{"text_format":"1","workbook":"xlsx","n_sheets":9,"sheets":["Cover Sheet","Introduction & Conclusion","1.Risk assessment","2.Total vol. - Mitigation","3.Containment volume-Total vol.","4.Current asset evaluation","5.Containment type-Total vol.","Template Settings","Settings"],"not_rendered":{"charts":0,"images":16,"macros":1,"external_links":1,"defined_names":58,"comments":1,"pivot_tables":0},"unopened":[],"bounds":{"document_bytes":16777216,"sheet_cells":100000,"rows_first":2000,"rows_last":500,"rows_between":2000,"halvings":0,"cell_chars":16384,"cell_head_chars":4096},"cells_cut":0,"cells_raw":0,"read":"whole","date_system":"1900"}

{"sheet":"Cover Sheet","index":0,"n_rows":43,"n_cols":11,"rows_kept":43,"cut":false,"hidden":false,"merged":[[47,2,47,4],[48,2,48,4],[49,2,49,4],[42,2,42,4],[43,2,43,4],[44,2,44,4],[45,2,45,4],[46,2,46,4],[41,2,41,4],[26,1,27,1],[26,2,26,4],[26,5,26,7],[34,1,34,7],[35,1,35,2],[35,3,35,5],[35,6,35,7],[36,1,36,2],[36,3,36,5],[36,6,36,7],[38,1,38,7],[40,2,40,4],[25,2,25,7],[18,1,18,5],[18,6,18,7],[19,1,19,5],[19,6,19,7],[20,1,20,5],[20,6,20,7],[22,1,22,7],[23,1,23,3],[23,4,23,7],[24,1,24,3],[24,4,24,7],[15,1,15,5],[15,6,15,7],[16,1,16,5],[16,6,16,7],[17,1,17,5],[17,6,17,7],[13,3,13,7],[2,2,2,7],[3,2,3,7],[5,2,5,3],[5,5,5,7],[6,2,6,3],[6,5,6,7],[7,2,7,3],[7,5,7,7],[8,2,8,3],[8,5,8,7],[9,2,9,3]]}
[]
[null,"Project Information"]
[null,"Workbook Name:","IED Risk Register-Ford"]
[null,"Project Title:","SWS EMA - Lot 8 - EIA "]
[]
[null,"Section:","Industrial Emission Directive Permit",null,"Divn/Dept:",null,null,null,"Please select from the dropdown or for enter manually"]
[null,"Subject:","Risk Assessment",null,"Project Nr:",790101]
[null,"Project Manager:","Daniel Watson",null,"File Ref:","790101-MMD-IED-FOR-CA-C-001","790101-MMD-IED-CA-C-004","790101-MMD-IED-CA-C-004","Please use the format Project Number/PIMS Unique number (e.g. 123456/5) or project specific format"]
[null,"Originator","Hari Prasath/Miranda Price",null,"Calc Nr:"]
[null,"Checker","Ashwin Powar/Rachael Cross/Daniel Watson/Tommaso Tosi",null,"Nr Sheets:",5,null,null,"This is updated automatically as sheets are added/removed"]
[null,"Template Version","E"]
[null,"Design Phase"]
[]
[]
[]
[null,"Computer Applications Used",null,null,null,null,"Version/Date",null,"Please enter any other programs used as part of the calculation"]
[null,"Microsoft Excel",null,null,null,null,2108]
[]
[]
[]
[]
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[null,"Scope of Checking"]
[null,"Manual calculations",null,null,"Computer generated calculations"]
[null,null,null,null,null,null,null,null,"Enter a description of the checks that are required/have been performed"]
[]
[null,"Sheets","Calculations by",null,null,"Checked by"]
[null,null,"Name","Signature","Date","Name","Signature","Date","Please keep an audit list of the authors and checkers of each calculation sheet"]
[292574555,"1.Risk assessment","Hari Prasath","HP","2022-07-01","Ashwin Powar","AP","2022-07-01"]
[292575378,"2.Total vol. - Mitigation","Hari Prasath","HP","2022-07-01","Ashwin Powar","AP","2022-07-01"]
[292576031,"3.Containment volume-Total vol.","Tom Reynolds","TR","2024-09-16","Anita Manns","AM","2024-09-17"]
[292576417,"4.Current asset evaluation","Hari Prasath","HP","2022-07-01","Ashwin Powar","AP","2022-07-01"]
[292576606,"5.Containment type-Total vol.","Tom Reynolds","TR","2024-09-16","Anita Manns","AM","2024-09-17"]
[]
[null,"Approved by"]
[null,"Approver",null,"Signature",null,null,"Date"]
[null,"Robert Kennett",null,"RK",null,null,"2022-08-16"]
[]
[null,"Version History"]
[null,"Version","Description",null,null,"Originator","Checker","Date"]
[null,"P01","Initial Calculation",null,null,{"$f":"Originator","v":"Hari Prasath/Miranda Price"},{"$f":"Checker","v":"Ashwin Powar/Rachael Cross/Daniel Watson/Tommaso Tosi"},"2022-07-28",null,"Latest Version","P02"]
[null,"P02","Containment solution updated, tank volumes added. Changes in line with RFI queries",null,null,"Tom Reynolds","Anita Manns","2024-09-16",null,null,{"$f":"IF(MAX(H27:H33)=0,\"\",MAX(H27:H33))","v":"2024-09-17"}]
[null,null,null,null,null,null,null,null,null,"Last Checked","2024-09-16"]

{"sheet":"Introduction & Conclusion","index":1,"n_rows":22,"n_cols":3,"rows_kept":22,"cut":false,"hidden":false,"merged":[]}
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[null,"Introduction"]
[null,"The IED permit application requires an assessment of \n1) the existing capacity available for accidental spills from the Sludge Treatment Centres (STC)\n2) identification of secondary containment solutions that could be implemented in order for the site to comply, as far as is reasonably practicable, with Best Available Technique (BAT), in terms of the requirement for the provision of secondary containment.\n","Please introduce what this spreadsheet is"]
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[null,"Purpose"]
[null,"The aim of the study is to support Southern Water’s permitting and sludge treatment strategy","Please enter the purpose of the spreadsheet"]
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[null,"Required Output"]
[null,"A high-level desktop-based risk assessment using the ABDA classification tool to calculate the sites overall risk rating based on a Source-Pathway-Receptor Analysis. Simulation of catastrophic failure of the largest above ground volume","Please define what the outputs of the spreadsheet should be"]
[]
[null,"Conclusions"]
[null,"The preferred option is outlined on worksheet 5. \nThe containment would provide the required spill volume to meet CIRIA C736, contain spills on site and prevent loss of sludge into surrounding water sources. ","If the spreadsheet/calculation has a conclusion please enter it here"]
[]
[null,"Assumptions"]
[null,"CIRIA 736 Proposal amended 201221, Clause 3.2 study, Points (7-18), Page 7.\n\n1.The failure risk is assessed for a Single tank\n2.Only the above ground volume is considered for failure","Please ensure all assumptions are stated\nPlease specify any assumptions that apply to the whole spreadsheet\nAssumptions on single sheets should be placed on the sheet\nAssumptions on a cell or range should be put next to the cell or in a comment on top of it"]
[]
[null,"Basic Design Information or Source and Reference"]
[null,"CIRIA report C736"]
[]
[]
[null,"Identify documents/technical records where output will be used"]

{"sheet":"1.Risk assessment","index":2,"n_rows":91,"n_cols":12,"rows_kept":91,"cut":false,"hidden":false,"merged":[[42,9,47,9],[43,1,43,2],[43,3,43,4],[44,1,44,2],[44,3,44,4],[41,1,41,2],[41,3,41,4],[42,1,42,2],[42,3,42,4],[42,8,47,8],[45,1,45,2],[45,3,45,4],[46,1,46,2],[46,3,46,4],[47,1,47,2],[47,3,47,4],[71,3,71,9],[48,1,48,2],[48,3,48,4],[49,1,49,2],[49,3,49,4],[50,3,50,4],[63,1,63,2],[66,3,66,9],[67,3,67,9],[68,3,68,9],[69,3,69,9],[70,3,70,9],[72,3,72,9],[73,3,73,9],[74,3,74,9],[82,1,82,2],[87,1,87,2]]}
