An Innovative Approach to Containing Contaminated Groundwater

Helia EHS is managing the environmental issues associated with a former quarry which was subsequently utilised as a municipal landfill. Historically, unlined landfills receiving mixed household and industrial waste can lead to the uncontrolled release of contamination via various media (soil, air, water). A key challenge of these legacy landfills is the management of leachate, a contaminated liquid that is generated as the waste degrades.

Leachate management is a complex issue which requires an understanding of hydrogeological conditions so appropriate controls can be implemented to prevent contamination to groundwater. Helia EHS has conducted comprehensive modelling and pumping trials to design a leachate management system appropriate for this site. The investigations have led to the development of a groundwater interception system, as pumping leachate directly from the landfill was impractical and costly.   

The Issue:

The purpose of the system is to extract groundwater at the site boundary, via a series of extraction wells. The overarching objective of the leachate management system is to create an inward gradient of groundwater back toward the site boundary to prevent leachate contaminated groundwater moving from the site.

Key steps in the Leachate Management Process:  

1. Understand the clients licence compliance requirements
2. Perform pump trials within the waste and outside the waste to determine an appropriate and feasible approach which will achieve the best outcome for the environment and the client
3. Install the extraction bores and commission pumps
4. Develop a monitoring program to assess the effectiveness of the interception system
5. Interpret and collate the data which has been collected, compare to the modelled data
6. Refine the system to achieve the required drawdown with the lowest flow rates, reducing extraction and disposal fees
7. Make recommendations to the client on the efficiency and long term sustainability of the interception system  

How did we do it?

The Contaminated Land Management (CLM) team considered multiple remediation options and performed various trials and hydrogeological modelling, in order to effectively control the migration of leachate impacted groundwater from the Site. The success of the interception system is reflective of a collaborative approach between industry experts and stakeholder engagement with land holders, the client, various regulators, and internal experts.

The Result:

• Client satisfaction
• Early stakeholder engagement avoided potential delays
• Long term strategic thinking to deliver a tailored solution
• Demonstration of technical expertise
• Improvement to the quality of groundwater at and surrounding the site
• Successful leachate management achieved through strategic thinking

Ultimately, the investigation has proven to be effective in the management of leachate on site.

Kate Sims

Environmental Scientist – Contaminated Land Management

If you want to know more on how we can help, contact me here or visit our website.