{"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":28,"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":[[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],[15,1,15,5],[15,6,15,7],[16,1,16,5],[16,6,16,7],[17,1,17,5],[17,6,17,7],[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],[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],[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]]}
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[null,"Project Information"]
[null,"Workbook Name:","IED Risk Register-Millbrook"]
[null,"Project Title:","SWS EMA - Lot 8 - EIA "]
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[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-MIL-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","Tom Reynolds",null,"Calc Nr:"]
[null,"Checker","Anita Manns",null,"Nr Sheets:",6,null,null,"This is updated automatically as sheets are added/removed"]
[null,"Template Version","E"]
[null,"Design Phase"]
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[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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[]
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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","2022-08-15","Ashwin Powar","AP","2022-09-02"]
[292575378,"2.Total vol. - Mitigation","Hari Prasath","HP","2022-08-15","Ashwin Powar","AP","2022-09-02"]
[292576031,"3.Containment volume-Total vol.","Hari Prasath","HP","2022-08-15","Ashwin Powar","AP","2022-09-02"]
[292576417,"4.Current asset evaluation","Hari Prasath","HP","2022-08-15","Ashwin Powar","AP","2022-09-02"]
[292576606,"5.Containment type-Total vol.","Tommaso Tosi","TT","2022-08-15","Daniel Watson","DW","2022-09-02"]
[]
[null,"Approved by"]
[null,"Approver",null,"Signature",null,null,"Date"]
[null,"Tom Reynolds",null,"TR",null,null,"2024-02-26"]
[]
[null,"Version History"]
[null,"Version","Description",null,null,"Originator","Checker","Date"]
[null,"P01","Initial Calculation",null,null,"Hari Prasath","Ashwin Powar","2022-09-02",null,"Latest Version",{"$f":"OFFSET(B40,COUNTA(B41:B51),)","v":"P03"}]
[null,"P02","Worksheet 5 revised to reflect design development",null,null,"Tom Reynolds","Tom Reynolds","2024-06-27",null,null,"2024-12-16"]
[null,"P03","Tank list amended to include Liquor tank on worksheet three.",null,null,"Tom Reynolds","Anita Manns","2024-12-16",null,"Last Checked","2024-12-16"]

{"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 identification secondary containment solutions 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.\nThis include risk assessment of the nature of the product stored.","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"]
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[null,"Conclusions"]
[null,"The solution requires multiple bunds due to existing topography and access requirements. The solution will impose significant operational constraints. ","If the spreadsheet/calculation has a conclusion please enter it here"]
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[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"]
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[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":[[72,3,72,9],[73,3,73,9],[74,3,74,9],[82,1,82,2],[87,1,87,2],[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],[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],[42,9,47,9],[43,1,43,2],[43,3,43,4],[44,1,44,2],[44,3,44,4]]}
[]
[1.1000000000000001,"Source"]
[]
[null,"Material","Physical properties","Maximum quantity","units","Storage","Flammability","Corrosive","Ecotoxicity (based on LD and quantity)","Hazard rating "]
[null,"Sludge for AD.\nAnaerobic digester 04 used as example and considered typical for the site for RA purposes. See worksheet 3 for each bund.","Liquid with sludge, Gas (methane)","3251 m3 (approximately) - total volume for tank\n\n[As per IED Permit, Main Supporting Document 790101_MSD_Main_MIL,Page 3]","m3","Steel tank ","Methane produced is flammable\n\nDigestate isn't flammable","Low","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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[null,"Figure 1.1 Site Layout with Source-Pathway-Receptor",null,null,null,null,null,"Figure 1.2 Site picture of Anaerobic digester 04"]
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[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 Tidal Flat Deposits underlying the site are classified by the Environment \nAgency as Unproductive strata, however the River Terrace Deposits below \nthese are classified as a Secondary A aquifer.\n\n[As per IED Permit, Site Condition report 790101_MSD_SCR_MIL,Page 3]",null,"Direct contamination but over an extended period of time",null,"M",null,null,"The River Test lies approximately 350m to the south-east of the site at its closest point (where the Southampton Docks are located). In the area it flows in approximately a north-west to south-east direction towards The Solent. There is a watercourse to the west of the site which has a low flood risk and depth of flood greater than 900mm,  which could impact the WTW site. \n\n[As per Site Condition Report 790101_MSD_SCR_MIL, Hydrology and flooding, Page 3],[As per Climate Change Risk Assessment,790101_ERA_CCRA_MIL, Page 8]","H"]