[]
[1.1000000000000001,"Source"]
[]
[null,"Material","Physical properties","Maximum quantity","units","Storage","Flammability","Corrosive","Ecotoxicity (based on LD and quantity)","Hazard rating "]
[null,"Digestor 03","Liquid with sludge, Gas (methane)","1732 m3 (approximately) - total volume for tank\n\n[As per IED Permit, Main Supporting Document 790101_MSD_Main_FOR,Page 2]","m3","Concrete","Sludge is flammable","Medium","Organic heavy - Nitrogen, \nPhosphorous, Ammonia, BOD, TSS, COD - Environmental hazard (algae blooms and death of organisms)\n\nPathogens - Human hazard (E.coli etc.)","M"]
[null,null,null,null,null,null,null,null,"Overall","M"]
[]
[1.2,"Pathway and Receptor"]
[]
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[]
[]
[]
[]
[]
[]
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[null,"Figure 1.1 Site Layout with Source-Pathway-Receptor"]
[]
[]
[null,"Pathway - the route from primary containment to receptor (extent of loss of containment)",null,"Time of concentration/ duration of source outside containment",null,"Hazard - Transport potential ",null,null,"Receptor","Hazard - Damage potential"]
[null,"The  River Terrace Deposits (RTD) superficial aquifer underlying the site is designated by the Environment Agency as a Secondary A aquifer. \n\nTanks are surrounded by Permeable gravel. Permeable sub-soils/strata will thus act as a pathway. \n\n[As per IED Permit, Site Condition report 790101_MSD_SCR_FOR,Page 3]",null,"Direct contamination but over an extended period of time",null,"M",null,null,"The River Arun is located 850m east of the site area, flowing south and joining the English Channel 3km downstream. A drain is present 200m south east of the site area and flows into the River Arun, and no further drains are located within 500m of the site area. The River Arun is listed on the OS Water Network Map as a tidal river; a river influenced by tidal action. \n\n\n[As per Site Condition Report 790101_MSD_SCR_FOR, Hydrology and flooding, Page 3]","M"]
[null,"If the permeable area were to get saturated (high groundwater) or became blocked with sludge, areas will act as impermeable and transport sludge downstream.",null,"Direct contamination but over an extended period of time",null,"M"]
[null,"There  is no history of recent flood events at the site. The majority of the site is located  within a very low risk flood extent area.\n\n[As per IED Permit, Climate Change Risk Assessment, 790101 _ERA_CCRA_FOR,Page 8]",null,"Direct contamination",null,"L"]
[null,"Existing underground services - ductwork, tunnels etc. (locations not known)",null,"Direct contamination but over an extended period of time",null,"L"]
[null,"Existing underground sludge pipework",null,"Direct contamination but over an extended period of time",null,"M"]
[null,"There is impermeable road surfacing around the tanks. Ground naturally drains to this area\n\nIf inventory is lost or cascaded onto the road (saturated permeable ground), sludge will be transported through the drainage channel to the head of the wastewater treatment works",null,"Minutes - hours",null,"L"]
[null,"If the drainage channel were to get blocked,  it may overflow locally to the permeable surrounding area.",null,"Minutes - hours",null,"M",null,null,"Sports recreational facility west of \nthe site at 65 m from boundary. Industrial facility north of the Site at 145 m from boundary. Industrial facility south east of site at 170 m. \n\n[As per Bioaerosol risk assessment, 790101_ERA_BioaRA_FOR,Page 11]","M"]
[null,"The site is located approximately 3km from the coast (to the south) and approximately 2.5km from the River Arun to the east. The River Arun is not considered a tidal river at the nearest point to the site. The site is at very low risk of coastal or riverine flooding.\n\n[As per Climate Change Risk Assessment,790101_ERA_CCRA_FOR, Page 11]",null,"Minutes - N/A (dependant on flooding extent)",null,"L",null,null,"There is one BGS recorded landfill site within 250m of the site area. The site is registered to R J Page and Sons Ltd, 93m north of the site area. The site was operational for one year in 1985 and deposited waste included inert waste.\n\n[As per Site Condition Report 790101_MSD_SCR_FOR,Recorded Landfill and Historic Landfill, Page 3]","M"]
[null,null,null,"Overall",null,"M",null,null,"Overall","M"]
[]
[]
[null,"*Flooding in flood zone 3 only have a 1 in 100 year probability of happening in a year"]
[]
[]
[null,"Combination of Hazards",{"$f":"J6&F51&J51","v":"MMM"}]
[]
[]
[null,"Overall risk rating for zone (Ciria 736) ","M"]
[]
[]
[]
[1.3,"Frequency of loss of containment"]
[]
[]
[null,"Failure mode","Description","Existing consequence and mitigation measure",null,null,null,null,null,null,"Annual probability of loss of containment","Rating"]
[null,"Operational failure - tank (partial)","Overfilling/overflow of tank\n\nFoaming","Imported liquid sludge is stored in 1 No. sludge reception tank, it is then screened by 2 No.strain presses and then mixed with indigenous sludge in 2 No. post screening sludge storage tanks. In the event of overfilling/overflow or foaming conditions, the site is manned 24 hours a day, 7 days a week and so any loss of containment can be dealt with immediately and with tankers being on site within 2hrs, as part of an emergency response KPI with local tanker operator MTSR. \n\nBoth clean and contaminated surface water is directed to a pumping station which recirculates it back into the system. The stormwater drainage of potentially contaminated areas from within the Site boundary is routed into the head of the works with no discharge outside of the site boundary. This allows site operations some time to deal with the leaks from operational failures. Flows exceeding the drainage system capacity will require mitigation with an improved inspection regime to catch spills prior to becoming significant.\n\nThe tanks are monitored by SCADA system",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Structural failure - tank (catastrophic)","Catastrophic failure due to significant external damage\n\nPotential to lose total volume if mixer pipework fails/break off of tank - has been a failure mode for digesters in the past","The tank is located above ground. For any loss of containment below ground, the sludge liquid will percolate into the permeable soil at a slow rate over a long period if not detected by the level or temperature alarms.