Counters Creek Flood Alleviation Scheme

Transcription

1 Counters Creek Flood Alleviation Scheme Emerging Route Options Report C680-MMT RP Thames Water

2 Contents Chapter Title Page Executive Summary i 1 Introduction 2 2 Design Investigations Review of hydraulic model and constraints Identification of project constraints Investigation of underground alignment constraints over the site search area 5 3 Pumping Station Locations Lots Road Hammersmith 6 4 Alignment Options Alignment general Lots Road area options Hammersmith options Sewer connections Conclusion on alignment options investigated 30 5 Further Assessment of Options Lots Road area options Hammersmith options Conclusion of further assessment 34 6 Review and Redefinition of Route Corridor Vertical alignment level change Site selection zones 36 7 Emerging Preferred Option Site Suitability Reports outputs L6 Alignment Development of L6 alignment 39 8 Conclusion 41 Appendices 42 A. Original Thames Water Alignment 43 B. Pumping Stations 45

3 B.1 Lots Road alternative concept 46 C. Lots Road Alignment Options 48 C.1 L1 Baseline alignment plan and profile 48 C.2 L2 modified baseline plan and profile Lots Road to Mund Street 50 C.3 L4 Lots Road, Gwendwr Gardens, Brook Green 52 D. Hammersmith Alignment Options 54 D.1 H1 West Alignment 54 D.2 H2 East Alignment 56 D.3 H4a Gwendwr Gardens 58 E. Refined Site Selection Zone 60 F. L6 Alignment 62

4 Executive Summary This report has developed the Counters Creek Tunnel alignment design to the level of a feasible preferred alignment, using the base concept (alignment L1) as and shown in Appendix A. The baseline tunnel alignment was developed prior to this report as a high level assessment, connecting the hydraulic interception points on plan. The base tunnel alignment has therefore been evaluated in this report with three different vertical profiles assumed. This report highlights the conflicts which prevent this alignment being accepted, and describes the development of an alternative preferred alignment option. The study undertaken has been ongoing with refinement of the hydraulic modelling and identification of project constraints. From this, alignments have been developed that reach pumping stations at both Lots Road and Hammersmith; in or adjacent to the existing outfalls and Thames Water (TW) facilities. The option of using a pumping station at Hammersmith has been excluded due to significant constraints from existing assets and the requirement for two pumping stations with this option. Therefore, a feasible alignment has been found to the Lots Road pumping station at Cremorne Wharf. This alignment (L4) has then been further refined: in line with the preferred sites resulting from the Site Suitability Reports; for vertical clearance to subsurface infrastructure; and to mitigate against identified impacts. The currently preferred alignment option (L6) to be carried forward for further consultation has been developed from this analysis with a pumping station at Cremorne Wharf. i

5 1 Introduction The objective of the Counters Creek Flood Alleviation Strategic Sewer and associated upgrade works is to alleviate basement flooding from approximately 1,700 properties within the London Borough of Hammersmith and Fulham and the Royal Borough of Kensington and Chelsea. This report outlines the alignment options development and assessment for the Counters Creek Project. At this stage the alignment route has been developed by engineering criteria, with mitigation against planning and environmental considerations input through the site selection process, to develop the preferred alignment option. The following process (Figure 1.1) was adopted in order to explore and develop the route options. Figure 1.1: Process for developing route options Design Investigations Route Alignment Options Site Selection Review the hydraulic model and explore hydraulic constraints. Baseline concept for route alignment (L1) Site Selection- Longlist of Sites Identify project constraints (levels, potential TTT interface, interception points) Investigate underground alignment constraints over the site search area (including underground utilities and piled foundations) Emerging Route Options Report Route options development and assessment Site Selection- Shortlist of Sites Review and redefine route corridor from stages 2a and 2b based on above investigations Preferred alignment option Site Suitability Reports Preferred Option and Sites Report 2