[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,"The site is located within Flood Zone 1 therefore at low risk of flooding from rivers or the sea under the current conditions. Increased rainfall as a result of climate change could exacerbate the existing flood risk.\n \n[As per IED Permit, Climate Change Risk Assessment, 790101 _ERA_CCRA_MIL,Page 10]",null,"Direct contamination",null,"M"]
[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,"The site is located within a nitrate vulnerable zone (NVZ) with concern over eutrophic water conditions in the Hamble estuary. There is also a Special Protection Area (SPA) 120m to the east.\n\n[As per Site Condition Report 790101_MSD_SCR_MIL,Sensitive land use, Page 3]","H"]
[null,"Risk of surface flooding on the site. There are areas with low and medium risk of surface water flooding across the site under the current conditions. Increased rainfall as a result of climate change could exacerbate the existing flood risk.\n\n[As per Climate Change Risk Assessment,790101_ERA_CCRA_MIL, Page 10]",null,"Minutes - N/A (dependant on flooding extent)",null,"M",null,null,"Four active contemporary trade directives are located within 250m of the site including; a cargo handling service, garage, gas supplier and a petrol filling station (Co-Op Millbrook, 140m north-east).\nAdditionally,14 inactive contemporary trade directives are present within 250m of the site along Southampton western docks predominantly entailing of freight, cargo and cleaning services.\n\n[As per Nearby industrial land uses,Main Supporting Document 790101_MSD_Main_MIL,Page 4]","H"]
[null,null,null,"Overall",null,"M",null,null,"Overall","H"]
[]
[]
[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":"MMH"}]
[]
[]
[null,"Overall risk rating for zone (Ciria 736) ","H"]
[]
[]
[]
[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","Thickened sludge with 7-8% TDS is stored in a small digester feed tank from where it is fed to 4 No. anaerobic digesters.Digested sludge discharges into 2 No. post digestion storage tanks from where it is fed to 3 No. centrifuges for dewatering.\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 southern boundary.",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[null,"Structural failure - tank (partial)","Most likely through defects formed in steel\n\nMost critical defects would at low level along the side of the tank walls or tank base. \n\nDefects would need to be large >6mm to allow for sludge to pass through freely. General screens at WwTW are 6-10mm, thus defects 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 surface defects.  In the case of significant defects forming above ground, the volume contained above ground would seep through the defects. If the defects are significant, 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 operational presence on site, large drops in levels in the tanks and significant leaks above ground would be noticed. Significant defects 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 digester, heatamix pipework or de-gritting pipework fails and breaks off, a significant volume would spill out. Tanks have level and temperature alarms 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 south and eventually into the drainage system.\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","The site is located in an Environment Agency zone 1 flood risk area. Areas within zone 1 have 1 in a 1,000 chance of river or sea related flooding. However, to the east of the site a section of Southampton docks is located within a zone 3 flooding risk area due to the proximity of the River Test. Areas within flood zone 3 have been shown to be at a 1% or greater probability of flooding from rivers or 0.5% or greater probability of flooding from rivers/ the sea.\n\n[As per Site Condition Report 790101_MSD_SCR_MIL, Hydrology and flooding, Page 3]",null,null,null,null,null,null,"1 in 100 to 1 in 1 Million","M"]
[]
[null,"*Site is manned. Probability and frequency thus reduced"]
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[null,"Frequency of loss of containment (Ciria 736)","M"]
[]
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[1.4,"Overall zone hazard rating"]
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[null,"Overall zone hazard rating (Ciria 736)","High"]
[]
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[1.5,"Containment required"]
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[]
[null,"Containment required","Class 3"]

{"sheet":"2.Total vol. - Mitigation","index":3,"n_rows":15,"n_cols":22,"rows_kept":15,"cut":false,"hidden":false,"merged":[[17,1,19,9],[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],[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]]}
[]
[]
[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. "]
[]
