Latest News from CQA

Tuesday, 14 March, 2017 - 12:54
Collyweston slate mine produces historic roofing slate

CQA International is proud to announce that mining has now commenced at an historic slate mine in Northamptonshire. CQA International Ltd has assisted with gaining planning permission for the mine, has prepared the designs for the new mine and has carried out associated environmental surveys.

The mine, which operated until the 1960s, has been left dormant ever since due to low demand for the roofing slate. However, due to a massive reduction in reusable reclaimed slate the mine is now deemed viable and CQA International were keen to assist with the reopening of the mine.

But why open a roofing slate mine in Northamptonshire when there is an abundance of cheap and plentiful roofing slate available? Collyweston roofing slate has been used on some of the country’s most iconic buildings and is found on over 2000 listed buildings within the UK. Some of the more well-known buildings to feature Collyweston Slate are the Guildhall in London and Kings College, Cambridge. It is even used on a public building in New York.

Collyweston Slate is produced by extracting the "Log" as it is termed and then subjecting it the elements where freeze thaw action slowly cleaves the individual layers until they are workable by hand. Traditional methods are employed to cleave the slates from the log and dress into a multitude of sizes before being used on a roof.

Several hurdles had to be overcome. First it is quite rare for new mines to open in the UK, so it is not something planning committees are faced with daily. Planning was complicated further as the site was not included in the local Mineral Development Plan and so a special case had to be made. Special measures had to be included to protect any bats which may use adjacent old workings as a roost.

The reopening of the mine is a great boost to traditional crafts in the small Northamptonshire village and will provide a secure source of authentic roofing materials to the benefit of both listed buildings and new constructions into the future.

Tuesday, 14 March, 2017 - 12:46
Secondary Containment costs are one of the single largest costs on most AD Plant developments and can often be greatly reduced

Cost savings of up to £1 Million per development have been identified as being possible across the sector if secondary containment options are investigated at an early stage in plant development.

All too frequently a common misconception is raised, being that concrete must be used for secondary containment systems. While there is no issue with using concrete for secondary containment, it should be the final of 3 options when selecting which containment system to install around your plant from both an environmental and cost perspective.

When undertaking a cost benefit analysis, the 3 options which should be investigated at a site selection stage are:

1 Mineral (engineered clay) containment system

2 Geosynthetic (with of without mineral liner) containment system

3 Concrete containment system

The best way of thinking about containment for your AD Plant is comparing it to how we go about containing waste across the world.

We do not construct landfills from reinforced concrete for very good reason. Firstly it is not impermeable and secondly the cost and environmental impact from doing so would be inordinate!

Household and commercial waste poses a much greater threat to groundwater from leachate than an AD plant presents from digestate and more commonly that not the point raised here is that the digestate poses little risk as it is spread on the land as fertiliser. While being very true, the risk from digestate is that gross discharge to a watercourse of vulnerable aquifer can have disastrous effects, hence its importance and requirement.

While not every site is suitable for a mineral (engineered clay) lining system, more often than not the local drift geology is perfectly suited to inclusion of a mineral liner, or a local source can be used for importing materials. With clay costs potentially being irrelevant if available on site the cost savings start to mount up very quickly.


Cost: The main benefit from a commercial perspective of using a mineral lining system is cost. If available on site these costs are negligible, if imported from a local source then costs can be as little as £2 m3. Add in engineering costs and construction of a mineral liner could be as little as £3-5 m2.

Speed: Mineral lining systems are fast to install. Engineering of up to 1,000 m2 per day is easily achievable.

Durability: Concrete isn't durable. In fact its not impermeable over such a large area as penetrations, joints and cracks all afford weakness to the system.

Indirect Cost Saving: Using a concrete secondary containment system limits the amount of buried pipework so gantries and insulation must be factored into the cost. A mineral liner allows the use of buried pipework systems as the mineral liner can be easily designed to allow fill to be placed above and increase levels where necessary.

Aesthetics: Lets face it the aesthetic appeal of concrete in a rural setting isn't great. A mineral liner should be covered with topsoil and vegetated which provides a great opportunity to both appease planners and the local community. Additionally, if vegetated in non trafficked areas the secondary containment area can even provide additional feed stock for the plant.

Piling: You cant pile through a mineral or geosynthetic clay liner (GCL) is something which frequently gets raised. Piles rely on friction provided by drift geology. Enhancing this medium could even reduce the number and depth of piles required. Even GCL can be piled through with tolerances of less than 6 mm between the pile and the GCL.

Self Healing Properties: Concrete doesn't take well to bangs and knocks. Once damaged repairs can be costly and difficult to undertake. One main advantage of a mineral or GCL liner is that they are self healing. Any small damage will self heal under normal conditions.

To Summarise

With tariffs reducing the need to cut CAPEX has never been greater. If you haven't yet looked at the possibilities of using a mineral or geosynthetic containment system there has never been a better time to do so.

CQA International Ltd are able to advise on all aspects of your containment needs from planning, site investigation, design, Quality Assurance and more. Feel free to contact us on 01782 338979 or email to discuss in further detail.

Monday, 13 March, 2017 - 13:23
3D Visualisation Services

As well as CQA International Ltd offering a full 3D design service, CQA International Ltd are able to offer a comprehensive Visualisation service to bring your plans to life.

Feel free to contact us to discuss requirements

Tuesday, 26 March, 2013 - 22:11
New Appointments at CQA Internatonal Ltd.

Cheltenham based environmental engineering consultant CQA International Ltd. has recently merged with its sister company Containment Quality Associates Ltd.
CQA International Ltd. is pleased to announce the following personnel changes:Andy Hall, formerly Manager of the Baku office, is appointed Director and General Manager, Baku Operations;
Darren Bland is appointed Director and General Manager, UK Operations.
Other senior appointments include Christopher Grew, Senior Engineering Geologist, Bob Stevens, Senior Environmental Engineer and Ismayil Eyvazov, Senior Construction Engineer

Tuesday, 26 March, 2013 - 22:10
CQA completes the first stage of a high tailings dam

CQA International Ltd. has recently completed the starter dam for a tailings storage facility at a gold mine in Azerbaijan. The dam is 40m high and will eventually reach 70m. CQA was responsible for the design and construction supervision, for a fixed fee, within strict time and budget constraints. The contract also included a 6km pipeline route and access road with major cuttings and embankments through mountainous terrain. This work is a continuation of CQA’s previous services in Azerbaijan, which include leach pads, ponds and other infrastructure.