\n\nIn the case of significant damage above ground, the total volume contained above ground could spill. \n\nIn the event of a catastrophic failure, sludge would flow in all directions as there is no containment immediately around the tank. The sludge would predominantly flow to the western boundary.",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Structural failure - tank (partial)","Most likely through cracks formed in concrete\n\nMost critical cracks would be at low level along the side of the tank walls or tank base. \n\ncracks would need to be large >6mm to allow for sludge to pass through freely. General screens at WwTW are 6-10mm, thus cracks would need to be in the same range to allow for sludge to pass freely.\n\nRoof failure","Partial structural failure of the tank would mainly be through cracks.  In the case of significant cracks forming above ground, the volume contained above ground would seep through the cracks. If the cracks are significant (>6mm), the tank could potentially lose the above ground volume over a long period of time if the level and temperature alarms are not functioning. However, this is unlikely. \n\nDue to 24/7 operational presence on site, large drops in levels in the tanks and significant leaks above ground would be noticed. Significant cracks (>6mm) below/above ground would also be easily spotted during the daily visual inspections. \n",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Structural failure - pipework (catastrophic)","Loss of containment due to failure of above ground connecting pipework and rising mains","In the unlikely event where the above ground rising mains to the tank, heatamix pipework or de-gritting pipework fails and breaks off, a significant volume would spill out. Tanks have level and temperature alarms and the site is manned 24/7 so any required valve could be immediately shut off by operational staff.\n\nThe consequence of a catastrophic failure of containment is it's able to flow in all directions as there is no containment bunds immediately around the tank. Based on topography, sludge will cascade towards the west.\n\nTotal loss of containment is unlikely. A partial loss of containment would be more likely to occur.",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Structural failure - pipework (partial)","Loss of containment most likely to occur where there are weak points in the pipework - Most likely through failures where pipe connects with the structure, bolts/sealant at pipe flanges/valves or along any pipe pitting.\n\nWeak point could be created through either human damage (during maintenance/operation), erosion (high velocities and silt content within the pipe) or environmental (corrosion)\n\nValve failure/seizure","Majority of pipework and connections are located above ground. Some of the pipework is located below ground or within the chambers below ground. \n\nIf loss of containment occurs underground (through leaks, joints and seals), sludge will percolate into the soil at a slow rate over a long period and localised wet areas will be present above ground.\n\nIf loss of containment occurs above ground through leaks or damage to pipework, due to the permeable stone around tank, sludge will also percolate into the soil at a slow rate over a long period.\n\nDue to operational presence on site and SCADA monitoring, significant leaks (above or below) ground would be noticed and loss of containment would be mitigated through operational measures (closing of valves). \n\nTotal loss of containment is unlikely (partial loss of containment would be more likely to occur).",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Vehicular impact (partial to catastrophic)","Impact from vehicles - damage to pipes or tank causing loss of containment","No known vehicle impacts - but no barrier/protection\n\nVehicles could potentially impact and damage tank which is located above ground. Vehicular impact could cause some damage to the tank, if significant, proportion of above ground volume could be lost. Vehicle is however unlikely to damage underground sections of tanks or displace any liquid within them. \n\nTotal loss of containment could occur if the vehicle impact causes significant damage to the tank. High speed impact unlikely, but vehicle could damage pipework connected to tank (mixer pump) and cause a significant hole in the tank at low level. Could impact a potential weak point.",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Vandalism","Vandalism of infrastructure - damage to pipes or tank causing loss of containment","No known vandalism to tanks or pipework.\n\nIf vandalism damage were to occur, total loss of containment is unlikely, but could occur if significant damage or on theft of mixer pumps and pipework. Partial loss of containment would be more likely to occur if slight damage was done.",null,null,null,null,null,null,"< 1 in 1 Million","L"]
[null,"Flooding","River flooding - Flood zone 2 and\nzone 3 - damage to pipes or tank causing loss of containment","There is no recent history of flooding at the site. The entire site is located within a very low risk flood zone (less than 0.1% annual probability) with the River Arun running approximately 2km to the east.\n\n[As per Climate Change Risk Assessment  Report 790101_ERA_CCRA_FOR,Page 11]",null,null,null,null,null,null,"< 1 in 1 Million","L"]
[]
[null,"*Site is manned. Probability and frequency thus reduced"]
[]
[]
[null,"Frequency of loss of containment (Ciria 736)","M"]
[]
[]
[1.4,"Overall zone hazard rating"]
[]
[null,"Overall zone hazard rating (Ciria 736)","Medium"]
[]
[]
[1.5,"Containment required"]
[]
[]
[null,"Containment required","Class 2"]

{"sheet":"2.Total vol. - Mitigation","index":3,"n_rows":15,"n_cols":22,"rows_kept":15,"cut":false,"hidden":false,"merged":[[4,1,4,9],[6,3,6,9],[6,11,6,20],[7,1,14,1],[7,3,7,9],[7,11,7,20],[8,3,8,9],[8,11,8,20],[9,3,9,9],[9,11,9,20],[10,3,10,9],[14,3,14,9],[14,11,14,20],[10,11,10,20],[11,3,11,9],[11,11,11,20],[12,3,12,9],[12,11,12,20],[13,3,13,9],[13,11,13,20]]}
[]
[]
[2.1,"Catastrophic/Partial failure - modes (loss of containment) "]
[]
[null,"The below proposed mitigation measures are recommended and should be read in conjunction with the proposed containment options in '5.Containment type-Total vol.' The risk rating after mitigation incorporates risk reduction due to the engineered containment options. Implementing the below measures will significantly reduce the probability and risk of failure from the tanks and significantly reduce the amount of secondary containment. As per CIRIA 736, the above will need to be implemented in conjunction with a good maintenance strategy as mentioned in Box 5.2,Page 60."]