[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$68","v":"Thickened sludge with 7-8% TDS is stored in a small digester feed tank from where it is fed to 4 No. anaerobic digesters.Digested sludge discharges into 2 No. post digestion storage tanks from where it is fed to 3 No. centrifuges for dewatering.\n\nBoth clean and contaminated surface water is directed to a pumping station which recirculates it back into the system. The stormwater drainage of potentially contaminated areas from within the Site boundary is routed into the head of the works with no discharge outside of the site boundary. This allows site operations some time to deal with the leaks from operational failures. Flows exceeding the drainage system capacity will require mitigation with an improved inspection regime to catch spills prior to becoming significant.\n\nThe tanks are monitored by SCADA system."},null,null,null,null,null,null,{"$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 (7am – 7pm). 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$69","v":"The tank is located above ground. For any loss of containment below ground, the sludge liquid will percolate into the permeable soil at a slow rate over a long period if not detected by the level or temperature alarms.\n\nIn the case of significant damage above ground, the total volume contained above ground could spill. \n\nIn the event of a catastrophic failure, sludge would flow in all directions as there is no containment immediately around the tank. The sludge would predominantly flow to the southern boundary."},null,null,null,null,null,null,{"$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$70","v":"Partial structural failure of the tank would mainly be through surface defects.  In the case of significant defects forming above ground, the volume contained above ground would seep through the defects. If the defects are significant, the tank could potentially lose the above ground volume over a long period of time if the level and temperature alarms are not functioning. However, this is unlikely. \n\nDue to operational presence on site, large drops in levels in the tanks and significant leaks above ground would be noticed. Significant defects below/above ground would also be easily spotted during the daily visual inspections. \n"},null,null,null,null,null,null,{"$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 tanks (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$71","v":"In the unlikely event where the above ground rising mains to the digester, heatamix pipework or de-gritting pipework fails and breaks off, a significant volume would spill out. Tanks have level and temperature alarms so any required valve could be immediately shut off by operational staff.\n\nThe consequence of a catastrophic failure of containment is it's able to flow in all directions as there is no containment bunds immediately around the tank. Based on topography, sludge will cascade towards the south and eventually into the drainage system.\n\nTotal loss of containment is unlikely. A partial loss of containment would be more likely to occur."},null,null,null,null,null,null,{"$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 the Site is restricted by automatically operated gates which are closed during operating hours. Access is through the use of a telecom system prior to entry or key fob.The Site perimeter is comprised of 8ft chainlink fencing. The site is manned during opening hours (7am – 7pm), and staff are on call. The Site has CCTV at the inlet, gas holder and access gate.\n\n[As per Main Supporting Document 790101_MSD_Main_MIL, Site Security, Page 36]",null,null,null,null,null,null,null,null,null,"L"]
[null,null,"Flooding",{"$f":"'1.Risk assessment'!$D$75","v":"The site is located in an Environment Agency zone 1 flood risk area. Areas within zone 1 have 1 in a 1,000 chance of river or sea related flooding. However, to the east of the site a section of Southampton docks is located within a zone 3 flooding risk area due to the proximity of the River Test. Areas within flood zone 3 have been shown to be at a 1% or greater probability of flooding from rivers or 0.5% or greater probability of flooding from rivers/ the sea.\n\n[As per Site Condition Report 790101_MSD_SCR_MIL, Hydrology and flooding, Page 3]"},null,null,null,null,null,null,{"$f":"'1.Risk assessment'!L75","v":"M"},"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":154,"n_cols":9,"rows_kept":154,"cut":false,"hidden":false,"merged":[[4,1,4,12],[75,4,75,8],[138,4,138,8],[153,4,153,8]]}
[]
[]
[3.1,"Secondary containment volume requirement - Inventory volume (above ground)"]
[]
[null,"A site-wide solution is not adopted for this site due to existing topography, the requirements for containment to be within the permitted area and identification of the most cost effective solution with respect to the extent of new impermeable areas."]
[null,"Additionally this application includes Slowhill Copse site as an DAA, this site is geographically distinct to the Millbrook site so requires separate containment solution."]
[null,"As such multiple bunds are utilised and each requires calculation for capacity and containment volume, this accounts for above and below ground volumes as noted in CIRIA C736."]
[]
[]
[null,"Millbrook STC"]
[]
[null,"An overview of the general bund areas is show to the right."]
[null,"Further detail on each is provided below."]
