Thames Group Tidal Water Resources
1 Executive Summary “Water resources in England and Wales (especially in south east England) are threatened by below average rainfall in the short-term and climate change in the longer-term. The use of these resources is also facing increasingly tight regulation in order to meet ever higher ecological requirements. Simultaneously, demand for water is increasing because of population growth, a decreasing average household size and growing use of water-intensive appliances.” (House of Lords : Science and Technology Committee , 2006)
It is clear from this statement that actions must be taken in order to maintain the current supply of water. A twin-track approach is being encouraged across the industry, aiming to reduce water demand and to invest in the development of new supply measures.
This report presents the range of possible solutions the Thames Group has considered since the Inception Report produced in October 2014 by the Thames Group found that a solution to this problem could be realised without the construction of new reservoirs was, in principle, viable.
The aims of this feasibility study have been to find an alternative solution for maintaining minimum residual flow in the River Thames and also to reduce the carbon footprint of the water supply in the Thames Valley region. The primary option considered has been the construction of a half tide weir in the tidal Thames to harness the water provided by the tides to maintain the minimum residual flow. Alternatives to this have been considered in the report and have been deemed constructible, but would require further investigation and analysis to conclude suitability. There are three main areas that need to be assessed to determine overall feasibility of the scheme: design suitability, costing and carbon footprint.
The water shortage has been of concern for some time, as a result there are existing proposals that aim to solve the issue. Thames Water has proposed to build a new reservoir in Abingdon, Oxford to supply the Thames River with water during times of drought. The construction aims to provide the Thames with sufficient water to achieve the desired river abstractions, whilst also maintaining the minimum residual flow. The scheme is the largest reservoir to be proposed in the U.K. in 25 years and has faced heavy opposition from many sources, not least the Environment Agency, DEFRA and local residents of Abingdon. The proposed Abingdon Reservoir is quoted to have the following specifications (GARD, 2014);
• Capacity of around 150 billion litres of water. • Has an estimated cost of £1 billion. • Estimated construction time of 8-15 years.
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• Will cover an estimated area of 10-12 km2. • Will ensure adequate supply of water for over a period of 25 years.
The Thames Group has determined that a half tide weir cannot provide a suitable solution to the water shortage in the south-east of England alone. Even with the existing abstractions being moved to a more efficient location (Teddington Weir) the water demand for the lifetime stated in the project brief of 100 years cannot be met. In order to achieve this, additional measures will need to be introduced at a later stage, such as the suggested improvements to Hogsmill Sewage Treatment Works discussed in the report. Additionally it has also been found that the provision of a lock is necessary if the full design life is to be aimed for. Therefore the options that do not include such a provision have been rejected at the conclusion of this report.
All of the options considered have minimal impact on the surrounding environment, with Kew Weir being fully submerged resulting in very little visual impact on the river. The moveable nature provides a reduced impact on navigation, especially with the options including the lock. An innovative approach has been taken wherever possible to ensure the most effective solution with consideration given to the wider scheme and surroundings at all times.
Overall the Thames Group have concluded that none of these solutions are viable in terms of carbon reduction when compared to Abingdon Reservoir. However the significant cost savings in the proposals considered leads the Thames Group to recommend option 1b for further development if the carbon issue can be resolved. Option 1b is the most appropriate solution from those studied in this feasibility report, but the water shortage in the south east will still be a problem unless significant changes in water consumption and/or finding new water sources can be achieved.
2 | P a g e Chapter 1 – Executive Summary Thames Group Tidal Water Resources 2 Table of Contents 1 Executive Summary ...... 1 2 Table of Contents ...... 3 2.1 Table of Figures ...... 7 3 Introduction ...... 11 4 Project Management ...... 12 5 Future Flows ...... 13 5.1 Thames at Kingston – Flow Data Processing ...... 13 6 Abstractions ...... 16 6.1 Current Abstraction Points and Values ...... 17 6.2 Future Abstractions & Water Demand ...... 17 The WRMP ...... 17
7 Alterations to Teddington Weir ...... 20 8 Abstraction Tunnel (Option 1) ...... 21 8.1 Geology ...... 22 8.2 Inlet Shaft ...... 23 8.3 Sluice Gate...... 24 8.4 Transfer Tunnel ...... 26 Calculations ...... 26
8.5 Transfer Tunnel Lining ...... 28 Primary Lining ...... 28
Secondary Lining ...... 29
8.6 Tunnel Alignment ...... 29 8.7 Pump-out shaft...... 30 Pump Requirements ...... 30
8.8 Programme of Works and Construction Methodology ...... 33 8.9 Financial Assessment ...... 34 9 Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) ...... 35 9.1 Abstraction Tunnel Alternatives ...... 36 Option 2 - Hogsmill STW Upgrade and direct discharge in the river at Hampton 36
Option 3 - Hogsmill STW Upgrade and Transfer Tunnel to Queen Elizabeth II Reservoir 37
10 Chemical Assessment ...... 38 10.1 Salinity ...... 38
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10.2 Dissolved Oxygen ...... 38 10.3 Other Factors ...... 40 10.4 Mitigation ...... 40 10.5 Option 1 ...... 41 10.6 Option 2 ...... 42 10.7 Option 3 ...... 42 11 Option 1 - Storage Required ...... 42 11.1 Volume Calculation ...... 42 11.2 Storage Available ...... 42 11.3 Sense Check on Calculation ...... 44 12 Comparing Future Flows to Future Abstractions ...... 44 13 Lock Necessity ...... 45 13.1 Options Considered for Kew Weir ...... 48 Option 1a ...... 48
Option 1b ...... 48
Option 1c ...... 49
13.2 Lock Dimensions ...... 49 14 Kew Weir...... 50 14.1 Environmental Impact Assessment ...... 50 14.2 Site Visit ...... 50 14.3 Substructure ...... 52 Geological conditions of the proposed location ...... 52
Foundations ...... 54
Scour ...... 55
14.4 Superstructure ...... 56 Construction Materials ...... 56
Waterproofing ...... 56
Water level management ...... 57
14.5 Sealing of Weir ...... 57 14.6 Fish Pass ...... 58 14.7 Mechanism ...... 59 Determining Type of Weir Movement ...... 59
Determining Method of Actuation ...... 59
Calculations ...... 62
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Financial Assessment ...... 66
Hydrodynamic Lift mechanism ...... 68
14.8 Option 1a ...... 69 Weir Design ...... 70
14.9 Option 1b ...... 74 Weir Design ...... 74
14.10 Option 1c ...... 76 Weir Design ...... 77
14.11 Construction Methodology ...... 77 Option 1a ...... 77
Option 1b ...... 79
Option 1c ...... 81
14.12 Bill of Quantities and Pricing ...... 81 15 Hydropower ...... 84 15.1 Weir Site Suitability Assessment ...... 84 15.2 Teddington Weir Site Suitability Assessment ...... 87 15.3 River Abstraction Inlet Shaft Suitability Assessment ...... 88 Power generation ...... 90
Prediction of Revenue ...... 91
Prediction of cost ...... 91
16 Control Systems...... 92 16.1 Sluice Gate...... 93 Design Specifications ...... 93
System Overview ...... 94
16.2 Operation During Power Failure and Fail safe mechanism...... 97 16.3 Financial Analysis ...... 97 16.4 Pump Out Shaft ...... 97 16.5 Teddington Weir ...... 98 16.6 Kew Weir...... 99 Design Specifications ...... 99
Design process ...... 100
The Control Circuit ...... 101
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Water Level Measurement ...... 102
Measurement of the Height of the weir above the ground ...... 103
Head measurement ...... 104
Generation of the input signal ...... 104
Outline design process of a controller ...... 105
Incorporation of a fail-safe Mechanism ...... 105
Financial Analysis ...... 105
17 Overall Scheme Financial Assessment ...... 106 17.1 Summary...... 107 18 Carbon Assessment ...... 107 18.1 Embedded Emissions and Management ...... 108 18.2 Operational Emissions and Management ...... 109 18.3 Project Life-Cycle Assessment ...... 109 Reservoir Emissions ...... 109
Kew Weir Emissions ...... 111
Transfer Tunnel Emissions ...... 112
18.4 Scheme Comparison ...... 114 19 Conclusion ...... 115 20 Areas for Further Research ...... 117 20.1 Locking Mechanism for Weir...... 117 20.2 Improvements to Teddington Weir ...... 117 20.3 Investigation into Varying Water Depth at Teddington Weir ...... 118 20.4 Sealing Panels for Weir ...... 118 20.5 Sluice Gates ...... 118 20.6 Weir Gate Sections ...... 118 20.7 Tunnel ...... 118 20.8 Weir Foundations and Structure ...... 119 20.9 Flooding Potential ...... 119 20.10 Water Quality ...... 119 20.11 Ecology ...... 119 20.12 Compliance with Legislation ...... 119 20.13 Predicted Carbon Emissions ...... 119 21 Assumptions Register ...... 120 22 Risk Register ...... 125
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23 References ...... 130 24 Appendices ...... 140 24.1 Appendix A – GANTT Chart 24.2 Appendix B - Borehole Logs 24.3 Appendix C – Tunnel, Sluice Gate & Carbon Assessment Calculations (IP) 24.4 Appendix D – Site Visit Photographs (HP) 24.5 Appendix E – Superstructure and Substructure Quantities Calculations (JJ) 24.6 Appendix F – Weir Gate Structural and Geometric Calculations (HP) 24.7 Appendix G - Drawings (HP, JJ, IP) Drawing Register
Drawings
2.1 Table of Figures Figure 5.1 - Quarter 1 projected flows at Kingston from 2010 to 2120 ...... 14 Figure 5.2 - Quarter 2 projected flows at Kingston from 2010 to 2120 ...... 15 Figure 5.3 - Quarter 3 projected flows at Kingston from 2010 to 2120 ...... 15 Figure 5.4 - Quarter 4 projected flows at Kingston from 2010 to 2120 ...... 16 Figure 6.1 - Locations of abstraction points and maximum abstractions allowed at each point (Base map taken from Google Maps)...... 17 Figure 6.2 - Future abstractions for full design life of 120 years ...... 20 Figure 7.1 - Aerial view of Teddington Weir (Miatt, 2006) ...... 21 Figure 8.1 - Proposed tunnel location ...... 21 Figure 8.2 - Borehole Maps ...... 23 Figure 8.3 - Proposed inlet shaft location ...... 24 Figure 8.4 - Vertical lift gate at Copperhouse Sluice ...... 25 Figure 8.5 - Layout indicating position of sluice gate relative to inlet shaft ...... 25 Figure 8.6 - Transfer tunnel cross section according to CIRIA C689 ...... 27 Figure 8.7 - Articulated shutters for cast in-situ secondary lining (Photo taken from (Jewell & Bellhouse, 2014)) ...... 29 Figure 8.8 - Proposed pump out shaft location ...... 30 Figure 8.9 - NPV Pump operation cash flow ...... 32 Figure 8.10 - Tunnel costs per m 3 in relation to diameter based on 2013 prices (Graph taken from (British Tunnelling Society, 2010)) ...... 34 Figure 9.1 - Schematic of Langford scheme. Shown in orange is the route that sewage water used to take before being disposed of into the sea ...... 35
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Figure 9.1 - Option 2: Alternative to abstraction tunnel at Teddington Weir – Hogsmill STW to Hampton ...... 37 Figure 1.2 - Option 3: Alternative to abstraction tunnel at Teddington Weir – Hogsmill STW to Queen Elizabeth II Reservoir ...... 37 Figure 10.1 - A section of a graph showing measured DO content along the river. Abstraction points are represented by green arrows and water input is represented by blue...... 39 Figure 10.2 - Compressed air is pumped through a tank containing zeolite pellets which adsorbs unwanted gas leaving oxygen to be stored in the buffer tank. In the opposite tank air is pumped out to clean the pellets. After Gazcon...... 41 Figure 11.1 - World Heritage Site at Kew Gardens and Buffer Zone (UNESCO, 2002) ...... 43 Figure 13.1 - 2014 Abstractions Vs. Future Flows at Kingston ...... 46 Figure 13.2 - 2020 Abstractions Vs. Future Flows at Kingston ...... 46 Figure 13.3 - 2050 Abstractions Vs. Future Flows at Kingston ...... 47 Figure 13.4 - 2080 Abstractions Vs. Future Flows at Kingston ...... 47 Figure 13.5 - 2098 Abstractions Vs. Future Flows at Kingston ...... 48 Figure 14.1 - Kew pier...... 51 Figure 14.2 - Span of river to be sectioned by the proposed Kew Weir ...... 51 Figure 14.3 - Outlet into the River Thames (unknown source or effluent type) ...... 51 Figure 14.4 - Mooring structure in the middle of the Thames immediately adjacent to proposed Kew Weir location ...... 51 Figure 14.5 - Playground on the South bank of the Thames at Kew Weir location ...... 52 Figure 14.6 - North bank of the Thames at Kew Weir location (residential street visible just beyond) ...... 52 Figure 14.7 - South bank of Thames at Kew Weir location - scour protection badly degraded. .... 52 Figure 14.8 - Borehole data map (British Geological Survey, n.d.) ...... 53 Figure 14.9 - Sections through boathouse boreholes in North-South direction (British Geological Survey, n.d.) ...... 53 Figure 14.10 - Sections through boathouse boreholes in East-West direction (British Geological Survey, n.d.) ...... 54 Figure 14.11 - Integral Waterproofing System (Sika Solutions, n.d.) ...... 57 Figure 14.12 - Tilting beamless weir gate (HC Watercontrol, n.d.) ...... 58 Figure 14.13 - Duramax Shaft Sealing System (Duramax Marine, 2015) ...... 59 Figure 14.14 - Moment Required to Raise Weir ...... 60 Figure 14.15 - Worst Case Resistive Moment at Upright Position ...... 60 Figure 14.16 – Indicative arrangement of counterweight and ram mechanism...... 61 Figure 14.17 – Sketch of the movement mechanism in situ ...... 62 Figure 14.18 - NPV Cash Flow Prediction for Operation of Weir ...... 67
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Figure 14.19 - Schematic of an aerofoil with a leading edge slat (SimHQ, 2002) ...... 68 Figure 14.20 - Option 1a cross section (Drawing 211) ...... 69 Figure 14.21 - Option 1a cross section ...... 70 Figure 14.22 - Pier cross section ...... 70 Figure 14.23 - Option 1a plan view ...... 70 Figure 14.24 - Sketch of approximation of section for weir gate ...... 71 Figure 14.25 - Proportional factors of total steel cost (Barrett, Byrd Associates, 2013) ...... 73 Figure 14.26 - Option 1b cross section ...... 74 Figure 14.27 - Lock cross section ...... 74 Figure 14.28 - Option 1b plan view ...... 74 Figure 14.29 - Option 1a, Stage 1 ...... 78 Figure 14.30 - Option 1a, Stage 2 ...... 78 Figure 14.31 - Option 1a, Stage 3 ...... 78 Figure 14.32 - Option 1a, Stage 4 ...... 78 Figure 14.33 - Option 1a, Stage 5 ...... 79 Figure 14.34 - Option 1a, Stage 6 ...... 79 Figure 14.35 - Option 1a, Stage 7 ...... 79 Figure 14.36 - Option 1a, Stage 8 ...... 79 Figure 14.37 - Option 1b, Stage 1 ...... 80 Figure 14.38 - Option 1b, Stage 2 ...... 80 Figure 14.39 - Option 1b, Stage 3 ...... 80 Figure 14.40 - Option 1b, Stage 4 ...... 80 Figure 15.1 - Hydro-turbine Selection Chart (Greenbug Energy Inc, 2014) ...... 85 Figure 15.2 - Commercially available Hydro-Kinetic Turbines (Sornes, 2010) ...... 86 Figure 15.3 - Archimedes Screw Efficiency Curve (Renewables First, 2014)...... 87 Figure 15.4 - Kaplan Turbine (Renewables First, 2014) ...... 89 Figure 15.5 - Predicted Abstractions ...... 89 Figure 15.6 - Kaplan Efficiency Curve Comparison Chart (Renewables First, 2014) ...... 90 Figure 15.7 - NPV Cash Flow for Kaplan Turbine Scheme ...... 92 Figure 16.1 - Block diagram of a typical control system (INTECH open science, n.d.) ...... 92 Figure 16.2 - Operation of the sluice gates to control flow rate, (Turnpenny Horsfield Associates, 2013)...... 93 Figure 16.3 - Block diagram of the control systems ...... 94 Figure 16.4 - A drive mechanism to move the gate (California Polytechnic State University, 2000) ...... 94 Figure 16.5 - Motor numbers and their characteristics (Joyce Dayton, 2013)...... 95 Figure 16.6 - The role of limit switches (California Polytechnic State University, 2000)...... 95
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Figure 16.7 - A typical sensor arrangement system (California Polytechnic State University, 2000) ...... 96 Figure 16.8 - Indicative sketch of how RTU links with the rest of the system, (Schneider Electric, 2012) ...... 97 Figure 16.9 - Systems outline ...... 98 Figure 16.10 - A pump system with cavitation monitoring, (United States of America Patent No. US6663349 B1, 2003) ...... 98 Figure 16.11 - Sketch of Kew Weir in an upright position...... 99 Figure 16.12 - Important parameters of the weir (Anon., 2015) ...... 100 Figure 16.13 - Block diagram of the control circuit ...... 101 Figure 16.14 - Sample water level sensor and how it would be installed, (Global Water, 2015), (Nivus, n.d.) ...... 102 Figure 16.15 - Schematic indicating a decrease in the water level at the weir crest, (Civil Engineering Portal, 2015) ...... 103 Figure 16.16 - Sample angle transducer, (Sensitec, 2009) ...... 103 Figure 16.17 - Spatial relationship between sensor chip and magnetic field (Anaheim Automation, 2011) ...... 103 Figure 16.18 - A block diagram of the summing junction ...... 104 Figure 17.1 - NPV cash flow comparing solutions of Abingdon reservoir, Option 1b with hydropower and Option 1b without hydropower ...... 107 Figure 18.1 - Carbon emissions break-down from an average of 13 reservoirs ...... 110 Figure 18.2 - Embedded emissions break-down from an average of 13 reservoirs...... 110 Figure 18.3 - Material emissions break-down from an average of 13 reservoirs ...... 110 Figure 18.4 - Operational emissions break-down from an average of 13 reservoirs ...... 111 Figure 18.5 - Embedded Emissions Break-down for Kew Weir Option 1a ...... 111 Figure 18.6 - Embedded Emissions Break-down for Kew Weir Option 1b ...... 112 Figure 18.7 - Carbon Emissions Break-down for Transfer Tunnel ...... 113 Figure 18.8 - Embedded Emissions Break-down for Transfer Tunnel ...... 113 Figure 18.9 - Carbon Emissions Break-down for Indirect Effluent Re-use ...... 114 Figure 18.10 - Embedded Emissions Break-down for Indirect Effluent Re-use ...... 114
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3 Introduction In the South-East of England we are nearly abstracting the maximum we can from the natural environment, with less water available per person than in Syria (Gibbs, 2013). London is drier than Istanbul and there has been no approved scheme to address this issue (Gibbs, 2013). Thames Water have proposed the construction of a large reservoir at Abingdon in Oxford, however this has faced heavy objection from locals, government bodies and environmental trusts. Measures taken to reduce water demand have included the implementation of water meters and investment into more effective leak detection. However, water meters have been found to have “little effect on average demand” (Staddon, 2012) And through considering figures published by Ofwat (The Water Services Regulation Authority), it is clear that companies often fail to reach annual leakage targets (Ofwat , 2011).
The current water supply is abstracted from reservoirs, rivers and underground aquifers, needing to reach around 18 billion tonnes on an annual basis, this leads to some cases of abstraction being unsustainable which can lead to water stress and have serious environmental impacts (Department for Environment Food and Rural Affairs, 2008). The primary method of abstracting water is through pumping, which consumes energy and releases greenhouse gas emissions (Department for Environment Food and Rural Affairs, 2008).
In the case of the River Thames, water is abstracted upstream of the estuary. This water is pumped into reservoirs, where it is stored. This affects the level of water flow along the river, the Environmental Agency has set a value of minimum residual flow, this level is measured at set points and when reached, procedures are put into place in order to maintain the river level. This often requires water companies to pump water back into the river from the reservoirs and can result in reduced abstraction rates (Environment Agency and Thames Water, 2013). This results in the reduction of water levels in the reservoirs and the increased financial and environmental cost of pumping the water back into the river.
The aim of this project is to look into the potential use of tidal resources as an alternative to constructing new reservoirs to supply the Thames Valley area, with the primary focus being on reducing the carbon footprint of any proposed scheme.
The key benefits of the scheme are as follows: • Reduced restriction on commercial abstraction • Increased availability of useable water in reservoirs • Reduced environmental impact • Reduced financial impact
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• Reduced political uncertainty
The key targets for the design are as follows: • To reduce the carbon footprint of Thames Water by: o reducing pumping requirements currently used in the Thames Water network. o potentially harnessing hydroelectric energy. • To provide a more environmentally sensitive solution.
4 Project Management Due to the complex nature of the project, effective project management was essential for facilitating collaborative work, whilst also measuring progress. The primary means of achieving this was through use of a Gantt chart (see Appendix A). The chart incorporated all tasks deemed necessary by the group, setting both a start time and finish time. Precedence’s were created so that the critical path at any stage could easily be recognised by the group; therefore potential delays to the overall project could be avoided if required. A different colour was allocated to each individual within the group, this made it clear who was responsible for each task, helping to structure communication.
The Gantt chart was reviewed and updated each week; as new areas of research emerged these could be added, in addition to this task durations which either became longer or shorter than predicted could be adjusted, the effect of this change in time frame quantified and any measures which were required to be made could be applied effectively. Progress was also tracked on a weekly basis, this allowed individuals to understand their influence on the overall progress, as well as helping to identify any potential issues.
Communication was mainly conducted through an online group page. This provided a hub for all members to share files and comments regarding the project, also the facility to organise meetings was provided in a way where all members can confirm attendance and have a record of both timing and location.
Meetings were regularly scheduled on a weekly basis; this provided a good opportunity for individuals to present their work, allowing all members to develop a more contextual view of the project as a whole. The roles of Chair and Secretary of meetings were rotated weekly. Agendas and minutes were produced for these meetings, providing clear documentation of what was discussed and any actions which were agreed on.
The project management as a whole provided an overlying administrative structure which allowed the individual work of each group member to work towards the desired outcome of the project. Considerable freedom was given to individuals regarding their own tasks which facilitated
12 | P a g e Chapter 3 – Introduction Chapter 4 – Project Management Thames Group Tidal Water Resources creativity within the design work and promoted the application of multi-disciplinary skills, whilst synergy was encouraged by the administrative overlay. In some situations such as report formatting and use of units, more prescriptive controls would have led to a greater efficiency in delivering the final report. In addition to this a greater amount of group orientated work would have proved beneficial, however, due to conflicting academic timetables this was found to be difficult.
5 Future Flows The flow monitoring station at Kingston is one of very few in the country which has data logs far enough back into the past to be able to produce a future flow prediction as part of the Future Flow and Groundwater Level Project (FF-HadRM3-PPE). A joint venture between the Environment Agency, the Department for Environment, Food and Rural Affairs, the UK Water Industry Research, the Natural Environment Research Council and Wallingford Hydrosolutions has used the 11 climate change models identified in the Had-RM3-PPE climate simulations based on emissions scenario A1B. This model produced predicted daily flow data for all 11 models, every day between 1951 and 2098 (Prudhomme, et al., 2012). Of these 11 models, 3 key ones were identified as being important to assess (Keller, et al., 2013); 1. Scenario AFGCX – the average climate change model 2. Scenario AFIXA – the wettest climate change model 3. Scenario AFIXK – the driest climate change model
5.1 Thames at Kingston – Flow Data Processing From the future flows data obtained from the CEH a quarterly 1 average was determined for every year for the three chosen climate change models from 2014-2098. From this it was then possible to divide the predicted flows into 4 sections of time to give averages of each quarter, the chosen time periods being: 1. 2014-2020 2. 2021-2050 3. 2051-2080 4. 2081-2098 The average quarterly figures for the recorded data at Kingston were then used to provide the current data (Centre for Ecology and Hydrology, 2013). This allows these values to be used to extrapolate to the full design life of the structure to obtain the values for the period to the 2120’s
1 The quarters in this instance are defined as: 1 – December to February 2 – March to May 3 – June to August 4 – September to November 13 | P a g e Chapter 4 – Project Management Chapter 5 – Future Flows - HP Thames Group Tidal Water Resources as can be seen in Figure 5.1, Figure 5.2, Figure 5.3 and Figure 5.4. The results of this analysis are summarised in Table 5.1. Table 5.1 - Future flows data at Kingston summarised for the chosen time periods
Quarter Climate 2000-2013 2014-2020 2021-2050 2051-2080 Change Model 1 Average 121.4854 123.775 129.797 120.908 Wettest 88.766 96.618 118.524 Driest 49.508 118.514 118.511 2 Average 72.27292 93.552 92.005 91.283 Wettest 88.766 78.855 87.571 Driest 87.029 92.536 93.514 3 Average 28.16583 49.508 47.460 41.451 Wettest 40.198 39.257 41.703 Driest 40.795 44.385 34.685 4 Average 45.96757 50.183 46.800 36.209 Wettest 34.047 39.327 45.605 Driest 28.767 43.055 33.764
Figure 5.1 - Quarter 1 projected flows at Kingston from 2010 to 2120
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Figure 5.2 - Quarter 2 projected flows at Kingston from 2010 to 2120
Figure 5.3 - Quarter 3 projected flows at Kingston from 2010 to 2120
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Figure 5.4 - Quarter 4 projected flows at Kingston from 2010 to 2120
6 Abstractions The Thames has six main abstraction points between Windsor and Teddington Weir which can be seen in Figure 6.1 below (Datchett, Staines, Laleham, Walton, Hampton and Kingston). The maximum values that can be abstracted per day from each point as defined in the Lower Thames Operating Agreement (LTOA), however there is also an overall daily abstraction limit. As it has not been possible to obtain exact figures of abstractions from each point that have taken place, the following has been assumed: • The maximums at each station total 100%, therefore each station maximum provides a percentage of the abstractions allowed at that point. • The percentages have then been applied to the total maximum limit to calculate the theoretical distribution of the abstractions.
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6.1 Current Abstraction Points and Values
Figure 6.1 - Locations of abstraction points and maximum abstractions allowed at each point (Base map taken from Google Maps).
It has been decided that stopping all abstractions before Teddington Weir is unreasonable and unfeasible, therefore we have chosen to stop the three nearest to Teddington Weir – i.e. Walton (1264Ml/day), Hampton (109Ml/day) and Kingston (109Ml/day).
6.2 Future Abstractions & Water Demand The future demand for water has been calculated using Thames Water’s “Water Resource Management Plan (WRMP)” which predicts the abstraction patterns for the next 30 years. This plan utilises the predicted increase in population and occupancy ratios of properties. The WRMP includes the SWOX (Oxford) and SWA (Swindon) regions within it, which have been removed for the purposes of these calculations as the weir discussed in this feasibility study cannot influence these areas. It has then been extrapolated to provide a future demand for the entire design life of the structure (i.e. 120 years). The WRMP The WRMP classifies each five year period into AMP (Asset Management Plan) numbers. We are currently in AMP5 and planning is underway for requirements for AMP6 which comes in to effect in 2015. The WRMP splits demand up into several categories: • Measured residential • Unmeasured residential • Non-household The plan provides three estimates of population and property projections produced by independent experts (Experian) summarised in Table 6.1. The first is the “plan-based” projection, a figure that has been produced in accordance with the various local authority plans. The second is
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the “trend-based” projection, based on sub-national estimates supplied to the Department of Communities and Local Government. The third is the “most-likely” projection, which is largely based on the trend-based projection but accounts for the changes in household size that have been occurring gradually (Thames Water, 2014). This has been deemed a valid methodology by Experian as it has been demonstrated when population changes are compared to the projections for that period, they are usually higher than the projection rather than lower. Thames Water have chosen to base their projected demand on the plan-based projection (Thames Water, 2014). Table 6.1 - Predicted increase in population and properties as per the WRMP All Thames Water Zones Years Population No. of Properties AMP Corresponding Planned Most Trend Planned Most Trend No. Years Likely Likely AMP5 2010-2015 9043407 9043407 9043407 3407100 3407100 3407100 AMP6 2015-2020 9325297 9381547 9402837 3505450 3565800 3520110 AMP7 2020-2025 9698787 9891087 9941717 3542480 3635170 3576900 AMP8 2025-2030 10015307 10349117 10439667 3579580 3699060 3633430 AMP9 2030-2035 10338917 10793077 10939097 3616460 3750330 3687860 AMP10 2035-2040 10683337 11243537 11437687 3653280 3800740 3740030 2040-2045 11052437 11698517 11936197 3689750 3850320 3791700
The values for the total water demand are therefore calculated using the climate change factors detailed in the WRMP and leakage is accounted for. Thames Water have forecast no change in their leakage values in the next 40 years according to the WRMP so this value has been taken as a constant. The combination of all these factors produces an estimate of the water demand for both the Dry Year Annual Average (DYAA) and the Average Day Peak Week (ADPW). These have been calculated in Table 6.2 and the average of these two has been carried forward. The aim of using the average value is to give a representative prediction of what the future abstractions are likely to be.
