Epping bluestone quarry remediation

The brief

Before its closure, the total size of the quarry was approximately 74 acres. Since closure, much of the land has been transformed with commercial developments.

One 60,000sqm portion of the quarry has remained vacant over the decades and the land was progressively contaminated by illegal dumping. The current landowner decided to proactively remediate the site. IES was engaged by the property developer to remediate 70,000 cubic metres of soil, remove soil containing contaminants, remediate asbestos containing materials and inert waste streams.

Execution

Due to the heavy equipment required to complete the job and because onsite vegetation was to be removed, a mob of 15 kangaroos needed to be relocated prior to commencing. Long term, relocation was essential for the wildlife as the land was surrounded by buildings, a busy road and earmarked for future development. A wildlife expert was engaged to relocate the animals to an appropriate, safe green open space.

At its deepest level, the original quarry ran to a depth of 12 metres. Once the quarry was no longer viable, it was backfilled approximately 20-30 years ago. While IES was engaged to process materials stockpiled on the surface, the overall depth of the former quarry remained a key consideration. This was due to the unpredictable nature of historical backfilling and the possibility of unidentified waste streams at greater depths. Works completed included:

• Abated asbestos from approximately 40,000m³ of soil. All abated soil was cleared independently and deemed suitable for reuse.
• Recovered asbestos materials were safely transported and disposed at an accredited facility.
• Extracted 10,000 tonnes of rock which was sent to a recycling facility for crushing.
• Screened and crushed an approximate 5,000m³
• of rock for reuse on site. A carpark was constructed on site utilising these materials.
• Excavated and disposed of 3,000 tonnes of Category C soil and 1,800 tonnes of Category D soil.

The exposed excavated surface was impact rolled to prepare a suitable base. The stockpiles of remediated soils were then placed on the base in layers and compacted under geotechnical supervision. This process was repeated until the surface achieved the specified levels. The overall design of the site included a 3° fall to achieve the desired run off flows when it rains. IES also constructed collection pits and a discharge point at the rear of the site to accommodate storm water, this included large spoon drains and rock beaching to ensure erosion was controlled.

The post works surface was then hydro seeded with grass to provide ground cover, help prevent erosion and provide a dust free surface

Outcome

Prior to commencing this project, the Epping quarry site required remediation of 146 separate stockpiles of contaminated materials covered by overgrown grass and vegetation. The site is now ready for development, featuring a flat, contaminant-free grass surface that is protected from erosion and equipped with effective drainage. The project was delivered on time, within budget and met or exceeded all Australian Standards, statutory regulations and guidelines.