and the point at where it leaves) taken in February 2022, showed that there was an improvement in a number of contaminants between the pre and post aeration sample result. This sampling has recently been repeated.

There was water pooling within the system in January of this year and leachate was spilling into the woodland and leaving the site. Why did this happen?

During December 2022 and January of this year, there was a substantial amount of rainfall which caused the groundwater levels to rise within the quarry.  When this happens, the groundwater pushes up any leachate within the quarry to the surface and it is collected by a series of drains which encourages it to the aeration chamber.
The aeration chamber failed to cope with the amount of surface and groundwater entering the system, this was compounded by blockages from silt and leaves that were being washed into it. As a result, the leachate within the chamber pooled and overtopped resulting in leachate flowing over our land and onto the highway.
Our Environmental Health Officers monitored the situation, took samples of the leachate at the point where it entered the highway and as a precaution positioned temporary hazard tape on the ‘unofficial footpath’ to try to discourage people from entering the area when the leachate was flowing. This incident was reported by the Council to Natural Resources Wales, who are investigating the matter as an incident.  

What were the results of the samples undertaken in January? Should I be concerned?

The samples that were taken in January at the point where the leachate left the site contained low levels of a contaminant called Benzo(b)Fluoranthene.

This is a Polyaromatic Hydrocarbon (PAH), which is typically associated with burning and incomplete combustion. They can also be found in petroleum-based products.

We discussed our sample results with Public Health Wales and from the level of contaminants found, there would be no significant risk to health, however as a precaution, the advice was to keep people away from the leachate as much as possible. 

This, combined with advice from the Council’s insurance risk assessor has driven the decision making for the erection of the fence around the Pantyfynnon woodland site, this way we can ensure that no person comes into contact with the leachate, negating any potential risks.

Is the Ty Llwyd Quarry site classed as contaminated land under Part 2A of the Environmental Protection Act 1990?

No, the site has not been formally determined as Contaminated Land.

Land is legally defined as ‘contaminated land’ where substances are causing or could cause:

  • significant harm to people, property or protected species
  • significant pollution of surface waters (for example lakes and rivers) or groundwater
  • harm to people as a result of radioactivity.

For land to be determined as Contaminated Land, there needs to be:

  • a source of contamination in, on or under the land  which has the potential to cause significant harm to a receptor or significant pollution to controlled waters,
  • a receptor that could be adversely affected by the contaminant,
  • and a pathway/route by which the receptor is or might be affected by a contaminant.

The regulator must prove that there is a ‘contaminant linkage’ between the three elements above, for any site to be formally determined as Contaminated Land.

In 2013, the Council via their specialist contaminated land consultants concluded that the site did not fall under the legal definition of contaminated land.

Due to the presence of leachate breakouts in more recent years, following periods of prolonged wet weather, the Council and their consultants are in the process of gathering sampling data to review this standpoint.

Due to the leachate breakouts only being a seasonal occurrence, sufficient data needs to be gathered to properly inform this process. 

This is likely to take a further 12-18 months to obtain the relevant data before the Council’s consultants are able to risk assess the site and conclude whether the land should fall within the legal definition of contaminated land.

What would happen if the Quarry site was legally determined as Contaminated Land?

If the monitoring indicated that the quarry was causing significant pollution of surface or ground waters or significant harm to people, the Council could formally determine the land as Contaminated Land.

If that was to occur, the Council would either serve a remediation notice on the responsible person(s) (those that deposited the contamination) or if the Council did not have sufficient evidence to be able to identify the responsible person(s) or to properly apportion liability, it is likely they would produce a remediation statement.

Both the notice and the statement would detail what works would be required to break the contaminant linkage/minimise the pollution of controlled waters or reduce the significant harm to health to an acceptable level. 

Does the land have to be determined as Contaminated Land?


The Statutory Guidance states that Part 2A should only be used where no appropriate solution exists and that land contamination can be addressed independently by landowners.

As the landowner, the Council is committed to monitoring and managing the site as it has done since Caerphilly County Borough Council was formed in 1996 and we will continue to do so, even if the site is not determined as Contaminated Land.

If the land was determined as Contaminated Land, who would bear the cost of remediation?

The process of determining liability & apportioning liability (where there are more than one person responsible for a contaminant linkage) is very complex. Because this site was an unregulated, private landfill and we do not hold accurate records of which companies deposited what waste and in what quantities, it could be extremely difficult to determine liability or apportion liability between those potentially responsible. There are also exclusions and financial tests that could also apply to this extremely complicated process.

If the person(s) potentially responsible for the contaminant linkage could not be identified, the linkage is referred to as an ‘orphan linkage’ and this would then fall to the Local Authority to fund the cost of the remediation.

Would the determination of the land as Contaminated Land lead to waste removal from the Quarry site?

No, not necessarily.

The Statutory Guidance states that in deciding what is reasonable, the authority must consider various factors, having particular regard to:

  • the practicality, effectiveness and durability of remediation;
  • the health and environmental impacts of the chosen remedial options;
  • the financial cost which is likely to be involved; and
  • the benefits of remediation regarding the seriousness of the harm or pollution of controlled waters in question.

If remediation was being considered, the Council would have to look at a variety of solutions, including a cost benefit analysis of each option.

NOTE: the remediation option would need to break the contaminate linkage by either removing/minimising the source, pathway or receptor.

I can sometimes smell the leachate from Twyn-gwyn Road & the footpath alongside the woodland site. Is this smell harmful to my health?

Some substances will have a low odour threshold, this means that you will smell it well before it becomes a human health risk.

Simply smelling something does not mean that there is a risk to human health. Our consultants undertook a vapour risk assessment, which concluded that the risk to human health was low to people using the footpath and passing by on the road. 

However, having discussed this with Public Health Wales, they feel it would be beneficial to undertake some vapour monitoring within the area in times of prolonged wet weather, when the leachate is present, to inform the risk assessment going forward.  We will ensure this is carried out.

There was a mention on the ITV News that people were advised not to grow vegetables in their garden - Can I grow vegetables in my garden?

Yes. Caerphilly County Borough Council has not advised residents of Ynysddu that they cannot grow or eat home grown fruits or vegetables.

Why is the woodland being fenced off?

Once the first round of drainage improvement works was completed in 2021, the access to the woodland was fitted with a locked gate, the aeration chamber was fenced off and the corner of the site (close to the footpath) was also fenced off to discourage unauthorised access to the area.

Unfortunately, we have been made aware that a number of people are regularly gaining access to the fenced off woodland site, without permission, despite being repeatedly informed that they should not enter the Council’s land.

As a result, the Council sought advice from  its insurers, who recommended that the site be fully secured with appropriate fencing and signage. The bilingual signs for the site are on order and temporary signs have been installed in the interim.

Will the woodland fencing block of any Rights of Way/footpaths

The formally adopted rights of way/footpaths will remain unaffected and we are currently working with Countryside colleagues on appropriate signage to ensure people know where these are.