[null,"See also worksheet 5."]
[]
[]
[null,"Post Screened Storage (PSST)"]
[]
[]
[null,"Main Bund - digestors & related"]
[]
[null,"Thickened Sludge Storage Tanks (TSSTs)"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Containment Volumes"]
[]
[null,"Main Bund - digestors & related"]
[]
[null,null,null,null,"Tank designation ","Volume (m³)"]
[null,null,null,null,"Digestor 1",2500,null,"Notes: all tanks are above ground so full volume used for calculation"]
[null,null,null,null,"Digestor 2",2500]
[null,null,null,null,"Digestor 3",2500]
[null,null,null,null,"Digestor 4",3251]
[null,null,null,null,"Post Digestion Tank PDST 1",535]
[null,null,null,null,"Post Digestion Tank PDST 2",535]
[null,null,null,null,"Liquor Buffer storage tank",572]
[]
[null,null,null,null,"Total Volume",{"$f":"SUM(Table2[Volume (m³)])","v":12393}]
[null,null,null,null,"25% of total",{"$f":"F46*0.25","v":3098.25}]
[null,null,null,null,"110% of largest",{"$f":"F41*1.1","v":3576.1000000000004}]
[]
[null,null,null,null,"Applicable rule is for containment of 110% of Digestor 4"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Post Screened Storage (PSST)"]
[]
[null,null,null,null,"Tank designation ","Volume (m³)","Footprint (m²)","Height Above ground (m)","Vol. above ground  (m³)"]
[null,null,null,null,"Post Screened Storage Tank 01",2500,276.5,1.2,{"$f":"Table24[[#This Row],[Height Above ground (m)]]*Table24[[#This Row],[Footprint (m²)]]","v":331.8}]
[null,null,null,null,"Post Screened Storage Tank 02",2500,276.5,1.2,{"$f":"Table24[[#This Row],[Height Above ground (m)]]*Table24[[#This Row],[Footprint (m²)]]","v":331.8}]
[]
[null,null,null,null,null,null,null,"Total Volume",{"$f":"SUM(Table24[Vol. above ground  (m³)])","v":663.6}]
[null,null,null,null,null,null,null,"25% of total",{"$f":"I70*0.25","v":165.9}]
[null,null,null,null,null,null,null,"110% of largest",{"$f":"I68*1.1","v":364.98}]
[]
[null,null,null,null,"Applicable rule is for containment of 110% of one tank's above ground volume with respect to a practical spill scenario."]
[]
[null,null,null,null,"Noting that with the limited volume stored above ground the containment solution is primarily with respect to potential overtopping of the tanks. An overall appropriate containment solution for these tanks will combine the containment outlined with other measures in relation to instrumentation and automated process controls (detection and shut off) to reduce the risk and management of spills from tanks."]
[]
[]
[null,"Thickened Sludge Storage Tanks (TSSTs)"]
[null,null,null,null,"Tank designation ","Volume (m³)",null,"Notes: both tanks are above ground so full volume used for calculation"]
[null,null,null,null,"Thickened Sludge storage Tank 01",639,null,"This cannot be included in the 'main bund' due to access requirements and existing topography"]
[null,null,null,null,"Thickened Sludge storage Tank 02",639]
[]
[null,null,null,null,"Total Volume",{"$f":"SUM(Table25[Volume (m³)])","v":1278}]
[null,null,null,null,"25% of total",{"$f":"F84*0.25","v":319.5}]
[null,null,null,null,"110% of largest",{"$f":"F82*1.1","v":702.90000000000009}]
[]
[null,null,null,null,"Applicable rule is for containment of 110% of one tank"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Slowhill Copse "]
[]
[null,"An overview of the general bund areas is show to the right."]
[null,"Further detail on each is provided below."]
[null,"See also worksheet 5."]
