Landfill Construction

Solid Waste Industry Construction

HG Leach and Company moved into contracting as a natural adjunct to its quarrying activities. Quarrying and earthworks have a logical fit, with skills learned from one discipline constantly being applied to the other. HG Leach currently concentrates its contracting efforts on waste industry projects, such as:

  • Landfill construction
  • Landfill closure works
  • Landfill remediation works
  • Landfill gas collection and destruction works
  • Leachate collection and treatment facilities

These types of waste industry sites present a range of challenges and hazards that require specialist knowledge. The company also undertakes:

  • Bulk earthworks
  • Site rehabilitation works
  • Minor earthworks, roading and drainage works
  • Quarry stripping and rehabilitation.

H.G. Leach & Co. has built the following major state-of-the-art modern landfills in New Zealand, all built to the highest specifications, including composite lining, leachate and gas collection systems:

H.G. Leach & Co. has built the Naboro Landfill, Suva, Fiji for the Department of Environment, Government of Fiji. The Naboro Landfill is a Class A Landfill, built to the highest specification, including composite lining, leachate collection and treatment facilities. Naboro is the only modern, high-standard landfill in the South East Pacific islands. The Naboro Landfill is operated by HG Leach (Fiji) Ltd.

H.G. Leach & Co. has built landfill gas collection and destruction systems at the following landfills in New Zealand:

Silverstream Landfill Construction


Silverstream Landfill start of construction – 2006


Silverstream Landfill end of construction – 2008

The contract comprised construction of formation and lining works. The work included:

  • Site clearance and excavation of unsuitable material for the
 side slopes of the new landfill
  • Construction and maintenance of sediment control measures
  • Disposal of unsuitable material
  • Bulk earthworks for the formation of the sides slopes
  • Groundwater drainage construction
  • Placement of backfill material for the formation of the base
 and side slopes
  • Disposal of surplus material
  • Excavation of suitable material from designated borrow areas
 for backfill and liner requirements for the base and side slopes
  • Placement of soil liner components on base and side slopes
  • Supply and installation of geosynthetic liner components
 on the base and side slopes
  • Leachate diversion works
  • Leachate drainage works
  • Construction of a temporary toe bund and associated works
  • Construction of access road

Total volume of earthworks: 135,000 cubic metres

Geogrid rockfill walls: 2,700 square metres

HDPE landfill liner: 22,000 square metres

600mm compacted clay liners: 18,000 square metres

Non fines concrete walls overlain by synthetic liners: 
1,800 sqm

Landfill drainage blankets 500 mm thick: 8,000 square metres

“Contracting is all about skill – and the ability to adapt to whatever challenges a site throws out. Innovation, flexibility and environmental sensitivity are vital if a contracting company is to be effective.”

HG Leach has specific experience in dealing with the challenges associated with contracting in the waste industry.  Hazards are found in this industry which make specialist contracting vital to a successful outcome.

These hazards can include:

  • High depth of refuse requiring rework
  • Unstable underfoot conditions resulting in plant or vehicles overturning
  • Safety issues working near heavy plant and machinery
  • Release of landfill gases – especially methane
  • Contaminated water / leachate
  • Fire risk working on a landfill
  • Dangerous materials in the landfill which can cause injury, odour, vermin, hepatitis and tetanus risks
  • Excavation in water
  • Excavation greater than 1.5 metres deep – OSH notification.

The company incorporates its Health and Safety System into all works, and each site is managed according to the Health and Safety Plan to ensure a safe work place.

Keeping it clean

Environmental responsibility is at the forefront of every HG Leach operation, including contracting. To ensure all HG Leach contracting works meet environmental requirements, the company also undertakes all its contracting works in compliance with:

  • The Resource Management Act
  • The Conditions of Consent for the site
  • Contract specifications.

The company prides itself on effective project management and quality assurance procedures, ensuring the environmental protections that clients seek are achieved on time and to budget.