New England Quarry Resource Recovery Centre Landfill Nr Ivybridge, Devon Environmental Permit (EP) Application Surface Water Management Plan

Transcription

1 New England Quarry Resource Recovery Centre Landfill Nr Ivybridge, Devon Environmental Permit (EP) Application Surface Water Management Plan February 2011 Ref: /SWMP

2 Viridor i Ref: /SWMP CONTENTS 1.0 INTRODUCTION Project Guidance Report Structure PROPOSED SURFACE WATER MANAGEMENT PLAN Site Drainage Application of Sustainable Drainage Systems Flood Risk Assessment General Scheme Arrangement Attenuation Pond Design Landfill Operational Phase Groundwater Control OPERATION, INSPECTION AND MAINTENANCE Overview Operations Site Specific Actions Maintenance MONITORING PLAN Introduction Monitoring Objectives Surface Water Monitoring Monitoring Equipment and Procedures Data Management and Reporting Surface Water Contingency Action Plan SUMMARY CLOSURE TABLES Table 2-1 Summary of Attenuation Ponds... 4 Table 4-1 Surface Water Monitoring Point Discharges... 8 Table 4-2 Surface Water Monitoring - Other Locations... 9 Table 4-3 Proposed Control and Trigger Concentrations Drawing SWMP1 DRAWINGS General Scheme Arrangement

3 Viridor 1 Ref: /SWMP 1.0 INTRODUCTION Consulting Limited () has been instructed by Viridor Waste Management Ltd (Viridor) to prepare an Environmental Permit (EP) application to operate a non hazardous landfill as part of the Resource Recovery Centre (RRC) at New England Quarry, Devon. The RRC will include a non-hazardous landfill and an Energy from Waste (EfW) and Incinerator Bottom Ash (IBA) facility that will be permitted separately. New England Quarry is a disused stone quarry approximately 20ha in area. This surface water management plan has been prepared as part of the EP application for the landfill. The landfill will be constructed within the existing quarry void and the EfW and IBA facility will be built on the former quarry stocking area to the north of the quarry void. 1.1 Project Guidance The SWMP presented in this report has been prepared in accordance with current best practice guidance documentation and software, which includes: Pollution Prevention Guideline 1: General Guide to the Prevention of Pollution; Pollution Prevention Guideline 5: Works in, Near or Liable to Affect Watercourses; Pollution Prevention Guideline 21: Pollution Incident Response Planning; Sustainable Urban Drainage Systems Best Practice Manual, CIRIA, 2001; The SUDS Manual, CIRIA, 2007; Planning Policy Statement 25 (PPS25): Development and Flood Risk, December 2006; Flood Estimation Handbook, CEH, 2006; and WinDes Software Suite published by MicroDrainage. 1.2 Report Structure The report structure is as follows: Section 2 details of the proposed surface water management system and ditch details for the site during development and following final restoration; Section 3 details of the operation, inspection and maintenance of the surface water management system; and Section 4 details of the proposed monitoring of surface waters; and Section 5 a summary of the report.

4 Viridor 2 Ref: /SWMP 2.0 PROPOSED SURFACE WATER MANAGEMENT PLAN Point source emissions to surface water will arise from the site s surface water drainage system. The surface water management system for the proposed development will be designed to: ensure that surface water runoff from the site is controlled at all stages of the site development and aftercare; segregate surface water runoff that is uncontaminated from surface water which may potentially be contaminated by leachate; collect surface water runoff from outside the landfill and prevent it from entering the landfill void; ensure that the drainage system has sufficient capacity to safely control and discharge runoff without impairing the stability of the restoration slopes, constructed lining/capping systems or monitoring installations; ensure that there is no increase in flooding risk at, or downstream of, the site; and ensure that the surface water discharged from the site is of an acceptable quality and compliant with the Environmental Permit. Detailed consideration of the possible impacts of the proposed development and proposed mitigation measures have been presented in the Environmental Impact Assessment which accompanied the proposed facility s planning application, a copy of which is included in Section 5 of this application. A detailed flood risk assessment accompanied the planning application which is enclosed in Section 5 of the application. This SWMP has been prepared with reference to this information. 2.1 Site Drainage Application of Sustainable Drainage Systems The implementation of SuDS as opposed to conventional drainage systems, provides several benefits by: reducing peak flows to watercourses or sewers and potentially reducing the risk of flooding downstream; reducing the volumes and frequency of water flowing directly to watercourses or sewers from developed sites; improving water quality over conventional techniques by removing pollutants from diffuse pollutant sources; and replicating natural drainage patterns, including the recharge of groundwater so that base flows are maintained. Current guidance promotes sustainable water management through a hierarchy of techniques:

