Coxhoe Leachate Treatment Plant – Frequently Asked Questions

Plans have been submitted for the construction and operation of a leachate treatment plant and associated infrastructure within Coxhoe, details of which can be found here. Coxhoe Parish Council are liaising with the Strategic Planning Team within the principal authority to bring more information to residents and the opportunity to discuss the plans in more detail.

To deal with misconceptions around the proposal, leachate itself and the treatment process, Durham County Council have released a helpful fact sheet to answer the most frequently asked questions (as below).  Thanks to our County Councillors for sharing this with The Parish Council and concerned residents during the Ordinary Meeting 7th February 2024.

What is the need for a Leachate Treatment Plant?
The main source is from the former Coxhoe East Landfill site. This site was landfilled prior to 1998 and has no basal engineered containment. This type of landfill is commonly known as a dilute and disperse landfill. Landfill leachate is continually being produced and drains into the treatment ponds to the west of Coxhoe East Landfill Site. The reed beds that currently exist in the ponds are not able to sufficiently treat the leachate and therefore we need to improve the way that this is managed to give water quality improvements.

What is Leachate?
Leachate is the liquid that has percolated through waste within landfill sites. As it does so it picks up contaminants which needs management and treatment to prevent environmental harm.
Why can’t Coxhoe East Leachate be tankered away?
Coxhoe East produces 150 – 200m3 per day or 6 – 8 tanker loads, this would cost the Council in excess of £1million per year and is not sustainable along with increased traffic movements and a negative impact on carbon footprint.

What are the benefits of the treatment plant?
The water quality and associated ecology in the treatment ponds and the stream will improve once the discharge is stopped. We have worked with the Environment Agency to develop an acceptable proposal. There will be reduced traffic movements compared with current tankering of leachate from Joint Stocks. All leachate will be managed in house by Durham County Council.

Where will the plant be built?
The plant is proposed to be built adjacent to the Landfill Gas Power Generation Compound, and the Coxhoe Household Waste Recycling Centre, on land that is currently Hawthorne Scrub. This is the location specified in the Environmental Permit.
The nearest residential area to the plant will be 550 meters away at Lime Close.

What about the scrub land?
The scrub will be removed however the planning requirements mean we must prove biodiversity net gain – habitat will be created and replaced elsewhere.

Has the Environment Agency given permission?
The existing Environmental Permit allows for Leachate Treatment at the proposed location for the Joint Stocks Phase 2 Landfill, which is just one part of the site. We have applied to the Environment Agency to vary the Environmental Permit to allow all the leachate to be treated from the other leachate sources.

How will the leachate be treated?
The leachate will be stored and treated in sealed tanks that are positioned within a secondary impermeable containment bund. The proposed treatment plant will use biological treatment technology, based upon using microbes and aeration of the leachate similar to the treatment processes used at sewage treatment works.

What will the Leachate Treatment Plant look like?
The proposed plant will consist of a main treatment tank, two storage / balancing tanks and a treated leachate discharge tank and associated containers tanks for the housing of equipment and materials. The plant will be below the height of the existing exposed quarry face.

Where will the treated leachate go?
The treated leachate will be discharged to sewer and then on to Northumbrian Water’s Wastewater Treatment Plant for further treatment. This is the same treatment plant where all the domestic sewage goes for treatment.

What currently happens to the leachate?
The leachate from Coxhoe East landfill is treated through a reed bed system in the treatment ponds however these are no longer sufficient despite all efforts to make improvements. The leachate from the other sources is currently stored in enclosed tanks and then tankered off site for treatment and disposal at a third-party treatment facility.

Will there be increased traffic movements?
No – There will be less movements than current as tankers will no longer be required to remove leachate from Joint Stocks.

Which route will the vehicles use?
Vehicles accessing the site will use the current haul road to enter and exit the site. No vehicles will travel through the centre of Coxhoe, Kelloe or Quarrington Hill.

Is the new pond on Joint Stocks a Leachate Pond?
No – The pond constructed in summer 2023 is for surface water storage prior to regulated discharge. This is clean uncontaminated water only stored on site during periods of heavy rainfall. Leachate is currently stored in enclosed bunded tanks prior to collection by tanker.

Will there be noise / odour from the plant?
The treatment tanks associated with the new plant will be fully enclosed to prevent odour emissions. The plants mechanical equipment will be designed to not increase background noise.

What were all the construction works taking place during the summer?
The older part of the Landfill Site was capped and remediated to fully seal the site. All areas of waste are now fully capped and restored to improve environmental performance. Active gas management and extraction is ongoing generating electric for the national grid. The cap is designed to keep landfill gas in and the rainfall out to minimise leachate production. Surface water runoff is attenuated in the new pond.

Are there high levels of ill health in Coxhoe & Kelloe?
Statistical analysis has been undertaken by Public Health and there is NO statistical difference of ill health in Coxhoe and Kelloe compared to the rest of County Durham.