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 stormwater from the footprint of the landfill shall be treated in the sediment retention ponds (SRPs) as shown on ‘Erosion & Sediment Control Plan Site Upgrade’ (Drawing Number ESCP-001-01, Sheet 1) and the plan entitled ‘York Valley Landfill Erosion and Sediment Control Sediment Retention Pond (SRP) 3 Plan’ (Plan Number CE-043), attached to this consent, or as shown on any amended drawings or plans that have been be submitted to the Council’s Monitoring Officer for certification and are subsequently certified.

RM975261V2

The total suspended solids (TSS) concentration of the discharge from SRP 3, as measured at Monitoring Point VI shall not exceed the greater of either 100 grams per cubic metre (g/m3), or twice the TSS concentration measured in York Stream using an automated TSS analyser at Monitoring Point IV shown on the drawing entitled ‘Erosion & Sediment Control Plan Site Upgrade’ (Drawing Number ESCP-001- 01, Sheet 1) attached to this consent.

RM975261V2

The Consent Holder shall monitor on each working day on which a rainfall event occurs, during or immediately after the rainfall event, and while a discharge from  SRP 3 is occurring, for electrical conductivity at Monitoring Point VI shown on Drawing  Number ESCP-001-01 Sheet 1 entitled ‘Erosion & Sediment Control Plan Site  Upgrade’ and Plan number CE-043 Titled ‘York Valley Landfill Erosion and Sediment  Control Sediment Retention Pond 3, attached to this consent or as shown on any  amended drawings or plans and submitted to the Councils Monitoring Officer for  certification and are subsequently certified. The trigger level for electrical conductivity is 750μS/cm. When the electrical conductivity measurement reaches the trigger level the stormwater shall be diverted into the leachate collection system.

Advice Note: A rainfall event is defined as 15 mm of rainfall in 1 hour or - 25 mm of rainfall in 24 hours as measured at the onsite weather station. This condition only applies when there is a discharge of stormwater from SRP 3 to York Stream.

RM975261V2

In the event that the monitoring requirements set out in the Management Plan are not complied with and the parameters exceeded, the Consent Holder shall undertake the following;

(a)        immediately notify the Manager, Consents and Compliance in writing;

(b)        immediately investigate the reason why the requirements were not complied with;

(c)        immediately identify and undertake whatever appropriate remedial action is required to the satisfaction of the Manager, Consents and Compliance to mitigate the effects, which action may include closing the landfill or removing the material which has led to such non-compliance;

(d)        advise the Manager, Consents and Compliance of the steps taken;

(e)        immediately take whatever other steps are necessary to bring the landfill operation to a position of compliance.

RM975261V2

The discharge of water from the SRPs shall not result in any noticeable scouring at the outlet from the SRPs.

RM975261V2

The discharges authorised by RM975261 E and G (and their changes) is limited to the following contaminants released to land and water during and following rainfall events:

a)         Flocculant (when used in accordance with the CTMP referred to in condition 40 and the other relevant conditions of this consent); and/or

b)         Sediment-laden water.

RM975261V2

Refuse, other than hardfill, shall not be placed in such a manner that it would lie in contact with the water table or in permanent contact with any ponded water. Suitable provision shall be made for stormwater and for the control of effluents arising during storm conditions.

Designation DN1 (accessed August 2023)

• The level of SRP3 is monitored by SCADA.

• When rainfall causes SRP3 to rise above the Minimum Level, a discharge should be planned in order to maintain usable pond capacity.

• The Minimum Level of SRP3 is 30% of pond capacity. At any level lower than this, discharge will start to pick up sediment from the bottom of the pond.

• Stormwater with a TSS of ≤100g/m3 (<100 mg/L) may be discharged without further checks. [ML - Need to agree safety buffer/accuracy margin for all instrument readings]

• There is an in-situ TSS sensor located in SRP3 which provides real-time TSS readings which are displayed via a SCADA system.

• The operator must check the TSS of SRP3 in SCADA before starting any discharge. The SCADA readings can be viewed 3 ways: mobile app, Floc Shed digital readout and on the NTRLBU office TV.