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Table 6.2 - Total predicted water demand based on WRMP excluding SWOX and SWA All Thames Water Zones Except SWOX and SWA Climate Change Years Impact on Leakage Total Water Demand Demand Total Total Non- Average No. of Household Household Average Population of Corres- Properties Consumption Consumption of DYAA AMP DYAA ADPW DYAA ADPW DYAA ponding (m 3/day) (m 3/day) DYAA ADPW m3/s m3/day and No. (m 3/day) (m 3/day) (m 3/s) (m 3/s) and Years ADPW ADPW (m 3/day) (m 3/s) 5 2010-15 7535784 2839213 1166550 418000 1 1 4.502 388972.8 1973522.8 1973522.8 1973522.8 22.842 22.842 22.842 6 2015-20 7777204 2917527 1177150 412000 1.1 1.4 4.502 388972.8 2137037.8 2613782.8 2375410.3 24.734 30.252 27.493 7 2020-25 8074030 2919733 1208940 410000 1.2 1.9 4.502 388972.8 2331700.8 3464958.8 2898329.8 26.987 40.104 33.545 8 2025-30 8339538 2927543 1246760 404000 1.3 2.5 4.502 388972.8 2534960.8 4515872.8 3525416.8 29.340 52.267 40.803 9 2030-35 8627681 2943030 1289570 402000 1.4 3 4.502 388972.8 2757170.8 5463682.8 4110426.8 31.912 63.237 47.574 10 2035-40 8938711 2960200 1336300 402000 1.5 3.7 4.502 388972.8 2996422.8 6820682.8 4908552.8 34.681 78.943 56.812 2040-45 9272293 2976406 1386630 402000 1.6 4.3 4.502 388972.8 3250780.8 8080081.8 5665431.3 37.625 93.519 65.572
Table 6.3 - Total predicted abstraction rates required at Teddington Weir
Abstraction Volume %age 2010's 2020's 2050's 2080's 2120's Point (Ml/d) Datchett 2273 39.18% 712.35 1135.65 2674.47 4096.34 5822.89 Staines 682 11.76% 213.73 340.74 802.46 1229.08 1747.12
Laleham 1364 23.51% 427.47 681.49 1604.92 2458.16 3494.25
Walton 1264 21.79% 396.13 396.13 631.53 631.53 1487.25 1487.25 2277.95 2277.95 3238.07 3238.07 Hampton 109 1.88% 34.16 34.16 54.46 54.46 128.25 128.25 196.44 196.44 279.23 279.23 Kingston 109 1.88% 34.16 34.16 54.46 54.46 128.25 128.25 196.44 196.44 279.23 279.23 Total 5801 100.00% 1818 464.45 2898.33 740.45 6825.60 1743.76 10454.40 2670.82 14860.80 3796.54 Total (m 3/day) 5801000 - 1818000 464450.3 2898330 740446 6825600 1743758 10454400 2670819 14860800 3796536 Total Abstraction 67.141 - 21.042 5.376 33.545 8.570 79.000 20.182 121.000 30.912 172.000 43.941 (m 3/s)
19 | P a g e Chapter 6 – Abstractions - HP Thames Group Tidal Water Resources
Figure 6.2 - Future abstractions for full design life of 120 years
Figure 6.2 gives the total of the abstractions taking place between Windsor and Teddington Weir, so we need to ensure these values are scaled to only account for Walton, Hampton and Kingston. These values can be seen in Table 6.3.
These values will be used to calculate the required tunnel diameter from Teddington Weir to the Queen Elizabeth II Reservoir in Chapter 8.
7 Alterations to Teddington Weir In order to maximise abstraction from the Thames, it will be necessary to have the ability to prevent flow from going over Teddington Weir in times of peak water demand. This is required to ensure that no freshwater goes into the tideway, therefore allowing all freshwater to be abstracted. Currently, this would not be possible as Teddington Weir does not have sufficient mechanical flow control (i.e. any form of gate or moveable weir to regulate flow) to stop water from entering the tideway. As seen in Figure 6.1, while the weir contains some gates to help regulate the river level, a large section is made up of an overspill weir that allows water to flow freely over it.
The design of the works that would be required at Teddington Weir are beyond the scope of this feasibility study, but would need to be considered at detailed design stage to ensure viability of the scheme.
20 | P a g e Chapter 6 – Abstractions - HP Chapter 7 – Alterations to Teddington Weir - BC Thames Group Tidal Water Resources
Figure 7.1 - Aerial view of Teddington Weir (Miatt, 2006)
8 Abstraction Tunnel (Option 1)
Figure 8.1 - Proposed tunnel location
The aim of this project is to provide adequate water resources in the Thames Valley area whilst maintaining the minimum residual flow of 800mL/d as measured across Teddington Weir by optimising tidal effects in the estuary. However, the installation of a weir downstream of Teddington Weir (as proposed in Option 1) will only provide storage and maintain the residual
21 | P a g e Chapter 7 – Alterations to Teddington Weir - BC Chapter 8 – Abstraction Tunnel (Option 1) - IP Thames Group Tidal Water Resources flow for the tidal Thames region (downstream of Teddington Weir). In order to maintain the minimum residual flow upstream of Teddington Weir, the proposed solution is to stop the current abstractions upstream at Walton, Hampton and Kingston (Table 6.3). In this way, the minimum residual flow will be maintained between Walton-on-Thames and Teddington Weir without the need to release water stored in a reservoir. The tunnel will therefore provide a single abstraction point right before Teddington Weir and will store the water in the Queen Elizabeth II Reservoir, the current abstractions feed into here already, meaning no further infrastructure changes would be necessary to this system.
For the design life of the structure at the 2120’s, given the predicted water demand and climate change models, the abstractions that will need to be replaced by the new tunnel at Teddington Weir (Table 6.3) will be equal to 43.941m 3/s . The total distance of the tunnel is 5.905km .
8.1 Geology Table 8.1 - Summary of geological formation from borehole data 1 2 3 4 5 6 7 8 9 10 (m) (m) Depth Depth Borehole Borehole Borehole Borehole Borehole Borehole Borehole Borehole Borehole Borehole Borehole 1 CLAY Medium MADE Sandy SAND TOPSOIL TOPSOIL MADE Clayey TOPSOIL to coarse GROUND CLAY and GROUND SAND SAND and stones GRAVEL 2.5 CLAY Dense Fine to GRAVEL SAND Coarse Soft green Soft grey Coarser TOPSOIL brown medium and brown SILT clayey clayey sandy fine SAND GRAVEL SAND SILT SAND to coarse with fine and GRAVEL to medium medium GRAVEL GRAVEL 5 CLAY Medium Medium GRAVEL SAND Stiff grey fine grey fine grey GRAVEL GRAVEL to coarse to coarse and silty SAND SAND and and SAND SAND GRAVEL CLAY and and medium SAND medium medium SAND GRAVEL GRAVEL 7.5 - Silty Silty GRAVEL CLAY Stiff grey Stiff Stiff Brown GRAVEL CLAY CLAY and brown silty fissured fissured sandy and with parts CLAY CLAY grey silty grey silty CLAY SAND of CLAY CLAY medium to fine SAND 10 - - - Blue CLAY Stiff grey Stiff grey Stiff grey Brown Grey CLAY silty silty silty sandy CLAY CLAY CLAY CLAY CLAY 15 - - - Blue CLAY Stiff grey Stiff grey Stiff grey Solid - CLAY silty silty silty black CLAY CLAY CLAY CLAY 20 - - - Blue CLAY - - - CLAY - CLAY 25 - - - Blue CLAY - - - CLAY - CLAY 30 - - - Blue CLAY - - - CLAY - CLAY 50 - - - Blue - - - - CLAY - CLAY
22 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
1
4 3 5 2
6 8
10 9
Figure 8.2 - Borehole Maps
Borehole data has been obtained from the British Geological Survey in order to establish the geological conditions in the area between Teddington Weir and Queen Elizabeth II Reservoir. The following maps in Figure 8.2 show the selected boreholes. Table 8.1 lists the geological data for each of the boreholes consulted. This information shows the geology is fairly uniform in the region between Teddington Weir and Queen Elizabeth II Reservoir.
8.2 Inlet Shaft The inlet shaft (Figure 8.3) will be used as a reception shaft for the Tunnel Boring Machine (TBM) and should therefore be of adequate depth and diameter to enable tunnelling operations. The depth of the shaft is chosen to ensure that the tunnel alignment starts at a sufficient depth to minimise disruption and settlement to existing structures and allow for water transfer through gravity. During the operation of the abstraction tunnel, the volume of water entering in the inlet shaft will be controlled by a sluice gate that will only allow the required abstraction from the river
23 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources up to a maximum (set at a later stage by the Environment Agency in conjunction with Thames Water).
Table 8.2 - Proposed inlet shaft dimensions
Item Value (m) Depth 15 Internal Diameter 10
Inlet Shaft: ID = 10m, depth = 15m
Figure 8.3 - Proposed inlet shaft location 8.3 Sluice Gate A sluice gate is needed in order to control the flow of water that is transferred from the river to Queen Elizabeth II Reservoir. The sluice gate will be placed before the inlet shaft (Figure 8.3) and it will not only control the water flow into the tunnel, but will also enable the maintenance of the shafts and the transfer tunnel. There are various types of gates that could be used (Lewin, 1995) – radial, flap and vertical lift – but for ease of maintenance a vertical lift gate is recommended. The disadvantage of this type of gate is that the overhead structure - where the gate is lifted - is not aesthetically pleasing and careful consideration to this should be given at detailed design. A control system will be used for the operation of the sluice gate, in order to allow for different levels of intake and complete shutdown of the gate for maintenance (Chapter 16.1).
Figure 8.4 shows a sluice gate at Copperhouse which has a similar layout to the proposed design for this project. A gate plate will be used to control the river flow and it will be sliding in a steel frame superstructure. A maintenance bridge is also necessary and a control room to house the control system of the sluice gate. The proposed dimensions of the sluice gate at Teddington Weir are proposed in Table 8.3.
24 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
Steel Frame Superstructure
Control Room
Sluice gate Maintenance plate Bridge
Figure 8.4 - Vertical lift gate at Copperhouse Sluice There is detailed guidance for the design of sluice gates in “BS7775:2005 – Penstocks for use in water and other liquid flow applications – Specification”. Different forces should be considered in the detailed design, with the most critical being the force of water when acting on the gate panel and frame together. Also, the forces due to lifting that act on the gate panel and frame should be considered, the frame and the gate panel should be designed to withstand the maximum static head from the water flow and the forces from the operating equipment. The design process would be very similar to that adopted in the design of the weir sections in Chapter 14.
Inlet Shaft
River Channel Sluice gate
Figure 8.5 - Layout indicating position of sluice gate relative to inlet shaft
25 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
Table 8.3 - Recommended sluice gate dimensions
Item Value (m) Channel width 10 Superstructure height 11 Superstructure width 10 Plate height 8 Plate Width 8 Plate thickness 0.03
The recommended material for the sluice gate is stainless steel, which though more expensive than carbon steel, provides better resistance to corrosion, meaning the life-cycle cost of the sluice gate is expected to be less. The schematic for the sluice gate is shown in Figure 8.5.
8.4 Transfer Tunnel In order to calculate the required cross-section of the tunnel for the given flows, the “CIRIA C689 Culvert Design Guide” was used (CIRIA, 2010). The equivalent length method and Manning’s equation were used to derive the required channel slope and consequently the tunnel diameter. An iterative approach was used in order to derive a tunnel diameter that would be able to accommodate the maximum flow (the predicted 2120 abstraction rate) (full calculations in Appendix C).
Calculations Based on future abstractions, the Reynolds number was derived (Equation 8.1) and consequently the friction factor was found using Moody’s chart. The equivalent length method (Equation 8.2) was chosen to account for the losses in the system and was calculated and added to the length of the tunnel and the inlet shaft (tunnel + inlet shaft = 5920m), to calculate a total length. Consequently, the slope was calculated, based on the total difference between the inlet shaft and the pump out shaft (minimum drop of 10m between the two).
Equation 8.1 - Reynold's number
Where: • ρ is the water density • u is the water velocity (m/s) • L is the length of the system considered (5920m) • µ is the dynamic viscosity of water at 20ºC (N s/m 2)
Equation 8.2 - Equivalent length
26 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
, Where:
• Leq is the equivalent length of the pipe, • K is the equivalent length factor for the various components, • d is the pipe diameter and • f is the roughness coefficient found from Moody’s chart.
The K values considered are those for sudden contraction (diameter of inlet shaft > diameter of tunnel) and for 90°elbow so Kcontraction = 0.38, K 90-elbow = 0.9.
Table 8.4 - Required channel slope based on future abstraction requirements
Year Abstractions Q v = Q/A Re f (Moody's leq Total Slope (m 3/s) chart) length (m) 2020 8.570 0.682 2601749622 0.000350 3654.684 9574.684 0.00261 2050 20.182 1.606 6127014105 0.000283 4527.367 10447.367 0.00239 2080 30.912 2.460 9384513924 0.000254 5036.588 10956.588 0.00228 2120 43.941 3.497 13339962679 0.000233 5499.486 11419.486 0.00219
From Table 8.4 it can be seen that the required slope for the tunnel is equal to S=0.00219. By trial and error, using CIRIA C689, a minimum internal tunnel diameter of 4m (max. flowrate of 44.475m 3/s) will be able to accommodate the required abstraction flowrate of the 2120 prediction.
Manning’s Equation (Equation 8.3) is used to calculate the flow rate that a 4.0m diameter tunnel can convey.
Figure 8.6 - Transfer tunnel cross section according to CIRIA C689
Equation 8.3 - Manning's Equation for open channel flow
/ / Q = V x A = × × × Where (values used summarised in Table 8.5): • A is the area of capacity of flow,
27 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
• R is the hydraulic radius of the channel (Area of capacity of flow/ wetted perimeter) • S is the water surface slope
Table 8.5 - Design values for abstraction tunnel in accordance with CIRIA C689
Item Value Unit bed depth 0.250 m freeboard 0.300 m pipe diameter 4.0 m S = water surface slope 0.00219
nc = manning’s of concrete 0.011
nb = manning’s of bed 0.023 r (Radius) 2.0 m j=angle when water level reaches freeboard 2.587
f=angle between centre line and bed level 0.505
Cross Sectional Area of bedding 0.327 m2 Cross Sectional Area of free space on top 0.428 m2 A = area of capacity flow 11.811 m2 P = wetted perimeter at capacity 10.262 m R = hydraulic radius = A/P 1.151 m n=compound manning’s 0.014
Vmax = velocity = 1/n * R2/3 * S1/2 3.765 m/s 3 Qmax = flow = V * A 44.475 m /sec The self-cleaning velocity for a concrete pipe is 0.75m/s whilst the maximum allowed velocity in a concrete channel should be 6m/s (Barr, 2006). Therefore, at this maximum flow velocity of 3.765m/s minimum maintenance will be required. It is likely however, that during the first few decades of the abstraction tunnel’s operation, the minimum velocity for self-cleaning will be less than 0.75m/s and therefore more frequent cleaning of the tunnel invert will be required.
8.5 Transfer Tunnel Lining A bored tunnel is constructed using a Tunnel Boring Machine (TBM), which excavates the soil when it advances and at the same time builds tunnel rings of specified diameter and length that comprise of pre-cast concrete segments. There are different types of TBMs and rings which depend on the ground conditions in the route of the tunnel. This tunnelling method has been selected for this project as it provides various benefits such as reduced capital cost, better production rates (which will result in a reduction in construction programme) and smaller shaft requirements (Lovat, n.d.).
Primary Lining Expanded lining (or wedge block lining) will be used as the primary lining. This method uses reinforced pre-cast concrete segments and wedge-shaped keys that when inserted, expand the
28 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources segments circumferentially (Lbassoc.co.uk, 2014). Segments of the lining should withstand handling, storing and erection stresses as well as permanent loads.
The minimum internal diameter of the final tunnel should be 4.0m and assuming a 100mm secondary lining thickness, the internal diameter of the primary lining should be a minimum of 4.2m. The segments that form each ring are 1m long each so for the given length of the tunnel and depending on the final alignment, approximately 5900 rings will be used.
Secondary Lining In order to minimise the secondary losses due to the openings and the rough surfaces of the segments, an internal secondary lining will be needed. The secondary lining is an additional layer of concrete that is placed against the primary segmental lining to ensure it is water-tight and achieve a smoother surface. Usually shortcrete is used as a secondary lining, however in this case it is not suitable, as due to its high roughness coefficient there would be large hydraulic losses. Therefore in-situ concreting would be more effective to achieve the low-friction surface that is required (n=0.011 for cast in-situ lining compared to n=0.016 for shortcrete) (Pennington, 1998). These dimensions are summarised in Table 8.6.
A thickness of 100mm is assumed for the cast in-situ secondary lining. It will be poured using articulated shutters (shown in Figure 8.7).
Figure 8.7 - Articulated shutters for cast in-situ secondary lining (Photo taken from (Jewell & Bellhouse, 2014))
Table 8.6 - Proposed transfer tunnel dimensions
Item Value (m) Internal diameter (m) 4.0 Primary lining (expanded segmental lining) thickness 0.4 Secondary lining (cast in-situ concrete) thickness 0.1 8.6 Tunnel Alignment The inlet shaft will be located adjacent to the river and be a total depth of 15m. It is therefore unlikely that the alignment of the main tunnel would cause any significant settlement to existing buildings and structures. For the scope of this feasibility study no existing services’ drawings
29 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources have been acquired, therefore a full statutory undertaker’s enquiry should be undertaken at detailed design stage, along with settlement calculations to ensure that existing structures are not affected.
8.7 Pump-out shaft The pump-out shaft will be located next to the Queen Elizabeth II Reservoir and will discharge directly into the reservoir. The overall depth of the shaft will be 41m; with 13m being above ground level and 28m below ground level. Table 8.7 - Proposed pump out shaft dimensions
Item Value (m) Depth 41 Internal Diameter 15
Different pumps will be used over the years to pump-out the required flowrate from the tunnel and can be seen in Chapter 8.7.1.
Pump -out Shaft
ID = 15m, depth = 41m
Figure 8.8 - Proposed pump out shaft location Pump Requirements Pumps will be required to transfer the water vertically from within the pump out shaft into the reservoir. Equation 8.4 can be used to determine the power required in order to transfer the water vertically in order to reach the reservoir (AECOM, 2014) – the results of which are summarised in Table 8.8. Equation 8.4 = Where; • Q=Flow rate • H = Water Head • G = Acceleration due to gravity 30 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
• Ρ = density of water • Η = pump efficiency
31 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources
Table 8.8 – Power requirements of pump out shaft systems
Time Flow rate Head Density of Pump Power g (m/s 2) Period (cubics) (m) Water (kg/m 3) Efficiency Required (W) 2020 8.57 28 9.81 1000 0.75 3138676.8 2030 12.5 28 9.81 1000 0.75 4578000 2040 15 28 9.81 1000 0.75 5493600 2050 20 28 9.81 1000 0.75 7324800 2060 22.5 28 9.81 1000 0.75 8240400 2070 27.5 28 9.81 1000 0.75 10071600 2080 30 28 9.81 1000 0.75 10987200 2090 32.5 28 9.81 1000 0.75 11902800 2100 37.5 28 9.81 1000 0.75 13734000 2110 40 28 9.81 1000 0.75 14649600 2120 43.94 28 9.81 1000 0.75 16092585.6
This data can then be used to determine the financial cost of pumping. The total costs per decade can be predicted for the operation of the pumps. The average cost per kWh of electricity was used as 9.397 pence (UK Power, 2014) and multiplying this value by the electrical usage in kWh gives an estimated cost for the pumps operation. From this the accumulative NPV cash flow was determined for pumping water to the reservoir over the design life of the scheme. Figure 8.9 shows the predicted cash flow for the operation of the pumps. NPV Pump Operation Cash Flow 50000000
40000000
30000000
20000000
10000000
0 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 -10000000
-20000000
Total ofCost Operation(£'s) -30000000
-40000000
-50000000 Time Period
Figure 8.9 - NPV Pump operation cash flow
The overall cost for the installation and maintenance of the pumps is included in the assumption for the pump out shaft costs. The most sustainable option would be to install pumps over time, depending on abstraction requirements. In the initial instance installing a number of pumps will 32 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources give the option to rotate the usage, in case of maintenance being needed and also so as to prevent premature wear. Installing all the pumps too early would be inefficient, as wear occurs whilst submerged, even if not in use, reducing the operating life of the pump.
It is also crucial to consider the possible cavitation of the pumps. The pump manufacturer will specify the level of water that can be pumped without causing cavitation. A simple float switch could be incorporated to ensure that the pumps are only active when the water level is high enough, however, ultimately this will be designed within the control system (Chapter 16).
For the purpose of costing this project the pumping costs will not be included in the final financial analysis as this will be replacing the pumping at the current abstractions which will theoretically be producing the same outputs. However, the costs of the current abstractions will need to be compared with the costs highlighted above at detailed design stage to confirm. Due to different layouts of abstraction systems, the costs between the current solutions and this costing may vary.
8.8 Programme of Works and Construction Methodology The duration of works for the tunnelling will be as shown in Table 8.9.
Table 8.9 - Programme of works: Tunnelling
Activity Duration (months) Site Set-up 6 Shafts Construction (x2) 15 Tunnelling 10 Secondary Lining 7 Sluice Gates 5 Reinstatement Works 4 Total duration 42 months = 3.5 years
Site Set-up: Includes establishing of all the access routes, hoarding around the perimeter of the site and setting up the site offices and welfare facilities.
Shaft construction: Diaphragm walls will be needed to support the excavation. Once they are complete the main shaft excavation will start, by excavating the soil to expose the walls and forming a steel reinforced concrete base at the base of the shaft. It is likely that dewatering will be needed whilst sinking the shaft, which should be done with the aid of pumps.
Tunnelling and Secondary Lining 2: These will be continuous operations (24/7) as they take place below ground and cannot disturb locals. All the excavated material will be transported to the surface by conveyor to the appropriate muck-away area. All the excavated material will be loaded
2 Tunneling rates are in accordance with the London Power Tunnel Rates which are in similar ground and tunnel diameter 33 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) – IP [Pump Requirements – DJ] Thames Group Tidal Water Resources onto barges and transported away on a 24/7 basis. Once the primary lining is complete the TBM will be dismantled at the pump-out shaft and the secondary lining will follow, in the form of cast- in-situ concrete.
Sluice gates: The sluice gate can begin construction any time after the launch of the TBM and can be completed in parallel with the tunnelling operations.
Reinstatement Works: After the main works are complete, site clean-out and landscaping works will take place.
8.9 Financial Assessment The following cost estimate has been based on the report from British Tunnelling Society (BTS) regarding Tunnelling Project Costs (Figure 8.10), where different tunnelling projects have been prepared in order to produce a benchmark for new projects (BTS, 2010). The 2010 prices have been adjusted to 2013 levels (accounting for inflation) for the Hammersmith Flyunder Feasibility study undertaken by Halcrow (Halcrow , 2014).
The following guidance prices of project cost per m3 of tunnel do not take into account any land costs, design fees, temporary and enabling works, M&E (Mechanical and Electrical) and any O&M (Operation and Maintenance) costs.
Figure 8.10 - Tunnel costs per m 3 in relation to diameter based on 2013 prices (Graph taken from (British Tunnelling Society, 2010))
Overall estimated cost for the tunnel drive (Internal diameter = 4.0m)
V = π × r 2 × L = π × 2 2 × 5905 = 74204m 3
Overall Tunnel Cost = 880£/m 3 x 74204m 3 = £65,299,888 = £65.3m
34 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) - IP Chapter 9 – Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) - BC Thames Group Tidal Water Resources
Cost/m = £11,058
Allowing a 20% for all the overheads and M&E Work: Total Estimated Cost = £78.36m
9 Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) A possible solution to the water shortage is to upgrade the existing Hogsmill Sewage Treatement Works (STW) to include facilities to enable the operators to recycle waste water into usable drinking water through indirect potable reuse (IPR). This will also involve a tunnel to pump the recycled water either into the Thames at Hampton (Option 2) or directly into the nearby Queen Elizabeth II Reservoir (Option 3).
Water recycling has already been implemented in several countries, with successful schemes implemented in Australia (Keremane & McKay, 2006), the United States (National Research Council, 2012) and several European countries (Angelakis, et al., 2007) among others, with schemes providing recycled water for both potable and non-potable use.
Figure 9.1 - Schematic of Langford scheme. Shown in orange is the route that sewage water used to take before being disposed of into the sea
Thames Water has already considered the possibility of implementing a water reuse scheme at Hogsmill STW, but so far has not carried out any study into its feasibility, hence there is no prediction of how much such a scheme would cost. There are two schemes put forward by Thames Water, one to produce 15 Ml/d and another to produce 30 Ml/d. For the purposes of this report the proposed scheme will output 30 Ml/d.
35 | P a g e Chapter 8 – Abstraction Tunnel (Option 1) - IP Chapter 9 – Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) - BC Thames Group Tidal Water Resources
The Langford Water Recycling Scheme in Essex (Figure 9.1) should provide a reasonable case to compare with the proposed Hogsmill STW scheme. The plant can provide a maximum of 40 Ml/d. The cost of construction for the scheme was £13 million (Northumbrian Water, 2013) and due to the similar output to the proposed Hogsmill STW scheme it would not be unreasonable to assume that the upgrade would cost a similar amount.
In addition, the scheme follows the same basic principle as Option 2 in that wastewater would be transferred from a sewage treatment plant and then recycled. It would then be discharged into the river before being abstracted to a reservoir for general supply.
In order to estimate the cost of upgrading Hogsmill STW and the operating costs of recycling water, further research needs to be conducted as both costs are highly dependent on several factors unique to the project, such as the technology implemented and the availability of freshwater. For example operating costs range widely between different schemes (National Research Council, 2012) with schemes in California being cited as costing being between $0.31- $2.38/kgal. This would place operating costs between £766,500 and close to £9,000,000 per year.
9.1 Abstraction Tunnel Alternatives Two alternative options to the abstraction tunnel at Teddington have been considered. Both of the options will require construction of a new tunnel and have been priced as follows.
Option 2 - Hogsmill STW Upgrade and direct discharge in the river at Hampton The first alternative considered is a transfer tunnel between Hogsmill STW and the abstraction point at Hampton (see Figure 9.1). The tunnel diameter is assumed to be 4m whilst the total distance is 4.3km. The estimated cost would be:
V = π × r 2 × L = π × 2 2 × 4300 = 54036m 3
Overall Tunnel Cost = 880£/m 3 x 54036m 3= £47,551,520 = £47.55m
Allowing a 20% for all the overheads and M&E Work: Total Estimated Cost = £57.06m
By using this alternative, the abstractions at Hampton and Kingston could continue to operate since water would be transferred to the river upstream of these from the Hogsmill STW and this would maintain the minimum residual flow between Hampton and Teddington Weir. However, the abstraction at Walton would still have to be terminated or reduced in order to ensure that the minimum residual flow between Walton and Hampton is maintained.
36 | P a g e Chapter 9 – Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) – BC [Abstraction Tunnel Alternatives – IP] Thames Group Tidal Water Resources
Total distance = 4.3km
Diameter = 4.0m
Tunnel Cost = £57.06m
Figure 9.1 - Option 2: Alternative to abstraction tunnel at Teddington Weir – Hogsmill STW to Hampton Even though in terms of tunnelling this is the most economical proposal, the total cost of the Hogsmill STW upgrade should be considered.
