Landfill CQA Actions up to the Start of Construction
Once the landfill design engineer has completed the landfill design and the specification has been substantially completed, it is possible to write the landfill Construction Quality Assurance (CQA) Plan, which the construction contractor will then be required to follow, and which will once completed be reported upon to the environmental regulator.
The end goal is for the environmental regulator to agree that the landfill has been designed to the required high quality standard of construction, and grant the waste management licence, effectively allowing the site to open and start accepting waste materials.
Each CQA programme is specific to the site and the detailed design adopted. It must reflect the unique requirements of the particular liner installation.
The monitoring and tests to be carried out during construction should be appropriate to the materials chosen, and be focussed on the essential requirements for ensuring compliance with the specification, primarily ensuring that re barrier is as low in permeability in use as intended when designed.
However, the importance of liner integrity (or liner failure) at each site will vary according to the results of the site Hydrogeological Risk Assessment (HRA). So, you should base the most detailed checking on the results of the HRA just as the liner design itself will have been chosen to comply with the degree of engineered containment required by the HRA.
So, now that we have explained how site-specific variations can be very important and may change the CQA plan a lot, we shall describe the requirements for a typical CQA programme.
A typical CQA programme is likely to necessarily include the following stages:
- Activities Before Construction, including liaison with the design engineer, a constructability review, preparation of a geomembrane construction specification and a pre-construction meeting with the installation contractor
- Construction Period activities, including monitoring of geosynthetic materials, subgrade, sampling, testing and repairs
- Post-construction activities, including provision of detailed as-built drawings and CQA report.
The stages listed above, before construction are examined in greater detail in the sections which now follow:
Activities Before Construction
The early involvement of the consideration of CQA and availability of materials/constructability within the design/build process is invaluable in ensuring that the installation of the design can be carried out without unnecessary difficulty.
The designer must check that construction can be achieved without compromising design requirements. For example, a clay cap would not be buildable in a part of the world where suitable clay was not available, and there are surprisingly many areas where this is the case.
Construction must also be devised to a programme and working methods to include only those geosynthetic configurations which can be properly monitored within the CQA programme.
The main stages of such a CQA programme are typically:
A review by the CQA engineer to verify that the design methods and construction techniques chosen can be properly constructed and adequately monitored. This stage of the CQA process will typically pay special attention to critical aspects of the design where deficiencies are most likely and the liner (barrier) would be most vulnerable, e.g. liner penetrations, pumping sumps etc.
Geosynthetic CQA Plan
The the CQA engineer prepares this document. In it are set out in detail the tasks of the CQA programme and the essential records and other outputs to be generated by it. Among its other uses, this document is typically used to demonstrate to the local environmental regulating authority the scope and level of CQA to be adopted in order to give them confidence that all necessary checks will have been undertaken.
Geosynthetic Construction Specification
A crucial element in the CQA programme which sets out requirements for both the materials and the workmanship involved in the liner construction. To provide the specification the design engineer will have carried out a detailed selection exercise during which he will have identified the most suitable material for the liner. Once identified these will be worked up in more detail as his detailed requirements for the chosen material in the specification.
Now that the material has been chosen and described, the minimum requirements for fabrication of the selected material into a liner, and the programme of checks must be stated by the engineer. The checks will be devised in a way that ensure that the minimum requirements will complied with.
The key to a really good design will be the extent of close co-operation between the design engineer and the CQA engineer. Both must work together to produce a practical, workable specification.
The idea of this meeting is that it can be a valuable opportunity for the design engineer, CQA engineer and geosynthetic installation contractor to verify that all parties have the same understanding of the specification. If there are any misconceptions found between the members of the team it is important that these are all ironed out and resolved before the work begins and membrane materials arrive on site.
This is as much as we can provide in this article, however, all the aspects of landfill barrier Construction Quality Assurance discussed above must then be followed through at a level of detail equivalent to that seen already, and once the work is complete a compliance report is prepared by the Engineer, which is sent to the environmental regulator for them to grant the permit to work/open the landfill.