6 2 Design Investigations 2.1 Review of hydraulic model and constraints The hydraulic model was built by Thames Water and verified by flow monitoring and site surveys at stage 1 defined in the Site Selection Methodology Report. The hydraulic model was used to identify the following interception points (the identification of the interception points is further explained in the Site Selection Report Stage 2a -Long List of Sites): Hammersmith Storm Relief Sewer Brook Green Branch: The interception near Shepherds Bush Green. Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch: The interception near Swanscombe Road. Counters Creek Sewer: The interception Holland Gardens /Upper Addison Gardens North End Sewer: The interception near Mund Street. Walham Green Storm Relief Sewer and Low Level 1 Sewer: The interception along Lots Road To re-confirm that the interceptions were located in optimised positions, they were repositioned along the existing sewer system to see the effect on the number of flooding protection outputs. It was found that the number of flooding outputs reduced when the interception points were moved to another location. This supported the earlier stage 1 assessment that the specified interceptions had been positioned to give the largest number of properties being protected against flooding. Reconfiguration of interception points to avoid major disruptions In order to avoid impact on major above and below ground structures (for example Thames Water Ring Main, Circle Line and Westfield Shopping Centre) in the north of the catchment, the interception location in Swanscombe Road was moved south along the Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch, geographically below Holland Park Avenue. This resulted in a reduction in the number of properties to be protected against flooding due to other flows entering the sewer in Holland Road. To recover the number of flooding outputs, the North Kensington Storm Relief Sewer has to be intercepted at Upper Addison Gardens. This created a new (additional) interception point at Upper Addison Gardens Further investigation, revealed that the Holland Gardens interception could be picked up at its most upstream limit in Upper Addison Gardens. This provides the opportunity to intercept the North Kensington Storm Relief Sewer at the same location, thus removing the need for an additional interception point In summary: The Holland Gardens interception was moved to Upper Addison Gardens 3

7 The acceptable location for the Swanscombe Road interception was extended downstream as far south as the car park adjacent to Kensington Olympia. This mitigated impact on the underground assets mentioned above The limits of the interception on the Hammersmith Storm Relief Sewer Brook Green Branch southern parts of this limit (i.e. along Shepherds Bush Road down to Brook Green Common area) to avoid disruptions within the road at Therefore, the revised interception locations became: Hammersmith Storm Relief Sewer Brook Green Branch: The section from Shepherds Bush common, down Shepherds Bush Road to Brook Green. Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch: The section south of Holland Park Avenue to car park adjacent to Kensington Olympia. Counters Creek Sewer: At Upper Addison Gardens where the North Kensington Storm Relief Sewer is also to be intercepted. North End Sewer: The section near Mund Street. Walham Green Storm Relief Sewer and Low Level 1 Sewer: The sections along Lots Road. 2.2 Identification of project constraints The following constraints were identified. These are also further discussed in the Background Technical Report (C680-MMT RP): 1. The Counters Creek Scheme will potentially connect into and interact with the Thames Tideway Tunnel (TTT) and various options for the interface are being considered and the subject of on-going technical analysis. One of the interface arrangements under consideration is a gravity connection to the TTT. Therefore, a constraint has been implemented to ensure that the depth of the tunnel is kept to a level such that a gravity connection could be possible in the future. Going deeper would mean an additional pumped connection into the TTT would be required if the scheme was adapted to connect into the TTT, in the event that both schemes obtain consent. This would result in not only an increase in the project cost, but also energy and operational costs. 2. The tunnel length and diameter must be adequately large to provide approximately 50,000m 3 of storage. The flows must be stored and pumped into the existing sewer network to be passed forward for treatment following storm subsidence. In intense storms, when the storage capacity of the tunnel is exceeded, the excess flows are then pumped into the river in compliance with the existing discharge consent. Flows should be passed forward to treatment for most typical rainfalls and discharge into the river should only take place for intense storms. It is therefore critical to provide the required storage capacity. 4

8 This means that the shorter the tunnel becomes in length, the larger its diameter will have to be to retain the required storage volume. 3. The gradient of the tunnel should not where possible result in fast flows in excess of around 3 metres per second. High velocities can result in scour of tunnel lining The vertical alignment should be such that it will allow sufficient clearances between the tunnel and other underground tunnels at crossing points. The clearance ideally should be typically no less than twice the tunnel diameter in order to mitigate the risk of adverse stress impact on the tunnel being crossed. At this stage in the assessment it has been assumed that a minimum clearance of one diameter should be used between the proposed sewer and existing assets. See Section Investigation of underground alignment constraints over the site search area These constraints related to other underground tunnels and structures which could interface with the new sewer The main constraints were identified to be: UK Power Network Tunnel National Grid London Power Tunnel Thames Water Ring Main Thames Water Thames-Lee Valley Tunnel London Underground assets (Central line and Piccadilly Line) Proposed Crossrail The main surface structures which could potentially have piled foundations and affect the sewer were identified to be Westfield Shopping Centre, Stamford Brook Football Stadium and At this stage the route options were developed and assessed (Section 4) Following the route development the constraints were further refined (Section 5) 5