[]
[null,"Risk","Cause","Existing consequence and mitigation measure",null,null,null,null,null,null,"Existing zone risk rating","Proposed Mitigation",null,null,null,null,null,null,null,null,null,"Risk rating after mitigation"]
[null,null,"Operational failure - tank (partial)",{"$f":"'1.Risk assessment'!$D$68","v":"Imported liquid sludge is stored in 1 No. sludge reception tank, it is then screened by 2 No.strain presses and then mixed with indigenous sludge in 2 No. post screening sludge storage tanks. In the event of overfilling/overflow or foaming conditions, the site is manned 24 hours a day, 7 days a week and so any loss of containment can be dealt with immediately and with tankers being on site within 2hrs, as part of an emergency response KPI with local tanker operator MTSR. \n\nBoth clean and contaminated surface water is directed to a pumping station which recirculates it back into the system. The stormwater drainage of potentially contaminated areas from within the Site boundary is routed into the head of the works with no discharge outside of the site boundary. This allows site operations some time to deal with the leaks from operational failures. Flows exceeding the drainage system capacity will require mitigation with an improved inspection regime to catch spills prior to becoming significant.\n\nThe tanks are monitored by SCADA system"},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L68","v":"M"},"All tanks undergo a delegated inspection regime and the process parameters are monitored and understood by site operatives.\n\nSite operators are on site 24 hours a day, 7 days a week. Daily site inspection regime will consist of a site walkover. Any defects located will be escalated to site manager for a repair resolution to be determined. If there is not an immediate risk posed by the defective asset and large scale repair is required then, the asset planning team will be informed in order to plan the necessary repairs. Any reactive works required will be undertaken by Site Operations team. \n\nInspection/Frequency\n>Walk round the site, identify and clear up any waste materials: Daily\n>Note signs of any deterioration of tanks or surroundings: Daily\n>Note any small leaks or spills, fix them and clean them up immediately: Daily\n>Integrity/Condition assessment all key sludge assets - Drain tank and inspect condition: 10 yearly\n\nFurther mitigation\n >A proactive planned preventative maintenance (PPM) and replacement programme linked to asset lifespan. Site Manager ensures the PPM is implemented effectively to minimise the probability of equipment malfunction. \n >A robust leak detection and repair plan will be set out and enacted.\n >The site will be monitored using a telemetry to monitor tank levels and process flows. Trigger levels will be assigned to risk rating and proportional response will be taken. Alarms that protect against a loss of containment will have a response time the same as for other emergencies (Approx. 1 hr).\n>Penstock valves will be placed at strategic SW chambers to reduce the risk of sludge flows getting in to the SW drainage system. An automated solution for closing them and also any need for regrading of surfaces to reduce risk will be looked into at detailed design.\n\nControl of substances hazardous to health (COSHH) assessment undertaken for all raw materials.",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Structural failure - tank (catastrophic)",{"$f":"'1.Risk assessment'!$D$69","v":"The tank is located above ground. For any loss of containment below ground, the sludge liquid will percolate into the permeable soil at a slow rate over a long period if not detected by the level or temperature alarms.\n\nIn the case of significant damage above ground, the total volume contained above ground could spill. \n\nIn the event of a catastrophic failure, sludge would flow in all directions as there is no containment immediately around the tank. The sludge would predominantly flow to the western boundary."},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L69","v":"M"},"The above inspection and further mitigation proposals will be applicable to structural failure, also.\n\nAs part of proposed mitigation, regular daily inspections of the site drainage systems and other equipment are to be undertaken, with any repairs and maintenance carried out if necessary.",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Structural failure - tank (partial)",{"$f":"'1.Risk assessment'!$D$70","v":"Partial structural failure of the tank would mainly be through cracks.  In the case of significant cracks forming above ground, the volume contained above ground would seep through the cracks. If the cracks are significant (>6mm), the tank could potentially lose the above ground volume over a long period of time if the level and temperature alarms are not functioning. However, this is unlikely. \n\nDue to 24/7 operational presence on site, large drops in levels in the tanks and significant leaks above ground would be noticed. Significant cracks (>6mm) below/above ground would also be easily spotted during the daily visual inspections. \n"},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L70","v":"M"},"The inspection and further mitigation proposals outlined as mitigation for Operational failure will be applicable to structural tank failure, also.\n\nTo minimise loss of containment underground, it is advised that the tanks be visually inspected on daily basis and structurally inspected with increased regularity. Falling head tests should also be regularly carried out to limit any potential leaks underground. Tank to be refurbished if necessary.\n\nPermeable areas around the tank (gravel) and low lying grassed areas are also to be replaced with impermeable hardstanding to remove the pathway to the ground. Soakaways to be filled in (concrete) and all connected drainage to connect to liquor return.",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Structural failure - pipework (catastrophic)",{"$f":"'1.Risk assessment'!$D$71","v":"In the unlikely event where the above ground rising mains to the tank, heatamix pipework or de-gritting pipework fails and breaks off, a significant volume would spill out. Tanks have level and temperature alarms and the site is manned 24/7 so any required valve could be immediately shut off by operational staff.\n\nThe consequence of a catastrophic failure of containment is it's able to flow in all directions as there is no containment bunds immediately around the tank. Based on topography, sludge will cascade towards the west.\n\nTotal loss of containment is unlikely. A partial loss of containment would be more likely to occur."},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L71","v":"M"},"To mitigate the very unlikely occurrence where the above ground pipework could fail/collapse, the necessary pump controls (Low and high pressure switches to trip the pump) need to be put in place, if not already, if there is a sudden loss of pressure in the rising mains (feed, mixing, hot water pumps rising mains), the pumps should stop. \n\nAll above ground pipework and chambers to be visually inspected daily. Structural inspections and falling head testing should be undertaken with increased regularity to test for any leaks. Pipework and chambers to be refurbished or replaced, if necessary to BAT standards. \n\nPermeable areas around the tank (gravel) and low lying grassed areas is also to be replaced with impermeable hardstanding to remove the pathway to the ground. Soakaways to be filled in (concrete) and all connected drainage to connect to liquor return.",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Structural failure - pipework (partial)",{"$f":"'1.Risk assessment'!$D$72","v":"Majority of pipework and connections are located above ground. Some of the pipework is located below ground or within the chambers below ground. \n\nIf loss of containment occurs underground (through leaks, joints and seals), sludge will percolate into the soil at a slow rate over a long period and localised wet areas will be present above ground.\n\nIf loss of containment occurs above ground through leaks or damage to pipework, due to the permeable stone around tank, sludge will also percolate into the soil at a slow rate over a long period.