Option 3 - Hogsmill STW Upgrade and Transfer Tunnel to Queen Elizabeth II Reservoir The second alternative considered is a transfer tunnel between Hogsmill STW and Queen Elizabeth II Reservoir (see Figure 1.2). Again, the tunnel diameter is assumed to be 4m and the total distance is 6.5km. The estimated cost would be:
V = π × r 2 × L = π × 2 2 × 6500 = 81682m 3
Overall Tunnel Cost = 880£/m 3 x 81682m 3= £71,880,060 = £71.9m
Total distance = 6.5km
Diameter = 4.0m
Tunnel Cost = £86.26m
Figure 1.2 - Option 3: Alternative to abstraction tunnel at Teddington Weir – Hogsmill STW to Queen Elizabeth II Reservoir
Allowing a 20% for all the overheads and M&E Work: Total Estimated Cost = £86.26m
37 | P a g e Chapter 9 – Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) – BC [Abstraction Tunnel Alternatives – IP] Thames Group Tidal Water Resources
This alternative would enable all three abstractions (Walton, Hampton and Kingston) to be closed, therefore maintaining the minimum residual flow between Walton and Teddington Weir as no water will be abstracted between.
10 Chemical Assessment In 2000, the European Union passed the Water Framework Directive (WFD) (The European Parliament and the Council of the European Union, 2000), a bill designed to improve the state of water quality in Europe. The WFD requires that all bodies of water meet certain standards with regard to chemical and ecological content such as pollutant levels and biodiversity (European Union Committee, 2012).
The proposed scheme’s solution to alleviate water supply issues during drought periods is two- fold: first is the construction of a tidal weir (herein referred to as Kew Weir) to store water in the river, the second is to have the potential to abstract all of the freshwater in the Thames at Teddington Weir. Kew Weir itself will alter the flow of the river in its immediate vicinity, while the abstraction at Teddington Weir will potentially reduce the amount of freshwater in the Thames tideway. Both of these will alter the chemical composition of the river, which will in turn have an effect on the river’s ecology.
10.1 Salinity A report carried out for Thames Water’s LTOA AMP5 investigation showed that the water between Teddington and Battersea was largely fresh water and that salinity was largely independent of the flow over Teddington Weir (Cascade Consulting, 2012). This is presumed to be due to the freshwater flows entering the tideway from the River Crane and the River Brent, both downstream of Teddington Weir. The report also showed a minimal variation in salinity, with only a gradual increase during low flow. It concludes that salinity in the Upper Thames Tideway is largely dependent on tidal conditions and therefore it could be assumed that any effect on salinity caused by the proposed scheme would not be significant enough to cause concern.
10.2 Dissolved Oxygen The level of oxygen in a body of water, known as the dissolved oxygen (DO) content or DO concentration, is an essential component in determining that body of water’s ecology (Baylar & Bagatur, 2000). Therefore the DO must be kept within certain limits so as not to cause significant harm to species living in the Thames. If the DO content drops below a certain level, the lack of oxygen causes large numbers of certain species to die off (Lakso, 1988) in events known as ‘fish kills’. Low DO can also hamper movement of fish going upstream. Conversely, high levels of DO can also kill fish through Gas Bubble Disease (Kemker, 2013).
38 | P a g e Chapter 9 – Hogsmill Sewage Treatment Works Re-use (Options 2 and 3) – BC [Abstraction Tunnel Alternatives – IP] Chapter 10 – Chemical Assessment - BC Thames Group Tidal Water Resources
Figure 10.1 - A section of a graph showing measured DO content along the river. Abstraction points are represented by green arrows and water input is represented by blue.
With regards to the Thames, areas with low DO are avoided by fish such as salmon and can represent a barrier to fish swimming upstream. In addition, low DO can give an advantage to some invasive species of molluscs and shellfish that prefer lower DO environments.
The (DO) content in the Upper Tideway drops in two locations: just upstream of Richmond Weir, and downstream of Mogden STW (Cascade Consulting, 2012). The first drop can be explained by the effect of Richmond slowing the flow of water upstream (reduced turbulence causes less aeration of the flow and therefore lower DO). Downstream of Richmond, the sewage overflow from Mogden STW causes a larger drop in DO content of the river, as shown in Figure 10.1.
The stretch of river between Teddington and Richmond is somewhat sensitive to flow levels, with a drop in flow over Teddington Weir corresponding to a drop in DO content and greater sensitivity to river conditions (such as algal blooms). This presents an issue with the proposed scheme; however there are options available to mitigate this effect (See Chapter 10.4).
Mogden STW represents a greater issue with regards to DO as it is sited only a few kilometres upstream of the proposed Kew Weir site. During a period of high rainfall, Mogden STW will overflow and discharge effluent water from its sewer drain directly into the River Thames. The pollutants in the effluent are broken down and in the process biological oxygen demand (BOD) increases, lowering the DO content in the river. This is also exacerbated during periods of low flow when there is less fresh water to dilute the effluent. This effect, combined with slowing of flow behind the weir, poses a potentially significant problem with construction at the chosen site.
39 | P a g e Chapter 10 – Chemical Assessment - BC Thames Group Tidal Water Resources
However, Mogden STW has recently expanded its capacity by 54% (Thames Water, 2013) which should reduce the number of discharges per year and therefore reduce impact on DO.
10.3 Other Factors Phosphorus and dissolved nitrogen (as well as compounds including these elements such as phosphates, nitrates and ammonia) are chemicals that are included in the WFD for monitoring and assessment of water quality. Phosphates and nitrates are plant nutrients; as such the plant life in the Thames is sensitive to levels of these chemicals. Ammonia is toxic to wildlife and is historically used as an indicator for pollution in bodies of water, in addition to conversion into nitrates.
Ammonia concentrations in the River Thames are greatest at Teddington and further downstream during the winter and spring months, at times when rainfall will be heaviest. Teddington Weir closures should not be required during these periods in the early decades of the project and therefore should have little effect on ammonia levels. Additionally, ammonia levels remain fairly constant during periods of low flow, so the abstraction scheme should also have minimal impact.
Increased sediment deposition between Teddington and Richmond during low flow periods suggest that the proposed weir will also cause a similar increase in deposition during its operation. However, it was found that the Richmond depositions were only temporary and would return to normal levels when flow increased (Cascade Consulting, 2013). Thus, it would be reasonable to assume that sedimentation would not be a long term issue for Kew Weir.
10.4 Mitigation There are options available to counteract some of the effects highlighted on the composition of the River Thames. Of the options investigated by Thames Water, the one that holds the greatest cost to benefit ratio for DO content would be to directly increase the level of oxygen through injecting hydrogen peroxide (H 2O2), oxygen, or air into the effluent discharges, depending on the chosen scenario. For less frequent operation, hydrogen peroxide injection would be the most attractive option, with a predicted cost of £14 million over 40 years and a carbon cost of 0.2 tonnes per year. Oxygen gas is another possible option, with the same financial cost as hydrogen peroxide injections, but a higher CO 2 emission at 2 tonnes per year. If injection is required more frequently, then using oxygen becomes more efficient as the carbon footprint of hydrogen peroxide increases dramatically. Due to its toxicity H 2O2 could also be unsuitable for regular use, though the extent of this would need to be further investigated.
Using compressed air and pressure swing adsorption (Figure 10.2) to produce oxygen would have an advantage over H 2O2, as it can be produced on site, whereas H 2O2 would have to be transported
40 | P a g e Chapter 10 – Chemical Assessment - BC Thames Group Tidal Water Resources in. On site production also has the benefit of not requiring personnel to handle either H 2O2 or oxygen, thereby saving on transport costs and CO 2 emissions.
Figure 10.2 - Compressed air is pumped through a tank containing zeolite pellets which adsorbs unwanted gas leaving oxygen to be stored in the buffer tank. In the opposite tank air is pumped out to clean the pellets. After Gazcon
Another option would be to deploy bubblers in the River Thames. This option is less efficient and has a significantly lower cost to benefit ratio than effluent injection. Both options, however, would not be critical to the operation of Kew Weir as the nature of a moveable weir means that any build-up of DO will likely be released once the gate is lowered at low tide. The proposed mitigation solutions would be primarily aimed at Mogden STW rather than Kew Weir, as that would still be the dominating factor in DO. In addition Mogden STW spills would be most common during periods of high rainfall, when Kew Weir would not be in use. Therefore it would be unlikely that operation of Kew Weir would exacerbate a drop in DO caused by Mogden STW spilling into the River Thames.
As salinity is largely tidal-driven, there would be little need to mitigate any changes in salinity especially considering the short-term, infrequent operation of Kew Weir. Similarly, other factors listed in this report are dependent upon tidal conditions or are unlikely to become an issue during operation of Kew Weir and increased abstraction periods; therefore it can be assumed that the proposed scheme will have minimum impact on the water quality of the Thames, therefore will not require costly mitigation measures.
10.5 Option 1 Option 1 involves stopping abstractions from Hampton, Walton and Kingston in order to maintain minimum residual flow to Teddington Weir. The lack of abstraction in this stretch of river would lead to an overall increase in the volume of water, leading to a dilution of pollutants. This option has the potential to benefit water quality and thus would require no mitigation measures.
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10.6 Option 2 Option 2 involves pumping treated water into the River Thames at Hampton. Whether or not this will impact the water quality of the Thames is dependent upon the quality of the recycled water and the level of pollutants it contains. This in turn will depend upon the technologies used at Hogsmill STW and the extent of the water purification. In any case, the water should be significantly less polluted than that from the Mogden STW discharges, so would require much less in the way of mitigation. If this option were to be chosen it would be unlikely to need any mitigation as the recycled water would essentially be the same as freshwater and the effect would unlikely be significant enough to impact the relatively high levels of DO upstream of Teddington Weir, as seen in Figure 10.2.
10.7 Option 3 Option 3 should have no impact on the water quality of the river as all of the recycled water would be fed directly into the Queen Elizabeth II Reservoir, completely bypassing the River Thames. Therefore, no mitigation measures would be necessary.
11 Option 1 - Storage Required The daily abstractions determined in Chapter 6 need to be provided by the tidal recharge scheme to maintain the river flow after the abstractions. As the tide comes in twice a day we need to store half a day’s total abstraction volume behind the weir each tide. As the minimum residual flow must also be maintained we need to add the 800Ml/day to every tide storage value to determine the total minimum storage volume required.
11.1 Volume Calculation The minimum residual flow of 800ml/day is equal to 9.259m3/s of flow over the weir. This needs to be added to half the abstraction values required. This will give a total flow over the weir at any point. The storage volume is then calculated by multiplying the total flow to give a volume required in 24 hours. Table 11.1 shows the total storage volume required. Table 11.1 - Total storage volume required per tide
2010’s 2020’s 2050’s 2080’s 2120’s Total Abstraction (m 3/s) 5.376 8.570 20.182 30.192 43.941 Minimum Residual Flow (m 3/s) 9.259 9.259 9.259 9.259 9.259 Total Flow (m 3/s) 14.635 17.829 29.442 40.172 53.201 Total Storage Required per Tide (m 3) 1,032,225 1,170,223 1,671,879 2,135,409 2,698,268 11.2 Storage Available To determine the position of the weir in the river, the storage space available in the Thames has to be calculated from Teddington Weir downstream at regular points. To do this the Port of London
42 | P a g e Chapter 10 – Chemical Assessment - BC Chapter 11 – Storage Required - HP Thames Group Tidal Water Resources
Authority (PLA) Hydrographic Surveys (Port of London Authority, 2010) were consulted and the PLA provided x,y,z data (Port of London Authority, 2014) from these surveys to allow more accurate sections to be drawn. From this we plotted sections along the Thames from Teddington Weir onwards at fairly regular intervals (we aimed for similar lengths between sections but tried to target changes in river section as well). From these average volumes between sections were calculated and compared to the required storage volumes. The drawings for these sections can be seen in Appendix G.
Table 11.2 - Sections and storage summary Total Storage Required Total Storage Provided to Years Section Per Tide (m 3) Section (m 3) 2010's 1032225 1164933 GG 2020's 1170223 1555994 HH 2050's 1671879 1761936 II 2080's 2135409 2200528 JJ 2120's 2698268 2698268 KK 3050444 LL
Figure 11.1 - World Heritage Site at Kew Gardens and Buffer Zone (UNESCO, 2002) 43 | P a g e Chapter 11 – Storage Required - HP
Thames Group Tidal Water Resources
Table 11.2 summarises the sections required to meet each of the demands calculated. It should be noted that although Section KK provides the required storage demands, it falls inside the protected buffer area surrounding Kew Gardens (See Figure 11.1). For this reason we have decided to move the weir position along to Section LL.
11.3 Sense Check on Calculation As an extra sense check, the required storage volume for the measured flows to maintain river level was compared to the storage volumes. The required volume was 232225m 3 per tide for abstractions and a further 800000m 3 for minimum residual flow. This gives a total volume of 1032225m 3 per tide which when compared to the storage available occurs at Section GG (1164933m 3). This is the section drawn at Richmond Weir which confirms the calculation basis to be approximately correct.
12 Comparing Future Flows to Future Abstractions To assess the impact the scheme can have on the future demand we have compared the future flows in the Thames calculated in Chapter 5 against the future abstractions calculated in 6.2 Future Abstractions & Water Demand. Table 12.1 highlights when the deficits are likely to occur, thus gives an indication of the potential scope of the project. It can be seen that although the scheme is always going to have a positive impact on the water supply system, the River Thames simply cannot produce enough flow to meet proposed future demands for the whole design life. In other words, the scheme would have to be supplemented with an additional water supply potentially from 2080 onwards.
Table 12.1 - Future flows compared to future abstractions and minimum residual flow (Green indicates no deficit, Red indicates deficit and amount) Years Quarter Flows in River at Kingston Abstraction Deficit in Flow at Kingston (m 3/s) & MRF (m 3/s) Average Wettest Driest (m 3/s) Average Wettest Driest Flow Flow Flow Flow Flow Flow 2010's 1 121.485 14.635 106.851 2 72.273 14.635 57.638 3 28.166 14.635 13.531 4 45.968 14.635 31.333 2020's 1 123.775 88.766 49.508 17.829 105.946 70.937 31.679 2 93.552 88.766 87.029 17.829 75.723 70.937 69.200 3 49.508 40.198 40.795 17.829 31.679 22.368 22.966 4 50.183 34.047 28.767 17.829 32.354 16.218 10.938 2050's 1 129.797 96.618 118.514 29.442 100.355 67.177 89.072 2 92.005 78.855 92.536 29.442 62.564 49.413 63.094
Chapter 11 – Storage Required – HP 44 | P a g e Chapter 12 – Comparing Future Flows to Future Abstractions - HP
Thames Group Tidal Water Resources
Years Quarter Flows in River at Kingston Abstraction Deficit in Flow at Kingston (m 3/s) & MRF (m 3/s) Average Wettest Driest (m 3/s) Average Wettest Driest Flow Flow Flow Flow Flow Flow 3 47.460 39.257 44.385 29.442 18.019 9.815 14.943 4 46.800 39.327 43.055 29.442 17.358 9.886 13.614 2080's 1 120.908 118.524 118.511 40.172 80.737 78.352 78.339 2 91.283 87.571 93.514 40.172 51.112 47.400 53.342 3 41.451 41.703 34.685 40.172 1.279 1.532 -5.487 4 36.209 45.605 33.764 40.172 -3.963 5.434 -6.407 2120's 1 125.000 106.000 117.000 53.201 71.799 52.799 63.799 2 101.000 91.000 104.000 53.201 47.799 37.799 50.799 3 51.000 47.000 43.000 53.201 -2.201 -6.201 -10.201 4 36.000 42.000 32.000 53.201 -17.201 -11.201 -21.201
13 Lock Necessity To determine the suitability of each of the options proposed for Kew Weir, a check on when the lock would be required based on the future flows and abstractions for the Thames upstream of Kew Weir. To do this the predicted abstractions for each period have been subtracted from the daily future flows data for Kingston and applied the logic that whenever this value is less than the minimum residual flow of 9.259m 3/s the weir will be in operation. Whenever the weir is in operation the River Thames will effectively be blocked to all navigation. The weir will be operational for the full 24 hours of any day it is required, with a small window at high tide where the weir will go from being flat against the seabed to being fully raised. The length of time in which this will occur cannot be quantified at this stage and therefore cannot be relied upon for passage of ships. Table 13.1 - Percentage of time navigation is disrupted due to weir
Climate Change Model Average Wettest Driest Recorded Total Months Closed 232 309 298 117 Total Months Considered 1764 1764 1764 744 Percentage Impassable 13% 18% 17% 16% 2020-2049 Percentage Impassable 5% 15% 5% 2050-2079 Percentage Impassable 35% 37% 41%
Every day has been analysed for completeness against the three climate change models identified earlier and against the recorded data from 1951 to 2013 (full results available on request – not included as over 1000 pages long). The defining characteristic of when the lock is necessary is when the weir is activated for three or more days in succession. This has been chosen as a
Chapter 12 – Comparing Future Flows to Future Abstractions – HP 45 | P a g e Chapter 13 – Lock Necessity - HP
Thames Group Tidal Water Resources reasonable point to determine if a lock is necessary or not as up to two days it is an inconvenience not to be able to navigate the River Thames but is not a significant disruption. To summarise the information Figure 13.1, Figure 13.2, Figure 13.3, Figure 13.4, Figure 13.5 and Table 13.1 have been produced.
2014 Abstractions Vs. Flows 450.000 400.000 350.000 300.000 /s) 3 250.000 200.000
Flow Flow (m 150.000 100.000 50.000 0.000
Date
Abstractions & MRF Future Flows - Average Future Flows - Wettest Future Flows - Driest
Figure 13.1 - 2014 Abstractions Vs. Future Flows at Kingston
2020 Abstractions Vs. Flows 450.000 400.000 350.000 300.000 /s) 3 250.000 200.000
Flow Flow (m 150.000 100.000 50.000 0.000
Date
Abstractions & MRF Future Flows - Average Future Flows - Wettest Future Flows - Driest
Figure 13.2 - 2020 Abstractions Vs. Future Flows at Kingston
46 | P a g e Chapter 13 – Lock Necessity - HP Thames Group Tidal Water Resources
2050 Abstractions Vs. Flows 450.000 400.000 350.000 300.000 /s) 3 250.000 200.000
Flow Flow (m 150.000 100.000 50.000 0.000
Date
Abstractions & MRF Future Flows - Average Future Flows - Wettest Future Flows - Driest
Figure 13.3 - 2050 Abstractions Vs. Future Flows at Kingston
2080 Abstractions Vs. Flows 450.000 400.000 350.000 300.000 /s) 3 250.000 200.000
Flow Flow (m 150.000 100.000 50.000 0.000
Date
Abstractions & MRF Future Flows - Average Future Flows - Wettest Future Flows - Driest
Figure 13.4 - 2080 Abstractions Vs. Future Flows at Kingston
47 | P a g e Chapter 13 – Lock Necessity - HP Thames Group Tidal Water Resources
2098 Abstractions Vs. Flows 450.000 400.000 350.000 300.000 /s) 3 250.000 200.000
Flow Flow (m 150.000 100.000 50.000 0.000
Date
Abstractions & MRF Future Flows - Average Future Flows - Wettest Future Flows - Driest
Figure 13.5 - 2098 Abstractions Vs. Future Flows at Kingston
It can be seen clearly in Table 13.1 that a lock is necessary by 2050 for all models of future flows. The figures indicate that the weir itself is not required until 2020 for the driest and the wettest climate change models and 2050 for the average model. As such we have decided to progress with three main options for Kew Weir.
13.1 Options Considered for Kew Weir Option 1a This option is to have no provision for a lock at Kew Weir and to have three sections of 30m for the weir. The existing abstractions at Hampton, Walton and Kingston will be stopped and the tunnel and the alterations to Teddington Weir will be constructed immediately. Kew Weir will be constructed for use by 2020. By 2050 navigation is severely restricted, effectively limiting the design life of this project to 35 years without further investment and alteration. This could be combined with Options 2 or 3 as discussed in Chapter 9 to provide further design life but this would need further investigation.
Drawings 201 & 211 show the details of Option 1a and can be found in Appendix G.
Option 1b This option is to have a lock provided at Kew Weir for navigational use resulting in three sections of 25m for the weir and to have 15m width for the lock. This allows for the passage of ships at all times during operation of the weir but the lock itself would be limited to use only a certain number of times a day. This is because each time it is used the stored water is used to move the
48 | P a g e Chapter 13 – Lock Necessity - HP Thames Group Tidal Water Resources ships from one side to the other and therefore the flow rates over the weir and the stored volume will be altered. As in Option 1a the existing abstractions at Hampton, Walton and Kingston will be stopped and the tunnel and the alterations to Teddington Weir will be constructed immediately. Kew Weir will be constructed for use by 2020, including the lock. At this point it is necessary to check the data collated in Table 12.1 detailing when the future flows are no longer sufficient to sustain the predicted increase in abstractions to determine the limit on the design life. This shows that by 2080 the flows coming down the river are no longer sufficient for the abstractions required and therefore this is the limit to the design, giving a design life of 65 years. As with Option 1a this could be combined with Options 2 or 3 as discussed in Chapter 9 to provide further design life but this would need further investigation.
Drawings 202 & 212 show the details of Option 1b and can be found in Appendix G.
Option 1c This final option is to have a staged construction scheme. The existing abstractions, tunnel and alterations to Teddington Weir would be identical to Options 1a & 1b. Kew Weir would be constructed for use by 2020 as well but the design would incorporate the reuse scheme from Hogsmill STW as discussed in Chapter 9 to be in use by 2080 to meet the deficits identified in Table 12.1. Kew Weir itself would have three sections of 30m initially, with the third section (closest to the North bank) being constructed such that the weir gate itself is split into two sections of 15m. This allows one section to be removed and the lock to be constructed for use in 2050. Following this the additional tunnels and shafts can be bored for implementing the Hogsmill STW reuse scheme to supplement the river flow by 2080. Depending on the flows possible from the Hogsmill STW reuse (we need 22m 3/s) this could provide the remaining flow needed to meet the full design life of 120 years. The figures quoted in Chapter 9 give a maximum contribution of 30Ml/d (0.347 m 3/s) so this does suggest this is not a reasonable method of meeting the full 120 year design life. Staging the construction reduces the carbon footprint of the scheme and reduces the costs associated as well.
Drawings 203 & 213 show the details of Option 1c and can be found in Appendix G.
13.2 Lock Dimensions The locks at Teddington Weir provide passage for various size vessels. There are three locks in operation here, the barge lock, the launch lock and the skiff lock. The sizes of each of these are different and the operating restrictions also vary between them dependent on the tidal patterns downstream of Teddington Weir and the flow upstream of Teddington Weir.
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If we are to provide a lock at Kew Weir we must make sure we can at least match the dimensions of Teddington Weir to ensure consistent passage along the Thames can be maintained. Table 13.2 gives the dimensions of the various locks at Teddington Weir.
Table 13.2 - Lock dimensions at Teddington Weir
Lock Type Length (m) Width (m) Depth (m) Barge 198 7.5 2.6 Launch 54 7.4 2.7 Skiff 15 1.7 1.0 14 Kew Weir
14.1 Environmental Impact Assessment The environmental impact must be assessed in order to maintain the climate that flora and fauna are dependent on. For example, potential changes to fish migration, flora and fauna and navigation are all possible results of a new structure in the river. These areas often have a chain effect on the rest of the inhabitants in the local environment.
Various archaeological elements and heritage sites and structures may be present in the area and must be sustained. In this specific case, the structure is proposed to be built just outside of Kew Gardens, a listed and protected area. Even though the location is just outside the buffer area, additional precautionary measures need to be in place before and during construction works take place. It would be recommended to undertake an archaeological survey in the construction site area as the likelihood of finding something ancient is moderate.
More importantly, land drainage and flood defence may be affected and can have serious consequences, such as local flooding, and must be considered in any detailed design. These have been included in the Risk Register in Chapter 22 for the purposes of this feasibility stage. River structures can have an impact on sedimentation and erosion, water quality and resources management and as a result can lead to planning and/or legal issues. (Good Practice Guide)
It is important to understand that a solution to one problem may be a cause of another and the design of such a structure should be aimed at avoiding any negative effect on the river and the surrounding areas, or introduce a plan on how these will be controlled to keep them to a minimum.
14.2 Site Visit To fully understand the location of the proposed weir, a site visit was conducted in January 2015. The photos from the site visit can be seen in Appendix D in larger format but are presented below for information.
50 | P a g e Chapter 13 – Lock Necessity - HP Chapter 14 – Kew Weir [Environmental Impact Assessment – JJ] [Site Visit – HP] Thames Group Tidal Water Resources
It can be seen there is space on both the north (Figure 14.6) and south bank (Figure 14.7) for construction of Kew Weir, although the South bank is significantly less congested and would be a much more suitable location for main construction material storage and site offices etc. (Figure 14.5). The existing mooring in the middle of the river (Figure 14.4) would have to be removed/relocated to avoid interference with Kew Weir. Kew Pier (Figure 14.1) will be largely unaffected by the proposed Kew Weir as it is a suitable distance upstream of the location. The area of the river that it is proposed Kew Weir will straddle is a sensitive one as not only are we just outside the Kew Gardens buffer zone, adjacent to Kew Pier and the existing mooring structure, there is also nearby Oliver’s Island – an important habitat for herons, cormorants and Canada geese (Figure 14.2). In addition, the tide was out during the site visit, where it was noted there is a large outlet into the river on the North bank (Figure 14.3) of unknown origin or effluent type. It is possible it is simply rainwater runoff from nearby roads and gardens, but it is also possibly a sewage outlet. This would require further investigation at detailed design stage as if the water level is raised higher than this outlet there is a possibility of backing up the outlet and flooding the source.
Figure 14.1 - Kew pier Figure 14.2 - Span of river to be sectioned by the proposed Kew Weir
Figure 14.3 - Outlet into the River Thames (unknown Figure 14.4 - Mooring structure in the middle of the source or effluent type) Thames immediately adjacent to proposed Kew Weir location
51 | P a g e Chapter 14 – Kew Weir [Site Visit – HP] Thames Group Tidal Water Resources
Figure 14.5 - Playground on the South bank of the Figure 14.6 - North bank of the Thames at Kew Weir Thames at Kew Weir location location (residential street visible just beyond)
Figure 14.7 - South bank of Thames at Kew Weir location - scour protection badly degraded. 14.3 Substructure The structural foundations are required to safely transmit the loads from the superstructure of Kew Weir whilst maintaining the required water tightness to prevent seepage flow underneath. The geological conditions are critical in establishing type of foundation, methods of construction and seepage prevention and design of the structure. Any structure that is built in a river environment needs to satisfy three fundamental requirements (Environment Agency, 2013) : • Hydraulic performance – the weir must provide the desired hydraulic performance throughout the full range of flow conditions, from low summer flow to flood. • Structural integrity – the weir must be able to resist the onerous hydraulic and structural loading throughout its design life, without the need for excessive maintenance expenditure. • Health and safety requirements – the weir must not pose any avoidable and unacceptable health and safety risks to members of the public or operational staff, both during construction and once completed and in use.
Geological conditions of the proposed location The geological information has been obtained from the British Geological Survey website, which maintains a vast amount of historical geotechnical information, including a substantial amount of borehole data throughout the United Kingdom continuously collected over more than a hundred
52 | P a g e Chapter 14 – Kew Weir [Site Visit – HP] [Substructure – JJ] Thames Group Tidal Water Resources years. A number of borehole scans are available in the vicinity of the proposed structure, with the map in Figure 14.8 showing the closest ones.
Indicative proposed location of Kew Weir
Figure 14.8 - Borehole data map (British Geological Survey, n.d.)
The borehole log data from the nearest survey locations, Kew Pier and Kew Boathouse, have been used to analyse the geological conditions in the area considered in this report. The complete log data can be found in Appendix B, however, summary sheets are also shown in Figure 14.9 and Figure 14.10.
Figure 14.9 - Sections through boathouse boreholes in North-South direction (British Geological Survey, n.d.)
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Figure 14.10 - Sections through boathouse boreholes in East-West direction (British Geological Survey, n.d.)
This information is insufficient as the structure will extend at least 15 m below the ground level (these only extend to 10m), not including the proposed sheet piling. Therefore before any detailed design stage can start, a geological ground investigation survey would need to take place to confirm the extent of the stiff clay layer beyond the proposed structural location. For the purposes of this feasibility study it is assumed that the stiff clay layer is sufficient to support the structure without consolidation, sedimentation or any other deformation of the soil.
