Pennant Hills Groundwater Barrier Wall

The project consisted of construction of a high rise residential development in Pennant Hills, NSW at 2-6 Trebor Road with basement close by to a nearby Shell petrol station. Over the years the station has contaminated the ground between Trebor Rd and Fisher avenue with hydrocarbons.

ERM were awarded the project on behalf of VIVA to prevent the future contamination of hydrocarbon into the development and to also remediate the site, removing all contaminated materials prior to the commencement of the development.

Cut-off wall

The ground conditions consisted of stiff clay overlaying shale bedrock.

Menard Oceania were appointed by ERM to provide a design & construct solution for a groundwater barrier wall at the South East boundary of 2-6 Trebor Road, Pennant Hills development site. The barrier wall scope had been defined by ERM as a 600mm wide, 11m deep wall, 85m long, with a proposed permeability of 1×10-9 m/s.

The barrier wall system consisted of a Soil Bentonite cut off wall (SB wall) within the overlying clay layer combined with a grout curtain within the underlying rock (shale).

Material between the proposed barrier wall and the proposed basement wall (1m width) would be removed prior to the barrier wall installation and replaced with stabilised sand. The rock mass in this zone was also grouted to reduce the ground water flow underneath the barrier wall.

The works were carried out successfully, without any incident and 17 days ahead of schedule – with Menard receiving a HSSE award from VIVA for their significant contribution within the Viva Energy Australia Environmental Program.


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