5 Viridor 3 Ref: /SWMP Prevention the use of good site design and housekeeping measures on individual sites to prevent runoff and pollution measures including: minimise topsoil stripping and earthworks in previously undisturbed areas; ensure that any areas which are subject to earthworks are restored as quickly as possible by dressing with topsoil and planting in accordance with the restoration plan; any long term stockpiles or bare earth slopes will be stabilised by either; mulching, covering with matting, temporary planting, or an alternative stabilisation technique; slope roughening and benching of stockpiles to encourage infiltration and reduce runoff velocities; all temporary access roads should drain laterally rather than along the roads length; and collection of rainfall on the working cells by the leachate collection and treatment system. Source Control control of runoff at or very near its source; measures include: a 5m buffer zone of established vegetations will, if possible, be allowed between any earthworks and any lagoons or drainage ditches; all runoff from areas of earthworks will whenever possible be conveyed to areas of established vegetation using as short a route as is possible; all runoff from temporary roads will when possible be managed in open drains incorporating check dams at regular intervals; and silt fences and straw bails will be used when necessary at the base of any bare earth slopes to provide temporary filtering of runoff. Site Control management of water from several sub-catchments (including routing water from roofs and car parks to one/several large soakaways for the whole site). Regional Control management of runoff from several sites, typically in a retention pond or wetland. 2.2 Flood Risk Assessment It is a requirement of PPS25 (Development and Flood Risk) that rates of surface water runoff do not increase after development of a site. The pre-development rate of runoff at site has been determined using the current industry best practice guidance as outlined in the Interim Code of Practice for SuDS 1. 1 Office of the Deputy Prime Minister, National SuDS Working Group, July 2004, Interim Code of Practice for Sustainable Drainage Systems

6 Viridor 4 Ref: /SWMP 2.3 General Scheme Arrangement Drawing SWMP1 shows the proposed design to control runoff generated from the operational, restored and aftercare phases of the landfill. Two attenuation ponds are proposed to attenuate flows from the landfill. Details are shown in Table 2.1. Table 2-1 Summary of Attenuation Ponds Pond North-West Pond South-East Pond Attenuation of Flows From The north-western part of landfill The south-eastern part of landfill The approximate surface area of the attenuation features is based on the following assumptions: attenuation pond side slopes of either 1:2 or 1:3; depth of attenuation is 1m; and it is proposed that the drainage system is progressively constructed as the site is developed. In summary it is proposed that: uncontaminated surface water from the north-western half of the landfill will be attenuated in a pond to the west of the EfW, North-West Ponds. Water from the attenuation ponds will discharge to a tributary of the River Yealm to the north of the RRC; uncontaminated surface water from the south-eastern half of the landfill and the haul road to the east of the landfill will discharge to the South-East Pond. Water from the attenuation pond will discharge to River Yealm immediately up-stream of Popples Bridge; 2.4 Attenuation Pond Design The attenuation ponds will be designed in accordance with good practice and Viridor Waste Management Ltd internal guidelines. This will include: stability of the proposed lagoon sidewalls will be subject to a geotechnical assessment; erosion protection will be provided at attenuation pond inflows and outflows; sediment fore-bay and reed planting will be provided at the entrances to the ponds; access will be provided for maintenance and cleaning; low level and high level take-offs will be provided to drain the lagoon system;

7 Viridor 5 Ref: /SWMP emergency shutoffs will be provided on all discharge points; facilities for safely recovery a sample of water will be provided; and a V-notch weir or flume compliant with MCERT and British Standards requirements will be provided to measure and record the discharge flow rates (North-West and South-East ponds only). 2.5 Landfill Operational Phase The surface water attenuation ponds will be constructed at an early stage so they are available to attenuate flows during the construction of the landfill and RRC infrastructure as well as during the operational phase of the landfill. The landfill will be filled in ten fully contained cells. Filling will start in the lowest part of the quarry and the final landform will be a gentle dome at a maximum elevation of 84m OD. The design of the landfill means that rainwater falling on an un-filled cell will be contained within the cell. Best practice will be adopted to separate clean water from contaminated water by the construction of temporary bunds in the cell. Clean surface water will be allowed to collect in the base of the cell to allow the settlement of fines before being to being pumped to either the North-West or South-East Attenuation ponds. Incident rainfall which collects in areas of construction and earth movement will be collected in temporary sumps to provide primary treatment for the removal of suspended solids prior to pumping to an attenuation pond for secondary treatment and disposal off site. Rainfall which falls on active areas of landfilling would be collected by the leachate management and abstraction system. 2.6 Groundwater Control Part of the quarry void is below the regional groundwater table and the void is currently filled with a combination of rainwater and groundwater up to an elevation of approximately 50m AOD. The void will be pumped dry prior to construction and kept dry during the construction period by pumping from a temporary sump in the base of the quarry. A groundwater under-drainage blanket will be installed in the base and sides of cells 1 and 2 of the landfill to reduce groundwater levels during the early phases of filling to prevent up-ward pressure on the liner. This dewatering water will be discharged to the North-West Pond with consent from the Environment Agency.