Foundations For this type of structure, foundations play a major part in the stability and durability of the whole structure. Kew Weir’s foundations must be designed to withstand a variety of different loadings, including self-weight, water imposed lateral loading on the structure (also causing rotational moments around the foundation axis), pull-out forces on one side of the foundation and further loading on the other. A number of other factors are also considered and discussed in the following paragraphs.
14.3.2.1 Introduction Weak foundations or loss of foundation support are the most common reasons for weir failure, with the exception of damage from hydraulic force to the superstructure. Seepage under a river structure allows fine soil particles to be removed (“piping”). As a result, voids are created which can both make the structure unstable and reduce the strength of the soil layer under the
54 | P a g e Chapter 14 – Kew Weir [Substructure – JJ] Thames Group Tidal Water Resources foundation. In some extreme cases, the structure can collapse as it no longer has sufficient soil supporting it. This can be avoided by providing cut-offs in the riverbed both upstream and downstream of the structure. The most common method is to install steel sheet piles, which compared to other types of piles, are strong, durable and easy to install, in a cofferdam type structure. This cut off method works by extending the seepage path and reducing the hydraulic gradient that causes piping. Piles must be installed sufficiently in both vertical and horizontal directions to be effective.
14.3.2.2 Uplift If the structure is submerged deeply in water, hydrostatic pressure under the structure can produce uplift forces that need to be adequately resisted by the self-weight of the structure. These forces can be dissipated by the provision of suitable drainage, such as pressure relief valves, or resisted by increasing the self-weight of the structure. Sheet piling also influences these forces, decreasing them upstream and increasing them downstream. Once the detailed design of the structure is complete, the loading must be checked against the worst case scenario, i.e. highest possible uplift force from the hydrostatic pressure. (Environment Agency, 2013)
14.3.2.3 Stability Weir structures are usually stable, but are very dependent on the supporting material and the foundation. In cases of weak soil layers at the foundation, piles are installed to transfer loads onto a more stable layer of soil. The analysis of the geological conditions at Kew Weir show that soil is relatively strong and sheet piles should be sufficient to keep the structure stable. The material in- between the two sheet pile walls should be well compacted during the early construction stage to prevent any settlement or deformation in the supporting soil.
Scour Scour depth and extent are always difficult to predict since it is based on the water depth, flow velocity, strength, type and thickness of the river bed material and the shape and extent of the temporary works. In the location of Kew Weir, there is some existing armouring or scour protection in the river bed, but it is badly degraded and therefore has limited impact on reducing the predicted scour. The Kew Pier and Kew Bridge have scour protection, indicating additional scour protection to both Kew Weir’s riverbed structure and embankments would be required (HR Halingford Limited, 2013)
Sheet piling will be used to prevent seepage under Kew Weir and will have additional protection on the riverbed foundation in terms of scour effect. This sheet piling will also extend into the embankments, however, this may disturb the ground or increase local saturation of the soil and armouring is recommended. The embankment scour problem is as important during the service of the structure as it is during the construction period. The sheet piled cofferdam that will be built
55 | P a g e Chapter 14 – Kew Weir [Substructure – JJ] Thames Group Tidal Water Resources during the construction phase will block the river flow and any potential scour development on the embankment construction from taking place. The permanent works will consist of a vertical reinforced concrete wall built within the boundaries of the sheet piled cofferdam, with the corners rounded to reduce turbulence and scour effects, as well as reducing the damage in case of any accidental strike from floating objects or navigation vessels.
A variety of approaches and instruments can be used to monitor scour and other changes in bed level. Three types of approach are proposed for monitoring bed levels prior to and during the construction phase. These are the use of bathymetry surveys, local scour monitoring using fixed instruments and visual inspection (including land surveys and photographic recording).
14.4 Superstructure The weir at the proposed location must have a substantial superstructure to withstand various continuously changing lateral loads from both wind and water. With the water level fluctuating regularly due to tidal patterns throughout the year, the height of the structure required above the water level also changes. Therefore it needs to account for these various scenarios and be designed to the worst possible case. The superstructure needs to be strong enough to transfer all the loading, including self-weight, to the foundations.
Construction Materials Kew Weir is to be constructed using reinforced concrete structural elements, both pre-cast and cast-in-situ, to maximise ease of construction and minimise time and space constraints. Reinforced concrete has been chosen because of the structure being continuously exposed to water. Besides the fact that timber rots when continuously saturated, it is relatively weak compared to steel and concrete and therefore was immediately rejected for a structure of this size. Steel, on the other hand, could sustain the loading quite easily, however, knowing Kew Weir will be located in the saline tidal waters of the Thames, the protection of steel against corrosion and the need for regular maintenance have made reinforced concrete a more favourable solution.
Waterproofing The weir structure must be water tight, firstly to maintain functionality of the weir, but also to prevent seepage and scour development. In Chapter 14.7 the movement mechanism for Kew Weir is designed, which will need to be accessed and maintained. Waterproofing both the mechanism and the access shaft is essential to ensure the weir can be operated and maintained at all times.
A potential solution for waterproofing the structure is shown in Figure 14.11, where certain admixtures are added into the concrete mixture to make it watertight. Joint sealing systems for connections and movement joints - also available in the brochure provided by Sika (available
56 | P a g e Chapter 14 – Kew Weir [Substructure – JJ] Thames Group Tidal Water Resources upon request) - that can be used in waterproofing the structure, however, are outside the scope of this feasibility study and would need further consideration at the detailed design stage.
Figure 14.11 - Integral Waterproofing System (Sika Solutions, n.d.)
Water level management In the past, the primary aim of constructing weirs in the U.K. has been for water level management. Increased water levels may be required to provide sufficient draft for navigation, to permit the diversion or abstraction of water, or to provide a source of power. When considering the construction of Kew Weir, the water level is also the main aim. During periods of low rainfall, usually from late summer to mid-autumn, also when the water abstraction rate is high, the location of Kew Weir in the river is subject to low water flow levels. This means the water flow is insufficient for navigation and the abstractions are limited or closed, all of which has both financial and environmental implications within the area, such as additional pumping costs from reservoirs and loss of species’ that are not able to live in shallow waters. (InCom Working Group 26, 2005)
Kew Weir will be used to retain water during these months by raising when the tide is high and gradually releasing it to maintain minimum residual flow in the tidal Thames when the tide is retreating. The operation and control systems of the weir are discussed in Chapter 16.6.
14.5 Sealing of Weir It is essential to ensure the weir remains watertight to maintain the storage capacity upstream and to protect the structural piers. As such it is proposed that a simple HDPE or steel panel will be attached to the ends of the weir gates (see Figure 14.12) in a quarter circle shape. These panels will be fixed in relation to the weir gate and will rotate with it to maintain the seal.
The design of these panels is beyond the scope of this project and would need to be considered further at detailed design stage.
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Figure 14.12 - Tilting beamless weir gate (HC Watercontrol, n.d.)
14.6 Fish Pass Fish passes are necessary for waters containing migratory Salmonids (Environment Agency, 2010), considerable pressure is placed on the river management authorities by various organisations (Thames Anglers' Conservancy , 2014) to maintain the diversity of fish, therefore there is a high likelihood construction of a fish pass will be required.
Approval for the “form and dimensions” must be given by the Environment Agency as of the Water Resources Act 1991 (Environment Agency, 2010). Fish passes are required for weirs as they cause an obstruction to fish passage; however, there is a possibility that due to the temporary nature of Kew Weir’s obstruction that the fish pass may be deemed unnecessary by the Environment Agency. This cannot be determined without application as there are no guidelines regarding moveable weirs; for the purpose of this feasibility study a fish pass has been included at 3m in width. The necessity of this would need to be determined on consultation with the Environment Agency at detailed design stage and if required, the dimensions will be confirmed on application (Environment Agency, 2010).
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14.7 Mechanism In order to raise and lower the weir when required, an operating system must be incorporated into the design. The system must be able to interpret signals from the control system (Chapter 16) in order to set the weir elevation to the level which is desired.
Determining Type of Weir Movement The design of the moveable weir system involves each weir gate rotating about a fixed axis. The height of the weir gate and therefore the amount of water stored, is dependent on the rotation of the weir gate from the horizontal plane.
This type of movement was chosen for a number of reasons, firstly, rotating about a fixed axis allows the system to be situated under water. A vertically moving weir would either need to be submerged beneath the foundations, resulting in maintenance, construction and sealant issues; or supported by a superstructure above the water surface, which would require far more construction and also be less discrete (the proposed location of Kew Weir is adjacent to an existing bridge [Kew Bridge] and therefore this would look crowded). Gated weirs have also been considered, however these would not allow for the level of accuracy required for elevating the weir that is necessary for this project.
There will be a separate axis point for each weir gate, these will pass through the weir gate body and be fixed with respect to the weir gate. The axis will pass into the pier structures, using water tight bearings (Figure 14.13), in order for water not to pass into the structures whilst also allowing a rotational movement.
Figure 14.13 - Duramax Shaft Sealing System (Duramax Marine, 2015)
Determining Method of Actuation From Figure 14.14 and it can be seen that the operating system must be capable of overcoming moment Ma in order to lift the weir gate from its horizontal position, and also to be able to
59 | P a g e Chapter 14 – Kew Weir [Mechanism – DJ] Thames Group Tidal Water Resources provide adequate support against Mb, in order to hold the weir gate at its vertical position and lower it safely.
Figure 14.14 - Moment Required to Raise Weir
Figure 14.15 - Worst Case Resistive Moment at Upright Position
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Figure 14.16 – Indicative arrangement of counterweight and ram mechanism
Figure 14.16 is a representation of the proposed system for operating the weir gates. It consists of a counterweight system coupled with the use of hydraulic rams. Much like an elevator system, the counterweight will assist in the raising of the weir gate from its horizontal position. The hydraulic rams will be used to assist in both the raising and support of the weir gate. As can be seen from Figure 14.14, the moment required to lift the weir gate (Ma) is considerably less than that which will be required to hold it in position at its maximum position under full load (Mb). The counterweight must not provide a turning force which exceeds Ma, as then the weir will require either a locking system or a constant application of power in order to remain in its horizontal position. Due to the infrequent use of the weir, a locking system should be avoided as it may be prone to seizing after periods of no use, which would stop the weir gate from operating when needed. As a result of this, it is necessary to provide additional force with the hydraulic rams in order to safely lift and lower the weir gates to their full range of positions.
Figure 14.17 represents how the system will be incorporated in the design; there will be a lever arm on each side of the weir gate sections. To remain accessible for maintenance as well as be protected from water damage, the systems will be full contained within the constructed piers. A lever arm will be connected to the axis of the weir which will transfer the turning moment through the pier wall. A water tight connection as shown in Figure 14.13 will allow for this to occur without the passage of water into the mechanism. The hydraulic rams will be mounted on two joints which will be able to rotate 90 o about the plane of the lever from both the ground and the ram’s connection with the lever. The force will be applied in the radial direction of the lever joint, resulting in a turning moment about the weir axis. The hydraulic rams will need to be attached to
61 | P a g e Chapter 14 – Kew Weir [Mechanism – DJ] Thames Group Tidal Water Resources a pump and motor system. The power supply cables for this can pass through the foundations of the weir structure itself.
Figure 14.17 – Sketch of the movement mechanism in situ
The counterweight will operate by moving linearly whilst being supported by pulleys. The cable from the pulley system will be attached to the lever, as with the hydraulic cylinders. As the counterweight lowers the lever will be rotated upwards from the horizontal to the point of 90 o and as the counterweight is raised the lever will rotate towards its horizontal rest position. The use of the fixed lever ensures the corresponding weir gate sections will move in the same fashion. For the 90 0 movement the counterweights will move a linear distance of 2m (the vertical distance travelled by the lever in the 90 o rotation). Being 13m in height the piers provide sufficient space in order to accommodate this. Calculations 14.7.3.1 Counterweight Firstly the mass of the counterweight must be determined as follows:
Assuming a lever arm length of 2m, the moment about the weir axis caused by the counterweight must be as close to, but without exceeding, the moment required to lift the weir gate from its stationary position in Figure 14.14.
As there will be two operating systems acting upon each weir gate section, the moment required by the system to lift the weir gate (997.5kNm) can be taken as half this value, as shown in Equation 14.1.
Equation 14.1
997.5 498.75 2
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The force applied by the cable will be at a 2m distance from the weir axis due to the length of the lever. Therefore the force required from the cable attached to the counterweight is determined by Equation 14.2.
Equation 14.2
498.75 249.375 For the simple pulley system illustrated2 in Figure 14.16 the mass of the counterweight is determined by Equation 14.3.
Equation 14.3
249.375 25420 25.42 9.81 There will be losses due to friction in the pulleys and other constituent parts, therefore using a counterweight of 25.4 tons should allow for a suitably small amount of force required to lift the system, compared with not having the counterweight, whilst also ensuring the system will not activate when not desired.
It should be noted that using a more complicated pulley system, the counterweight required to produce the moment required could be reduced in mass. However, this would require the counterweight to travel a longer linear distance in order to produce the required rotation. Due to the mechanism being housed within the piers, the available height is limited. Further analysis would be needed at detailed design stage to compare the cost of additional space to that of the mass of counterweight in order to reach the optimum solution.
For easier installation and maintenance the counterweights for each operating mechanism section should be split into smaller component parts. This will result in the individual weights being lower, therefore they will be easier and cheaper to transport and to fix into place. Also if any damage to one was to occur it would be far more cost effective to replace a single, smaller counterweight than the entire, larger counterweight. Another reason for this is that if adjustments (for whatever reason) needed to be made to the counterweight system, adjusting the load would be far easier in small chunks.
14.7.3.2 Hydraulic Rams Secondly, the force required by the hydraulic rams must be calculated. As shown in , the maximum moment which will be required to resist the downwards turning moment of the weir gates due to the weight of water behind each is equal to 11402 kNm. It is crucial that the system is capable of achieving this moment so that it is not only capable of holding the vertical position under full loading, but is also capable of lowering the system safely, in a controlled manner.
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Assuming a 498.75kNm moment exerted by the counterweight system, the moment the hydraulic ram will need to produce is shown by Equation 14.4.
Equation 14.4
11402 − 498.75 5202 Again with a lever length of 2m,2 the force required to produce this moment is calculated in Equation 14.5.
Equation 14.5
5202 2601.13 Therefore from the value shown in Equation2 14.5 it is possible to determine which hydraulic ram arrangement will be suitable for the design. Rotational actuators were initially explored, which would mitigate the need for the lever, however, due to the large force requirements, no suitable actuators could be found.
There are two main considerations in the selection of the hydraulic ram to be used. The force output must be great enough to provide the derived force shown in Equation 14.5; and the fully extended length must be large enough to have produced the 90 0 turning moment required for the lever.
As the lever is 2m in length, the stroke length must be equivalent to 2.8m in order to rotate the lever by 90 o. This stroke length is not readily available commercially; however, there are a number of companies which offer custom build hydraulic rams such as C.S.C Ltd (C.S.C Ltd, 2014).
There is the option for each lever to be lifted by either 1 hydraulic ram producing a force equal to or greater than 2601kN, or for 2 to be installed, as shown in Figure 14.16, which will collectively achieve this force. The selection of a ram arrangement would be determined more easily if the range of forces required was known in greater detail. Although an individual, larger hydraulic ram may be less expensive than purchasing 2 smaller ones, its force output may be too large in some situations to be efficient. The operation of two rams around one joint should be considered carefully, as if the control of their extension or retraction is not accurate enough, this could cause bending moments about the join, requiring more accurate and robust construction.
14.7.3.3 Power Requirements For the purpose of this analysis, assuming the use of two 140 ton (1386kN) hydraulic rams, the fully extended capacity of the cylinder is quoted as 16145cm 3, this is equivalent to 16.15 litres (Enerpac, 2014). However as the stroke length for this cylinder is 0.815m and this design requires
64 | P a g e Chapter 14 – Kew Weir [Mechanism – DJ] Thames Group Tidal Water Resources a 2.8m stroke, it can be assumed that as the stroke is 3.4 times smaller than desired, the volume will in fact be multiplied by the same factor. Therefore for the purpose of this analysis, the cylinder volume for full extension will be assumed to be 54893 cm 3 (54.9 litres).
The maximum pressure requirement for this actuator is quoted as 700 bar and a motor and pump system is available from the supplier of the hydraulic ram. A model is available which has two outlets, each providing 700 bar per outlet at a flow rate of 4.2 litres/min. The power consumption of this system is 11 kW (Enerpac, 2014). This system would be capable of powering the two hydraulic rams at the maximum required force.
Assuming that the weir gates would need to be in the raised position for maximum of a 6 hour duration (average time between high and low tides for the summer months), a worst case power consumption per operation can be estimated. Equation 14.6 shows the power consumption for lifting half the weight of one weir gate section.
Equation 14.6
Therefore the total power consumption11 is found × 6usin g 66 Equation 14.7.
Equation 14.7
This value could be reduced if a locking66 mechanism ×6ℎ 396 ℎ is introduced to the system. This system would need to be able to hold the weir gate in place at designated positions without the force from the hydraulic ram. As stated before, this will need careful consideration as due to the infrequent use, especially if submerged in water, the system could be susceptible to seizure, rendering it useless. However, if a locking system was successfully installed, the power would only be required to raise and lower the weir gates, not hold them in place.
The time required to fully extend the cylinder can be determined using the fully extended capacity and the flow rate provided by the pump. Equation 14.8 calculates the time required to fully extend the cylinder.
Equation 14.8
54.9 14 4.2 Therefore the time required to raise the weir gates will be 14 minutes. Assuming that the same time is required to lower it, the total operation time of the pump and motor system will be 28 minutes. In this case, Equation 14.9 shows the power consumption for this arrangement.
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Equation 14.9
66 × 0.46ℎ 30.36 ℎ Financial Assessment Using the predicted flow data, it can be estimated when the weir will require activation. Assuming that this occurs when flow passing over Teddington Weir is below the minimum residual flow, the number of days for each decade from 2020 – 2098 (future flows data is only available until 2098) were calculated for the average climate model predictions. These values were then in turn multiplied by a factor of 2, assuming that the weir would be required for both tides during the day. Table 14.1 shows the predicted costs of Kew Weir until 2098, using the worst case power consumption as calculated above, assuming that the price/kWh of electricity remains at 9.37p/kWh (UK Power, 2014). Table 14.1 - Predicted weir activations and cost
Time Number of Times Power Price/kW Total Average Annual Period Activated Consumption h (p) Cost (£) Cost (£) (kWh) 2020 160 63360 9.40 5953.94 595.39 2030 108 42768 9.40 4018.91 401.89 2040 44 17424 9.40 1637.33 163.73 2050 1538 609048 9.40 57232.24 5723.22 2060 1476 584496 9.40 54925.09 5492.51 2070 1514 599544 9.40 56339.15 5633.91 2080 2596 1028016 9.40 96602.66 9660.27 2090 1964 777744 9.40 73084.60 7308.46
For comparison purposes, the cost of operating the mechanism was analysed for the case where a locking system is in place, meaning that the system will not need to be in operation for the full duration of the weir’s activation. The results of this are shown in Table 14.2. Table 14.2 - Predicted weir activation and cost for operating system with locking mechanism
Time Number of Times Power Price/kWh Total Average Period Activated Consumption (p) Cost (£) Annual Cost (kWh) (£) 2020 160 4857.60 9.40 456.47 45.65 2030 108 3278.88 9.40 308.12 30.81 2040 44 1335.84 9.40 125.53 12.55 2050 1538 46693.68 9.40 4387.81 438.78 2060 1476 44811.36 9.40 4210.92 421.09 2070 1514 45965.04 9.40 4319.33 431.93 2080 2596 78814.56 9.40 7406.20 740.62 2090 1964 59627.04 9.40 5603.15 560.32
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It can be seen that this would provide a far cheaper means of raising the weir gates, therefore it should be given further consideration at detailed design stage. However it is important to consider that the additional costs involved with constructing and maintaining the locking system could outweigh the saved operating costs.
Table 14.3 shows the estimated part and installation costs (the hydraulic cylinder and hydraulic pump and motor are as quoted by the supplier) (Enerpac, 2014). The installation costs are assumed as 8 engineers at £20 per hour, with an expected duration of 4 weeks. The counterweights were priced using the SPON pricing book for civil construction (Langdon, 2007), assuming a reinforced concrete counterweight would be used. The remaining ancillaries were assumed at 10% of the total costs. Using the data from both Table 14.1 and Table 14.3, the NPV cash flow was calculated for the weir movement mechanism, as shown in Figure 14.18. Table 14.3 - Predicted parts and installation costs
Name of Component Unit Cost (£) Number of Units Total Cost (£) Hydraulic Cylinder 3000 12 36000 Hydraulic Pump and Motor 25000 6 150000 Pulleys, Cables, Bearings and Hoses 26000 1 26000 Counterweight 5000 6 30000 Installation 3200 1 25600 Total Cost (£) 267600
-262000 2020 2030 2040 2050 2060 2070 2080 2090 2098 -264000
-266000
-268000
-270000
-272000 NPV Cash Flow(£'s)
-274000
-276000
-278000 Year
Figure 14.18 - NPV Cash Flow Prediction for Operation of Weir
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Hydrodynamic Lift mechanism A hydrofoil is identical to an aerofoil in principle, with the only difference being the working fluid (air for an aerofoil and water for a hydrofoil). As such, for the purposes of this report the two terms will be used interchangeably. Because of the constant flow of water over the weir, an additional mechanism attached to the weir, in the form of a deployable hydrofoil, was considered in order to provide hydrodynamic lift and therefore reduce the energy required to raise the weir. The mechanism would, at least superficially, resemble that of a leading edge slat on an aircraft wing, as shown in Figure 14.19. However as the weir is attached to the ground at one end (i.e. there is no net fluid flow over the bottom surface) it cannot be accurately modelled as a hydrofoil-slat system and a different method is required to model the effects. For the purposes of this study, the mechanism will be modelled as a separate aerofoil in its own right.
Figure 14.19 - Schematic of an aerofoil with a leading edge slat (SimHQ, 2002)
The lift of an aerofoil is given by Equation 14.10: Equation 14.10
1 2 Where:
• Cl is the non-dimensionalised coefficient of lift • L is the lift provided by the aerofoil • ρ is the density of the fluid (in this case water, which is assumed to be 1000kg/m 3) • U is the fluid velocity - from tidal data, U will be taken to be 2.7 m/s • c is the chord length of the flap
As the weir is stationary and the fluid velocity is low, drag does not need to be considered and so a high lift coefficient design can be chosen in order to maximise lift. We will assume a C l of 1.3, which is typical for a single-element aerofoil. The chord length is assumed to be 0.5m.
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Rearranging the above equation, L can be found to be 2370N per metre run along the length of the flap.
Approximating the flap as an ellipse allows us to get a rough volume and therefore a mass of the flap. Assuming a thickness of 5cm (a thickness-to-chord ratio of 10%), we can find the cross- sectional area, A, of the flap using Equation 14.11: Equation 14.11
Where a is 0.5m b is 0.05m A = 0.0785m 2
Assuming the flap is constructed from steel (with a density of 7951kg/m 3); this gives a mass of 624kg per metre, or a weight of 6120N per metre run.
This means that the weight of the flap would be more than double the lift it would be able to provide, making it an unfeasible option. Various modifications could be made to the parameters of the flap, but as lift is proportional the square of the fluid velocity, a flap will remain unfeasible at such low flow speeds.
14.8 Option 1a
Figure 14.20 - Option 1a cross section (Drawing 211)
The first sub-option of the superstructure, as seen in Figure 14.20, consists of two 10m wide abutment walls, three 4m wide piers separating the river, one 3m fish pass and three 30m wide weir gates. The full drawing can be seen in Appendix G; additionally, a model has been created using Google SketchUp software to allow better visualisation of the structure (Figure 14.21, Figure 14.22 & Figure 14.23).
69 | P a g e Chapter 14 – Kew Weir [Hydrodynamic Lift Mechanism – BC] [Option 1a – JJ] Thames Group Tidal Water Resources
Figure 14.21 - Option 1a cross section
Figure 14.22 - Pier cross section Figure 14.23 - Option 1a plan view
Figure 14.21 shows the sheet piled foundation as well as the proposed superstructure for the solution. Figure 14.23 shows the plan view of the weir when water is at the highest tide. Lastly, Figure 14.22 shows the access staircase within each pier of the weir to allow for inspection and maintenance of the weir mechanism (the mechanism itself is not modelled – see Chapter 14.7).
This option does not allow for provision of navigational lock. This option has been developed assuming the weir operation will be low enough that navigation can either pass over the top of the structure or be delayed by short time periods until the next high tide. However, the water height above the weir will be insufficient for navigation of many vessels. The cost of the project and the environmental impact are both lower in this option as the lock is a significant contributor to the carbon footprint and construction costs.
Weir Design 14.8.1.1 Geometric Design The weir proposed consists of three 30m span weir gates that rotate about an axis at the base of the river. To maintain minimum residual flow, each weir gate must be designed such that it always allows a minimum flow of 3.086m 3/s over them at any time. Using the Weissbach Equation (Equation 14.12) and the Basin Equation (Equation 14.13), an iterative approach to determine the height of the weir can be adopted (full calculations can be found in Appendix F). This results in the height of the weir needing to be 3.477m when fully raised (see Drawing 211 in Appendix G for details). This means that a minimum water level over the weir must be maintained at 143mm (see Chapter 16.6 for Control Systems to manage this).
70 | P a g e Chapter 14 – Kew Weir [Option 1a – JJ] [Weir Design – HP] Thames Group Tidal Water Resources
Equation 14.12 - Weissbach Equation
2 2 ℎ + − 3 2 2 Equation 14.13 - Basin Equation for discharge coefficient of sharp crested weirs
0.0045 ℎ 0.6075+ 1 + 0.55 ℎ + ℎ There can be greater flows over the weir than this as this value has been calculated based on the lowest high tide seen at the weir location. The control system will need to manage a minimum depth of water over the weir and only allow the mechanism to be activated when this level is not reached. 14.8.1.2 Structural Design To ensure the weir can support the force of the water behind it when fully raised it is necessary to design the weir gate itself. For this stage of design it has been simplified for analysis purposes to a box section of depth D, thickness t, width B and length L.
t
D
B Figure 14.24 - Sketch of approximation of section for weir gate
The design has been conducted using simple beam theory and has been analysed for both moments in the plan view plane and perpendicular to the weir gate. These moments have been calculated using static and dynamic pressures and have been based on the worst case scenarios as follows: i. The weir is fully raised, only minimum residual flow is being allowed over the structure and the tide is out. ii. The weir is fully raised with both river flow and tidal flows being applied to the weir. iii. The weir is horizontal and is being raised.
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The full calculations for this analysis for Option 1a can be found in Appendix F. These calculations demonstrate that the worst case moment occurs in scenario i. and that the thickness of the box section is most critical when the forces are applied in the plan view plane (24597kNm). Therefore the thickness has been determined based on this analysis and Table 14.4 summarises the results. Table 14.4 - Design figures for Option 1a weir gate design
Parameter Value Unit E Young's Modulus of S275 Steel 210 N/mm 2 y Distance to Neutral Axis 0.335 m m Moment Applied 24596.764 kNm I Second Moment of Area 0.0406 m4 b Internal Width 3.357 m d Internal Depth 0.55 m B External Width 3.477 m D External Depth 0.67 m t Thickness 0.060 m σ Tensile Stress in Beam 202955.24 kN/m 2 2 σRd Tensile Strength of Steel 210000.000 kN/m
This design gives a minimum steel thickness of 60mm for the weir gate section (see Figure 14.24 for sketch of this simplification). In reality it would be necessary to conduct structural design for the exact shape required for the weir gate as shown in Drawing 211. It would also be pertinent to optimise the design and maintenance of the structure to design the gate to comprise of several internal compartments rather than the single large compartment in this design. This would allow the gate to be stiffened and the overall moment applied to each section reduced. It would also enable one compartment to flood without compromising the entire gate.
To check the design in the horizontal position the self-weight must be applied as a moment on the hinge point. This moment is not the critical design moment and therefore all checks have been satisfied. The moment induced by the self-weight has been calculated to be 997.5kNm (full calculations in Appendix F).