9 3 Pumping Station Locations Two locations for outfalls and pumping stations were considered: Lots Road (Cremorne Wharf) and Hammersmith. These locations were selected due to having existing Thames Water assets and outfall consents. Section 3 looks at these 2 alternatives in terms of the construction working sites and potential working conflicts. 3.2 Lots Road Lots Road Pumping Station is the location of the terminal pumping station for the baseline proposed new Counters Creek Sewer. Working site The working site available for the new Lots Road Pumping Station is restricted by the limits of the land for Cremorne Wharf. An alternative site to Cremorne Wharf is shown in Appendix B, but this was rejected due to its inadequate area and UKPN tunnel crossing the site Access to the site is constrained from Lots Road by narrow entrances restricted by the listed pumping station to one side and the property boundary to the other. One access is available to the northeast and one access is available to the southwest of the site The river wall and jetty may require strengthening in order to allow construction to take place on the site The land proposed as a working space at Cremorne Wharf is in the region of 3,470m 2. This is small for the scale of the works to be undertaken and programming of the works will need careful consideration to remove conflicts during construction. The use of this site as a drive site concurrently with pumping station construction may be a challenge. Conflicts This site is also identified for development of the proposed TTT drop structure. The functional solution to accommodate both schemes would need to be developed in a joint manner so as to best manage the use of the restricted area. 3.3 Hammersmith Working site Several options have been considered at high level for an assumed site location at Hammersmith (identified in Figure 3.1): Old Hammersmith Pumping Station, shaft constructed within car park. Old Pumping station demolished to provide site working area (1) Frank Banfield Park (North East of New Hammersmith Pumping station). (2) 6

10 Park/grass area to the South of Hammersmith Pumping Station / Fulham Reach site. (3) Figure 3.1: Hammersmith Pumping Station Options The site at Hammersmith is to provide a pumping station and outfall. With further investigation required to assess the potential option of developing a connection into the proposed Thames Tideway Tunnel (TTT) The proposed Hammersmith worksites are located close to the TTT Hammersmith Shaft Site transport access routes and local impacts will be shared by all sites, therefore close liaison is recommended between all three projects whilst progressing this site concept The required above ground structures for a pumping station on a selected site include a Motor Control Centre, a sub-station/electrical transformer compound for incoming electrical supplies, vent column, air extraction/intake structure and possible odour treatment plant plus road access to the pumping station covers for a mobile crane and maintenance. These are estimated to occupy an area of approximately 200m 2. Conflicts Construction of a shaft in the car park of the Old Hammersmith Pumping station is restricted due to the Hammersmith Storm Relief Sewer West Branch, which runs through the centre of 7

11 the site at approximately -7.4m AOD. This results in a maximum shaft construction area for a pumping station of approximately 30m long x 10m wide to the south of the SRS, as shown in Figure 3.2 Figure 3.2: Hammersmith Old Pumping Station Site Construction on the Frank Banfield site is also restricted by the Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch (-8 m AOD) and Mainline (-7.5 m AOD) connections, which run through the west of the park. Use of the Frank Banfield site would also require construction of an access road and permanent above ground structures for the operation of the pumping station and hence loss of a public amenity The park area to the South East of the Fulham Reach development could use river access to transport materials from site. However, road access to this site is constrained and requires access via private roads Both park area sites would require restoration works after construction. 8

12 4 Alignment Options 4.1 Alignment general This section on alignment options presents the development of a feasible alignment, which could be constructed to avoid all significant constraints, from the baseline design (L1). The options presented in this report have concentrated on the vertical alignment to mitigate impacts with the existing subsurface assets. At the next phase these alignments will need to be reviewed and the horizontal alignment refined to fully understand impacts The baseline design proposes a storm relief sewer, approximately 5.5km long, 3.6m in diameter and at a depth of approximately 30 to 36m (envisaged to be in London Clay). Initial appraisal carried out between 2009 and 2012 indicates potential discharge of the sewer into a new pumping station, provisionally located at Lots Road, Chelsea. Feasible alignments are presented which connect the identified hydraulic interception points and allow flow to be transmitted to pumping stations at both Lots Road (Cremorne Wharf) and Hammersmith It is noted that sites were selected across the catchment to enable analysis of potential alignment options at this early stage in the site selection process. However, the preferred alignment route and associated sites should be developed following the Site Suitability Report assessments to match the preferred sites identified. Interface with existing underground assets The baseline alignment trending south to north encounters significant existing subsurface infrastructure. The degree of potential impact has been quantified in Table 4.1 to allow comparison between alignments. This is a high level classification and is not fully binding. Variations to the category may be made with back up from engineering analysis and judgement. For example, a tunnel passing within 2 diameters above a non-pressurised water tunnel may, with the required engineering assessment be acceptable whereas crossing of a pressurised water tunnel with the same clearance may not be acceptable. Table 4.1: Clash Definition Categories Category Label Description Clearance Accept I Clearance is such that mitigation is not expected to be required. Accommodate II Engineering mitigation is required to manage impacts Avoid III Predicted impact is unacceptable. Greater than 2 diameters Less than 2 diameters Less than 1 diameter or direct conflict Within the tables of clearances in the alignment sections of this report, clearances between the proposed Counters Creek Sewer and the existing infrastructure is given for each alignment investigated. This is stated as tunnel clearance in metres and whether the 9