\n\nDue to operational presence on site and SCADA monitoring, significant leaks (above or below) ground would be noticed and loss of containment would be mitigated through operational measures (closing of valves). \n\nTotal loss of containment is unlikely (partial loss of containment would be more likely to occur)."},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L72","v":"M"},"As tank was fit for purpose at the time of construction, secondary containment provision is not considered for the underground pipework.\n\nTo assess the condition of underground pipework and chambers, CCTV and leakage detection (falling head tests) should be done on a regular basis to check if any leakage is experienced.  All above ground pipework and chambers to be visually inspected on daily basis for any leaks. Pipework and chambers to be refurbished or replaced, if necessary to BAT standards.\n\nPermeable areas around the tanks (gravel) and low lying grassed areas is also to be replaced with impermeable hardstanding to remove the pathway to the ground. Soakaways to be filled in (concrete) and all connected drainage to connect to liquor return.",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Vehicular impact (partial to catastrophic)",{"$f":"'1.Risk assessment'!$D$73","v":"No known vehicle impacts - but no barrier/protection\n\nVehicles could potentially impact and damage tank which is located above ground. Vehicular impact could cause some damage to the tank, if significant, proportion of above ground volume could be lost. Vehicle is however unlikely to damage underground sections of tanks or displace any liquid within them. \n\nTotal loss of containment could occur if the vehicle impact causes significant damage to the tank. High speed impact unlikely, but vehicle could damage pipework connected to tank (mixer pump) and cause a significant hole in the tank at low level. Could impact a potential weak point."},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L73","v":"M"},"Vehicle barriers or bollards are proposed around front of the tanks along the road. Potential for the fence installed to be stronger and to be able to withstand some vehicular impact. The likelihood of such occurrence in low.\n\nThis is to mitigate any potential impacts from vehicles and potential damage which could lead to loss of containment. ",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Vandalism",{"$f":"'1.Risk assessment'!$D$74","v":"No known vandalism to tanks or pipework.\n\nIf vandalism damage were to occur, total loss of containment is unlikely, but could occur if significant damage or on theft of mixer pumps and pipework. Partial loss of containment would be more likely to occur if slight damage was done."},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L74","v":"L"},"Access to site is restricted by a 2.8m high chain link security fence. An 8ft high steel palisade gate secures the main access and is automatically operated. The Site is staffed 24 hours a day, 7 days a week. For visitors and unauthorised personnel an intercom\nsystem at the Site entrance is used. The Site also benefits from a CCTV system.Regular inspections of the boundary fencing, and buildings are undertaken to ensure that these have not been compromised and continue to prevent easy access to site.\n\n[As per Main Supporting Document 790101_MSD_Main_FOR, Site Security, Page 25]",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Flooding",{"$f":"'1.Risk assessment'!$D$75","v":"There is no recent history of flooding at the site. The entire site is located within a very low risk flood zone (less than 0.1% annual probability) with the River Arun running approximately 2km to the east.\n\n[As per Climate Change Risk Assessment  Report 790101_ERA_CCRA_FOR,Page 11]"},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L75","v":"L"},"Ensure flood plan for site follows EA guidance.\n\nInclude provision of sump pump to keep site clear of floodwater.\n\nEnsure diesel generators are at sufficient height to ensure they are not at risk of flooding (coastal or otherwise)",null,null,null,null,null,null,null,null,null,"L"]

{"sheet":"3.Containment volume-Total vol.","index":4,"n_rows":28,"n_cols":5,"rows_kept":28,"cut":false,"hidden":false,"merged":[]}
[]
[]
[3.1,"Secondary containment volume requirement - Inventory volume (above ground)"]
[]
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[]
[null,"Tank name / refs.","Tank Stated Capacity\n(m³)","Tank Above Ground Volume\n (m³)","Comment"]
[null,"Digestor 1",1848,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1848},"Tank above ground"]
[null,"Digestor 2",1848,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1848},"Tank above ground"]
[null,"Digestor 3",1848,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1848},"Tank above ground"]
[null,"Sludge Reception Tank",100,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":100},"Tank above ground"]
[null,"Post Screening Sludge Storage Tank 1",1732,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1732},"Tank above ground"]
[null,"Post Screening Sludge Storage Tank 2",1732,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1732},"Tank above ground"]
[null,"Surplus Activated Sludge Tank",1131,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":1131},"Tank above ground"]
[null,"Liquor Return Tank",1885,0,"Fully buried - roof only above ground"]
[null,"Thickened Sludge Storage Tank",700,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":700},"Tank above ground"]
[null,"Post Digestion Storage Tank 1",352,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":352},"Tank above ground"]
[null,"Post Digestion Storage Tank 2",352,{"$f":"Table1[[#This Row],[Tank Stated Capacity\n(m³)]]","v":352},"Tank above ground"]
[]
[null,"Total of Tank Volumes",null,{"$f":"SUM(D8:D19)","v":11643},"m³"]
[null,0.25,null,{"$f":"D20/4","v":2910.75},"m³"]
[null,"110% of largest",null,{"$f":"D8*1.1","v":2032.8000000000002},"m³"]
[null,null,"Applicable rule",0.25]
[]
[null,"Containment volume required",null,{"$f":"D21","v":2910.75},"m³"]
[]
[null,null,null,"Above ground volume used in line with 'realistic spill scenario' as outlined in CIRIA C736."]
[null,null,null,"Other tanks are independently bunded (double skin or 'collared' tanks)"]

{"sheet":"4.Current asset evaluation","index":5,"n_rows":24,"n_cols":3,"rows_kept":24,"cut":false,"hidden":false,"merged":[]}
[]
[]
[4.0999999999999996,"Current Asset Evaluation","Post Screening Sludge storage tank 02"]
[null,"Description","Imported liquid sludge is stored in 1 No. sludge reception tank, it is then screened by 2 No.strain presses and then mixed with indigenous sludge in 2 No. post screening sludge storage tanks."]
[null,"Number of tanks","11\n(Risk assessed for one tank only as example/typical for site)"]
[null,"Volume of tank","1732 m3 (approximately) - total volume for tank"]
[null,"Material of tank","Concrete"]
[null,"Above/below ground?","Above ground tank"]
[null,"Pipe material","All connecting pipework is thick-walled – some above ground and some below ground."]
[null,"Drainage for zone","The drainage is directed towards the Western direction\n\n[As per Ford WTW Drainage, 720116/M104/2001]"]
[null,"Year of construction","-"]
[null,"Surrounding area","Permeable gravel surrounding the tank"]
[]
[null,"Pump rate - to Post Screening Sludge storage tank 02","-"]
[null,"Pump rate - from Post Screening Sludge storage tank 02","-"]
[]
[]
[null,"Is asset fit for purpose?","The tanks were originally designed and constructed to hold digested sludge and has been operating with no notable concerns.  \n\nTank has not undergone a change of use"]
[null,"Condition of the tank\n\nAny tank failures - cracks, flaking, corrosion, overflows, overfilling?","no structural concern"]
[null,"Condition of pipework\n\nPipe leaks, corrosion?","No visible issues/leaks reported by operational staff"]
[null,"Protection of assets ","No vehicle impact protection - Vehicle barriers or bollards are proposed around front of the tanks along the road. Potential for the fence installed to be stronger and to be able to withstand some vehicular impact."]