14.8.1.3 Costing The cost of manufacturing a custom steel section such as this is hard to pinpoint. As such the following cost estimate has been based on the price of stainless steel metal as quoted in the Foundry Trade Journal (Foundry Trade Journal International , 2014) of £1600.00 per tonne. According to Tata Steel (Barrett, Byrd Associates, 2013) the raw material cost accounts for approximately 30-40% of the total steel cost (see Figure 14.25) – for this case it is assumed fire protection is roughly equivalent to waterproofing and can be interchanged directly. Therefore
72 | P a g e Chapter 14 – Kew Weir [Weir Design – HP] Thames Group Tidal Water Resources from this raw material value we can determine a cost estimate bracket for the steel for the weir gates (Table 14.5).
Figure 14.25 - Proportional factors of total steel cost (Barrett, Byrd Associates, 2013)
Table 14.5 - Cost estimate for Option 1a weir gates
Parameter Value Percentage of Cost Cost of Stainless Steel (£/per tonne) 1,600.00 Cross Sectional Area of Steel (m 2) (See Drawing 211) 0.550 Length of Steel (m) 90.00 Volume of Steel (m 3) 49.50 Density of Steel (kg/m 3) (Cobb, 2011) 7951 Mass of Steel (kg) 393,574.5 Mass of Steel (tonnes) 393.575 Material Costs (£) – LOWEST ESTIMATE 629,720.00 30% Erection (£) – LOWEST ESTIMATE 209,906.67 10% Waterproofing (£) – LOWEST ESTIMATE 209,906.67 10% Steelwork Design (£) – LOWEST ESTIMATE 41,981.33 2% Transport (£) – LOWEST ESTIMATE 20,990.67 1% Fabrication (£) – LOWEST ESTIMATE 629,720.00 30% Material Costs (£) – HIGHEST ESTIMATE 839,626.67 40% Erection (£) – HIGHEST ESTIMATE 314,860.00 15% Waterproofing (£) – HIGHEST ESTIMATE 314,860.00 15% Steelwork Design (£) – HIGHEST ESTIMATE 41,981.33 2% Transport (£) – HIGHEST ESTIMATE 20,990.67 1% Fabrication (£) – HIGHEST ESTIMATE 839,626.67 40% TOTAL LOWEST ESTIMATE (£) 1,742,225.34 TOTAL HIGHEST ESTIMATE (£) 2,371,945.34
It can be seen from this that the cost of the weir gates alone will be in excess of approximately £1.75million at a minimum.
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14.9 Option 1b As seen in Chapter 13, it may be necessary to provide a lock to allow vessel passage when the clear water height above the weir is less than required for navigation over an extended period of time. As a result, option 1b includes a lock (Figure 14.27) on the northern bank side of the structure, replacing the need for such a large abutment on this side (Figure 14.26). The weir gates consist of three spans of 25m (instead of the 30m in Option 1a), allowing the lock to be built further into the river (Figure 14.27) to ease navigation and to reduce interference with the urban area on the northern bank of the River Thames at Kew Bridge.
Figure 14.26 - Option 1b cross section
Figure 14.27 - Lock cross section
Figure 14.28 - Option 1b plan view
Weir Design 14.9.1.1 Geometric Design The weir proposed consists of three 25m span weir gates that rotate about an axis at the base of the river. The calculations follow the same principle as those in Option 1a and can be found in Appendix F. This results in the height of the weir needing to be 3.458m when fully raised (see Drawing 212 in Appendix G for details). This means that a minimum water level over the weir must be maintained at 162mm (see Chapter 16.6 for Control Systems to manage this).
There can be greater flows over the weir as this value has been calculated based on the lowest high tide seen at the weir location. The control system will need to manage a minimum depth of water over the weir and only allow the mechanism to be activated when this level is not reached.
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14.9.1.2 Structural Design The analysis process follows the same pattern as in Option 1a and analyses the same three critical loading scenarios: i. The weir is fully raised, only minimum residual flow is being allowed over the structure and the tide is out. ii. The weir is fully raised with both river flow and tidal flows being applied to the weir. iii. The weir is horizontal and is being raised. The full calculations for this analysis for Option 1b can be found in Appendix F. As in Option 1a these calculations demonstrate that the worst case moment occurs in scenario i. and that the thickness of the box section is most critical when the forces are applied in the plan view plane (16,987kNm). Therefore the thickness has been determined based on this analysis and Table 14.6 summarises the results. Table 14.6 - Design figures for Option 1b weir gate design
Parameter Value Unit E Young's Modulus of S275 Steel 210 N/mm 2 y Distance to Neutral Axis 0.335 m m Moment Applied 16987.429 kNm I Second Moment of Area 0.0276 m4 b Internal Width 3.382 m d Internal Depth 0.594 m B External Width 3.458 m D External Depth 0.67 m t Thickness 0.038 m σ Tensile Stress in Beam 206197.85 kN/m 2 2 σRd Tensile Strength of Steel 210000.000 kN/m
This design gives a minimum steel thickness of 38mm for the weir gate section (see Figure 14.24 for sketch of this section). As before, it would be necessary to conduct structural design for the exact shape required for the weir gate as shown in Drawing No. 212.
To check the design in the horizontal position the self-weight must be applied as a moment on the hinge point. This moment is not the critical design moment and therefore all checks have been satisfied. The moment induced by the self-weight has been calculated to be 165.108kNm (full calculations in Appendix F).
14.9.1.3 Costing The same approach to costing Option 1a will be applied to Option 1b. The summarised numbers can be seen in Table 14.7. Table 14.7 - Cost estimate for Option 1b weir gates
Parameter Value Percentage of Cost
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Cost of Stainless Steel (£/per tonne) 1,600.00 Cross Sectional Area of Steel (m 2) (See Drawing 212) 0.397 Length of Steel (m) 75.00 Volume of Steel (m 3) 29.775 Density of Steel (kg/m 3) (Cobb, 2011) 7951 Mass of Steel (kg) 236,741.03 Mass of Steel (tonnes) 236.741 Material Costs (£) – LOWEST ESTIMATE 378,785.64 30% Erection (£) – LOWEST ESTIMATE 126,261.88 10% Waterproofing (£) – LOWEST ESTIMATE 126,261.88 10% Steelwork Design (£) – LOWEST ESTIMATE 25,252.38 2% Transport (£) – LOWEST ESTIMATE 12,626.19 1% Fabrication (£) – LOWEST ESTIMATE 378,785.64 30% Material Costs (£) – HIGHEST ESTIMATE 505,047.52 40% Erection (£) – HIGHEST ESTIMATE 189,392.82 15% Waterproofing (£) – HIGHEST ESTIMATE 189,392.82 15% Steelwork Design (£) – HIGHEST ESTIMATE 25,252.38 2% Transport (£) – HIGHEST ESTIMATE 12,626.19 1% Fabrication (£) – HIGHEST ESTIMATE 505,047.52 40% TOTAL LOWEST ESTIMATE (£) 1,047,973.61 TOTAL HIGHEST ESTIMATE (£) 1,426,759.25
This option has much lower expected steel costs for the weir gates than Option 1a, but this will need to be analysed against the costs of the lock and the additional pier that need to be included instead. Chapter 17 has a full financial breakdown of each option.
14.10 Option 1c Some of the initial studies undertaken as part of this project indicate that the lock would not be necessary for the first three decades, but would be necessary after this to provide passage for navigation. As a result of these findings, option 1c has been developed, which makes provision for the lock to be installed at a later date.
The initial structure that is to be built would look the same as the one described in Option 1a, except for the northernmost weir gate, which will be made up of two independent 15m sections that will be connected until the lock is required. Once this point is deemed to have been reached, one 15m section of the weir gate, as well as the northern abutment, would need to be dismantled and the lock structure installed in its place. When completed, the structure would have two 30m weir gates, one 15m weir gate and a 15m wide lock.
However, construction would be very difficult due to potential for seepage and scour to the embankment, existing structure and, particularly, the lock under construction. Nevertheless, the
76 | P a g e Chapter 14 – Kew Weir [Weir Design – HP] [Option 1c – JJ] Thames Group Tidal Water Resources water level is expected to drop to lower levels as described in the future study, which may allow for longer construction periods and easier accessibility.
Weir Design The weir design for Option 1c has not been conducted as part of this feasibility study as it would consist of the same properties as 1a initially and latterly the weir height would have to be determined for two gates of 30m span and one gate of 15m span. The structural design would then follow as before. The variation in height of the weir gates between Options 1a and 1b is minimal (<20mm) and therefore the variation in height is likely to be minimal for this option. Full calculations would need to be conducted at detailed design to check the results.
14.10.1.1 Costing For the purpose of this design it has been assumed that the weir gates will have the same cross sectional properties as Option 1a. The same costing as in Option 1a will be applied to Option 1c as the initial arrangement calls for the same weir gate arrangement and this will still have to be manufactured and installed etc. even if removed at a later date. Therefore the cost brackets for Option 1c are between £1,742,225.34 and £2,371,945.34. Additional costs would likely be incurred for the additional work at the joint between the two 15m sections, however this could be recovered through sale of the scrap metal from the redundant weir gate once it is removed to install the lock.
14.11 Construction Methodology The River Thames is often used as a transport route and in the area near Kew Weir there is a significant movement of various modes of water transport, such as barges, ferries, canal boats. It is critical to avoid any disruption to the river transport and, therefore, the proposed construction methodology has been based on staged construction to allow for the river to be navigable at all times during the construction of Kew Weir.
With the water level dependant on tidal patterns and time of the year, it was essential to choose the most favourable conditions for construction, i.e. when the water is at the lowest possible level. The tidal patterns discussed in the inception report (Thames Group, 2014) showed that the lowest levels are expected between early August and late October.
Option 1a
The first sheet pile wall will be installed to half the required depth at this time of the year (Figure 14.29). Half height installation is required because initially it will act as a cofferdam for the construction of the foundations. The water can then be pumped out, with the cofferdam supported
77 | P a g e Chapter 14 – Kew Weir [Weir Design – HP] [Construction Methodology – JJ] Thames Group Tidal Water Resources to prevent collapse under the water loading. Excavations can then begin followed by the placement of the reinforced concrete slab (Figure 14.30).
As the construction phase continues, the first pier and the abutment will be built upwards and as the required height is reached, the first weir gate will be installed (Figure 14.31). The construction is to continue while the water level gradually rises with the approach of the rainy winter season and beyond (Figure 14.32). Following completion of the piers and abutments, the construction works are to halt until late July the following year.
Figure 14.29 - Option 1a, Stage 1 Figure 14.30 - Option 1a, Stage 2
Figure 14.31 - Option 1a, Stage 3 Figure 14.32 - Option 1a, Stage 4
As the water level lowers once again, the construction of the remaining structure on the opposite side of the river can begin in the same sequence. To maintain the navigational requirement through the river, the sheet piling wall to first pier is to be installed in its final position and navigation will be re-directed through the first 30m weir section. The installation of the remaining length of the sheet pile wall should then follow. Once again, the water is to be pumped out to allow construction (Figure 14.33). Once the foundations, piers, abutment wall and fish pass are all completed, the third 30m weir gate can be installed (Figure 14.34).
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Figure 14.33 - Option 1a, Stage 5 Figure 14.34 - Option 1a, Stage 6
Figure 14.35 - Option 1a, Stage 7 Figure 14.36 - Option 1a, Stage 8
The works will stop again until the next summer, when the sheet pile wall over the third weir gate span is to be installed in its final position. At the same time, the perpendicular separating sheet pile wall will be removed from the ground to allow installation of the weir and the gap filled with concrete (Figure 14.35). The area of the second weir gate is then drained and the final weir gate is installed. The remaining length of the sheet pile wall will be installed to the required final depth and the structure will be complete (Figure 14.36).
Using this methodology, the structure can be built within 2.5 years with very little or no disruption to river navigation.
Option 1b The alternative option considered includes the construction of the lock, if it is confirmed at detailed design it is required. The construction of a lock would make the building process for the rest of the structure simpler as the lock could be used for navigation while the rest of the structure is being built.
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Figure 14.37 - Option 1b, Stage 1 Figure 14.38 - Option 1b, Stage 2
Figure 14.39 - Option 1b, Stage 3 Figure 14.40 - Option 1b, Stage 4
Construction of the lock would include sheet piling round the perimeter of the lock, except for the embankment side, where sheet pile walls at both ends of the lock would extend into the embankment (Figure 14.37). Once the sheet piling is in place, excavation to the required level is to be completed and reinforced concrete foundations placed. The structure is then to be built upwards gradually. Once the structure is in place, pumping and control mechanisms together with the lock gates would be installed and become operational (Figure 14.38).
As the construction of the lock is completed, the remaining weir structure can be built in a similar process to Option 1a. However, the sheet piling will be installed to the required depth immediately and the excavation to required level would follow (Figure 14.39). The structure is built upwards from the foundation, with temporary steel or timber formwork as required depending on the water level at the time. Finally, all three 25m sections of the weir are to be installed and once completed, the weir can be used for water management and navigation (Figure 14.40). In this option, during construction of the weir, all navigation will be diverted via the lock. The construction of the lock prior to the rest of the structure will take an additional 12 months, therefore, the estimated construction time for this option is 3.5 years, however the programme could be reduced in other areas as the three weir spans can be constructed simultaneously.
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Option 1c The third possible option is to have the main weir structure built first as per option 1a with the provision for the lock to be installed later, when it becomes necessary. The initial structure would follow the same methodology as Option 1a, except the weir gate on the northern side of the river is split into two 15m sections. One of these sections would then be dismantled and the lock would be installed in the same location.
As a result, the option would end up looking like Option 1b, with the exception of having different lengths of weir gates, but is essentially a combination of options 1a and 1b. Two different construction periods means an even longer period for construction. Therefore allowing for various enabling works and handover periods, the final total construction period would extend to as long as 5 years with a break in the middle when the lock is not required.
14.12 Bill of Quantities and Pricing The construction costs associated building Kew Weir have been produced by quantifying the different elements of the structure and allocating a relevant price rate. Spon's Civil Engineering and Highway Works Price Book (Langdon, 2007) has been used to acquire rates, however, since the book is out of date, an inflation rate of 10% has been assumed to adjust the rates making them more realistic for the proposed time of construction. The design drawings have been used to take quantities (Appendix E) of these elements and can be found in Appendix G.
Table 14.8 - Construction cost estimate for the proposed weir structure Option 1a
Item Description Quantity Units Rate, £ Total Cost, £ No. OPTION 1A IN-SITU CONCRETE – including labour, 1. plant, material costs for excavation, provision and placing of concrete 1.1 Foundations 2500.00 m3 250.00 625,000.00 3 1.2 Abutments 2600.00 m 250.00 650,000.00 1.3 Fish pass 103.20 m3 250.00 25,800.00 PRECAST CONCRETE - including 2. labour, plant, material costs for excavation, provision and delivery of concrete 2.1 Piers 507.00 m3 2000.00 1,014,000.00 STEEL - including labour, plant, material 3. costs Reinforcement for in-situ concrete 596.37 tons 5000.00 2,981,850.00 3.1 elements 3.2 Sheet piling wall 3.3 Lock gate 5400.00 m2 209.58 1,131,732.00 TOTAL CONSTRUCTION COST 22.08 tons 5000.00 110,400.00
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Item Description Quantity Units Rate, £ Total Cost, £ No. OPTION 1A 4. Additional costs, inflation effect 6,538,782.00 Ancillaries (e.g. steel staircase, covers etc.) 980,817.30 4.1 allow 15% of total cost 4.2 Inflation rate, allow 10% of total cost 653,878.20 Enabling works, site setup, handover 300,000.00 4.3 period, demobilisation FINAL COST – Option 1a 8,473,477.50
These quantities are summarised in Table 14.8 (Option 1a), Table 14.9 (Option 1b) and Table 14.10 (Option 1c) and multiplied by the rates from Spon’s Price Book allowing a cost estimate to be produced for each option.
For example, the cast-in-situ concrete foundations price has been calculated using the following procedure: 1. The total quantity (volume) has been calculated using the design drawings (reinforcement influence on quantity of actual concrete pour is neglected). 2. Excavation cost is calculated using the rates provided on p. 172 of Spon’s Price Book for general excavation. Total rate combines labour, plant and material costs (if any). The rate for general excavation of 10.0 – 15.0 m maximum depth is given as £18.10 per m 3. 3. Provision of concrete rates are found on p. 189, however, since the concrete design is not included in the scope of this feasibility study, a rate of £90 per m 3 has been chosen as a reasonable value as the rate varies between £80-95 per m 3 of concrete. 4. Finally, rates of placing concrete can be found on p. 192, for reinforced concrete bases exceeding 500 mm depth it is given as £18.46 per m 3. 5. Adding all that together to find the final rate per m 3 gives a rough estimate of total cost for the construction of the foundations. In this case, it comes to £126.56 per m 3. However, considering the difficulty of access, the rate of work and environment that the structure is exposed to, this would rise increasingly, therefore it has been doubled for this calculation, i.e. £250 per m 3, to ensure a conservative estimate.
Note that excavation of the ground above the foundation, for example the embankments, will be included in pricing of the elements that will actually be built in that location. Other elements are to follow similar process with the relevant associated rates. For precast concrete elements, the indicative costs would be misleading for tailor-made units, however, specialist manufacturers cannot provide quotes without a detailed design and therefore the rates have been proportioned from closest possible rate. Steel costs are based on the weir gate steel costs.
Table 14.9 - Construction Cost Estimate for the Proposed Weir Structure Option 1b
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Item Description Quantity Units Rate, £ Total Cost, £ No. OPTION 1B IN-SITU CONCRETE – including labour, 1. plant, material costs for excavation, provision and placing of concrete 1.1 Foundations 5664.00 m3 250.00 1,416,000.00 3 1.2 Abutments 1300.00 m 250.00 325,000.00 1.3 Fish pass 103.20 m3 250.00 25,800.00 1.4 Lock structure 10786.00 m3 250.00 2,696,500.00 PRECAST CONCRETE - including 2. labour, plant, material costs for excavation, provision and delivery of concrete 2.1 Piers 507.00 m3 2000.00 1,014,000.00 STEEL - including labour, plant, material 3. costs Reinforcement for in-situ concrete 596.37 tons 5000.00 2,696,500.00 3.1 elements 3.2 Sheet piling wall 6800.00 m2 209.58 1,425,144.00 TOTAL CONSTRUCTION COST 9,598,944.00 4. Additional costs, inflation effect Ancillaries (e.g. steel staircase, covers etc.) 1,439,841.60 4.1 allow 15% of total cost 4.2 Inflation rate, allow 10% of total cost 959,894.40 Enabling works, site setup, handover 400,000.00 4.3 period, demobilisation FINAL COST – Option 1b 12,398,680.00
Table 14.10 - Construction Cost Estimate for the Proposed Weir Structure Option 1c
Item Description Quantity Units Rate, £ Total Cost, £ No. OPTION 1C IN-SITU CONCRETE – including labour, 1. plant, material costs for excavation, provision and placing of concrete 1.1 Foundations 2500.00 m3 250.00 625,000.00 1.2 Abutments 2600.00 m3 250.00 650,000.00 1.3 Fish pass 103.20 m3 250.00 25,800.00 1.4 Lock structure 10786.00 m3 250.00 2,696,500.00 PRECAST CONCRETE - including 2. labour, plant, material costs for excavation, provision and delivery of concrete 2.1 Piers 507.00 m3 2000.00 1,014,000.00 STEEL - including labour, plant, material 3. costs Reinforcement for in-situ concrete 596.37 3.1 tons 5,000.00 2,981,850.00 elements
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Item Description Quantity Units Rate, £ Total Cost, £ No. OPTION 1C 3.2 Sheet piling wall 6,800.00 m2 209.58 1,425,144.00 TOTAL CONSTRUCTION COST 9,418,294.00 4. Additional costs, inflation effect Ancillaries (e.g. steel staircase, covers etc.) 4.1 1,412,744.10 allow 15% of total cost 4.2 Inflation rate, allow 10% of total cost 941,829.40 Enabling works, site setup, handover 4.3 400,000.00 period, demobilisation Demolition works in the future to allow 4.4 500,000.00 construction of weir FINAL COST – Option 1c 12,898,680.00 15 Hydropower The possibility of the application of hydropower generation has been assessed for the purpose of this feasibility study. Due to the electrical consumption of the proposed options, successfully incorporating a means of hydropower generation could lead to a considerable reduction on carbon emissions in addition to increased financial sustainability.
15.1 Weir Site Suitability Assessment Drawing 305 shows the section of the river at the proposed site based on the data from the PLA. Due to the tidal nature of the estuary, the water level will vary throughout the year. It can be seen that the water depth will vary from approximately 3m-8m throughout the year due to tidal effects.
Using the available data for future flows at Kingston and future predicted abstractions the volumetric flow rate over the weir can be predicted assuming that due to the construction of the moveable weir, the minimum residual flow of 800 Ml/day is achieved. The velocity of the water can be estimated by adapting the volumetric flow with the cross sectional area shown in Table 11.2. Dividing the volumetric flow by the cross sectional area gives an estimate for the water velocity at the site (Table 15.1). Table 15.1 - Average water velocity at weir site
Time Period Quarter Water Speed (m/s) 1 0.30 2 0.21 2020's 3 0.09 4 0.09 1 0.28 2 0.18 2050's 3 0.05 4 0.05 2080's 1 0.23
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Time Period Quarter Water Speed (m/s) 2 0.14 3 0.03 4 0.03 1 0.20 2 0.14 2120's 3 0.03 4 0.03
Figure 15.1 - Hydro-turbine Selection Chart (Greenbug Energy Inc, 2014)
Considering the installation of a hydropower turbine, Figure 15.1 shows the different commercial hydropower turbines available and the flow rates and water heads they can operate at effectively.
Initially it can be seen that due to the possible water head indicated by Drawing 305 (Appendix G) and the flow rates indicated in Table 12.1, the possible turbines that can be considered for application are the Archimedes, Crossflow and Kaplan Turbine. However, on further inspection
85 | P a g e Chapter 15 – Hydropower - DJ Thames Group Tidal Water Resources these turbines will not be suitable for this site as they require a change in water level between inlet and outlet. There is no significant natural change in gradient experienced by the river at this site and with the weir only being active for temporary durations throughout the year, the change in water level created by the impoundment of water above the weir would not be for a great enough time period to be cost effective. The only other option would be to install a fixed weir or dam to create a water impoundment permanently, or to create a channel separate to the main body of the river in order to redirect the flow and create an artificial drop (Office of Energy Efficiency and Renewable Energy, 2014). These options would not only reduce the positive impact created by the moveable weir, they would involve high costs and difficult construction.
Figure 15.2 - Commercially available Hydro-Kinetic Turbines (Sornes, 2010)
Kinetic turbines do not use the potential created by water head, depending entirely on the kinetic energy available in the water flow for the generation of power. Therefore the change between upstream and downstream water level is not required. Comparing the minimum water speeds shown in Figure 15.2 with the water velocities predicted in Table 15.1 shows that the water speed is too low in order to install a hydrokinetic turbine effectively.
In summary, due to the nature of this site the incorporation of hydropower generation will be ineffective if using commercially available systems. Leading to possible loss on investment and increased complications with construction and operation. As a result, other sites have been considered.
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15.2 Teddington Weir Site Suitability Assessment Due to Teddington Weir’s position being fixed, it provides a better possibility for hydropower generation than the proposed Kew Weir site.
A feasibility study has already been conducted by Thames Renewables into the installation of hydroelectric power generation on Teddington Weir. The study concluded that the most suitable turbine for this site is the Archimedes Screw generator. The proposed solution involves cutting away a section of the spillway with a concrete trough embedded within the body of the weir in order to house 1-3 Archimedes Turbines (Parker & Moreno, 2009).
Figure 15.3 - Archimedes Screw Efficiency Curve (Renewables First, 2014)
The Archimedes screw converts the potential and kinetic energy of the water into rotational movement. This in turn with the use of a generator produces electricity. Although compared with other reaction generators the Archimedes turbine produces less power, it is more suitable to the river environment. The slow movement and large flow passage of the screw allows fish to pass downriver without harm, mitigating the need for a fish screen at the turbine intake, reducing the likelihood of debris build up and reducing maintenance requirements. Also without the need for draft tubes and discharge sumps, the civils work involved with installing the turbine are less extensive. The device doesn’t require a control system and the turbines efficiency doesn’t vary greatly over a dynamic flow rate (Renewables First, 2014) (see Figure 15.3). These qualities all result in the turbine although less powerful, having a smaller investment and ecological impact.
The financial assessment of this scheme is summarised in Table 15.2.
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Table 15.2 - Teddington Weir hydropower financial summary (Parker & Moreno, 2009)
Option 1 Option 2 Option 3 Number of Turbines 1 2 3 Max Power kW 150 300 450 Total Installation Cost £848,232 £1,228,284 £1,564,272 Total Annual Costs £5,700 £10,400 £15,100 Total Annual Revenue £130,000 £207,668 £269,185 Payback Period (years) 7 6 6 25 Year NPV (7% discount rate) £600,314 £1,070,598 £1,396,728
The value of the energy produced will be greater than predicted in Table 15.2 as following the formulation of these numbers, government feed-in tariffs were introduced which would generate a larger income per kWh.
In summary this would be a useful site to install hydropower generators, although not worth pursuing as a planning application for the scheme has already been made in September 2014 (HR Wallingford, 2014).
15.3 River Abstraction Inlet Shaft Suitability Assessment An alternative option is to install a hydropower generator between the sluice gates and inlet shaft in order to harness the potential energy of the river water flowing due to gravity through the tunnel system. Assuming the river to be 5m deep before Teddington Weir, then using the predicted abstractions (Table 6.3) as water flow rate, Figure 15.1 can be used to assess suitable hydropower options.
Comparing crossflow and Kaplan Turbines it can be seen that Kaplan Turbines have greater potential for energy production under higher flow, lower head situations, compared with that of cross flow turbines. Figure 15.4 shows a similar arrangement to what would be proposed in this situation, the inlet to the system would be situated after the sluice gates, the outlet would pass into the tunnel inlet shaft.
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Figure 15.4 - Kaplan Turbine (Renewables First, 2014)
Assuming a 25 year design life for the Kaplan turbine, it will need to manage flows between 2020 and 2045. Figure 15.5 is a more detailed look at the future abstractions for this period (compiled from Table 6.3 and Figure 5.1).
50 45 40 /s) 3 35 30 25 20 15
Abstraction Rate(m 10 5 0 2000 2020 2040 2060 2080 2100 2120 2140 Time Period
Figure 15.5 - Predicted Abstractions
From Figure 15.5, it can be seen that the incident flow rate is predicted to be between 8m 3/s and 18 m 3/s for the design life of the turbine. Figure 15.6 shows the efficiency of Kaplan Turbines under different configurations, and how the efficiency changes under varying load (flowrate). The minimum predicted average flow is 44.4% of the maximum. Therefore (as shown by line A), a double regulated turbine (Adjustable blades – adjustable gates) would retain an 85 – 92% efficiency on average throughout its operation. More simplistic options such as B and E could also be feasible. Although less efficicent, the more simplistic design would likely result in a lower costs (these values are however difficult to predict without further consultation) therefore, if the scheme is acted upon these options should also be explored further at detailed design. It should
89 | P a g e Chapter 15 – Hydropower - DJ Thames Group Tidal Water Resources also be noted that this is the individual turbine efficiency and does not take into account additional losses due to other pipes and mechanical systems.
Figure 15.6 - Kaplan Efficiency Curve Comparison Chart (Renewables First, 2014)
There will be some resistance introduced to the system by the turbine, crossflow turbines introduce a head loss of 10% due to the turbines presence (Nasir, 2013). For the purpose of this feasibility study the same has been assumed for the Kaplan turbine.
For the transportation of water flow to the turbine to occur, a pipe would need to be installed after the sluice gates at the end of the channel. The pipe would need to be large enough to obtain the maximum design flow rate of 18 m3/s and the sluice gates designed in Chapter 8.3, would be used to control this flow as desired for abstraction. The system will need to be removed entirely after the 25 year component lifetime, as when future higher abstractions are desired the systems resistance will reduce flow rates such that the flow requirements cannot be met. If the flow is reduced greatly, the water level in the pump out shaft could fall too low which could in turn lead to cavitation of the submersible pumps. Also this restriction to flow could result in the desired river abstractions no longer being possible as the flow of water will not be great enough to achieve the amount required.