13 infrastructure that is crossed is above (A) or below (B) or directly conflicting (C) with the Counters Creek Sewer It is noted that a clearance of 1 x the diameter of the proposed sewer between existing and proposed underground assets is taken as a best practice minimum. At this stage the sewer alignment has been set using a minimum of 1x the diameter clearance to reduce the potential need for any mitigation measures on existing assets. Following ground investigations, and further asset information from the asset owners this criterion can be reviewed to obtain the optimum alignment. 4.2 Lots Road area options The baseline alignment (L1) starts at a proposed pumping station located on the Cremorne Wharf site between the existing Lots Road Pumping Station and the river wharf. It is noted that there are also planned works for the proposed Thames Tideway Tunnel Scheme on this site. Accommodation of the two projects will be required and this is a subject of ongoing discussion as the Counters Creek project develops. This is common for Lots Road options L1 to L The alignment for the baseline option (L1) is considered in detail as this is the concept which was proposed by Thames Water. This alignment has been modified to optimise the route and mitigate against constraints that are present, developing alignment L2. Development of the hydraulic design and the optimisation of the hydraulic interception zones i.e. the location of where sewer connections are made, has allowed further alignments to be studied, L3 to L4. These alignments are all constrained by existing underground infrastructure, notably the north south National Grid London Power Tunnel (LPT) and the east west trending: Thames Water Thames-Lee Valley tunnel and Thames Water Ring Main Alignment L4 is discussed in detail and is presented as a preferred alignment option as it best avoids the existing subsurface infrastructure. This alignment has been taken forwards for further development and detailed analysis in Section 7. 10

14 Alignment L1- Baseline option Figure 4.1: L1 Alignment Schematic Figure 4.1 shows a schematic of the baseline L1 alignment. The alignment profile is detailed in Appendix C.1. The L1 alignment has been interpreted from the original Thames Water Strategic Tunnel alignment presented in Appendix A. Plan Description The L1 alignment terminates at the proposed Lots Road Pumping Station (located adjacent to the existing pumping station) with a pumping station entry level of -31.1m AOD (invert level with nominal 4.0m ID tunnel). The tunnel is designed to lie at a higher level of -26.6m AOD at approximately 50m from the pumping station inlet, this gives a 1 in 10 gradient descending to the pumping station inlet. The purpose of this gradient is to ensure that the pumps are always submerged. Upstream, the tunnel vertical alignment rises at a constant gradient of 1:2000 for the length of the tunnel which is conceptually considered as a nominal 4.0m internal diameter The alignment heads west from Lots Road towards the London Overground rail lines, crossing beneath these. The alignment then turns north, following the rail lines to an intermediate tunnel shaft located on the Earls Court car park- shaft H. The tunnel continues north, to a drop shaft located at Mund Street shaft G, and then crosses the London Overground to Holland Gardens shaft A. Continuing north the tunnel connects to Swanscombe Road shaft B and then completes a 180 degree gradual curve to the west, turning from north, crossing the London Overground again, before terminating at Shepherds Bush Green- shaft C. 11

15 Vertical profile The existing predominantly east west tunnel infrastructure across the catchment belongs to both Thames Water and TfL; and north south tunnel infrastructure belongs to EDF energy and National Grid (tunnel under construction). Future infrastructure is planned and needs to be avoided such as the proposed Crossrail 2 alignment which is a safeguarded route The differing levels of the existing tunnel structures and the varying forms of construction, compromise the ability for the Counters Creek Sewer to follow the desired plan alignment. Key constraints The impacts to the L1 alignment with a tunnel invert level of -26.6m AOD are shown in Table 4.2. Table 4.2: L1 invert level -26.6m Infrastructure Clearance (m) Above / Below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Holland Park Pipetrack (Thames Water Ring Main) TW Low Level Sewer No. 2 Main line TW North Western Storm Relief Sewer Proposed Thames Water Ring Main TW Thames-Lee Valley Tunnel TW Ring Main (Barnes- Barrowhill) TW Walham Green Storm Relief Sewer Central line (2no. tunnels) 13.5 A I 13.5 A I 5.0 A II 21.0 A I 14.5 A I 1.5 A III 3.0 B III 0.0 C III 13.5 A I 13.5/12.0 A/A I/I Piccadilly Line 10.5 A I Proposed Crossrail 2 North Proposed Crossrail 2 South 0.0 C III 0.0 C III National Grid LPT 5.5/11.0/2.5 B/B/B II/I/III 12

