Combined risk assessment for landfill gas and leachate – informing contaminated land reclamation for appropriate construction projects.

Tools

Sagoo, A. ORCID: 0000-0002-9969-0771, Butt, T., Entwistle, J., Akram, H. and Massacci, G., 2019. Combined risk assessment for landfill gas and leachate – informing contaminated land reclamation for appropriate construction projects. In: Sardinia 2019: 17th International Waste Management and Landfill Symposium. Proceedings. Padova, Italy: CISA Publisher. ISBN 9788862650144

Full text not available from this repository.

Abstract

Theoretical Rationale/Background/Introduction

Landfills are one of the most (if not the most) common types of contaminated land, while landfilling is still a predominant waste management option in many countries around the globe, thus new contaminated lands are being generated at a high rate, let alone the ones that are already there as a legacy from the past. On the other hand, decreasing availability of new development sites due to short supply of land, and mounting pressures to preserve the natural environment, communities and pressure groups are demanding not to develop on green-fields. Also, government policies and planning authorities strongly favour developments on brown-fields, i.e. contaminated land regeneration and reclamation, which can also include former landfills. Furthermore, the construction industry, one of the largest, most multi- and inter-disciplinary, is seeing an increasing shift towards landfill redevelopment, as experts in the relevant sectors try to help more businesses and landowners identify real land regeneration opportunities. However, still developers face major obstacles when constructing on former landfill sites.

Among the main challenges to construct on former landfills is that a landfill is such a pollutant-source that can contaminate all the three principal dimensions of the environment which are: water/hydrosphere via leachate; land/lithosphere via leachate and more-or-less degraded waste; and air/atmosphere via landfill gas and leachate vapours – eventually leading to biosphere/life including humans.

Risk assessment and management is a key approach to enable mitigation of risks during the design and construction stages of a development proposed to be built on a contaminated land which has been a landfill. So that appropriate remedial measures are adopted to safeguard constructors who would be working on the former landfill site and users/occupiers who would be occupying the development later on, once constructed and handed over. Since a landfill is a multi-dimensional pollutant source, as stated above, therefore a more integrated and holistic risk assessment is required which can cover risks related to both leachate and gas, together. However, there is fundamental lacking of systematic environmental risk-assessment approaches and tools to assist assessing risks associated with leachate and gas, combined/together, simultaneously, so that a total, overall risk picture of a given landfill can be drawn to inform construction/development projects. This ‘integration’ challenge is what the proposed research torches light upon and from various angles.

Additionally, environmental legislations are increasingly becoming stringent, versatile, inclusive, and integrated. For instance, Directives and regulations regarding Water Framework, Landfill, and Habitat together cover ground-waters, surface-waters, ecological systems, natural habitats, wild fauna and flora. Such a diversity requires risk-assessments be more multi- and inter-disciplinary than ever before. This leads to even greater inconsistency in risk-assessment reports – generally produced by environmental consultants for environmental regulators, who are finding it increasingly more challenging to consistently evaluate risk assessment reports as a part of planning application process. Subsequently, this does not help planning authorities in their decision-making with confidence and yet to the face of wide-ranging stakeholders that whether a proposed construction development is appropriate and safe, and if safe then how safe, on the former landfill site. This requires both landfill gas and leachate are considered together to assess overall risk from a given landfill rather them both being considered completely independent of each as presently is the case.

Thus, there is an escalating need for a more integrated and holistic environmental risk-assessment approaches, even from legislative perspective, let alone that the technical fact that for landfills, gas and leachate related risks need to be considered combined. So that a more holistic and integrated picture can be painted which can more effectively inform a decision-making process on what proposed development can be most suitable and safe for a given contaminated land which has been a landfill.

To meet afore-mentioned multi- and inter-layered challenges via bridging the knowledge-gaps currently existing, it is necessary more than ever before that there is a substantially more inclusive, holistic, integrated, unified/standardized, systematic, sequential and yet user-friendly methodology of environmental risk assessment. Such a methodology should assist environmental consultants to produce risk assessment in a consistent format to ease evaluation by environmental regulators and productively inform planning authorities.

Purpose/Aim:
From the perspective of integration i.e. a risk assessment approach which allows to consider risks from both landfill gas and leachate in one place, this research aims to establish the state-of-the-art and outlines ways forward in view of knowledge-gaps. This ‘combined’ consideration of gas and leachate risks, is investigated along all factors and sub-factors of risk assessment process (from the start to the end), whereas the aimed investigation includes both, computer-aided as well as non-computer-aided approaches.

Design/methodology/approach:
1. Particularly from the perspective of landfills and associated legislative aspects, create an account of all factors and sub-factors which constitute a holistic/integrated risk assessment (process from start to end e.g. all hazards such as carcinogenic and non-carcinogenic; all pathways; all receptor types – biotic and non-biotic; exposure; concentrations; hazard indices; temporal and spatial variations; uncertainty assessment; fate and transport; risk characterisation; and the like).
2. Conduct a systematic review of literature regarding risk assessment approaches (including both computer-aided and non-computer-aided) for landfill gas, and produce a matrix of existing-knowledge and knowledge-gaps covering all factors and sub-factors of full risk assessment process established in 1, above.
3. Repeat 2, above, to produce a similar matrix from the perspective of landfill leachate.
4. Combine matrices of gas and leachate from 2 and 3 to produce an amalgamated matrix, where common and uncommon denominators between gas and leachate are identified in the risk assessment context.
5. The third matrix from 4, above, would also assist to figure out which computer-aided and non-computer-aid approaches of risk assessment for landfill gas and leachate, can and can not produce a complete risk assessment report (covering the whole spectrum from the start to the end) for gas as well as leachate, individually.
6. Based on 4 and 5, it is possible to identify knowledge-gaps more objectively in terms of:
Landfill Gas Risk Assessment,
Landfill Leachate Risk Assessment, and
Combined Risk Assessment of Landfill Gas and Leachate.

Originality/Value/Significance:
Risk assessment approaches for landfill gas and leachate have not been considered together as this research brings out. Furthermore, for the whole risk assessment process (i.e. including all components and sub-components of it), an account of current approaches is produced covering both categories, computer-aided and non-computer-aided. Finally, knowledge-gaps are not only identified but recommendations are also formulated for what and how innovative building blocks of new knowledge can be generated to overcome the identified knowledge-gaps, so that a ‘combined’ risk assessment system (of landfill gas and leachate) can be produced to help the construction industry in contaminated land reclamation and regeneration.
Outputs and outcomes:
This research paves a path for design and development of a more inclusive, holistic, integrated, unified/standardized, systematic, sequential and yet user-friendly methodology of environmental risk assessment in which risks from landfill gas and leachate are established together, in one place and still covering both common as well as uncommon denominators between gas and leachate. Furthermore, this work is to inform a wide range of stakeholders in a number of ways:
Environmental consultants would be more able to induce consistency in their risk assessment reports;
That would enable environmental regulators to evaluate risk assessment reports more effectively and efficiently, and better inform the associated planning authorities;
Planning and other authorities would have more confidence and effectively communicate with wide-ranging stakeholders associated with a proposed development on a former landfill – whereas the associated stakeholders can be both, for and against the proposed development/construction project;
Eventually, this would benefit the construction industry to more confidently prefer brown-fields over green-fields;
Thereby, leading to more possibilities of contaminated land regeneration and reclamation, as government policies advocate (for even wider sustainability and climate change agendas).