Power generation The power generated by the Kaplan turbine is found using Equation 15.1, where • Q = flow rate • H = effective water head, • g = acceleration due to gravity • Η = efficiency
Equation 15.1
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The average power generated was calculated for each year of operation, using the flow rate predicted for that time period, an effective water head of 4.5m due to the 10% losses and an efficiency of 75% to account for mechanical losses in the generator. The average power generation was found to range from 284 kW to 530kW over the component lifetime of the turbine.
Prediction of Revenue The revenue for the power generated is predicted using Government Feed in Tariffs. The generator would be attached to the mains and the scheme would be reimbursed per kWh of power generated. The tariffs vary for different types of power generation and also different power outputs. In the case of hydroelectric power in excess of 500kW output, the income generated is 10.96 pence/kWh. For power generated below 500kW but above 100kW the income is 14.03 pence/kWh.
Prediction of cost Cost is difficult to gauge on projects such as this, however, there are methods in place for estimating based on other projects which have been completed. Lancaster University produced Equation 15.2 for estimating the cost of a Kaplan turbine for flow rates between 5m 3/s and 30m 3/s (Lancaster University , 2014).
Equation 15.2 46000 . × This gives an estimated overall turbine cost of £222,199.
The cost of installation can then be estimated with Equation 15.3 for the worst case scenario (Lancaster University , 2014).
Equation 15.3 6000 ×
The installation cost, Cl, is found to be £3,178,440, giving a total set up cost of £3,400,639 as a worst case estimate.
The operation and maintenance costs of hydropower systems are estimated to be 2.5% of initial investment per year (IEA, 2010). Therefore annual maintenance costs can be estimated at £8501.
As the system will need to be removed after the 25 year period, the cost of decommissioning must also be considered. As a conservative assumption, this has been assumed at half of the installation costs, therefore £1,589,220.
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Figure 15.7 shows the financial summary for the Kaplan Turbine Scheme, with a payback period of 10 years and a predicted profit of £5,500,000 from this analysis, the use of Kaplan Turbines in this scheme seems viable.
Kaplan Turbine Revenue Generated 8000000
6000000
4000000
2000000
0 NPV Flow Cash(£'s) NPV 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 -2000000
-4000000 Year
Figure 15.7 - NPV Cash Flow for Kaplan Turbine Scheme
16 Control Systems A control system is how different devices interact given an input value in order to control the value of an output. The input is usually an ideal value that we want the output to be. A typical control system block diagram takes the following form;
Figure 16.1 - Block diagram of a typical control system (INTECH open science, n.d.)
From Figure 16.1, the output value is measured through sensors and compared to the input value, labelled ‘desired output’ on the diagram. The difference between the two signals is the error and an error signal will be sent to the controller which will then figure out what needs to be done to reduce the error, hence producing corrective action. A controller is a device that is designed using analogue electronic components or that can be programmed to produce the relevant corrective action. The controller is connected to the control element, sometimes referred to as a plant, this
92 | P a g e Chapter 15 – Hydropower - DJ Chapter 16 – Control Systems – LM Thames Group Tidal Water Resources can be a hydraulic actuator, a motor, etc. that can be controlled using electricity. The controller will therefore dictate the behaviour of the control element, and in-turn controlling the process and producing a new output value, the whole cycle is then repeated. This means that the control system will be constantly trying to make the output value equal to the input value even in the presence of disturbances which may be trying to increase the error, (Franklin, Abbas, & Powell, 2010). However, the error signal can never be zero because the controller needs an electric signal to function, and because the error signal is sometimes too small to operate the controller, an amplifier to amplify the electric signal may be attached to the controller.
Control systems will be implemented at Kew weir with the primary aim of maintaining minimum residual flow, at the sluice gates to control the flow rate inside the abstraction tunnel and at the Teddington weir.
16.1 Sluice Gate The sluice gates will need to be lowered or raised to control the flow rate inside the tunnel. The amount of flow rate required will vary depending on the abstraction rate which depends on the demand on that particular period and therefore one particular value to be maintained cannot be set permanently, but instead, an operator will keep adjusting the amount of opening of the sluice gates depending on the required flow rate (Figure 16.2). It is ideal that the control systems be operated remotely as opposed to requiring a person to be constantly on site just to lower and raise the gates as required. It is understood that the flow rate required will not change very often and as such the system does not require closed loop control. A simple Supervisory Control and Data Acquisition (SCADA) is proposed to enable remote control and monitoring.
Figure 16.2 - Operation of the sluice gates to control flow rate, (Turnpenny Horsfield Associates, 2013).
Design Specifications • Ability to be controlled remotely • Robust • Control the flow rate inside the tunnel • The costs should be reasonable.
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System Overview
Figure 16.3 - Block diagram of the control systems
The sluice gates control system (Figure 16.3) is made up of but not limited to the following; • Electric motor (linear actuator). • Limit switches • Position sensors • Remote Telemetry Units • A host computer (SCADA master unit).
16.1.2.1 Motor
Figure 16.4 - A drive mechanism to move the gate (California Polytechnic State University, 2000)
Figure 16.4 shows a drive mechanism including an electronic motor to lift and lower the gates. The motor is the one that introduces mechanical energy into the system and has to be powerful enough to overcome the weight of the gate, frictional forces, etc. The table below shows various motors from the company Joyce and their various lifting capabilities and speed of the gates as a result of the motors which can be used when choosing a motor. A detailed list with more powerful
94 | P a g e Chapter 16 – Control Systems – LM Thames Group Tidal Water Resources motors is also provided by the company Joyce (Figure 16.5). In order to perform both lifting and lowering, the motor has to be able to operate in the forward and reverse direction and this is made possible by motor starters (California Polytechnic State University, 2000).
Figure 16.5 - Motor numbers and their characteristics (Joyce Dayton, 2013).
16.1.2.2 Limit switches
Figure 16.6 - The role of limit switches (California Polytechnic State University, 2000).
Limit switches will ensure that the sluice gates do not travel beyond their allowed movement. They are usually placed at an upper and lower limit of travel. If the gate is being raised or lowered and it encounters a limit switch, the motor will be switched off and the gates will stop moving. The only way the motor will start is if it is moving the gates in the reverse direction, (California Polytechnic State University, 2000). This ensures that important structures are not damaged by trying to force movement when the limit of travel has been reached (Figure 16.6). 16.1.2.3 Position sensors Position sensors communicate the position of the gates (Figure 16.7). This is important because the operator will need to know by how much to raise the gates or lower them and he/she cannot
95 | P a g e Chapter 16 – Control Systems – LM Thames Group Tidal Water Resources do that unless he/she knows the current position of the sluice gates. A 5 turn potentiometer sensor can be chosen and will send an output signal that change linearly with the gate position. As a way to calibrate the sensor, when the gate is closed the lowest output value of the sensor will be output, usually 4mA and will increase linearly until the maximum determined position of the gate, where the sensor will output its maximum value, usually 20mA. This can be programmed in a chip to show percentage opening of the gate and hence give a sense of knowing how much opening there is under the gate. This information can be read from the SCADA master units. The sensor should be weather proof and robust. This sensor will send its data to the Remote Telemetry Unit, RTU, for further processing.
Figure 16.7 - A typical sensor arrangement system (California Polytechnic State University, 2000)
16.1.2.4 Remote Telemetry Unit The RTU collects data from the position sensor then sends it to a SCADA master unit, which is a computer at the control room or office where the control system is controlled remotely from. The connection to this SCADA host can be via a radio link utilising some frequency spectrum, which eliminates the need for many cables. It can also be via a dedicated phone cable, which is a much cheaper way of doing as opposed to using radio where a licence is required to transmit. However, some useful frequency spectrum are free to use and do not require a licence, (Schneider Electric, 2012). The RTU also receives instructions from the SCADA host which will be used to control the relay switch connected to the motor, this allows the motor to be controlled and switched on or off remotely through the relay switch (Figure 16.8).
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Figure 16.8 - Indicative sketch of how RTU links with the rest of the system, (Schneider Electric, 2012)
16.1.2.5 The SCADA host The SCADA host is a computer located at the control room or office. It interfaces the control system, e.g. sensor readings, etc. with the humans. It uses the communication link with the RTU to pass commands to the control system.
16.2 Operation During Power Failure and Fail safe mechanism. A hand wheel permanently attached to the actuation will ensure that the sluice gates can be raised or lowered even during a power cut, (California Polytechnic State University, 2000). However, this cannot be done remotely. In the event of failure, the control systems will be powered off and the hand wheel can be used to operate the sluice gates while the control mechanism is being serviced or fixed. The onsite control system will be housed and locked to keep personnel without expertise away so that in the event of failure, no one may get hurt.
16.3 Financial Analysis Table 16.1 - Financial breakdown of sluice gate control system
Component Cost Joyce Machine Screw comDRIVE (includes motor) £262.46 NetGuardian 832A G5 (RTU) £375 5 turn potentiometer sensor £12.20 SCADA master unit £1570.00 Total £2219.66 16.4 Pump Out Shaft Cavitation is an undesirable phenomenon in pumping systems because it accelerates mechanical wear of pipes and other important components such as impellers in the case of centrifugal pumps. It is therefore important to have a cavitation monitoring device or sensor in the pumping system so that if cavitation is suspected or detected, appropriate actions may be taken. The control systems will be in place to produce the required action basing on the output from the cavitation monitoring device. Figure 16.9 is a block diagram outlining the control system.
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Figure 16.9 - Systems outline
The cavitation monitoring device attached to the pipes (Figure 16.10) will feed the controller with its output which reflects the state of the system. The controller will take this output as its input, together with the system’s parameters such as the design flow rate and will use this information to produce the corrective action. The controller, which is usually embedded on the motor, will either increase the speed of the motor drive or reduce it, hence controlling the flow rate, in order to eliminate or reduce the occurrence of cavitation. The motor drive will drive the pump motor accordingly, depending on the available or required Net Positive Suction Head (NPSH) and cavitation within the system will be avoided, (Sulzer Centrifugal Pumps, 1998).
Figure 16.10 - A pump system with cavitation monitoring, (United States of America Patent No. US6663349 B1, 2003) 16.5 Teddington Weir There needs to be a way to completely close Teddington Weir during periods where water will be scarce to avoid losing any fresh water to the saline water downstream. It is during these times that Kew Weir will be operational. So before Kew Weir is raised on the next tide, Teddington Weir will need to be completely closed first. Since for this feasibility study a detailed alteration was not developed, a detailed way of controlling Teddington Weir cannot be developed but it will need to be in place. A SCADA system whereby Teddington Weir can be completely closed remotely can
98 | P a g e Chapter 16 – Control Systems – LM Thames Group Tidal Water Resources be looked into as an area for further study. Assuming the two weirs will be operated by different personnel, which will most likely be the case unless a remote controlling system is in place, a simple way whereby the operators of Teddington Weir find a way to communicate with the operators of Kew Weir after closing Teddington Weir may well be considered. The Kew Weir operators will now know that they will have to raise the weir on the next high tide. In other words, Teddington Weir will dictate when to power the Kew Weir control systems on or off depending on the demand and how much water is available.
16.6 Kew Weir
Figure 16.11 - Sketch of Kew Weir in an upright position.
The weir will be used to maintain minimum residual flow downstream whenever necessary. This will be done by maintaining a minimum water depth of either 140mm or 160mm above the weir, depending on the option chosen. If the weir is activated, then at high tide the weir will be in an upright position making an angle of 90 degrees with the riverbed and foundations as shown in Figure 16.11. As the flow rate reduces and the water depth above the weir reaches the minimum, the weir should begin to move clockwise. Once the water depth above goes below the minimum to keep it constant.
Design Specifications The control system design should meet the following specifications; • A reasonable response time • Robust • Maintain minimum water depths to maintain minimum residual flow • Should only be activated when required
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Design process If electronic control systems are to control the physical world, a way to interface between the physical world and the electronic world becomes necessary. The interfacing mechanism can be achieved through the use of sensors or transducers. These devices will measure a physical quantity and produce a corresponding electrical signal. The use of transducers is important here because the minimum residual flow is to be maintained by monitoring the amount of water depth above the weir; hence a way to measure this water depth becomes necessary. Using Figure 16.12, it can be seen it is possible to measure the water level ( H + P) and the height of the weir above the ground ( P) such that the difference between the two values would give the water depth ( H) above the weir.
Figure 16.12 - Important parameters of the weir (Anon., 2015)
It is proposed that water level sensors/transducers be used to measure the water level and angle transducers be used to determine the position of weir. However, the water level sensor and the angle transducer are two different measuring components with a different calibration and so directly taking their signal difference will not be ideal. Since their output signals are linear with change in their respective physical quantities they measure, there must be a factor which can make the output of one device equivalent to the output the other would produce. It is proposed that the output of the angle transducer be multiplied by a factor which will make it equal to the output the water level sensor would produce if it were at the particular height of the weir. For example, if the height of the weir is 2m above the ground, the output from the angle transducer when the weir is 2m above the ground should be multiplied by a factor such that the output will now equal a value that the water level sensor would produce if the level of the water was 2m. In this way, the difference between the two readings gives a much more meaningful value which can be determined and which will correspond to the height of the water depth above the weir. The device to provide the multiplying factor can be an amplifier with a gain equal to the required multiplication factor.
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The control system only needs to be activated when Teddington Weir is closed. As such a mechanism to detect when the control system becomes necessary and when they don’t needs to be put in place. The mechanism will come in the form of two circuits: 1. A transducer circuit which will alert the lock-keeper to power on the control system when the water depth falls below the minimum level. 2. Another transducer circuit to alert the lock-keeper to power the control systems off when they become unnecessary.
The Control Circuit
Figure 16.13 - Block diagram of the control circuit
The primary aim of the control circuit is to maintain minimum residual flow. A control system taking the form of the block diagram in Figure 16.13 is proposed. An electrical signal of a magnitude that is equal to the signal the sensors would produce when the water depth above the weir is at the minimum is the input to the control system. This is basically the signal a water level sensor would produce when submerged just over the minimum level of either 140mm or 160mm. This signal can be easily achieved by getting power from the standard AC mains plug then using an electronic converter to convert the power to an appropriate DC value. This is necessary because power from the standard mains is AC at approximately 240V. So a converter converting AC to a predetermined DC voltage value becomes important. The output of the control system will be the difference between the output from the water level sensor and the output from the angle transducer. This output value will be compared to the input value at the summing point and the difference between the two values will become the error signal which will be picked up by the controller. The controller will process the signal and send a signal to the actuator which will produce corrective action. The actuator will then lower the weir or raise it depending on the required corrective action. As the weir is raised or lowered, the angle transducers will produce a signal of corresponding magnitude depending on the direction the weir moves. At the same time water level sensors will be sending the signal they pick enabling the difference to be taken. This means that once the control systems are activated as a result of the water depth falling below the
101 | P a g e Chapter 16 – Control Systems – LM Thames Group Tidal Water Resources minimum, the output value from the control systems will try to follow a predetermined input value which corresponds to a water depth of the minimum and hence maintaining minimum residual flow.
Water Level Measurement A WL400 water level sensor is recommended for water level measurement. It is a submersible transducer with a waterproof cable that will output 4-20 mA that is linear with change in pressure; the higher the water level, the greater the pressure and hence a greater output. It is rugged, extremely robust and requires minimal maintenance and care. It can operate in harsh environments with operating temperatures of -40°C to 85°C. The fact that it has in-built barometric compensation means that it is not affected by atmospheric pressure and it is also not affected by rain or wind, making it extremely suitable for this purpose.
Figure 16.14 - Sample water level sensor and how it would be installed, (Global Water, 2015), (Nivus, n.d.)
Figure 16.14 shows a picture of the WL400 water level sensor and how it can actually be installed to measure the water level. The way in which it would normally be installed is such that the pressure probe is placed just below the lowest expected water level and held securely by combined fastening and protective pipe. The sensor requires 8-36 VDC of supply voltage to operate.
Since close to the weir the water experiences a drawdown effect (Figure 16.15), to measure the head correctly, which is a function of flow rate, the pressure sensor should be positioned sufficiently upstream. If the sensor is positioned too close to the weir, it will not measure the true level of the water.
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Figure 16.15 - Schematic indicating a decrease in the water level at the weir crest, (Civil Engineering Portal, 2015)
Measurement of the Height of the weir above the ground
Figure 16.16 - Sample angle transducer, (Sensitec, 2009)
The height of the weir above the ground at any one point is proportional to the angle the weir makes with the ground. The anisotropic magneto-resistive AA700 series Sensitec angle transducers are recommended to measure the angle the weir makes with the ground. These transducers are extremely robust and contactless, hence allowing free movement of the weir. They evaluate the direction of the magnetic field and not the field strength and hence they continue to work well even when the magnetic field strength fades away with age. They also work well under harsh conditions and operate under a wide range of temperatures (-40°C to 150°C).
Figure 16.17 - Spatial relationship between sensor chip and magnetic field (Anaheim Automation, 2011)
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Figure 16.16 shows magneto-resistive transducers. They output an analog signal that will be linear with change in the angle of the weir. They require a supply voltage of 5V. Ideally, the way they would be installed is such that, the sensing chip is attached to the fixed part of the weir to avoid any moving cables and the other part is attached such that it moves with the weir (Figure 16.17).
Head measurement The head, which is a function of the flow rate (Mays, 2001) is the difference between the water level and the height of the weir above the ground. The measurement of the head is done by taking the difference between the two sensor readings. For accurate measurement of the head, the output of the angle transducer needs to change at the same rate as the output of the water level sensor and therefore the angle transducer output needs to be converted to an equivalent reading of the water level sensor. The difference between the two readings is done by taking the water level sensor output and converting it to a negative signal before it is added to the angle transducer output. The resulting signal is a measure of the head, which will be a negative signal since the water level will always be greater than the height of the weir above the ground (Figure 16.18).
Negative output from water level sensor .
Signal Angle transducer corresponding to K output. water level abo ve weir
Figure 16.18 - A block diagram of the summing junction
Generation of the input signal As outlined above, the input signal should be an idealised output of the control systems. The ideal output when the control systems are powered on is a signal corresponding to a head measurement of 140mm for Option 1a and Option 1c (Drawings 211 and 213 in Appendix G) and 160mm (Drawing 212 in Appendix G) for Option 1b. This signal can be predetermined by measuring the water level sensor output when the sensor is submerged in water just over 140mm or 160mm deep. This signal can then be generated by connecting a power converter pre-set to generate the signal when connected to the standard mains. Once the signal is being generated, it will be fed into the control systems and its difference with the output will be used to produce the relevant corrective action.
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Outline design process of a controller For this feasibility study, a controller was not designed as it is a fairly predictable process. However, it was decided to outline how it would actually be designed and implemented. A controller is responsible for interpreting the error signal and producing corrective action. During the design of the controller, the first step is to derive the specifications of the system, for example, how much time the system takes to respond to change, how much error can be tolerated between the desired output and the actual output, etc. Once the desired system specifications are known, the actual system characteristics are determined using an appropriate function. The choice of the function will depend on the nature of the control system, but in this case, a step function and a ramp function seem appropriate because switching on the control systems follows a step function and the change of the actual output is gradual and hence a ramp function will be appropriate. An examination of the actual system characteristics will determine what needs to be done to produce the desired system specifications. The system will be modelled in a mathematical form. A controller will be determined by determining what mathematical changes are needed to get to the desired mathematical model, which will usually be in the form of a mathematical function. This function will then be implemented by analogue electronic components or programmed in a board if digital control is to be used. However, it is proposed that analogue control be implemented because of its robustness, as opposed to digital control which will be exposed to program crashes, etc. A slightly longer time constant or response time will ensure a more fluid movement of the weir.
Incorporation of a fail-safe Mechanism Since the control system uses analogue control, which is extremely robust, the risk of failure of the control system is very low. All the forces acting on the weir and the potential forces have been catered for by using strong structures and a powerful lifting and lowering actuator, further lowering any risk of malfunction. However, since the control system only try to control the movement of the weir, which will be underwater most of the time, even if they fail or malfunction, no one will get hurt. A powerful locking mechanism will be incorporated to ensure that the weir does not go over the wrong direction by exceeding an angle of 90degrees with the river bed. In the unlikely event that the control systems pose a threat to human safety, they can simply be powered off and the weir will remain where it was when they system was powered off.
Financial Analysis The costs of implementing the control system are mainly capital costs and are detailed in Table 16.2, the only operational costs being the power being used to operate the control systems.
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Table 16.2 - Financial breakdown of Kew Weir control systems
Component Cost Converter £38 Analog controller £158.07 WL sensor £506.62 Angle transducer £50.00 Total £752.69 17 Overall Scheme Financial Assessment This summary provides an informed estimate of total project cost. Table 17.1 shows a summary of the costs determined by the feasibility study. Costing was obtained from a variety of sources, including industry quotes, engineering guidelines and conservative assumptions when necessary. For all financial analysis a discount rate of 10% has been implemented in order to give a more realistic financial overview for the duration of the project. As can be seen from Table 17.1, the Tunnel and Pumping costs analysed in this summary include only the value stated earlier in the report for the abstraction tunnel spanning from Teddington Weir to the Queen Elizabeth II Reservoir. This has been selected because as discussed earlier, the costing for improvements to Hogsmill STW was beyond the scope of this project. Therefore with only the costs for the tunnel from Hogsmill STW to the Thames available, a reasonable assumption could not be made into total cost, leading to a disproportionate representative of cost if included in the analysis. Table 17.1 - Summary of costs for proposed options Total Tunnel Operating Control Total Weir Structural Hydropower and Mechanism System Solution Gate Costs System Pumping Option Cost Costs Cost Cost (million Costs Costs (million (million (million (million £'s) (million £'s) (million £'s) £'s) £'s) £'s) £'s) 1a £2.372 £8.473 £0.209 £0.0015 £3.401 £78.36 £92.817 1b £1.427 £12.400 £0.209 £0.0015 £3.401 £78.36 £95.797 1c £2.372 £12.900 £0.209 £0.0015 £3.401 £78.36 £97.242
It should also be noted that the cost implemented for the control system is disproportionately low, this should be revised in order to ensure an accurate representation of required investment.
For the purpose of this analysis Option 1b has been selected. This option includes the construction of the Lock which will ensure that in times of more constant operation, the Lock will allow for relatively uninterrupted navigation of the river. There is also the potential to charge a nominal sum for use of the Lock, this will require further analysis into river traffic to gauge any income, however, may provide a reasonable contribution to maintenance.
Figure 17.1 shows a NPV cash flow comparison for the design life of Option 1b (with and without hydropower generation) and the construction and operation of Abingdon Reservoir for the same
106 | P a g e Chapter 16 – Control Systems – LM Chapter 17 – Overall Scheme Financial Assessment - DJ Thames Group Tidal Water Resources time period. The results clearly show that Option 1b provides a considerably lower financial investment and cost of operation than the proposed Abingdon reservoir. The indicated NPV savings are indicated by Figure 17.1 to be £916.075-£923.751million depending on successful implementation of the hydropower scheme.
0.000 -100.000 Time Period -200.000 -300.000 -400.000 -500.000 -600.000 -700.000 -800.000 -900.000 -1000.000
NPV Cash Flow (million NPV £'s) -1100.000 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 Abingdon -1000.5 -1003.5 -1004.7 -1005.2 -1005.3 -1005.4 -1005.4 -1005.4 -1005.4 -1005.4 -1005.5 With Hydropower -95.797 -84.724 -84.725 -84.725 -84.727 -84.728 -84.728 -84.729 -84.729 -84.729 -84.729 Without Hydropower -92.397 -92.400 -92.401 -92.402 -92.404 -92.404 -92.405 -92.405 -92.405 -92.405 -92.405 Figure 17.1 - NPV cash flow comparing solutions of Abingdon reservoir, Option 1b with hydropower and Option 1b without hydropower
Figure 17.1 also indicates the beneficial impact of the hydropower scheme proposed in this study with a NPV saving of £7.676million over the design life of the project.
17.1 Summary In conclusion the financial saving of the tidal recharge scheme regardless of the orientation of options is considerable compared with that of Abingdon reservoir. As can be seen from Table 17.1, the costs range from £92.817million - £97.242 million; all costs within this range are small compared with that of constructing Abingdon reservoir. The methods carried out to acquire the costs involved at feasibility stage are not as accurate as receiving direct bids for services from contractors; therefore in the event of the projects implementation, it is reasonable to assume some variance in cost. However, Option 1b as compared in Figure 17.1, has a NPV of 8.4% - 9.2% compared with that of Abingdon Reservoir, which leads to suggest that with any variance the cost is likely to still result in considerably better financial results.
18 Carbon Assessment Climate change is a dominant issue in today’s society and carbon emissions are at the forefront of the problem. After the Kyoto Protocol all the signatory countries have targets to reduce their 107 | P a g e Chapter 17 – Overall Scheme Financial Assessment – DJ Chapter 18 – Carbon Assessment – IP Thames Group Tidal Water Resources carbon emission by – these targets being legally binding in the UK by the Climate Change Act 2008. This act sets legally binding targets for the UK to reduce its greenhouse gas emissions by at least 80% by 2050 compared to the 1990 levels.
Even though the water and wastewater sector emissions contribute only 0.7% to the UK’s total greenhouse gas emissions (Ofwat, 2010), each sector should still aim to reduce the emissions by 80% irrespective of the overall contribution to the problem (Crawford-Brown, 2009). Also, despite carbon production falling by roughly 15% compared to 1990, the carbon consumption has increased by 19% because carbon produced by energy intensive industries offshore are now included (Helm, 2009). The water industry still remains a very large consumer of energy - 8100GWh per annum and more than 4 million tonnes of carbon emissions (Butler, 2009) – mainly due the energy intensive processes (such as pumping) that are required for its operation.
In order to achieve these targets, each proposed project in the water industry should consider both the embedded emissions and the operational emissions, meaning that a Life-Cycle approach should be adopted accounting for the overall emissions. For this feasibility study, a Carbon Assessment tool created in accordance with the Environmental Agency’s Carbon Assessment Tool will be used in order to calculate the embedded emissions of the proposed scheme. The operational emissions will be calculated from the estimated energy required for the scheme’s operation. The overall carbon assessment for the project will then be compared to the average emissions from the average carbon assessment of 13 studied reservoirs.
18.1 Embedded Emissions and Management These emissions result from construction and maintenance activity, therefore they should be considered during the design stage. For example, material selection, transportation to and from site, construction emissions etc. all contribute to the embedded emissions of a project. It is estimated that over the period of AMP5, the sector’s embedded emissions was approximately 11.6 million tonnes CO 2 (Ofwat, 2010), meaning an additional 50% to the operational emissions over that period.
In order to manage the embedded carbon emissions in this design, the material selection will play a key role. Specifying standard sizes to avoid site cutting and welding, pre-cast concrete units and making use of opportunities to use recycled aggregates should be considered. Also, by using locally sourced materials and utilising or minimising waste in the construction of new projects, the design can reduce the embedded carbon emissions significantly (Helm, 2009).
During the construction of the project, office accommodation will be important in reducing the embedded energy use. The measures outlined below can reduce significantly this: • CAT2 lighting in all areas
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• Dual air conditions/ heating systems, timed, one per bay where indicated • ZIP boilers in canteen facilities • Door closers to welfare facilities and stair well units The plant and power tools should be carefully selected as well based on their carbon emissions and all plant should have an idle mode, in order to avoid unnecessary emissions when not in use.
18.2 Operational Emissions and Management Operational emissions have increased by more than 40% since 1996 levels, mainly due to increased demand and more energy-intensive water treatment processes (Ofwat, 2010). At the end of the AMP5 period, six out of the ten water companies have projected an increase in their operational carbon emissions. Thames Water has projected a decrease, however this is associated with the company’s plan to buy ‘greener energy’ from a low emission source rather than reducing emissions directly (Ofwat, 2010). For all the water companies, the primary driver for operational emissions is the energy use and it is estimated that 85% of the operational emissions come from this energy use (Ofwat, 2010). However, the water companies could generate more than 600GWh of renewable energy per year which is approximately 8% of the sector’s annual energy use.
18.3 Project Life-Cycle Assessment In order to produce a project life-cycle assessment, both the embedded and operational emissions should be considered. The overall project carbon assessment will be compared to 13 reservoir schemes that have been assessed by the Environment Agency.
The embedded emissions will be expressed in terms of CAPEX, which is the capital cost combining the embodied carbon in materials, with manufacture and construction and including construction energy usage. The operational emissions will be expressed in terms of OPEX, the operational cost of the energy required for the operation of power supply, using an electricity conversion factor of 0.43kgCO 2e per kWh.
