Find out what borehole monitoring and attenuation layers information you must include in your construction quality assurance (CQA) plan.
If you want to apply for a bespoke permit to carry out waste recovery to land, you’ll need to carry out a risk assessment to support your application.
Your risk assessment may show that you need to do engineering work to:
- protect the environment from your activity
- monitor changes to the environment as a result of your activity
For example, you may need to build an attenuation layer across the base and sides of the recovery site to protect soil and water. You may also need to install boreholes in the wastes you deposit to monitor for soil gas or to monitor groundwater.
You must agree your construction proposals with the Environment Agency before you start work. The Environment Agency will normally accept a single set of construction proposals to cover an attenuation layer for the whole site.
If the Environment Agency gives you a permit, you must then submit detailed construction proposals and a construction quality assurance (CQA) plan to your local Environment Agency office at least 4 weeks before starting work.
Construction quality assurance plan contents
Your CQA plan must specify which codes of practice and guidance you plan to follow.
It must also show how you’ll make sure that you use suitable materials to construct the attenuation layer and any monitoring infrastructure.
Your CQA plan must include certain information.
CQA plan information
You CQA plan must show this information:
- the design of the engineered attenuation layer
- a method statement for the construction and placement of the attenuation layer
- criteria you will use for rejecting any materials not suitable for the attenuation layer
- how specific design criteria are to be assessed with clearly defined acceptable limits
CQA plan details
Your CQA plan must include details of:
- the records to be kept and methods of reporting
- the surface water drainage system
- groundwater monitoring boreholes
- gas monitoring boreholes
- permeability testing at a minimum frequency of 4 tests per hectare for sites over a principal aquifer (the CQA engineer must carry out these tests)
- your field trial to verify the construction method and demonstrate the thickness and equivalent performance of the attenuation layer
CQA plan guarantees
Your plan must show how you’ll:
- achieve and check the geotechnical properties of materials you’ll use
- achieve and check the shape and size of the structure you’re building
- train site staff on the requirements of the CQA plan, including record keeping and procedures for selecting site-specific material
- record compliance with the construction method so that the CQA engineer or inspector can audit the records
- use CQA procedures to make sure that any material used in the attenuation layer is physically and chemically suitable
Using waste in your construction works
You must only use materials that can achieve the construction and placement of the attenuation layer when you follow your CQA method statement.
If you’re going to use waste in your construction works, you must confirm that it’s chemically and physically suitable by:
- making sure that the waste is from a single source or of a single waste type
- making sure it meets the definition of inert waste
- using suitable cohesive material in the attenuation layer (you must test this waste as part of your material assessment)
- confirming that the attenuation material won’t leach non-hazardous pollutants into groundwater
- including evidence that the material contains no hazardous substances at sites over a principal aquifer or below the water table
The Environment Agency requires different levels of CQA supervision depending on if your site is a secondary or principal aquifer.
Secondary aquifer site
The CQA engineer must carry out 1 visit per 10,000 cubic metres of attenuation material laid, or 1 visit for each 2 weeks of engineering works.
Principal aquifer site
The CQA engineer must carry out 1 visit per 5,000 cubic metres of attenuation material laid or 1 visit for each week of engineering works.
The CQA engineer must be appropriately qualified and have at least 6 months’ experience of earthworks on landfill or recovery sites.
An appropriate qualification is a formal qualification in science or engineering. For example, an OND or ONC or higher in civil engineering, mining engineering, engineering geology, building, quantity surveying or science with training in soil mechanics.
The engineer must be supervised by a chartered engineer or geologist with more than 5 years’ experience.
You must keep records at the site of all construction activities. Include all of the following:
- photographs of the works
- a site diary maintained by site staff showing works carried out, CQA visits, non-conformance and remedial actions
- the identity (source, quantity, dates of delivery) of all material used in the attenuation layer
- the results of any chemical testing on attenuation layer material
- dates and times when the attenuation layer was constructed
- details of any unsuitable materials including source of material, reasons it was considered unsuitable and action taken
- the progressive construction of the attenuation layer, marked on a plan
- thickness of the layer as placed, either by records of the location and depth of the trial pits or isopachyte survey plans
The validation report confirms that your construction method has produced an attenuation layer, or other infrastructure, that meets the required standards.
Your validation report must include certain information.
Validation report records
Your validation report must provide:
- records showing that you placed the specified thickness of attenuation layer
- records showing you used physically and chemically suitable material to construct the attenuation layer
- details showing you’ve followed the construction method and CQA procedures set out in the CQA plan
- records of periodic visual inspections by CQA staff
- records of any problems or non-conformance and the solution you applied
- copies of the site engineer’s daily records
Validation report results
Your validation report must show:
- the results of any specific post-acceptance testing on attenuation layer material to demonstrate suitability
- the results of any conformance testing and field trials on attenuation layer material to demonstrate suitability
- validation by a qualified person that the construction was carried out in accordance with the agreed construction proposals
- details of any unsuitable materials, including source of material, the reasons it was considered unsuitable and action you took
- any other site-specific information to prove the integrity of the construction
Validation report details
Your validation report must show:
- details of how you complied with the CQA plan
- justifications for any changes or deviations from the agreed plan
- a site plan showing progressive layer construction
- dates and times of attenuation layer construction
- ‘as-built’ plans and sections of the works
- plans showing the location of all tests
A chartered civil engineer or geologist must sign the validation report.
Send the validation report to your local Environment Agency office when the work is complete.