8 Viridor 6 Ref: /SWMP 3.0 OPERATION, INSPECTION AND MAINTENANCE 3.1 Overview The surface water system will be inspected at a minimum frequency of monthly intervals for excessive silting, blockages or damage. It is noted that the system (both ditches and lagoons) is designed to attenuate silt and that the presence of silt within the system does not represent failure of the system. Excess silt does however require maintenance actions. The results of the inspections will be recorded in the site log together with any remedial actions that are taken. The frequency of inspection will be increased at times of higher risk under the direction of the Unit Manager. Prior to construction of any element of the SWMP a Construction Quality Assurance plan with supporting construction drawings will be submitted to the Environment Agency. 3.2 Operations Site Specific Actions In achieving the above objectives, the site s management team under the direction of the Unit Manager will undertake the following tasks; 1. Review daily automated meteorological forecasts to identify possible periods of future heavy rainfall at the site. 2. Complete and document a visual check of the state of the lagoons above the low outfall levels. 3. Complete and document in accordance with the Company s Business Management Systems a visual check on the water quality within the lagoons, paying particular attention to suspended solids concentration and the presence of any free hydrocarbon products on the surface of the lagoon. In the event that heavy rainfall is forecast, then the following actions are proposed to ensure that the site surface water system is prepared as well it can be for the additional rain water forecast for the area: 1. Open all lower outfall valves ideally at least twelve hours prior to the weather event, allowing for additional storage capacity in the lagoons to be created. 2. In the event of extreme weather being forecast, lagoons may be lowered further by using a mobile pumping unit to lower the levels. 3. Once the rainfall event has started, ensure the outfall points are closed. This will allow rain water to accumulate in the lagoons, providing the required time for sedimentation of suspended solids, ensuring water quality when discharged is in compliance with the permitted standards. Upon inspection of the final lagoon prior to any discharge, should the turbidity of suspended solids be deemed through visual inspection to be unsuitable for discharge, the following actions will be taken under the direction of the Unit Manager:

9 Viridor 7 Ref: /SWMP 1. Close off outfalls within the internal lagoons within the system to provide additional attenuation within the site. 2. Contact the Environment Agency to agree appropriate mitigation measures and/or disposal of the accumulated water. Such measures may include temporary pumping of water onto restored areas of the site to attenuate suspended solids within the grass profile. The actions taken above and any visual inspections conducted will be recorded in the site daily log. 3.3 Maintenance Routine maintenance of the drainage system within the site will include the following: clearance of growing or fallen vegetation; repairing any damage caused by operational activities or burrowing animals; removal of any excess accumulations of sediment; and temporary repairs will be carried out as appropriate, with permanent repair works to commence within 28 days of the defect being recognised, unless it is causing an immediate problem. In order to ensure that the lagoons are fit for purpose on an ongoing basis, routine de-silting of lagoons and areas of the surface water drainage system that utilize storage of water will be required. The rate of silt accumulation in the base of the lagoon will be monitored on a quarterly basis by the Unit Manager, although an increased frequency of inspection will occur during periods of high siltation risk. If the inspection reveals high levels of silt, the Unit Manager will arrange for de-silting of the lagoons. These works will be programmed into the site s Operational Plan and undertaken in a controlled manner to ensure that the activity does not give rise to any release of water containing elevated concentrations of suspended solids either during the works or whilst the system returns to equilibrium conditions following the works.