Reservoir Emissions 13 Reservoirs have been assessed for the Environment Agency by Halcrow (Environment Agency, 2008) and the emissions are shown in Figure 18.1, Figure 18.2, Figure 18.3 & Figure 18.4. The average values used in calculating the following carbon emissions are a 15500Ml Reservoir Volume, 42Ml/day Deployable output, 100kW pump capacity and scheme operation 289 days/year for 22hours/day. Also, a planning period is fixed for 60 years, with the carbon emissions calculated over this period.
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Figure 18.1 - Carbon emissions break-down from an average of 13 reservoirs
As can be seen in Figure 18.1, the main emissions in reservoir construction come from the embedded emissions such as materials, construction operations, personnel travel and material transportation.
Figure 18.2 - Embedded emissions break-down from an average of 13 reservoirs
13.8 % 0.4% 0.004 %
14.4% 71.4%
Figure 18.3 - Material emissions break-down from an average of 13 reservoirs
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The embedded emissions can be further broken down as seen in Figure 18.2 and Figure 18.3, illustrating that more than 60% of the embedded emissions comes from material selection.
Finally, the operational emissions during the life of the reservoir show that the majority of the emissions come from the water treatment rather than the pumping itself (Figure 18.4).
Figure 18.4 - Operational emissions break-down from an average of 13 reservoirs
Kew Weir Emissions For Option 1a, where no lock is in place and the total weir length is 90m, the carbon emissions will result 100% from the materials and construction activities rather than the operation of the weir. The operational emissions are equal to 1.7tCO2e compared to the embedded emissions which account for 73614.5tCO 2e. The embedded emissions can be broken down as shown in Figure 18.5.
Figure 18.5 - Embedded Emissions Break-down for Kew Weir Option 1a
For option 1b, there will be an operational lock since the beginning, so the weir will only span 75m instead of 90m. Again, it can be observed that the operational emissions of the moving the
111 | P a g e Chapter 18 – Carbon Assessment – IP Thames Group Tidal Water Resources weir and operating the lock are insignificant compared to the embedded emissions. The main contributor again is the material selection as shown in Figure 18.6.
Figure 18.6 - Embedded Emissions Break-down for Kew Weir Option 1b
Finally, option 1c involves staged construction of the weir and the lock. This will result in an overall increase in the project duration due to the need for enabling works and handover twice over the lifecycle of the project. The operational emissions are again insignificant (less than 0.1 tCO 2e) but there in an overall increase in the carbon emissions compared to option 1b – from
212889.06 tCO 2e to 213163.8 tCO 2e.
Transfer Tunnel Emissions The emissions of the proposed transfer tunnel in Option 1 have been calculated based on the proposed volumes on materials and from data taken from the London Power Tunnels project for estimates for electricity, water and diesel usage. The emissions are estimated in
Figure 18.7 and Figure 18.8:
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Figure 18.7 - Carbon Emissions Break-down for Transfer Tunnel
0.6%
Figure 18.8 - Embedded Emissions Break-down for Transfer Tunnel
The key reason that the construction emissions are insignificant is because carbon minimisation during construction is assumed by employing measures as described above, using “green” plant and equipment and optimising construction best practices to minimise carbon emissions. Again, the pattern of the materials being the biggest contributor to embedded emissions can be observed.
18.3.3.1 Hogsmill STW Upgrade and Transfer Tunnel Two alternatives have been proposed to the transfer tunnel between Teddington Weir and Queen Elizabeth II Reservoir – both of them involving the upgrade of Hogsmill STW. Halcrow has assessed the associated carbon emissions from indirect effluent reuse for the Environment Agency (Environment Agency, 2008) and the results are shown in Figure 18.9 and Figure 18.10:
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Figure 18.9 - Carbon Emissions Break-down for Indirect Effluent Re-use
Figure 18.10 - Embedded Emissions Break-down for Indirect Effluent Re-use
Again, it can be observed that the greatest contributor to the embedded emissions are the materials.
18.4 Scheme Comparison
Table 18.1 summarises the emissions from each scheme – both in terms of tonnes of CO 2 equivalent and as a percentage of the total scheme emissions.
Table 18.1 - Carbon Emissions: Scheme Comparison
Embedded Embedded Operational Total Operational Emissions Emissions Emissions tCO 2e Emissions % tCO 2e % tCO 2e Reservoirs 185388 149268 80.5 36120 19.5 Kew Weir Option 1a 73616.1 73614.5 100 1.7 0 Kew Weir Option 1b 212889.1 212888.9 100 0.13 0 Kew Weir Option 1c 213163.8 213162.1 100 1.8 0
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Transfer Tunnel 112739.5 108643 96.4 4097.0 3.6 Proposal Effluent Reuse 78205 6925 8.9 71280 91.1 (Options 2 & 3)
As it can be seen the least carbon emissions would be produced by Kew Weir Option 1a, however the design life of this scheme would be very limited due to the lack of the lock. Option 1b, which involved both a lock and the weir structure, results in fewer emissions than the staged construction of the weir and the lock (Option 1c). For maintaining the minimum residual flow upstream of Teddington Weir, the least carbon emissions would result from the proposed transfer tunnel in Option 1, as the effluent reuse emissions calculated above only refer to upgrade of wastewater treatment works and do not include the tunnelling works that would be associated with them.
19 Conclusion The solutions proposed have been shown to have the potential to maintain minimum residual flow at Teddington Weir through application of the tidal recharge concept. A variety of options have been explored, finding that the moveable weir mechanism and Queen Elizabeth II tunnel abstraction alone can maintain the required flow until the 2080s, with further development, such as improvements made to Hogsmill STW having the potential to contribute to the scheme at a later point in order to achieve the 100 year design life stated in the project brief.
The first stage of the design was to determine a method to maintain the minimum residual flow upstream of Teddington Weir. The proposed solution stops three current abstractions (Walton-on- Thames, Hampton and Kingston) and a new abstraction tunnel from Teddington Weir to the Queen Elizabeth II Reservoir is to be constructed. This element of the solution is deemed to be feasible in terms of overall cost, as it would provide a long-term solution for maintaining the residual flow for that stretch of the river. Two further alternatives have been considered (Options 2 and 3) that involve upgrading Hogsmill STW to enable the reuse of the treated water for supplementing the existing river flow. However, these options have not been studied in detail in this report and require further investigation.
The second stage in the design was to analyse the tidal Thames to see if a half tide weir could provide the capacity required for maintaining the minimum residual flow. It can be seen from the report that overall the primary scheme proposed (Option 1) is constructible and can solve the water shortage issues in the London area until the 2080’s. In addition the aim of the project is to provide a solution for the 100 year design life and this cannot be achieved without supplementary flows based on the predicted abstraction rates. It is important to remember that the construction of
115 | P a g e Chapter 18 – Carbon Assessment – IP Thames Group Tidal Water Resources the tunnel and Kew Weir have been based upon a number of assumptions (see Chapter 21 for Assumptions Register) that would need to be closed out at detailed design stage.
The proposed scheme is an innovative solution when compared with provision of additional reservoirs. The scheme has considered the options based on the wider surroundings by incorporating alterations to existing abstractions and river structures as well as sewage re-use. It does not require significant land take or aesthetic impact on its surroundings. Thames Group have looked into the use of innovative raising mechanisms, such as the hydrofoil concept, as well as the combination of counterweight and hydraulic actuation. The hydropower takes advantage of the long term nature of the new abstraction tunnel proposing to be temporarily installed to maximise the production of “green” power without affecting the overall flow later in the design life of the scheme.
Although the proposed scheme will alter the flow of the river, both physically and by changing its composition, overall effects on the quality of the water will not be significant enough to cause concern. Should the project move forward with any of the options listed in the report, it is unlikely that additional mitigation measures will be required due to the impact of the scheme on the river’s water quality and therefore its ecology. The addition of a water recycling plant at Hogsmill STW (Options 2 and 3) also has the potential to benefit the water quality of the river in addition to increasing the amount of water available for abstraction. This would then not only aid in meeting freshwater demand, but also in bringing the status of the river more in line with the Water Framework Directive.
In terms of the wider sustainability, all of the proposed options would involve minimal disturbance to the surrounding local environment, with both environmental and archaeological impacts being considered in this report. However, the carbon emissions produced by the transfer tunnel combined with Kew Weir would result in greater carbon emissions overall than alternative options that have been proposed (such as Abingdon Reservoir). This means the proposed scheme is not feasible based on the carbon emissions produced at this stage. Due to the fact that the emissions of the proposed scheme result mainly from material selection and construction operations, if carbon-reduction measures are implemented during construction and materials that produce less emissions are specified in detailed design – a more sustainable design could be considered which may produce a different outcome for the carbon footprint of the scheme. Lastly, it has been hypothesised that as the proposal stops three existing abstraction points, the overall pumping contribution to the carbon of the proposed scheme will be balanced by the savings in carbon at these existing abstractions.
Comparing the scheme with that of Abingdon reservoir, the financial savings are considerably more for both installation and the NPV predicted cash flow for the design life of the Thames tidal
116 | P a g e Chapter 19 – Conclusion Thames Group Tidal Water Resources scheme. The carbon emissions, however, have been far in excess for the implementation of the scheme, compared with the published figures for Abingdon reservoir. The majority of the carbon emissions were found to be due to the construction of the abstraction tunnel suggested between Teddington Weir to the Queen Elizabeth II Reservoir. The Abingdon scheme also includes a tunnel which may not be included in the carbon figures used in this report. It was difficult to predict as Abingdon is a very different scheme to the ones with figures available that have been used in the carbon analysis. Abingdon reservoir is predicted to maintain the water supply in the Thames for 25 years after its construction; this is 35 years less than the tidal recharge scheme.
Despite this, the intended design life of 100 years cannot be achieved by any of the solutions explored in this report. A combination of the options presented here may provide a more effective solution, for example construction of both Option 1b and either Option 2 or 3. However this would push the carbon footprint even higher, reducing the sustainability of the scheme further. The decision that would need to be made with further consultation would be whether the embedded carbon can be reduced sufficiently to justify this as an alternative solution when combined with the much lower cost and the lower environmental impact.
Due to the high carbon emissions determined by this study, the feasibility of the solution is brought into question. The installation and operation of the moveable weir is predicted to emit comparably little carbon in comparison with the abstraction tunnel construction therefore the tidal recharge concept in itself has been found to be feasible. The issue lies in replacing the abstractions of Hampton, Walton and Kingston with the abstraction tunnel between Teddington Weir and the Queen Elizabeth II reservoir. Unless the issue of carbon emissions can be solved the proposed solution is deemed infeasible, regardless of the considerable financial savings.
20 Areas for Further Research
20.1 Locking Mechanism for Weir Further research should be conducted into the possibility of a locking mechanism for the Kew weir gates. This will allow the weir gate to be held in various positions along its 90 0 designed rotation. This will considerably reduce operating costs as the operating system will not need to hold the weir in position for extended periods of time, reducing both carbon and financial costs. The issue may be in the complexity of the design and also the potential maintenance and operation problems of such a system being permanently submerged and used infrequently.
20.2 Improvements to Teddington Weir Further research must be made into the feasibility of making alterations to Teddington Weir in order for the fresh flow of water over Teddington Weir to be shut off when Kew Weir is in
117 | P a g e Chapter 19 – Conclusion Chapter 20 – Areas for Further Research Thames Group Tidal Water Resources operation. This will ensure that the abstractions can be made whilst also maintaining minimum residual flow. It would need to ensure that Teddington Weir would not be closed at low tide.
20.3 Investigation into Varying Water Depth at Teddington Weir Further research will need to be conducted into the variance of water depth on an annual basis at Teddington Weir where the river abstraction will take place. The power generated by the hydropower is dependent on this value; an accurate range should be determined in order to both determine its suitability and also its design. The river depth at this point will also determine the maximum flow that can pass into the inlet shaft for abstractions, therefore this design will need to take this into consideration. This analysis should take place after determining the feasibility of shutting off Teddington Weir, and also the effect that this will have on the river level.
20.4 Sealing Panels for Weir Further research needs to be conducted into the sealing of the Kew Weir gates, due to its rotation there is the potential for either leaking of water between the piers and the weir gate, or excessive scour and wear. A suitable sealing system will need to be explored, and also the necessity for this to be done.
20.5 Sluice Gates Further research needs to be made into the design of the sluice gates. Further information into the forces applied will need to be found in order to ensure the safe operation of the gates, also consideration into the aesthetic design should be made to minimise the visual impact. In addition to this the positioning and dimensions required to allow the desired abstraction flows should be further investigated. This analysis should collaborate with that of the water depth at Teddington Weir.
20.6 Weir Gate Sections Structural Analysis will need to be carried out on the Kew Weir gate sections in order to determine the ideal structure for the final design. The possibility of other materials to decrease weight should also be investigated. This may increase initial costs, but reduce operational costs.
20.7 Tunnel A full statutory undertaker’s enquiry of tunnel alignment will need to be made in addition to a full geological ground investigation survey.
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20.8 Weir Foundations and Structure A geological ground investigation survey should be carried out for the Kew Weir foundations. Further research into the structures ability to cope with the maximum forces should be made, and the design altered if necessary.
20.9 Flooding Potential Further research into the potential of flooding due to both the operation of Kew Weir and the closing of Teddington Weir need to be conducted. If a possibility of flooding is found, measures will need to be put into place to either deactivate the appropriate system or include further flood defence options. The likelihood of this is unlikely however, due to Kew Weir being operational at times when there is a lack of water, as well as systems such as the Thames barrier which will be in place by the time of the designs installation.
20.10 Water Quality Further research must be made into the chemical content of the water. This will be done by sampling and chemical analysis, the results of which will give information which can be used to measure the ecological impact.
20.11 Ecology A full ecological survey must be conducted in order to determine the designs impact on the river environment.
20.12 Compliance with Legislation All aspects of the design will need to be confirmed with the appropriate governing bodies against their legislation. Alterations may need to be made in order to allow construction of the design. The relevant bodies are those which were discussed in the inception report.
20.13 Predicted Carbon Emissions The predicted carbon emissions compared in this report have been based on reservoirs which have been constructed already. Abingdon Reservoir is a unique scheme of a considerably larger scale, therefore comparison is difficult using the method outlined in this report. Comparing the proposed scheme with that of Abingdon Reservoir suggests that due to the construction required for Abingdon that the published figures may not include embedded carbon emissions for the tunnel construction at Abingdon. This should be researched in further detail to ensure a like-for-like analysis is conducted.
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21 Assumptions Register Item Assumption/Issue Basis Closed Out Assumed By 1 The maximum daily abstractions provided in the LTOA Thames Water cannot provide actual abstraction No - To be confirmed at HP are utilised simultaneously at times of peak demand. data. LTOA is only information available. detailed design stage. 2 The future flows from Kingston have been used to The future flows modelling has been conducted Yes HP calculate the defecits in flow in the future. in conjunction with the Environment Agency and the Centre for Ecology and Hydrology, both have significant experience in this area. 3 It is assumed modifications to Teddington Weir will be If Teddington Weir cannot be blocked Yes HP permitted to enable the design to function. completely during drought times the scheme is irrelevant. 4 Hampton, Walton and Kingston abstractions have been It is not feasible to stop all abstractions upstream Yes - This has been set HP/IP stopped but Datchett, Staines and Laleham have been of Teddington Weir as the distance to the areas as the aim of the project. retained. they supply would become too great to justify. 5 The cross sections produced from the data provided by It is not possible to predict changes in channel Yes HP the PLA are assumed to be correct and constant cross section for the next 120 years. throughout the design life of the project. 6 The future water demand has been based on the Thames Measures to reduce water consumption in the Yes HP Water WRMP and projected forwards linearly for the future cannot be accurately considered as many full design life of the project. will not have been invented/implemented yet. 7 Three or more consecutive days of the weir in operation Whilst not ideal to have any points the river No-to be done so at HP is a significant disruption to the navigation of the river. cannot be navigated, the figures used are the detailed design stage worst case tidal and flow values and therefore the times the river is not navigable are likely to be even lower than indicated in the report and calculations. It is a cost benefit analysis that would require additional study to confirm.
120 | P a g e Chapter 21 – Assumptions Register Thames Group Tidal Water Resources
Item Assumption/Issue Basis Closed Out Assumed By 8 Assumed density of seawater to be 1025kg/m 3. Taken from (Douglas, Gasiorek and Swaffield, Yes HP 2001). 9 To calculate tunnel diameter a steady uniform flow has Steady, uniform flow occurs in long channels of Yes IP been assumed. constant cross-section and slope. 10 Pressure at the free surface is constant (equal to Because of freeboard allowance in the CIRIA Yes IP atmospheric) and does not vary in the direction of flow. C689 Guide, it will always flow as an open channel. 11 Dynamic Viscosity µ of freshwater at 20˚ is 0.001. Standard Value taken from: Douglas, Gasiorek Yes IP and Swaffield, 2001. 12 Inlet Shaft Capacity will always be sufficient for the Transfer tunnel has sufficient capacity (see Yes IP required flows, because it is larger and steeper than the calculations). transfer tunnel. 13 Freshwater Density ρ = 1000kg/m 3. Standard Value taken from: Douglas, Gasiorek Yes All and Swaffield, 2001. 14 >3 days of weir activation consecutively is considered a <3 days is an inconvenience to navigable traffic. No - To be confirmed at HP major disruption. detailed design stage. 15 Density of steel to be 7951kg/m 3. Taken from (Cobb, 2011) Yes HP 16 The cost of upgrading Hogsmill STW will be Only comparable project in the UK. Similar Yes BC comparable to cost of upgrading Langford, Essex. output values. 17 100mm thickness for secondary tunnel lining will be Similar to other tunnelling projects. Yes IP sufficient. 18 The tunnel size for the alternative options 2 and 3 will be Calculations to confirm are beyond the scope of No - To be confirmed at IP the same as option 1. this feasibility study. detailed design stage. 19 Salinity increases will be of negligible concern. Current salinity varies with tide greatly, Yes BC therefore any changes would likely be within this range already.
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Item Assumption/Issue Basis Closed Out Assumed By 20 Siltation of proposed Kew Weir will not be of concern. Siltation at Richmond was found to be only a Yes BC problem at low flows, not something expected at Kew Weir location (Cascade Consulting, 2013). 21 Stiff clay layer in borehole logs is assumed to have No further geological data available to confirm. No - To be confirmed at JJ sufficient depth to support Kew Weir structure. Central London therefore highly likely. detailed design stage. 22 Fire protection cost component of steel is assumed to be Similar processes used (protective layers, No - To be confirmed at HP roughly equivilent to cost of waterproofing. treatment of metal surface, etc.) therefore similar detailed design stage. work and resource required. 23 Option 1c is assumed to have same weir gate dimensions In initial option state it will be identical to Yes HP as Option 1a. Option 1a. 24 Resistance introduced by Kaplan turbine to be same as Both are hydropower generators and Kaplan No - To be confirmed at DJ by crossflow turbine. turbines are generally more efficient so this is detailed design stage. conservative estimate. 25 Decommisioning of hydropower assumed to be half Not all infrastructure needs removal, therefore No - To be confirmed at DJ installation cost. less work involved. detailed design stage. 26 The soil under the proposed structure is homogenous, Sheet piling needs to be completed quickly due No - To be confirmed at JJ uncontaminated and free of hazardous and impenetrable to limited time on low tide. Soil under such detailed design stage. objects. heavy loading may fail if there are any weaknesses below structure as well. 27 There will be no catastrophies, seismic events or other Any natural disaster could severely disturb the Yes JJ natural disasters during the construction periods. construction of the structures and would need a remedial plan created on whether to continue the works and how. 28 The layout of the river does not dramatically change Structures are designed to fit in with the current Yes JJ with time between present and start of construction. layout of the river.
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Item Assumption/Issue Basis Closed Out Assumed By 29 The sheet piling wall is sufficient to provide foundations The flow of water will build large lateral loading No - To be confirmed at JJ with enough rotational resistance and piled foundation is on the piers and the rest of the structure, which detailed design stage. not required. will cause pull-out and push-in forces at beginning and end of foundations respectively. 30 In-situ cast reinforced concrete will be vibrated to Any joints, air bubles or spaces that are less Yes JJ required levels and built in a single cast, making the compacted will be weak spots and under structure homogenous. continuous flow of water are subject to errosion and eventual loss of structural stength. 31 Local suppliers with sufficient resources are chosen for It must be ensured suppliers have sufficient Yes JJ the construction materials. resources of construction material locally so to guarantee continuation of the construction programme. 32 The tidal patterns in the future remain similar to those in Some construction methodology and Yes JJ the past. calculations have been based on tidal patterns of the river. 33 The weir will not be at full loading in excess of 6 hours. The average times between high and low tide Yes DJ have been calculated, the average value being 6 hours. Therefore for on an average basis the weir will not be at full load for over 6 hours. 34 The river level at Teddingion remains above 5m in Surveying needs to be carried out at No - To be confirmed at DJ depth. detaileddesign stage to provide better detailed design stage. information. 35 Discount rate has been assumed at 10% for all financial Conservative figure based on alternative case Yes DJ analysis. studies. 36 Increase in interest has been assumed at 10% for all Conservative figure based on alternative case Yes JJ future costings. studies.
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Item Assumption/Issue Basis Closed Out Assumed By 37 Volume of Aerofoil is comparable to an ellipse. Aerofoils can vary significantly in shape and No - To be confirmed at BC require complex integration to find volume. detailed design stage. Early Aerofoils were based on ellipses so this could be a reasonable starting point. 38 Mogden discharges will not coincide with weir Comparing Thames Water's data for storm Yes BC operation. surges shows much reduced discharges during summer months after upgrade in 2013. 39 Hogsmill STW recycled water would not affect water Langford scheme discharges recycled water into Yes BC quality of Thames. River Chelmer with no ill effect. 40 Water quality factors remain constant. Increased regulation and future projects should Yes BC ensure water quality of the Thames does not further deteriorate. 41 A convenient source of power will always be available It is relatively easy to transport power from one Yes LM where needed. location to the other, so even when it’s not readily available, it can always be sourced somewhere. 42 The sensors/transducers available can always be The basic principle of operation will not be Yes LM customised to our unique needs. disturbed anyhow, but other features of the particular sensor such as the length of the cable, etc. can be easily done to our specific needs. 43 The weight of the sluice gates will be light enough to be The design of the sluice gates is beyond the No - To be confirmed at LM lifted by an electromechanical motor. scope of this feasibility study but detailed design stage. electromechanical come in a large variety of power outputs and it should be possible to specify a suitable motor/combination of motors for any size.
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Item Assumption/Issue Basis Closed Out Assumed By 44 For the years beyond the future flows data at Kingston No data available for dates further into the Yes DJ the weir activation has been taken as the worst case for future. Weir is almost in constant use by this the data available up til 2098. point anyway. 45 Datum levels for the tunnel have not been obtained and a Establishing a relative datum is a suitable No - To be confirmed at IP relative datum level has been assumed with Teddington method of calculation for the tunnel levels detailed design stage. Weir inlet shaft being at 0m AD and the top surface of because these can be converted to OS datum at a the Queen Elizabeth II Reservoir – where the pump-out later date. shaft will be discharging – at 10m AD. 46 The geotechnical data used is assumed to be correct Historical records are the only available No - To be confirmed at IP based on historical boreholes. geotechnical data. Full ground investigations detailed design stage. would need to be conducted at detailed design stage to confirm. 22 Risk Register
Residual Risk Date Risk ID Author Hazard Identified Key Associated Risks Suggested Mitigation / Control Measures following Mitigation Added Owner (If Applicable) Optimum weir location is in Protected zones have many Move weir to outside buffer zone. protected buffer zone of Kew limits on construction and Thames 1 25/11/14 LM Gardens. alterations to flow. Permissions None Group will be far more difficult to obtain. Weir position is close to Residents may complain about Considerate construction scheme to be Main residential area. noise levels during construction implemented during construction and noise Contractor / 2 28/11/14 LM Low and operation. barriers to be constructed if required during Thames operation. Water Only one available borehole Limited geotechnical data BGS have sent full cross sectional data. Thames 3 24/11/14 LM None in area of construction. means accuracy of soil profile Group
125 | P a g e Chapter 2221 – RiskAssumptions Register Register Thames Group Tidal Water Resources
Residual Risk Date Risk ID Author Hazard Identified Key Associated Risks Suggested Mitigation / Control Measures following Mitigation Added Owner (If Applicable) is also limited.
Tunnel stability during Earth falls or collapse may Safe method of construction and monitoring Main 4 20/11/14 LM Low construction. occur. to be implemented. Contractor Use of plant and machinery Excessive noise and risk of Considerate construction scheme to be during construction. injury. implemented during construction and noise Main 5 20/11/14 LM barriers to be constructed if required during Low Contractor operation. Safe method of construction to be implemented. Settlement of surrounding Damage to property and Detailed design to calculate settlement values properties and infrastructure infrastructure. within acceptable levels. Careful monitoring Detailed during tunnel construction. during construction and for a specified period Designer / 6 25/11/14 LM Low after completion and mitigation measures Main such as injection of expanding foam if Contractor settlement does occur. Tunnel clash with existing Damage to property and Full services survey to be conducted prior to Detailed 7 21/11/14 LM None services or basements. infrastructure. construction. Alignment altered if required. Designer Construction in estuarine Tides may limit construction Account for limited construction time in conditions. time available each day. Tide project program. Monitor stability during Main 8 24/11/14 HP Medium could cause scour during construction. Contractor construction causing instability. Vegetation clearance on Destabilisation of banks or Full stability assessment to be conducted and Detailed banks of Thames. destruction of habitats. appropriate construction methods to be used. Designer / 9 24/11/14 HP Ecological survey to be conducted prior to Low Main construction and any species that require Contractor movement to be moved.
126 | P a g e Chapter 22 – Risk Register Thames Group Tidal Water Resources
Residual Risk Date Risk ID Author Hazard Identified Key Associated Risks Suggested Mitigation / Control Measures following Mitigation Added Owner (If Applicable) Danger to ecological life in Death of ecological life or Fish pass to be included in design. Fish the River - particularly fish disruption to migratory routes. screens on all moving elements. Thames 10 24/11/14 HP and invertebrates that use it None for feeding/ passage/ Group breeding. Construction adjacent to Traffic disruption (road Traffic management systems to be existing road. closures or material deliveries). implemented to minimise disruption to traffic. Main 11 24/11/14 HP Low Material deliveries to be taken via the river Contractor wherever possible. Adverse weather conditions. Works in river particularly at Weather conditions to be monitored and site risk as if flood condtitions evacuated and works stopped if dangerous occur collapse of coffer dam or conditions occur. Main 12 24/11/14 HP Medium temporary structures could Contractor occur. Risk to site workers and bank stability. Water borne diseases (Weil's Work in water environment Adopt cleanliness procedures for workers on LM & disease, Leptospirosis) means workers at risk of site. Main 13 24/11/14 Low HP contracting water borne Contractor diseases. Weir design based on current Design does not include for Design to include consideration for Thames tide data (averages). extreme events. procedures to be followed in an extreme Group / 14 24/11/14 HP Low event. Thames Water Risk of flooding. Weir water storage can lead to Control system to include system for increased flood risk upstream monitoring level of water behind weir and Thames 15 24/11/14 HP Low of weir. lowering at quicker rate if flood risk becomes Group a possibility.
