• The decomposition of refuse releases liquids.

• The landfill accepts limited volumes of liquid waste for disposal (up to 150 tonnes per year). [RM975261-D(15)].

• Stormwater control systems are required to minimise soil erosion, to prevent sediment contamination, and keep clean stormwater separate from contaminated stormwater and leachate, and to minimise infiltration of water into the landfill.

• The landfill development has been designed to shed water away from the working face and minimise the amount of leachate and prevent contamination of the stormwater system.

• Any stormwater that contacts refuse is assumed to be contaminated and must be kept out of the stormwater system.

• Stormwater from active filling areas is treated as leachate.

• The stormwater system is designed to control stormwater runoff to minimise soil erosion, to minimise leachate generation and to keep clean stormwater separate from stormwater that is generated from the areas that have been landfilled.

• Stormwater is collected through a network of drains sumps and ponds where it is treated before discharge from the SRP3 to York Stream.

• NTRLBU must install and maintain the proposed remedial leachate collection system in accordance with York Valley Landfill Leachate Drainage Platform System, Earthtech Consulting Ltd, revised Plan No. 20 0053 dated Jan 2001. [LINK to Plan] [RM975261-D(17)]

• The leachate control system is designed to: [LMP 3.3]

  • minimise leachate production.

  • be protected from clean stormwater inflow.

  • minimise leachate migration to groundwater and York Stream.

  • maximise collection of leachates produced.

• The leachate is collected through a network of porous and sealed pipes.

• The original (and still existing) leachate and contaminated stormwater system collected leachate from the landfill area at the base of the original valley floor into a leachate collection system.

• A secondary leachate collection system was installed around 2000. The 110mm collection pipeline needs to be flushed and inspected annually using a camera. [MS - Not sure if this is being carried out annually?]

• The buttressing of the front face of the landfill involves the installation of five lower and eight upper monitoring wells. The wells are to be fitted with overflow pipes to prevent leachate levels from rising above a particular height in the monitoring wells, and the overflow pipes connect to a toe manifold pipe to drain leachate to the main collection system. [MS - Need to check this description against the new lower buttress design.]

• Rodding points are provided to the overflow pipes and manifold pipe to enable them to be inspected by camera and flushed out, which must be done annually.

• All leachate collected from the York Valley Landfill must be discharged to the Nelson City sewerage system. [RM975261-C(2)]

• The leachate is gravity piped down to the base of the landfill and into the Nelson City sewerage system.

• All leachate discharges to wastewater must be recorded and reported.

• Discharge to wastewater system is measured by a ‘Ravens Eye’ flowmeter (see location photo below) which provides real-time discharge flowrate readings which are displayed via a SCADA system (see readout photo below).

• The SCADA readings can be viewed 3 ways, mobile app, Floc Shed digital readout and on the NTRLBU office TV.

No stormwater coming in contact with refuse shall be discharged as stormwater but shall be considered leachate and discharged into the leachate collection system.

RM975261V2

All leachate and groundwater collected at the base of Gully 1 of the York Valley Landfill shall be discharged to the Nelson City sewerage system.

RM975261V2

The discharge of municipal solid waste and leachate shall occur only on the area of the site identified as Gully 1, as shown in Plan Number 20/49-02 York Valley Sanitary Landfill Sites, Designated Areas.

RM975261V2

3.3       Leachate Collection

4.5.2    Control of Leachate

[LMP 2023]