10 Viridor 8 Ref: /SWMP 4.0 MONITORING PLAN 4.1 Introduction Surface water monitoring will consist of an assessment of quality of the surface water within the surface water management system. Quality will be measured by means of chemical analyses carried out on samples obtained from the permitted discharge point to surface watercourse, in addition to Viridor s own routine monitoring points set out in this plan. 4.2 Monitoring Objectives The monitoring will be carried out for the following main purposes: to facilitate ongoing assessment of the impact of the proposed development on the environment; and to ensure that the quality of discharges from the site is compliant with the requirements of the Environmental Permit. 4.3 Surface Water Monitoring Where quantitative flow monitoring is undertaken this will be done by open channel monitoring of flow rates from the discharge points using a flume or a v-notch weir. The quality of collected surface water will be measured by the sampling and analysis of water taken at the points listed in Table 4-1 and Table 4-2. The former provides details of the monitoring of point source discharges while the latter provides details of the monitoring of the quality of the River Yealm up-steam and down stream of the site. Table 4-1 Surface Water Monitoring Point Discharges Monitoring Location SW1 - Discharge from North-West Pond SW2 - Discharge from South-East Pond Frequency Continuously Monthly Quarterly Measurement and Analytical Suite Discharge volume Ammoniacal nitrogen, chloride, electrical conductivity, ph, suspended solids, visible oils or grease As monthly plus; total alkalinity (CaCO3), BOD, COD, TON, and TOC SW5 Quarry void dewatering and groundwater underdrainage discharge to North-West Pond *1 Monthly Quarterly Ammoniacal nitrogen, chloride, electrical conductivity, ph, suspended solids, visible oils or grease As monthly plus total alkalinity (CaCO 3 ), magnesium, potassium, calcium, sodium, sulphate COD, TON, TOC iron, zinc, lead, chromium, manganese, nickel, cadmium, copper, xylene, toluene

11 Viridor 9 Ref: /SWMP Monitoring Location Frequency Annually Measurement and Analytical Suite Hazardous substances screen Notes:*1 Groundwater under-drainage will be undertaken for a period of 4 to 7 years subject to the rate of filling of the landfill Table 4-2 Surface Water Monitoring - Other Locations Monitoring Location SW3 Up stream River Yealm SW4 Down stream River Yealm Frequency Monthly Quarterly Measurement and Analytical Suite Ammoniacal nitrogen, chloride, electrical conductivity, ph,, suspended solids, visible oils or greases As monthly plus total alkalinity (CaCO3), sulphate, magnesium, potassium, calcium, sodium, COD, BOD, TON, TOC, iron, zinc, lead, chromium, manganese, nickel, copper In the event that key water quality parameters obtained above show deviation from the normal statistical range, supplementary samples of surface water may be obtained for a broader range of parameters. 4.4 Monitoring Equipment and Procedures Collection of surface water sampling will be carried out in accordance with the current Viridor Standard Operating Procedure for obtaining samples of surface water. 4.5 Data Management and Reporting Comparison of monitoring data with assessment levels will be carried out each time monitoring data is collected. When an adverse trend or breach of an assessment level is indicated by the monitoring results, appropriate contingency actions will be implemented as detailed in the Surface Water Action Plan. All continuous data logging and laboratory results will be transferred electronically from the site to the Company s environmental database.

12 Viridor 10 Ref: /SWMP 4.6 Surface Water Contingency Action Plan Should the monitoring or sampling of the surface water exceed the specified permit levels or observations made such as those listed below, then the following Surface Water Contingency Action Plan will be implemented:- Visual Alerts Visual signs of hydrocarbons; Leachate breakout or seepage into surface water drain; or Significant suspended solids, which discolour the discharge. Analytical Alerts Breach of permitted levels. The overarching surface water action plan is documented as follows, with site specific detail for the proposed development detailed in the subsequent text. In setting out the contingency actions, it is noted that the actions will reflect the time period for awareness of an incident/control or trigger level exceedence which will range from immediate (for visual alerts during inspection or sampling) through to a period of between five to seven days after a spot sampling event has occurred (the typical laboratory turnaround time for surface water samples by an analytical laboratory) Visual Alerts The following management actions will be undertaken under the direction of the Unit Manager following a visual inspection indicating a potential issue. It is noted that no quantitative control or trigger levels are likely to be applicable to the management actions documented below: 1. Notify the Unit Manager; 2. Notify the site s Environmental Manager/Officer; 3. The surface water discharge point will be closed to prevent discharge; 4. The surface water lagoons will be isolated to promote additional storage and attenuation within the site; 5. Visually inspect the surface water network upstream and downstream of the identified issue to identify any obvious source of poor quality water or change to the site s drainage network; 6. Confirm via inspection whether there has been any offsite release on water from the site into the Yealm; 7. Inform the Environment Agency including as required submission of a Schedule 6 Part A Notification; 8. As appropriate under direction of the site s Environment Manager/Officer, obtain spot samples of water to quantify the nature of the issue; 9. Obtain all other supporting factual information up to the time of the incident including meteorological data, site activities; 10. Document with the Environment Agency further management and monitoring activities associated with the incident to demonstrate the issue has been addressed and the environmental risk posed by the site has returned to normal.