[]
[]
[null,"Screened sludge storage tanks bund"]
[]
[]
[]
[null,"Unscreened Sludge Tanks bund"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Unscreened Sludge Tanks bund"]
[]
[null,null,null,null,"Tank designation ","Volume (m³)","Footprint (m²)","Height Above ground (m)","Vol. above ground  (m³)"]
[null,null,null,null,"Unscreened sludge tank 1",1889,276,5.84,{"$f":"Table246[[#This Row],[Height Above ground (m)]]*Table246[[#This Row],[Footprint (m²)]]","v":1611.84}]
[null,null,null,null,"Unscreened sludge tank 2",2055,276,5.84,{"$f":"Table246[[#This Row],[Height Above ground (m)]]*Table246[[#This Row],[Footprint (m²)]]","v":1611.84}]
[null,null,null,null,"Unscreened sludge tank 3",2055,276,5.14,{"$f":"Table246[[#This Row],[Height Above ground (m)]]*Table246[[#This Row],[Footprint (m²)]]","v":1418.6399999999999}]
[]
[null,null,null,null,null,null,null,"Total Volume",{"$f":"SUM(Table246[Vol. above ground  (m³)])","v":4642.32}]
[null,null,null,null,null,null,null,"25% of total",{"$f":"I133*0.25","v":1160.58}]
[null,null,null,null,null,null,null,"110% of largest",{"$f":"I130*1.1","v":1773.0240000000001}]
[]
[null,null,null,null,"Applicable rule is for containment of 110% of one tank's above ground volume with respect to a practical spill scenario."]
[]
[null,null,null,null,"Noting that with the limited volume stored above ground the containment solution is primarily with respect to potential overtopping of the tanks. An overall appropriate containment solution for these tanks will combine the containment outlined with other measures in relation to instrumentation and automated process controls (detection and shut off) to reduce the risk and management of spills from tanks."]
[]
[]
[null,"Screened Sludge Storage Tanks bund"]
[]
[null,null,null,null,"Tank designation ","Volume (m³)","Footprint (m²)","Height Above ground (m)","Vol. above ground  (m³)"]
[null,null,null,null,"Post Screened Storage Tank 01",1141,192,2.44,{"$f":"Table247[[#This Row],[Height Above ground (m)]]*Table247[[#This Row],[Footprint (m²)]]","v":468.48}]
[null,null,null,null,"Post Screened Storage Tank 02",1141,192,2.44,{"$f":"Table247[[#This Row],[Height Above ground (m)]]*Table247[[#This Row],[Footprint (m²)]]","v":468.48}]
[]
[null,null,null,null,null,null,null,"Total Volume",{"$f":"SUM(Table247[Vol. above ground  (m³)])","v":936.96}]
[null,null,null,null,null,null,null,"25% of total",{"$f":"I148*0.25","v":234.24}]
[null,null,null,null,null,null,null,"110% of largest",{"$f":"I146*1.1","v":515.32800000000009}]
[]
[null,null,null,null,"Applicable rule is for containment of 110% of one tank's above ground volume with respect to a practical spill scenario."]
[]
[null,null,null,null,"Noting that with the limited volume stored above ground the containment solution is primarily with respect to potential overtopping of the tanks. An overall appropriate containment solution for these tanks will combine the containment outlined with other measures in relation to instrumentation and automated process controls (detection and shut off) to reduce the risk and management of spills from 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","Anaerobic digester 04"]
[null,"Description","Thickened sludge with 7-8% TDS is stored in a small digester feed tank from where it is fed to 4 No. anaerobic digesters.Digested sludge discharges into 2 No. post digestion storage tanks from where it is fed to 3 No. centrifuges for dewatering."]