• The decision is then made to open the discharge valve or not depending on the readings.

• A discharge of stormwater with a TSS of >100mg/L is still permitted if the SRP3 TSS is less than twice the TSS of York Stream upstream at monitoring point IV.

• To assess whether this condition is met, the operator must compare the TSS readings in SCADA for SRP3 and York ‘Top Stream’ (upper TSS sensor).

• The TSS of SRP3 is measured by an insitu sensor with an upper limit of 750mg/L.  If the SCADA shows the SRP3 TSS at 750mg/L the actual TSS may be higher.  The valve must be closed if the SRP3 TSS reaches 750mg/L.  At this point, flow may overtop the spillway.  Refer also to (7) for emergency discharge to leachate system.

• The TSS of York Stream is measured by an insitu sensor mounted permanently in the stream.  This sensor also has an upper limit of 750mg/L.  Additionally, the protective screen around the sensor can trap debris, leading to artificially high readings.  It is important to visually inspect the stream and sensor at monitoring point IV to confirm that readings remain representative.

• Electrical Conductivity must be measured during or immediately after a rainfall event if flow is discharged from SRP3.

• A rainfall event is defined as either a) 15 mm of rainfall in 1 hour or b) 25 mm of rainfall in 24 hours, as measured at the onsite weather station.

• If it rains for days without end, measure Electrical Conductivity on each working day on which a rainfall event occurs and we are discharging from SRP3.

• Site rainfall is measured by an in-situ rainfall sensor which provides real-time readings displayed via a SCADA system. [ML - Need to have alert for 15mm rain in 1hr or at least a way of seeing this.  Running 1 hr cumulative rain total with peak value from each day recorded?]

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

• Prior to an expected heavy rain event (15mm/hr or 25mm/24 hrs), and within 12 hours of such an event (at first light), the landfill site should be inspected to ensure that there is or has been no damage to the stormwater system.

• Within 4 hours of inspection (prior or post event), a report must be completed in the Survey 123 ‘YVLF Rainfall Inspection’ form which includes:

  • The assessment of the site, noting conditions, such as (but not limited to), site features, quantity of rain received, current TSS readings from all monitoring points,

  • Confirms whether the stormwater system discharges have occurred. The conditions of these discharges and whether a breach of discharge conditions have occurred.

  • Photos of the following are to accompany the report; SRP1, SRP3, Landfill Surface, Sealed Access Road, and Stormwater drains. [ML - Add in notes re using SRP1. NTRLBU to provide more information.]

• In the event of a stormwater system failure or any site issues, NTRLBU must be notified immediately. NCC must also be notified if the failure leads to a non-compliant discharge, see 14 - Notify NCC of non-compliant discharge (below).

• Stormwater system drains need to be kept clear and running freely. Minor slumps or accumulations of sediment shall be cleared immediately to ensure that flows are not impeded and that ponding of surface water does not occur.

• SRPs must be cleaned out if the accumulated sediment volume reaches 20% of the total volume. Forebays are to be cleaned out after each rain event if there is any evidence of sediment deposition.

[WN - Step 5 does not work, as we are automatic, valve will open. Suggest combine steps 5 & 6.]

[WN - We need to repeat survey on each working day until discharge is complete.]

• Measure the Electrical Conductivity of SRP3 using the handheld instrument and record readings in the Survey123 ‘YVLF Electrical Conductivity’ form.

• The trigger level for electrical conductivity is 750μS/cm. We can’t discharge stormwater to the stream if it gets above this.

• The discharge is started by opening the valve via SCADA.

• Continue to monitor SCADA so as to close the valve if conditions go out of spec (TSS in SRP3 is more than 100mg/L or more than twice TSS upstream). Note that the TSS in the stream drops much more rapidly after rainfall than TSS in the SRP3. The valve should not be left open, unmonitored, eg overnight.

• Monitor the level of SRP3. When the Minimum Capacity Level is reached, cease the discharge by closing the valve via SCADA.

• The discharge of water from the SRPs must not result in any noticeable scouring at the outlets from the SRPs. [RM975261 Sch 1 (22)]

• While discharging from SRP3, take TSS samples from SRP3 discharge and from the stream at the upper stream instrument location (monitoring point IV) for lab testing.

