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Summary of Stormwater System Requirements

Disclaimer: This procedure guides the operation of YVLF. It is intended as a working document that is improved through operational experience and updated accordingly. Please send updates, changes and comments to landfill@ncc.govt.nz

• All stormwater from the footprint of the landfill must be captured and treated in the sediment retention ponds. [RM975261-A(6)]

• Diversion channels and cut-off drains shall be maintained to minimise the infiltration and run-off of stormwater onto the landfill from areas outside the landfill footprint. [RM975261-A(2)]

• All diversion channels shall be designed to manage a 1% AEP (Annual Exceedence Probability) design flood. The diversion channels shall be designed such that if this capacity is exceeded the preferential (secondary) flow path is away from the landfill. [RM975261-A(3)]

• Any water coming in contact with refuse must not be discharged as stormwater but must be treated as leachate and discharged into the leachate collection system. [RM975261-A(5), B(4)]

• Exposed waste shall typically be bunded (min 0.5m) to divert away surface water and contain any leachate.

• The following drawings give the general arrangement of the stormwater system:

  • ‘Erosion & Sediment Control Plan Site Upgrade’ (Drawing Number ESCP-001-01, Sheet 1).

  • ‘York Valley Landfill Erosion and Sediment Control Sediment Retention Pond (SRP) 3 Plan’ (Plan Number CE-043). [RM975261-A(6), B(3)]

• The contractor shall maintain an ESCP with more detail around the operational area.

• All new pipes, structures, and rock channels shall be captured by as built survey.

• The discharge of stormwater to York Stream from Sediment Retention Pond 3 (SRP3) is controlled by a valve so that discharge only occurs when the stormwater quality adheres to the resource consent conditions. [RM975261-E(2)]

• SRP3 operates between 2 levels:

  • Minimum Capacity Level – 30% [WN3 - Need to check what pond level corresponds to mRL 86.8] 86.8 mRL – The minimum level of the pond where any discharge should cease.

  • Maximum Capacity Level – 100% 88.0 mRL - The maximum level the pond can fill to before emergency discharge over the spillway will occur.

• The quality of the surface water is sampled and assessed in detail every 3 months for a range of chemical and biological parameters. The results are compared with national standards and reported to the Council. Adverse results may require investigation and changes to the Erosion and Sediment Control Plan. [RM975261-E(6), G(6)]

• Chemical flocculants may be used to assist the removal of suspended solids from the stormwater. Flocculent use must be in general accordance with the York Valley Landfill Chemical Treatment Management Plan (CTMP) (Appendix C of the SCP Rev B prepared by Southern Skies and dated August 2024. [RM975261 Sch 1 (39)]

• SRP3 must be cleaned out before the accumulated sediment reaches 20% of the total sediment retention ponds volume. [RM975261 Sch 1 (21)]

• All erosion and sediment control measures or methodologies must be maintained and/or undertaken in accordance with GD05 (this is the Erosion and Sediment Control Guide for Land Disturbing Activities in the Auckland Region, Auckland Council). [ESCP Chapter 7]

• All erosion and sediment control measures must be inspected at least once a week and after each rainfall event. Any necessary maintenance and repairs must be undertaken immediately. [ESCP Chapter 7]

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