[null,"Control/monitoring/alarming measures in place?","All tanks undergo a delegated inspection regime and the process parameters are monitored and understood by site operatives"]
[null,"Secondary containment provided?","None"]
[null,"Secondary containment condition?","N/A"]

{"sheet":"5.Containment type-Total vol.","index":6,"n_rows":177,"n_cols":15,"rows_kept":177,"cut":false,"hidden":false,"merged":[[166,1,166,10],[155,1,155,10],[161,1,161,10],[162,1,162,10],[163,1,163,10],[164,1,164,10],[135,1,135,10],[136,1,136,10],[137,1,137,10],[138,1,138,10],[165,1,165,10],[130,1,130,10],[131,1,131,10],[132,1,132,10],[133,1,133,10],[134,1,134,10],[125,1,125,10],[126,1,126,10],[127,1,127,10],[128,1,128,10],[129,1,129,10],[120,1,120,10],[121,1,121,10],[122,1,122,10],[123,1,123,10],[124,1,124,10],[4,1,5,10],[65,1,65,4],[65,5,65,11],[56,1,58,9],[62,1,62,4],[62,5,62,11],[63,1,63,4],[63,5,63,11],[64,1,64,4],[64,5,64,11],[107,1,107,10],[109,1,109,10],[110,1,110,10],[111,1,111,10],[112,1,112,10],[114,1,114,10],[115,1,115,10],[116,1,116,10],[118,1,118,10],[119,1,119,10],[117,1,117,10]]}
[]
[]
[5.0999999999999996,"Containment to be provided"]
[]
[null,"Based on a 'High' site risk rating for the zone, all tertiary options in Section 5.4 are based on Class 3 containment which includes impermeable lining to protect soil and groundwater infiltration."]
[]
[]
[null,null,null,null,null,null,null,null,null,null,null,null,"Typical Bund section view"]
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[null,null,null,null,null,null,null,null,null,null,null,null,"Typical reinforced concrete wall section view"]
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[5.2,"Catastrophic failure"]
[]
[null,"Catastrophic failure assumes the tank loses all its above ground volume and that the total volume would need to be contained."]
[]
[]
[]
[null,"Suitability of containment to be provided"]
[]
[null,"Type",null,null,null,"Applicability",null,null,null,null,null,null,null,null,"25% volume applies - no single tank failure."]
[null,"Reinforced concrete/masonry flooring and bund",null,null,null,"Due to relatively large volume from loss of containment, use of a masonry/concrete bund is generally not appropriate for local containment. Because local containment necessitates a deeper bund or a long concrete wall, difficulties arise. The containment's high wall height poses a health and safety danger of a potential fall and being trapped if the tank breaks while someone is within the enclosure. Furthermore, because concrete is vulnerable to heat shrinkage and expansion, which can cause cracks, concrete/masonry bunds require constant inspection and maintenance to ensure their impermeability. Sheet pile walls are preferred to achieve complete impermeability of the containment, if space for bunded areas is not available."]
[null,"Earth banked basins, bunds and flooring",null,null,null,"Soil within site is of permeable nature - soft to firm consolidated, compressible silty \nclay, but may also include layers of silt, sand, peat and gravel.\n\nPotential for stabilised soil (lime and cement used to make it impermeable) for bund construction is limited.Importing of sufficient volumes of non porous material would likely be required.\n\nDependant on space required, might be applicable"]
[null,"Containment tank",null,null,null,"Nature of catastrophic failure and type of primary containment makes the use of a containment tank not appropriate"]
[]
[]
[5.3,"Catastrophic failure in existing situation (Do Nothing) - Visualisation"]
[]
[]
[]
[]
[]
[]
[null,null,null,null,null,null,null,null,null,null,null,null,"This is provided to illustrate the existing condition only and does not represent a containment proposal."]
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[]
[5.4,"Containment Proposal"]
[]
[null,"Proposal Summary"]
[null,"The solution is a whole-site solution, whereby the containment provided is considered as one bund."]
[null,"As such the containment volume required is based on the larger of the 110% of the largest tank or 25% of the total volume of the tanks."]
[null,"In this scenario the 25% rule applies and equates to a containment bund requirement of 2,911m³ (see worksheets 3) \nNoting that above-ground volumes are used in line with CIRIA C736 and reflecting a practical maximum spill that could be encountered.\nFor info the 110% rule is calculated to a required containment volume of 2,033m³."]
[null,"New impermeable areas will be installed to provide an impermeable surface to the full spill/ bund area. Where of suitable condition and type, existing roads and surfaces will be utilised to minimise new impermeable surfaces.\nThis is not shown to the right but includes the full extent of the area shown on the spill model output. New impermeable surface is estimated to be ~5,000m2.\nDetailed survey outcomes regarding the remediation and reuse of existing surfaces in line with the below comments may determine the need for additional new impermeable surfaces."]
[null,"New walls will be installed to contain a spill, these are illustrated to the right and comprise of an estimated total of:\nLining of existing earth banks of typical 0.7m height - Yellow line - total of 660m (illustrated by yellow line to the right)\nA combination of kerbs, low concrete walls and speed humps/road tables of less than 500mm (illustrated with red line) will restrict the spill to predominatly the STC area and away from the site entrance, total of 270m. An additional 80m of concrete wall will protect the gas bag and related systems.\nSome existing kerbs may be used, remediation extent not shown.\nNote final freeboard height to be determined in detailed design, see narrative provided below for specific topics of consideration."]
[null,"Note the existing topography is relatively flat and with an earth bank around the majority of the permimeter. A failure of any tank will broadly achieve the same settled position and thus be contained by the proposed solution. This is apparent on site and has not been modelled.\n"]
[null,"Containment Solution Scope"]
[null,"New walls will be built to contain 25% of the total tank volume"]
[null,"The final local wall type remains subject to confirmation following further detailed design development and contractor input. \nThe current anticipated solutions are a combination (as most suited to a given area):\nReinforced concrete walls of various heights based on local need.\nEarth banks lined with concrete canvas are proposed where there are existing earth banks or suitable volume of appropriate material is available in the area. This offers the opportunity for compliant solution at lower cost and lower embodied carbon.\nAdditional wall types are available and form part of the ongoing design development considerations to ensure the most appropriate solution is adopted. These are typically formed of a structural wall element (pre-formed concrete blocks, sheet piles, gabion cages) with a liner. Until the full review has been completed and appropriate competent person has signed them off this remains subject to context-specific evaluation."]
[null,"Extensive new impermeable surfaces meeting the required 10-9m/s impermeability will be installed in line with CIRIA C736. \nThis is planned to be a combination of reinforced concrete and concrete canvas but some localised applications may be more suited to alternative solutions from table 8.2 of CIRIA C736.\nNew impermeable areas will provide a continuous surface over the area identified as within the bund, this includes existing gravel areas between tanks and equipment. Details for tie in to existing structures to ensure an appropriate containment solution will either be to manufacturers details or developed on specifically for the application.\nSome existing surfaces will be utilised, the extent remains subject to detailed survey and identification of appropriate remediation to ensure it meets an appropriate standard."]