• Use the sampling procedure set out in Surface Water Quality Monitoring (LINK).

[ML - I think we need a follow up step either here or at the bottom to cross check the lab results (when they are received) against the insitu readings and take any required action if there are discrepancies outside the [to be] agreed tolerances eg recalibrate insitu sensors, report breach to NCC, etc]

• If the stormwater exceeds the permitted TSS or electrical conductivity levels it cannot be discharged into York Stream.

• If this occurs, a decision is required on whether to defer the planned discharge to allow the sediment to further settle in SRP3, or whether an emergency discharge to the leachate collection system is required.

• The key trigger for this decision is the level of SRP3, as well as the current and forecast weather. If SRP3 is below the Maximum Level [ML1 - NTRLBU needs to decide numerically what this level is and then put this in Greg's definitions at the top of the document], the discharge can likely be deferred to allow the stormwater in SRP3 to settle. If SRP3 is at the Maximum Level, then an emergency discharge to the leachate collection system is required (refer to 11 - If SRP3 is full and TSS exceeds permitted levels divert discharge stormwater to leachate collection system below).

• If SRP3 is below the Maximum Level and weather conditions allow, the discharge can likely be deferred to allow the stormwater in SRP3 to settle.

• Monitor the level and TSS (and EC as required) of SRP3 closely.

• Plan a future discharge after settling has occurred and the TSS level has reached permitted levels (either ≤100g/m3 or less than twice the TSS of York Stream).

• If SRP3 has reached the Maximum Level, and flocculent dosing has failed to reduce the TSS to permitted discharge levels (either ≤100g/m3 or less than twice the TSS of York Stream), then an emergency discharge to the leachate collection system is required.

• A pump and hose will need to be set up to discharge the stormwater into the leachate collection system. [ML - Need to say exactly where to discharge to, how cross road, etc]

• The emergency stormwater discharge to the leachate collection system must be maintained within the leachate system capacity.

• The maximum discharge permissible through the leachate collection system is 20L/s under the tradewaste agreement however the leachate collection system capacity is less than this.

• A discharge of stormwater in excess of the leachate system capacity will cause the leachate collection system to overflow into the adjacent leachate overflow pond. This must not be allowed to happen.

• The chamber leading to the leachate overflow pond has a level alarm to indicate a rise in leachate levels. If this alarms, discharge of stormwater to the leachate collection system must immediately reduce or cease.

• An overflow of out-of-spec stormwater to York Stream from the SRP3 spillway will breach the Resource Consent conditions for the landfill. It is the last possible option and the NTRLBU must be informed before any emergency discharge to York Stream occurs.

• However, an overflow of stormwater over the SRP3 spillway is preferable to any risk of breach of the leachate containment system.

• A reduction (or cessation) of pumping of out of spec stormwater to the leachate system in order to avoid exceeding the capacity of the leachate collection system would likely mean that SRP3 fills above the Maximum Level in SRP3 and result in an emergency discharge of stormwater to York Stream over the spillway.

• In the event of a non-compliant discharge, the NTRLBU must immediately: [RM975261 Sch 1 (20)].

  • notify the Manager, Consents and Compliance in writing.

  • investigate the reason for the non-compliant discharge and why the discharge consent requirements were not complied with.

  • identify and undertake whatever appropriate remedial action is required to the satisfaction of the Manager, Consents and Compliance to mitigate the effects, which action may include closing the landfill or removing the material which has led to such non-compliance

  • take whatever steps are necessary to bring the landfill operation back to a position of compliance.

• The NTRLBU must complete an Incident Report which:

  • sets out the findings of the investigation into the reasons for the non-compliant discharge.

  • identifies any appropriate remedial action required to mitigate the effects of the non-compliant discharge.

  • sets out the measures taken to prevent recurrence of the same or a similar discharge.

• The NTRLBU must provide the Incident Report to the Manager, Consents and Compliance within 2 weeks of the non-compliant discharge.

• Stormwater discharge TSS and electrical conductivity records must be provided on request and included in the Annual Report. [RM975261 Sch 1 (18).]