127 | P a g e Chapter 22 – Risk Register Thames Group Tidal Water Resources
Residual Risk Date Risk ID Author Hazard Identified Key Associated Risks Suggested Mitigation / Control Measures following Mitigation Added Owner (If Applicable) Risk of scour around new Could cause destabilisation of Scour protection to be included in structure Thames 16 24/11/14 HP weir. the structure and bank and bed design. To include methods of reducing Medium Group erosion. velocity of flow and protecting impact zones. Chemical changes caused by Disrupt aquatic life and Full chemical assessment to be conducted in Thames removal of freshwater from habitats. May encourage detailed design stage to ensure adverse effects Group / 17 24/11/14 BC Medium estuary. encroachment of invasive are minimised. Detailed species. Designer Failure of automated control Weir movement would be Design to include warning systems and Thames systems. stopped and could cause manual override failsafe. Group / 18 24/11/14 HP Low flooding or navigational Thames restrictions. Water Deep water. Risk of drowning (construction Handrails to be provided at all accessible Thames 19 24/11/14 HP workers, maintenance workers edges. Life rings to be provided on site. Low Group and members of the public). Restriction to navigation. Navigation will be restricted by Design to consider how often navigation will the structure both during be restricted and consider provision of a lock Thames 20 24/11/14 HP construction and operation. if necessary. Program of works to be designed Low Group to enable navigation passage throughout scheme construction. Alterations to existing May be rejected as a proposal. Detailed design to fully assess impact of Teddington Weir. May affect salinity of water alterations required to Teddington Weir. downstream. May affect Outside scope of feasibility study to redesign Detailed 21 24/11/14 HP Medium passage of fish. May affect Teddington Weir. Designer oxygen content upstream. May affect navigation. Effect of proposed weir on Could cause increase in water Full assessment of maintained levels to be existing structures and weirs level or possibly cause some conducted for length of river and compared to Thames 22 24/11/14 HP Medium such as Richmond Weir and areas of river to be dry. existing heights. Group Kew Bridge.
128 | P a g e Chapter 22 – Risk Register Thames Group Tidal Water Resources
Residual Risk Date Risk ID Author Hazard Identified Key Associated Risks Suggested Mitigation / Control Measures following Mitigation Added Owner (If Applicable) Siltation of Kew Weir. Could inhibit movement of Regular maintenance to be conducted to keep Port of 23 10/01/15 BC weir and render the structure channel free of silt. Medium London useless. Authority River levels upstream of Reduce revenue from Ability to close Teddington Weir should Teddington Weir may fall hydropower system and mitigate this problem. Thames 24 14/01/15 DJ Low below 5m depth. reduced flows from abstraction Group tunnel. Mogden discharges may Water quality would be Unlikely to coincide because Mogden Thames 25 14/01/15 BC cause sewage backup behind impaired and ecological impact discharges occur in Winter and Kew Weir is Low Water Kew Weir. could be severe. mostly operated in Summer. May find hazardous or Risk to life. Full ground investigations to be conducted Main 26 14/01/15 JJ military material during prior to construction and suitable treatment Low Contractor excavation. methods in place if discovered. Hazardous chemicals Oxygen is stored at high Careful management of hazardous chemicals associated with oxygenation pressure and is highly including use by trained operators and Thames 27 14/01/15 BC process. flammable. Hydrogen peroxide suitable storage methods to be used. Low Water is toxic and at risk of explosion if exposed to heat. Water quality may be Ecological damage. Rigorous testing and appropriate upgrades to Thames 28 14/01/15 BC impaired by Hogsmill STW be implemented. Low Water re-use options. Effect of future flows on Structural damage and/or risk Detailed modelling of future flows and Detailed 29 15/01/15 IP abstraction tunnel and sluice of flooding. abstractions upstream of Teddington Weir is Low Designer gate. required and design refined.
129 | P a g e Chapter 22 – Risk Register Thames Group Tidal Water Resources 23 References AECOM, 2014. The Mathematics of Pumping, London: Royal Academy of Engineering.
Anaheim Automation, 2011. Anaheim Automation. [Online] Available at: https://www.anaheimautomation.com/manuals/forms/images/Configuration%20with%20magnet. png
Angelakis, A. et al., 2007. Three Valleys Water Witness Session: Further Information 1. s.l., EUREAU EU 1/2 RECYCLING & REUSE WORKING GROUP.
Anon., 2015. Low Cost Easy to Use Spreadsheets for Engineering Calculations. [Online] Available at: http://www.engineeringexcelspreadsheets.com/wp-content/uploads/2011/05/sharp- crested-weir-parameters.jpg
BabyHydro, 2012. Kinnaird Weir: Preliminary Construction Method Statement, Dunfermline: BabyHydro Ltd..
Barford, V. & Everitt, L., 2012. Eight Radical Solutions for the Water Shortage. [Online] Available at: http://www.bbc.co.uk/news/magazine-17600062 [Accessed 17 October 2014].
Barr, D. I. H., 2006. Tables for the Hydraulic Design of Pipes, Sewers and Channels.. 8th ed. ed. Wallingford: Thomas Telford Ltd. .
Barrett, Byrd Associates, 2013. Steel Construction Cost - TATA Steel and BCSA. s.l.:s.n.
Baylar, A. & Bagatur, T., 1999. Study of Aeration Efficiency at Weirs, s.l.: Tubitak .
Baylar, A. & Bagatur, T., 2000. Study of Aeration Efficiency at Weirs. Turkish Journal of Engineering and Environmental Sciences, Volume 24, pp. 255-264.
BBC News, 2006. Reservoir 'biggest in 25 years'. [Online] Available at: http://news.bbc.co.uk/1/hi/england/5343646.stm [Accessed 18 October 2014].
Berman, B., Almanac Web site. Spring Tides and Neap Tides: almanac. [Online] Available at: http://www.almanac.com/content/spring-tides-neap-tides [Accessed 19 October 2014].
Bowen, A. J., 1972. The Tidal Regime of the River Thames; Long-Term Trends and their Possible Causes. Phil. Trans. R. Soc., 272(272), pp. 287 - 199.
British Geological Society, 2014. Geology of Britain Viewer. [Online] Available at: http://mapapps.bgs.ac.uk/geologyofbritain/home.html [Accessed 22 October 2014].
British Tunnelling Society, 2010. Infrastructure UK - Cost Study Tunnels., s.l.: British Tunnelling Society.
130 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Budenholzer, 2014. Turbine: Encyclopaedia Brittannica. [Online] Available at: http://www.britannica.com/EBchecked/topic/609552/turbine [Accessed 16 October 2014].
Butler, D., 2009. A Low Carbon Water Industry by 2050?. A Low Carbon Water Industry in 2050., Bristol: Environment Agency.
C.S.C Ltd, 2014. Hydraulic Cylinder Manufacture. [Online] Available at: http://www.cylinder.co.uk [Accessed 9 January 2015].
California Polytechnic State University, 2000. Actuators for Sluice Gates, California: California Polytechnic State University.
Carr, F. & Tovey, D., 2014. Tidal Energy Resources, s.l.: University of East Anglia.
Cascade Consulting, 2012. Lower Thames Abstraction Investigation Stage 2. s.l., s.n.
Cascade Consulting, 2013. Lower Thames Operating Agreement:Stage 2 - Completion of AMP5 Investigations, s.l.: Thames Water.
Centre for Ecology and Hydrology, 1983. Flow Gauging on the River Thames - The First 100 Years, Wallingford: Centre for Ecology and Hydrology.
Centre for Ecology and Hydrology, 2013. NRFA Public Dataset - Thames at Kingston. s.l.:s.n.
Chanson, H., 1995. Predicting Oxygen Content of Downstream of Weirs, Spillways and Waterways, London: Proc. Instn Civ. Engrs Wat. Marit & Energy.
CIRIA, 2010. Culvert Design and Operation Guide. CIRIA C689, London: CIRIA.
City of Westminster, 2007. Chapter 11: City of Westminster Unitary Development Plan. [Online] Available at: http://transact.westminster.gov.uk/docstores/publications_store/planning/udp/UDP_Chapter_11_ River_Thames.pdf [Accessed 14 October 2014].
Civil Engineering Portal, 2015. Civil Engineering Portal. [Online] Available at: http://www.engineeringcivil.com/weirs.html
Cobb, F., 2011. Structural Engineer's Pocket Book. Second ed. Abingdon: Routledge.
Construction Industry Training Board, 2014. E: Enviroment:Construction site safety. 3rd ed. Norfolk: CITB.
Crawford-Brown, D., 2009. Rapid Decarbonisation of the Water Industry for a Sustainable U.K.Rapid Decarbonisation of the Water Industry for a Sustainable U.K.. A Low Carbon Water Industry in 2050. , Bristol: Environment Agency .
Day, M., 2011. The Turning of the Tide - Richmond Lock. [Online] Available at: http://www.stmgrts.org.uk/archives/2011/05/the_turning_of_the_tide_richmond_lock.html
131 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Department for Environment Food and Rural Affairs, 2008. Future Water, London: DEFRA.
Department of Environment Food and Rural Affairs , 2014. River Basin Planning Standards: Legislation. [Online] Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/307788/river- basin-planning-standards.pdf [Accessed 13 October 2014].
Discenzo, F. M., Chung, D. & Zevchek, J. K., 2003. United States of America, Patent No. US6663349 B1.
Duramax Marine, 2015. Water Seal Systems. [Online] Available at: http://www.duramaxmarine.com/shaft-stuffing.htm [Accessed 7 January 2015].
Ebner, P., Glenn, J. & Jenkins, L., 2014. Tidal Energy. Engineering Tomorrow.
Enerpac, 2014. RR-Series Double-Acting Cylinders: Enerpac. [Online] Available at: http://www.enerpac.com [Accessed 9 January 2015].
Enerpac, 2014. SFP-Series 700 bar Split Flow Hydraulic Pumps: Enerpac. [Online] Available at: www.enerpac.com [Accessed 9 January 2015].
Environment Agency and Thames Water, 2013. LTOA Description and Operation. [Online] Available at: http://www.thames21.org.uk/wp-content/uploads/2013/08/LTOA-Description-and- Operation.pdf [Accessed 14 October 2014].
Environment Agency and Thames Water, 2013. LTOA Description and Operation. [Online] Available at: http://www.thames21.org.uk/wp-content/uploads/2013/08/LTOA-Description-and- Operation.pdf [Accessed 14 October 2014].
Environment Agency, 1975. Reservoirs Act 1975: Legislation. [Online] Available at: http://www.legislation.gov.uk/ukpga/1975/23/pdfs/ukpga_19750023_en.pdf [Accessed 13 October 2014].
Environment Agency, 2008. Science Report – Greenhouse gas emissions of water supply and demand management options. , Bristol: Environment Agency.
Environment Agency, 2010. Fish Passes in River Systems: Environment Agency. [Online] Available at: http://evidence.environment- agency.gov.uk/FCERM/en/SC060065/MeasuresList/M4/M4T1.aspx [Accessed 17 October 2014].
Environment Agency, 2014. Fish Pass Approval: Environment Agency. [Online] Available at: https://www.gov.uk/fish-pass-approval [Accessed 13 October 2014].
132 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Environment Agency, 2014. Hydropower Schemes:Guidlines and Applying for Permission: Environment Agency. [Online] Available at: https://www.gov.uk/government/collections/hydropower-schemes-guidelines-and- applying-for-permission [Accessed 13 October 2014].
Environment Agency, 2014. Reservoirs: A Guide for Owners and Operators: Environment Agency. [Online] Available at: https://www.gov.uk/reservoirs-a-guide-for-owners-and-operators [Accessed 13 October 2014].
Environment Agency, 2014. Waste Support: EWC Codes. [Online] Available at: http://wastesupport.co.uk/ewc-codes/ [Accessed 14 10 2014].
Environment Agency, 2014. Water Management: Abstract or Impound Water: Environmental Agency. [Online] Available at: https://www.gov.uk/water-management-abstract-or-impound-water [Accessed 13 October 2014].
European Commision, 2012. Directive of the European Parliament and of the Council, Brussels: European Commission.
European Union Committee, 2012. An Indispensable Resource: EU Freshwater Policy, s.l.: The House of Lords.
Fondriest Environmental, Inc, 2013. Dissolved Oxygen: Fundamentals of Environmental Measurements. [Online] Available at: http://www.fondriest.com/environmental-measurements/parameters/water- quality/dissolved-oxygen/ [Accessed 17 October 2014].
Foreshore Recording and Observation Group, 2014. Home: FROG Blog. [Online] Available at: http://www.thamesdiscovery.org/frog-blog/ [Accessed 14 October 2014].
Foundry Trade Journal International , 2014. Metal Prices. [Online] Available at: http://www.foundrytradejournal.com/metal-prices.asp [Accessed 08 01 2015].
Franklin, G. F., Abbas, E.-N. & Powell, D. J., 2010. Feedback Control of Dynamic Systems. New Jersey: Pearson.
GARD, 2014. Abingdon Reservoir Specifications. [Online] Available at: http://www.abingdonreservoir.org.uk [Accessed 15 January 2015].
GHD, 2007. Final Report for Tuckombil Canal Management - Structure Review of Gate Alternatives, Richmond : Richmond River County Council.
133 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Gibbs, K., 2013. Consumer Council for Water. [Online] Available at: http://www.ccwater.org.uk/waterissues/currentkeywaterissues/drought/ [Accessed 08 01 2015].
Global Water, 2015. Global Water. [Online] Available at: http://www.globalw.com/products/levelsensor.html [Accessed 14 January 2015].
Greenbug Energy Inc, 2014. About Micro Hydro: Greenbug Energy Inc. [Online] Available at: http://www.greenbugenergy.com [Accessed 12 December 2014].
Guy, A., 2013. Introduction: Thames21. [Online] Available at: http://www.thames21.org.uk/wp-content/uploads/2013/09/WFD-introduction.pdf [Accessed 13 October 2014].
Halcrow , 2014. Hammersmith Flyunder Tunnel Feasibility Study - Tunnel and Geotechnical Engineering. , London: s.n.
Halver, J., 1972. Fish Nutrition. London: Academic Press.
HC Watercontrol, n.d. Tilting Weirs. [Online] Available at: http://hcwatercontrol.webplace4u.nl/HCwaterbeheersing/Tilting%20Gate/Beamless%20Tilting%2 0Gate,%20HCKS-BL%207100%20x%201600%20x%20200mm.JPG [Accessed 08 01 2015].
Helm, D., 2009. A Low Carbon Water Industry in 2050. , Bristol: Environment Agency.
House of Lords : Science and Technology Committee , 2006. Water Management, London: House of Lords.
HR Wallingford, 2014. Teddington hydropower scheme Planning application September 2014, London: HR Wallingford.
HSE, 2007. Construction (Design and Management) Regulations 2007, s.l.: HSE Books.
Hutton, R., 2012. Damage to fish by hydroturbines: A new fish friendly approach using the Archimedes screw, s.l.: New England Hydropower Company .
IEA, 2010. Hydropower: Energy Technology Systems Analysis Programme. [Online] Available at: http://www.iea-etsap.org/web/e-techds/pdf/e07-hydropower-gs-gct.pdf [Accessed 2 January 2015].
INTECH open science, n.d. INTECH open science. [Online] Available at: http://www.intechopen.com/source/html/44514/media/image4_w.jpg [Accessed 14 January 2015].
Jewell, P. & Bellhouse, M., 2014. Engineering the Lee Tunnel and Shafts through Chalk at Depth.. s.l., s.n.
134 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Joyce Dayton, 2013. Joyce Dayton. [Online] Available at: http://joycedayton.com/products/multipurpose-actuators/multipurpose-actuators- 120-vac-lift-3500n
Keller, V. D. J., Lloyd, P. & Williams, R. J., 2013. Impact of Climate Change on a Risk Assessment for Intersex in Fish Due to Steriod Estrogens. s.l., Unpublished.
Kemker, C., 2013. “Dissolved Oxygen.” Fundamentals of Environmental Measurements.. [Online] Available at: http://www.fondriest.com/environmental-measurements/parameters/water- quality/dissolved-oxygen/
Keremane, G. B. & McKay, J., 2006. Successful wastewater reuse scheme and sustainable. Water and Environment Journal, Volume 21, pp. 83-91.
Kipling, R., 1911. The River's Tale. s.l.:s.n.
Lakso, E., 1988. Aeration at Overflow Weirs. Publications of the Water and Environment Institute.
Lancaster University , 2014. Hydro Resource Evaluation Tool: Engineering Options. [Online] Available at: http://www.engineering.lancs.ac.uk/lureg/nwhrm/engineering/turbine_costs.php [Accessed 3 January 2015].
Langdon, D., 2007. Spon's Civil Engineering and Highway Works Price Book 2008. s.l.:s.n.
Lbassoc.co.uk, 2014. London Bridge Associates - Delivering Value Across the Construction Cycle., London: Lbassoc.co.uk.
Lewin, J., 1995. Hydraulic gates and valves.. London: Thomas Telford Ltd. .
Lovat, R., n.d. TBM Design Considerations: Selection of Earth Pressure Balance or Slurry Pressure Balance Tunnel Boring Machines.., s.l.: s.n.
Marine Management Organisation, 2014. Do I need a marine licence: Marine Management Organisation. [Online] Available at: https://www.gov.uk/apply-to-construct-on-remove-from-and-dispose-to-the-seabed [Accessed 16 October 2014].
Mays, L. W., 2001. Water Resources Engineering. New York: John Wiley & Sons.
Nasir, B. N., 2013. Design of High Efficiency Cross-Flow Turbine for Hydro-power Plant, Izmir: International Journal of Engineering and Advanced Technology .
National Geographic, 2014. Tidal Education: Education. [Online] Available at: http://education.nationalgeographic.co.uk/education/encyclopedia/tidal- energy/?ar_a=1 [Accessed 17 October 2014].
National Oceanic and Atmospheric Administration, 2008. What Affects Tides in Addition to the Sun and Moon?: Tides and Water Levels. [Online]
135 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Available at: http://oceanservice.noaa.gov/education/kits/tides/tides08_othereffects.html [Accessed 19 October 2014].
National Research Council, 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press.
Nemati, K., 2007. Temporary Structures: Cofferdams, Washington: University of Washington.
Nivus, n.d. [Online] Available at: https://www.nivus.com/applications/wastewater-treatment-plant/intake-area/level- measurement-in-grease-trap
Oates, R. & Yorke, W., 2012. Facts and Figures. [Online] Available at: http://thamesriverstrust.org.uk/facts-and-figures/?full-site=true [Accessed 18 October 2014].
Office of Energy Efficiency and Renewable Energy, 2014. Home: Office of Energy Efficiency and Renewable Energy. [Online] Available at: http://energy.gov/eere/water/types-hydropower-turbines [Accessed 16 October 2014].
Office of Energy Efficiency and Renewable Energy, 2014. Types of Hydropower Plant: Energy. [Online] Available at: http://energy.gov/eere/water/types-hydropower-plants [Accessed 11 Desember 2014].
Ofwat , 2011. Summary of Performance 2010-11: Ofwat. [Online] Available at: http://www.ofwat.gov.uk/regulating/prs_web201110perf_summ [Accessed 23 October 2014].
Ofwat, 2010. Playing our part – reducing greenhouse gas emissions in the water and sewerage sectors., s.l.: Ofwat.
Parker, P. & Moreno, M., 2009. A Feasibilty Study Into The Use Of An Archimedes Screw At Teddington Weir, London: Thames Renewables.
Pennington, M., 1998. Hydraulic roughness of bored tunnels., s.l.: s.n.
Port of London Authority, 2010. Hydrographic Surveys: 301-314. s.l.:Port of London Authority.
Port of London Authority, 2014. About us: Richmond Lock and Weir. [Online] Available at: http://www.pla.co.uk/About-Us/Richmond-Lock-and-Weir [Accessed 24 October 2014].
Port of London Authority, 2014. Home: Port of London Authority. [Online] Available at: http://www.pla.co.uk/ [Accessed 13 October 2014].
Port of London Authority, 2014. Legislation: Port of London Authority. [Online] Available at: http://www.pla.co.uk/Environment/Legislation [Accessed 13 October 2014].
136 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Port of London Authority, 2014. x, y, z data for hydrographic surveys. s.l.:Not Published .
Prandle, D., 1975. Storm Surges in the Southern North Sea and River Thames. Proc. Royal Soc. Lond. A, 344(1639), pp. 509-539.
Prudhomme, C. et al., 2012. Future Flows and Groundwater Levels - Products and Datasets, Wallingford: Centre for Ecology and Hydrology.
Renewables First, 2014. Archimedian Screw: Hydropower. [Online] Available at: http://www.renewablesfirst.co.uk/hydro-learning-centre/archimedean-screw/ [Accessed 13 December 2014].
Renewables First, 2014. Kaplan Turbines: Hydropower. [Online] Available at: http://www.renewablesfirst.co.uk/hydro-learning-centre/kaplan-turbines/ [Accessed 10 December 2014].
River Thames Society, 2014. About Us: River Thames Society. [Online] Available at: http://www.riverthamessociety.org.uk/about.aspx [Accessed 13 October 2014].
Schneider Electric, 2012. SCADA Systems. [Online] Available at: http://www.schneider- electric.com/solutions/ww/en/med/20340568/application/pdf/1485_se-whitepaper-letter- scadaoverview-v005.pdf
Sensitec, 2009. Sensitec. [Online] Available at: http://www.sensitec.com/upload/SENSITEC/PDF_Downloads/Informationsmaterial/4Seiter_AA7 00.pdf
SimHQ, 2002. Secondary Flight Controls – Flaps. [Online] Available at: http://www.simhq.com/_air/air_002b.html
Sornes, K., 2010. Small-scale Water Current Turbines, Oslo: Zero Emission Resource Organisation .
Staddon, C., 2012. Do Water Meters Reduce Domestic Consumption?, Bristol: University of West England.
Sulzer Centrifugal Pumps, 1998. Sulzer Centrifugal Pump Handbook. Guildford: Elsevier Advanced Technology.
Thames 21, 2013. LTOA Description and Operation. [Online] Available at: http://www.thames21.org.uk/wp-content/uploads/2013/08/LTOA-Description-and- Operation.pdf [Accessed 14 October 2014].
Thames Anglers' Conservancy , 2014. Home: Thames Anglers' Conservancy. [Online] Available at: http://www.rivertac.org/ [Accessed 13 October 2014].
137 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
Thames Anglers' Conservancy, 2010. 10 Questions for Thames Water - The Answers. [Online] Available at: http://www.rivertac.org/2010/09/10-questions-for-thames-water-the-answers/ [Accessed 14 October 2014].
Thames Group, 2014. Inception Report - Tidal Recharge , Guildford: s.n.
Thames Tideway Tunnel (2), 2014. The Project. [Online] Available at: http://www.thamestidewaytunnel.co.uk/the-project [Accessed 16 October 2014].
Thames Water, 2012. Keeping London on Tap. [Online] Available at: http://www.thameswater.co.uk/media/10888.htm [Accessed 16 October 2014].
Thames Water, 2012. Water Resources Management Plan - Volume 3 - Appendix F, s.l.: Thames Water.
Thames Water, 2013. Sewage Works Upgrades: Mogden Sewage Treatment Works. [Online] Available at: http://www.thameswater.co.uk/about-us/10096.htm
Thames Water, 2014. Final Water Resources Management Plan 2015-2040 - Section 3: Current and Future Demand for Water, s.l.: s.n.
Thames Water, 2014. Final Water Resources Management Plan 2015-2040 - Section 3: Current and Future Demand for Water, s.l.: s.n.
Thames Water, 2014. Final Water Resources Management Plan 2015-2040 - Section 3: Current and Future Water Demand for Water, s.l.: s.n.
Thames Water, 2014. Final Water Resoures Management Plan 2015-2040 - Section 3: Current and Future Demand for Water , London: Thames Water.
Thames Water, 2014. Our Long Term Strategy 2015-2040. [Online] Available at: http://www.thameswater.co.uk/tw/common/downloads/about%20us%20- %20corporate%20responsibility/About-us-Our-long-term-strategy-2015-2040.pdf [Accessed 20 October 2014].
Thames Water, 2014. Water Resource Management Plan 2015-2040. [Online] Available at: http://www.thameswater.co.uk/tw/common/downloads/wrmp/WRMP14_Section_0.pdf [Accessed 20 October 2014].
The Environment Trust, 1994. How and Why the Half-Tide Lock and Weir Were Built. A New River at Richmond , pp. 1-4.
The European Parliament and the Council of the European Union, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework of Community action in the field of water policy. Official Journal of the European Communities.
Turnpenny Horsfield Associates, 2013. Sluice Gate Calculator. [Online] Available at: http://thaaquatic.info/fig9.png
138 | P a g e Chapter 23 – References Thames Group Tidal Water Resources
UK Power, 2014. Gas and electricity tarrif prices per kWh. [Online] Available at: http://www.ukpower.co.uk/home_energy/tariffs-per-unit-kwh [Accessed 6 January 2015].
UK Technical Advisory Group, 2008. Media: Water Framework Directive United Kingdom. [Online] Available at: http://www.wfduk.org/sites/default/files/Media/Environmental%20standards/Environmental%20s tandards%20phase%201_Finalv2_010408.pdf [Accessed 13 October 2014].
UNESCO, 2002. Map 1.2: Kew Gardens - The Site Boundary and Buffer Zone Map, London: s.n.
Union of Concerned Scientists , 2014. Environmental effects of Hydropower: Union of Concerned Scientists. [Online] Available at: http://www.ucsusa.org/clean_energy/our-energy-choices/renewable- energy/environmental-impacts-hydroelectric-power.html#.VEDxL_ldVqU [Accessed 17 October 2014].
Visit Thames, 2014. Teddington Lock on the River Thames. [Online] Available at: http://www.visitthames.co.uk/about-the-river/river-thames-locks/teddington-lock [Accessed 18 October 2014].
Waterfront Fluid Controls Ltd. , 2014. Tilting Weir , s.l.: Waterfront Fluid Controls Ltd. .
Wild Trout Trust , 2014. Weirs, dams and other river structures: Their effects on wild brown trout: WTT. [Online] Available at: http://www.wildtrout.org/sites/default/files/library/Obstructions%20information%20paper%2020 082013.pdf [Accessed 17 October 2014].
World Commision on Evironment and Development , 1987. Our Common Future, Oxford: Oxford University Press.
World Wildlife Fund, 2008. Thames Basin Vulnerability Report: Technical Summary, London: World Wildlife Fund.
139 | P a g e Chapter 23 – References Thames Group Tidal Water Resources 24 Appendices • 24.1 Appendix A – GANTT Chart • 24.2 Appendix B – Borehole Logs (JJ) • 24.3 Appendix C – Tunnel, Sluice Gate & Carbon Assessment Calculations (IP) • 24.4 Appendix D – Site Visit Photographs (HP) • 24.5 Appendix E – Superstructure and Substructure Quantities Calculations (JJ) • 24.6 Appendix F – Weir Gate Structural and Geometric Calculations (HP) • 24.7 Appendix G – Drawings
140 | P a g e Chapter 24 – Appendices Thames Group Tidal Water Resources
24.1 Appendix A – GANTT Chart
Thames Group Tidal Water Resources
24.2 Appendix B - Borehole Logs (JJ)
Thames Group Tidal Water Resources
24.3 Appendix C – Tunnel, Sluice Gate & Carbon Assessment Calculations (IP)
Thames Group Tidal Water Resources
24.4 Appendix D – Site Visit Photographs (HP)
Figure 14.1 - Kew pier
Figure 14.2 - Span of river to be sectioned by the proposed Kew Weir
Thames Group Tidal Water Resources
Figure 14.3 - Outlet into the River Thames (unknown source or effluent type)
Figure 14.4 - Mooring structure in the middle of the Thames immediately adjacent to proposed Kew Weir location
Thames Group Tidal Water Resources
Figure 14.5 - Playground on the South bank of the Thames at Kew Weir location
Figure 14.6 - North bank of the Thames at Kew Weir location (residential street visible just beyond)
Thames Group Tidal Water Resources
Figure 14.7 - South bank of Thames at Kew Weir location - scour protection badly degraded.
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24.5 Appendix E – Superstructure and Substructure Quantities Calculations (JJ)
Thames Group Tidal Water Resources
24.6 Appendix F – Weir Gate Structural and Geometric Calculations (HP)
Thames Group Tidal Water Resources
24.7 Appendix G - Drawings (HP, JJ, IP) Drawing Register Drawing Series Series Title Drawing Title Drawn By Number 000's 001 Option 1 - Sheet 1 HP General 002 Option 1 - Sheet 2 HP Arrangement 100's 101 Options 2 & 3 - Sheet 1 HP Plans 102 Options 2 & 3 - Sheet 2 HP
200's 201 Weir Layout - Option 1a HP Weir Layout 202 Weir Layout - Option 1b HP
203 Weir Layout - Option 1c HP
210's 211 Weir Details - Option 1a HP Weir Details 212 Weir Details - Option 1b JJ
213 Weir Details - Option 1c JJ
300's 301 Section Locations HP 302 Sections AA, BB & CC HP
303 Sections DD, EE & FF HP River Sections 304 Sections GG, HH & II HP
305 Sections JJ, KK & LL HP
306 Sections MM & NN HP
Tunnel & Sluice 400's 401 Schematic of Tunnel IP Gate Drawings
Drawings