[null,"Number of tanks","1 (Risk assessed for one tank only as example of typical tank)"]
[null,"Volume of tank","3251 m3 (approximately) - total volume for tank"]
[null,"Material of tank","Steel"]
[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 Southern direction\n\n[As per Millbrook WTW Drainage, 720116/M104/2101]"]
[null,"Year of construction","-"]
[null,"Surrounding area","Gravel\n\n[As per IED Permit, Site Condition report 790101_MSD_SCR_MIL,Page 21]"]
[]
[null,"Pump rate - to Anaerobic digester 04","-"]
[null,"Pump rate - from  Anaerobic digester 04","-"]
[]
[]
[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":282,"n_cols":15,"rows_kept":282,"cut":false,"hidden":false,"merged":[[109,1,109,10],[110,1,110,10],[118,1,118,10],[119,1,119,10],[71,12,72,12],[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],[227,1,227,10],[243,1,243,10],[234,1,234,10],[235,1,235,10],[236,1,236,10],[237,1,237,10],[238,1,238,10],[233,1,233,10],[228,1,228,10],[229,1,229,10],[230,1,230,10],[231,1,231,10],[232,1,232,10],[272,1,272,10],[273,1,273,10],[274,1,274,10],[116,1,116,10],[117,1,117,10],[246,1,246,10],[263,1,263,10],[269,1,269,10],[270,1,270,10],[271,1,271,10],[244,1,244,10],[245,1,245,10],[239,1,239,10],[240,1,240,10],[241,1,241,10],[242,1,242,10],[210,1,210,7],[214,1,214,7],[173,1,173,9],[113,13,113,21],[128,1,128,6],[126,1,126,6],[165,1,165,7],[167,1,167,7],[181,1,181,7],[163,1,163,7],[148,1,148,7],[152,1,152,7],[161,1,161,7],[185,1,185,7],[115,1,115,10]]}
[]
[]
[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"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,null,null,null,null,null,null,null,null,null,null,null,"Typical reinforced concrete wall section view"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[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,"Site overview"]
[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 area required and nature of surrounding area, 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,"Provided for information only - does not represent a solution"]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[5.3,"Containment Solution"]
[]
[]
[null,"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 all scenarios outlined below the 110% rule applies, see worksheet 3. \nNoting that above-ground volumes are used in line with CIRIA C736 and reflecting a practical maximum spill that could be encountered."]
[null,"New impermeable areas will be installed to provide an appropriate containment bund floor surface for the full bunded area. Detailed 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,"Millbrook STC"]
[null,"Proposal Summary"]
[]
[null,"The solution comprises of three distinct bunds based on local needs."]
[null,"It should be noted that this site has proved particularly complex to provide a solution that appropriately balances the containment requirements whilst ensuring an appropriate operational basis. The operational impact of providing containment is considerable from the walls required and the equipment this isolates for maintenance etc. Risks remain that require specific consideration including HazOp review in detailed design. "]
[null,"Whilst this is not considered insurmountable (being technically feasible) it incurs a considerable cost which may influence the final outcome more than most other sites."]
[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 - Orange line - total 510m (250m East side, 260m west)\nNew concrete wall of [average] 0.7m height (local heigh varies in line with existing topography to achieve required top of wall height relative to local spill depth), total 170m. This includes the replacement of some existing walls which are not to CIRIA C736 standard.\nKerb remediation extent not shown but required at the perimeter of the spill and remediation of walls at the cake bays in the middle.\nNote final freeboard height to be determined in detailed design, see narrative provided below for specific topics of consideration."]
[null,"Note the existing topography ensures a failure of tanks of the west side of side will flow to the east and thus be contained by the proposed solution.\n"]
[]
[]
[null,"Main Bund - digestors & related"]
[]
[null,"Solution is for a new reinforced concrete wall on the line shown in yellow to the right."]
[null,"Total length of 330m and typical local height of 1.3m"]
[null,"The existing area is largely level, re-profiling of the bund floor during construction will provide a uniform depth for the containment and avoid the low spot showing as orange."]
[null,"This will significantly impact operational activities so requires new access and egress routes"]
[null,"The line of the wall has been selected to balance protection of other assets from a feasible (though complex) route around existing assets. Further detailed surveys will determine the full extent of the modifications required to accommodate the wall."]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Post Screened Storage (PSST)"]
[null,"Two predominantly below ground tanks."]
[null,"A new wall of 145m length and 0.5m will provide the required containment."]
[null,"This mitigates impacting key vehicle manoeuvring areas to the north and provides containment greater than calculated requirement of 365m3 (on worksheet 3)."]
[null,"New impermeable surface will be installed within the bund and tie into the tank external wall"]
[null,"A new sump and drain pump will be installed to return rainwater to the head of works."]
[]
[null,"Spill modelling has not been completed on this area as the existing ground is largely flat and will have a small amount of reprofiling (lowering the existing ground) to provide the required drainage falls. This will be detailed in the construction phase drawings subject to further surveys. \nA 2D calculation has been determined to be sufficient to demonstrate appropriate containment capacity."]
[]
[]
[]
[]
[null,"Thickened Sludge Storage Tanks (TSSTs)"]
[null,"Two above ground tanks."]