[null,"The spill includes some areas around WtW primary settlement tanks which (currently gravel) will be made impermeable. Utilising this area allows for a reduction in the overall spill height and to allows for retention of safe operational access and vehicle routes.\nThe need for WtW-STC operational coordination is acknowledged, the site is owned by one company and managed by one operational team. "]
[null,"Buildings and cake storage areas are excluded from use for containment volume calculations based on a provisional assumption that they will be protected from flood (where possible) and reflects a more conservative position for the calculation of containment volumes."]
[null,"In the event of a spill the contained sludge and any rainwater will not be returned to the works inlet. It is proposed that sludge tankers will be utilised to empty the bund with suction hoses. This will form part of revised spill procedure based on the final design and further assessment and planning.\nThe site operator will have a daily action to empty the bund (STC-side drainage system in this instance) of rainwater. The scope includes new sumps, electrical pumps, sample points and the required pipework to return the rainwater to the works inlet. This will be a manual start pump and require a check by the operator for evidence of any spills prior to starting the pump. The pump will have an anti-syphon arrangement and auto-shutoff at low-level. The location of sumps and pipework routes will be identified in detailed design. \nThe rainfall containment volume accounts for 24hours at AEL rainfall. Noting the CIRIA C736 requirement for 8 days at AEL, further design and operational planning will determine the detail of a recovery scenario (re. tanker removal vs rainfall accumulation), the outcome of this will inform the final allowance for freeboard for rain and the findings will be reflected in the final wall heights."]
[null,"The site operator will have a daily (or with cause) action to manage rainwater levels within the bund. \nThe scope includes new sumps, electrical pumps, sample points and the required pipework to return the rainwater to the works inlet. This will be a manual start pump and require a check by the operator for evidence of any spills prior to starting the pump. The pump will have an anti-syphon arrangement and auto-shutoff at low-level. The location of sumps and pipework routes will be identified in detailed design. "]
[null,"CIRIA C736 requires rainfall allowance in capacity calculations for 10% AEP rainfall for; 24 hours [prior to the incident], the duration of the incident, eight days [after the incident] (or other period appropriate to the particular site circumstances).\nThe final wall heights will include for appropriate freeboard and rainwater containment volumes based on the completion of design and calulations.\nA rainwater allowance of up to 136mm in line with a worst-case region 3 rainfall for 24 hours plus 8 days will be applied to the final wall height. \nThe solutions shall remain 'as drawn' but the wall height will vary to accomodate the final calculation.\n"]
[null,"Additionally a firefighting foam allowance of >100mm is required if the contents are combustable. These products are not combustable so this alowance does not need to be applied.\nSurge allowance of 250/750mm is recommended in line with CIRIA C736 table 6.3.\nThe final confirmed height of walls including freeboard allowance remains subject to detailed design and final calculations.\nNo bunds are covered so rainfall is relevant.\nAn operator action for starting the bund drain pumps daily as required aligns to the 24 hours pre-incident requirement.\nThe duration of the event depends on the severity (partial failure/catestropic) but it is considered feasible to utilise road tankers (for holding) to empty bunds at any given point. These are used widely by the company. The CIRIA C736 allowance for 8 days post incident rainwater capacity is considered in relation to the ability to manage water levels post-incident. In this scenario it is considered feasible to remove the spill from the bund and into tankers in the event of significant rain."]
[null,"The allowance for post incident rainwater is anticipated to be related to particular site circumstances as CIRIA C736 allows.\nThis requires completion of the design and [it is anticipated] this will be part of further sdiscussion with local EA officers to gain agreement.\nFurther design and operational planning will determine the detail of a recovery scenario (ie. calculations for tanker attendance time, pump rate for removal vs rainfall accumulation), the outcome of this will inform the final allowance for freeboard for rain and the findings will be reflected in the final wall heights.\nThe suggested freeboard allowance for surge does not align to the peak heights from the spill modelling (allowed by CIRIA C736 as alt. to standard allowance).\nAs such the overall freeboard remains subject to confirmation to ensure a given solution is able to contain a practical spill scenario."]
[null,"No allowance for firefighting foam capacity has been made as the substances under consideration are not flammable.  As such, fire is not a scenario that is considered practically feasible and is considered to align to CIRIA C736 figure 4.3 for non-combustible contents\nThis remains subject to acceptance by the Environment Agency in design development and acceptance of improvement condition plans. Should it be deemed required an allowance can be made on wall heights to accommodate this."]
[null,"Overfilling tanks has not been modelled as the operational control processes (level gauges, SCADA etc) are thought to be sufficiently robust to demonstrate this spill scenario requires less containment than a catastrophic tank failure scenario. Additionally the tank modelled is the largest tank and tank transfers are only completed from single tank to single tank. Surveys in relation to level gauges etc to address BAT 19 and subsequent analysis of findings will determine if this correct."]
[null,"Surge allowance will be made on a standardised basis of additional height on the bund wall."]
[null,"The use of flood gates has been excluded from all solutions (on all sites) on the basis their operation is not guaranteed to be timed correctly, presents a single point of failure and may adversely impede any response scenario."]
[null,"The distance of tanks from walls means jetting to outside of the bunded area is thought unlikely, this remains subject to further evaluation and calculation in the next stage of design including consideration of tank types and the orientation (e.g. concrete tanks, other buildings/existing fences etc). Should a jetting risk be determined appropriate mitigating measures will be implemented as part of the overall solution to ensure any liquids remain within the bunded area."]
[null,"The bunded areas will be re-profiled locally to achieve the required falls to accommodate new sumps and pumps."]
[null,"The drainage solution for the area will be reviewed and further intrusive surveys completed to ensure any existing drainage that may be utilised is of good condition and retains water in line with the bunding requirements. It is anticipated that extensive drainage modifications will be required to ensure all bunded areas are captured and surface water dealt with in line with BAT. This requires additional design work to determine the most appropriate solution.\nAny existing soak aways (or similar) within a bunded area will be removed and appropriate BAT compliant drainage solutions provided.\nRoof areas where BAT permits for uncontaminated rainwater to be directed to the ground (outside the bund) will be considered to reduce the amount of water flowing in drains or returned to the WtW."]
[null,"Firewater within a newly bunded area will be contained by the bund and allow for appropriate disposal. There will be no gravity hydraulic connection from the bund to the drainage system/return to head of works. Manual intervention by an operator will be required to start the pumps and remains subject to the pre-acceptance (sample/test) procedure to ensure the water is appropriate for discharge to head of works. In the event of an incident, depending on the nature of the contamination (firewater in this context) the product will be held within the bund and be subject to alternative disposal methods. Depending on the scale and nature of the incident this may include temporary holding in road tankers to facilitate safe recovery activities. The detail regarding this procedure remains subject to further evaluation as solutions are designed and implemented.\nFirewater use on other process/equipment areas (which either have existing, or will be provided with new, impermeable surfaces) will drain to site drainage systems. A robust means of isolating the site drainage from returning to the head of works is required. Where sites have pumped return to head of works stopping the pump and ensuring no hydraulic link (syphoning) is required. Where return to head of works is (or could be) gravity returned, a new isolation valve is required which is to be shut in the event of an incident.\nImplementation of these measures will ensure no firewater returns to the WtW without appropriate controls including sampling/testing. Further design development is underway to determine the most appropriate solution to address this requirement and ensure compliance."]