13 Viridor 11 Ref: /SWMP In the event that the cause of the non-compliance is due to the presence of hydrocarbons within the surface water system, all practical measures will be taken to isolate the cause of the leak and contain the hydrocarbons within the surface water system using portable booms and absorbent pads Quantitative Quality Alerts Quantitative sampling of water quality will be undertaken in accordance with the permit requirements. Control and trigger levels have been proposed by Viridor to ensure that early warning alerts of potential problems are obtained and assessed in a timely manner. The key quantitative indicators of unsuitable water being discharged from the site are: Ammoniacal Nitrogen an indicator of a potential emission of leachate into the surface water Chloride an indicator of a potential emission of leachate into the surface water Suspended Solids reflective of a lack of performance of the attenuation characteristics of the surface water system of lagoons and ditches. The actions related to suspended solids failures are covered by the Contingency Action Plan for Visual Impacts documented above. An initial appraisal of the possible origins and management strategies for assessment of any exceedences of the permit trigger levels is as follows: Proposed control and trigger levels for the point source discharge locations are shown in Table 4-3; these will be reviewed going forward in light of data obtained from the site once operational: Table 4-3 Proposed Control and Trigger Concentrations Parameter Control Level (mg/l) Trigger Level (mg/l) Chloride Ammoniacal Nitrogen 1 2 Control levels will be reassessed at regular intervals to ensure the limits remain fit for purpose in providing an early indication of a change in water quality at the site. As such, these limits should not be included in the permit. In the event of each of the scenarios set out above, the following actions will be undertaken by Viridor: Control Level Exceedences In the event of a control level exceedence, Viridor s Environment Team will: 1. Review all key performance data for surface water parameters within and external to the site to assess whether the event was local or regional / a one off or a reflection of a sustainable trend; 2. Review with the Unit Manager any changes to site activities;

14 Viridor 12 Ref: /SWMP 3. Assess with the Unit Manager the variability of the data set and whether further supplementary sampling is required to further quantify the data set; and 4. Assess with the Unit Manager whether supplementary inspection of the site s surface water drainage network is required 5. Report control level exceedences through the Quarterly Environmental Reporting System established at the site. Trigger Level Exceedences In the event of a trigger level exceedence, Viridor s Environment Team will: 1. Inform the Unit Manager; 2. Review all key performance data for surface water parameters within and external to the site to assess whether the event was local or regional / a one off or a reflection of a sustainable trend; 3. Submit a Schedule 6 Part A Notification to the Environment Agency within 24 hours of receipt of the analytical data; 4. Assess with the Unit Manager the variability of the data set and whether further supplementary sampling is required to further quantify the data set; 5. Assess with the Unit Manager whether supplementary inspection of the site s surface water drainage network is required. Where a high risk event has occurred, inspection and verification of the performance of leachate and/or landfill gas (condensate) systems will be undertaken to confirm sustained containment of leachate within the site; 6. Obtain all other supporting factual information up to the time of the incident including meteorological data, site activities; 7. Document with the Environment Agency through the Schedule 6 Part B Notification further management and monitoring activities associated with the incident to demonstrate the issue has been addressed and the environmental risk posed by the site has returned to normal.

15 Viridor 13 Ref: /SWMP 5.0 SUMMARY has been appointed by Viridor to prepare a surface water management plan for the landfill element of the proposed New England Resource Recover Centre. Detailed consideration of the potential sources of runoff, runoff rates and possible quality has been presented in the site application and supporting environmental impact assessment; this included a site flood risk assessment. This reports details proposed measures for the control and management of surface water runoff at site and makes recommendations for the monitoring of surface water quality at site during development and operation. It is proposed that prior to construction of any element of the surface water management system that Construction Quality Assurance procedures are followed to the satisfaction of the Environment Agency.

16 Viridor 14 Ref: /SWMP 6.0 CLOSURE This report has been prepared by Consulting Limited with all reasonable skill, care and diligence and taking account of the manpower and resources devoted to it by agreement with the client. Information reported herein is based on the interpretation of data collected and has been accepted in good faith as being accurate and valid. This report is for the exclusive use of Viridor; no warranties or guarantees are expressed or should be inferred by any third parties. This report may not be relied upon by other parties without written consent from. disclaims any responsibility to the client and others in respect of any matters outside the agreed scope of the work.