[null,"A new reinforced concrete wall of 110m length and 1.5m height will provide the required containment."]
[]
[null,"Some existing impermeable surface will be utilised to minimise the changes to the tank foundations (subject to detailed survey). Additional detailing is required for the tie-in of the new wall into the existing surface and  this is likely to be a concrete impermeable surface solution."]
[null,"A new sump and drain pump will be installed to return rainwater to the head of works."]
[null,"A jetting solution is required and is likely to be a form of fencing on top of the wall, this remains subject to further calculations and design development"]
[]
[null,"Spill modelling has not been completed on this area as the existing ground is largely flat and will have a small amount of reprofiling (lowering the existing ground) to provide the required drainage falls. This will be detailed in the construction phase drawings subject to further surveys. \nA 2D calculation has been determined to be sufficient to demonstrate appropriate containment capacity."]
[]
[null,"The tanks are a challenge to provide containment for given the vehicle access routes and public road. Relocation of the tanks has been considered but no appropriate  location has been identified due to extensive planned works on the wider site and operation need for proximity to supporting assets (thickeners). Additionally replacement with collared tanks has been considered but at this stage is thought to be more technically complex than localised bunding."]
[]
[]
[]
[null,"Slowhill Copse"]
[]
[null,"Millbrook site receives sludge transfers via a pipeline from Slowhill Copse approx. 1km away on the south side of the River Test. As such the IED permit application has been updated to include Slowhill Copse and containment solutions are provided here for Slowhill Copse to align.\nSlowhill Copse takes sludge from imports and the adjacent water treatment works and transfers it to Millbrook STC.\nThe same risk basis outlined in worksheet 2 has been adopted for Slowhill Copse on a conservative basis as the risks are perceived to be no greater than for Millbrook STC."]
[]
[]
[null,"Unscreened Sludge Tanks bund"]
[null,"Three partially buried tanks. See worksheet 3 for containment calculations."]
[]
[null,"A new wall of 215m length and provisionally varying from 0.4 to 2.3m will provide the required containment."]
[null,"This area is not level as shown by the spill model output below and improvements are thought to be realisable"]
[null,"Opportunities to reprofile the area to provide a level (with drainage falls) base will be explored following further surveys and calculation to confirm tank structural considerations (ensure embankment at tank side was is not an original design requirement).\nShould the be realisable it is anticipated that a more uniform wall height of around 1.3m could be achieved. This also requires consideration of the wider area/assets."]
[null,"New impermeable surface will be installed within the bund and tie into the tank external wall"]
[null,"A new sump and drain pump will be installed to return rainwater to the head of works."]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[]
[null,"Screened Sludge Storage Tanks bund"]
[null,"Two predominantly below ground tanks."]
[null,"A new wall of 100m length and 1.2m will provide the required containment volume."]
[null,"Restriction to the area shown mitigates impacting key vehicle manoeuvring routes."]
[null,"New impermeable surface will be installed within the bund and tie into the tank external wall"]
[null,"A new sump and drain pump will be installed to return rainwater to the head of works."]
[]
[null,"Spill modelling has not been completed on this area as the existing ground is largely flat and will have a small amount of reprofiling (lowering the existing ground) to provide the required drainage falls. This will be detailed in the construction phase drawings subject to further surveys. \nA 2D calculation has been determined to be sufficient to demonstrate appropriate containment capacity."]
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[null,"Containment Solution Scope for all solutions outlined above"]
[null,"New walls will be built to contain 110% of the largest tank, the final height of the walls remains subject to confirmation but illustrative heights are shown on the images to the right."]
[null,"The 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,"Buildings and other operational equipment are excluded from use for containment volume calculations based on a provisional assumption that they will be protected from flood 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 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,"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,"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,"All process areas will be provided with hardstanding where not existing and appropriate drainage and instrumentation to determine leak presence, thus a failure of equipment within the process area would be appropriately contained."]
[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."]
[]
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[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)"]
[]
[]
["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,"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"]
[null,"Millbrook STC is part of the Bioresources consolidation plan whereby, in a future phase beyond AMP8, it is planned to be developed into an Advanced Anaerobic Digestion (AAD) site."]
[null,"The current digestion activities will remain beyond the end of AMP8, as such compliant containment proposals are planned for all STC assets."]

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