[null,"Existing pits, chambers and other existing assets in the bunded area will be reviewed on a local basis to determine the most appropriate solution to provide appropriate containment.\nThis is anticipated to require the replacement of pit covers with water tight/sealed versions to ensure containment. This is not reflected in CIRIA C736 but is considered appropriate and the wholesale removal of pit and ducts, underground chambers and pipework is cost-prohibitive."]
[null,"No retrofitted leak detection under existing tanks is proposed, alternative solutions to manage the risk will be developed. This will include tank inspections, tank periodic hydrotesting and (subject to contamination hydrogeologist review of the application) boreholes to monitor for leakage.\nThe basis for this is that retrofitting may cause settlement issues or create voids under tanks which would counter the objective of the leak detection. Additionally most tanks have either a concrete tank base, or a concrete foundation under the tank base, thus providing an appropriate impermeable surface in line with CIRIA C736."]
[null,"The majority of the pipework would be within the existing bund and thus provided with appropriate containment. Existing underground pipework would not be replaced wholesale but will be tested/inspected and appropriate solutions developed based on the findings. \nOver time the underground pipework would be replaced with above-ground pipework as and when other projects require changes to the site layout/operation. Where pipework is not within the bunded area a case by case review will determine an appropriate means of leak detection and secondary containment (based on factors like insulation, condition, routing, pumped/gravity system)."]
[null,"This solution incorporates all process areas, thus a failure of equipment within the process area would be appropriately contained within the bunded area."]
[null,"Existing walls and kerbs will be utilised for shallow spill areas, these will undergo a detailed survey to identify appropriate remediation which will be completed to provide an appropriate containment 'wall'. Speed humps will be installed on the roads to reduce the spread of any smaller spills."]
[null,"Spill modelling has not been completed for all tanks as CIRIA C736 does not require this, nor is it thought required as part of normal good practice. The containment of all tanks and the suitability of the design for this scenario has been assured through consideration of existing topo and consideration of the flows in a given area relative to the volume of the other (smaller) tanks in question."]
[null,"Provisional DSEAR guidance suggests any methane present would disperse rapidly and not present a potentially explosive atmosphere. Further evaluation of this will be undertaken in design and may determine the need for design changes which would be incorporated to the solution outlined."]
[]
[null,"Modelling notes."]
[null,"The model was built in Infoworks ICM 2021.9 and provides a 2D output of a 3D scenario"]
[null,"The model utilised a combination of LiDAR / Digital Terrain Model data with topographical survey data as an additional reference"]
[null,"A mesh was created by the modeller to represent the topography of the existing site"]
[null,"Drainage was excluded on the basis that modification of drainage systems will be required to ensure no links to outside the bund."]
[null,"Building areas were excluded from containment volume areas - assumes no flooding of internal areas of the building"]
[null,"The whole area is treated as impermeable surface reflecting the required final state for the bund floor"]
[null,"Levels and wall heights represent 'settled' levels"]
[null,"Rainfall has been accounted for in the model scenarios - however this will be verified in relation to final wall heights (see design development)"]
[]
[]
[null,"Solution Development Notes with respect to the wider context within which IED will be delivered"]
[]
[null,"The design for the containment continues to progress and remains subject to further development."]
[null,"The design will require sign off by a competent civil or structural engineer."]
[null,"CIRIA C736 compliance is the objective (and BAT is the referenced requirement). \nA few elements regarding CIRIA C736 details in the context of this application will be reviewed by a qualified engineer for suitability and as outlined in CIRIA C736 we will look to discuss this with the EA as our regulator. \nSome queries are in line with additional guidance offered by the Agency in other forums (TaF, Defra meetings et. al.).\nThis may include:\n\n\n\n\n\n\n"]
[null,"Accounting for rainfall accumulation in bunds will be reviewed in further detail to determine final wall heights - this will look to consider:"]
[null,null,"Operational process in no-spill scenario for daily removal of rainwater and return to head of works (inc. determining the presence of spilled sludge)"]
[null,null,"Emergency response in spill scenario for removal of sludge (likely using road tankers and suction)"]
[null,null,"Allowance for climate change in rainfall calculations"]
[null,null,"Duration of AEL rainfall required to be accommodated with respect to CIRIA C736 and the final operational basis for normal and spill scenarios"]
[null,"Steel plating over joints as the origin of this (within CIRIA C736) was in related to a fire scenario for hydrocarbon storage and may not be required for STC/sludge facility/storage."]
[null,"The relationship between the risk assessment 'CIRIA classification' and the details for the solutions proposed, particularly differentiating between Class two and class three requirements."]
[null,"The use of Concrete Canvas (as it is not listed in CIRIA C736 table 8.2 but can be demonstrated to meet the 10^-9m/s impermeability requirement)"]
[null,"The need for sub-surface 1m impermeable soil based on type of stored material (re. CIRIA C736 figure 8.4) and the requirement for under-bund lead detection (class 3). An alternative solution with lower carbon impact may be proposed for the sub-surface and based on SMR in-situ remediation solution. "]
[null,"Where existing surfaces are proposed to be utilised the details in CIRIA C736 may not be fully achieved as retrofitting of water bars is not considered feasible. A suitably qualified person will be required to approve any proposed solutions."]
[null,"The use of sealed covers for existing pits as not clearly defined in CIRIA C736"]
[null,"The context in which IED will be delivered at this site will look to reflect the wider guidance provided around IED implementation."]
[null,"The following points are considered relevant factors in provision of the final solution implemented at the site:"]
[null,"Wording of improvement conditions and agreement for acceptable solutions with Local Agency Installation Officers only being possible upon receipt of permit/draft permit"]
[null,"Appropriate accommodation of the SW Bioresources Strategy regarding future site use and remaining asset life requirements"]
[null,"Specifically the plan to stop AD at this site at the end of AMP8 (March 2030) and thus the retirement of the digestor related assets."]
[null,"This leads to investment focussed on the assets that are retained longer term and a risk-evaluated investment basis for the digestor related assets."]
[null,"This may (subject to assessment) be supported by additional measures such as enhanced tank inspections and boreholes for leak identification"]
[null,"To include Director commitment to site closure"]
[null,"This element is reflected in an Uncertainty mechanism with respect to Ofwat submissions"]
[null,"Demonstration of appropriate risk-management for the time period required, including consideration of the tank condition, material and inspection report for remaining life"]

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