16 Infrastructure Clearance (m) Above / Below Category UKPN Tunnel 0.0/0.0 C/C III/III The L1 alignment has direct and or significant impacts in seven locations. Of these, five locations are direct interfaces and the other two considered unacceptable due to the small clearances of the crossing. These interfaces and small clearances could result in substantial distress to the existing tunnels, unless significant engineering enhancement is undertaken on the existing assets in question. The Thames Water Thames- Lee Valley and Ring Main tunnels are significant both due to the proximity of the tunnel and the fact that the tunnels are formed of wedge-block linings and operate under internal water pressure The L1 alignment at elevation -26.6m AOD is not feasible due to direct interfaces with UKPN, Crossrail 2 and the TW Ring Main. L1 alternative profiles Given the conceptual design level of the Lots Road Pumping Station and the L1 tunnel invert level of -26.6m AOD, alternative profiles have been checked. These alternatives have used tunnel inlet levels to the proposed pumping station of -31.1m AOD and the deepest alignment that could gravitate into TTT -37.1m AOD (should a connection be designed at a later stage). These would require a change to the pumping station concept as the change in level over the first 50m from the pumping station to facilitate the pumps being surcharged is removed. This would need to be accommodated in any pumping station design. The conflicts are shown on Table 4.3 and Table 4.4 Table 4.3: L1 invert level maod Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Holland Park Pipetrack (Thames Water Ring Main) TW Low Level Sewer No. 2 Main line TW North Western Storm Relief Sewer Proposed Thames Water Ring Main TW Thames-Lee Valley Tunnel 18.5 A I 18.5 A I 10.0 A I 25.5 A I 18.2 A I 6.0 A II 0.1 C III TW Ring Main (Barnes- 0.0 C III 13

17 Infrastructure Clearance (m) Above / below Category Barrowhill) TW Walham Green Storm Relief Sewer Central line (2no. tunnels) 18.5 A I 18.5/16.5 A/A I/I Piccadilly Line 15.5 A I Proposed Crossrail 2 North Proposed Crossrail 2 South 0.0 C III 0.0 C III National Grid LPT 0.5/6.5/0.0 B/B/C III/II/III Table 4.4: UKPN Tunnel 1.5/1.5 A/A III/III L1 invert level AOD (max depth to gravitate to TTT) Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Holland Park Pipetrack (Thames Water Ring Main) TW Low Level Sewer No. 2 Main line TW North Western Storm Relief Sewer Proposed Thames Water Ring Main TW Thames-Lee Valley Tunnel TW Ring Main (Barnes- Barrowhill) TW Walham Green Storm Relief Sewer Central line (2no. tunnels) 24.5 A I 24.0 A I 16.0 A I 31.7 A I 25 A I 12.2 A I 0.4 A III 6.0 A II 24.5 A I 24.5/22.5 A/A I/I Piccadilly Line 21.5 A I Proposed Crossrail 2 North Proposed Crossrail 2 South 5.3 A II 5.3 A II National Grid LPT 0.0/0.3/0.0 C/B/C III/III/III 7.5/7.5 A/A I/I 14

18 There are direct vertical alignment interfaces with all of the vertical options for the L1 alignment. Deepening the tunnel at the downstream end does not remove these issues. However, in the deepest case, they are reduced to a level where only a direct interface occurs with the National Grid LPT and a close crossing beneath the TW Thames-Lee Valley Tunnel. These are considered alignment limiting constraints From this assessment, it is concluded that all options for the L1 baseline alignment are not feasible. Therefore the L2 alignment was developed to mitigate against these issues. Alignment L2 Figure 4.2: Alignment L2 Schematic Description Alignment L2 has been developed to mitigate against the impacts on existing tunnelled infrastructure between Lots Road and Mund Street in the L1 alignment and optimises the vertical alignment north of Mund Street. The invert level at the Lots Road Pumping Station has 15

19 been lowered to that which is considered, at this stage in the project development, as optimum to balance the impacts further north The National Grid LPT is a significant constraint to alignment options leaving the Lots Road area to the west. Unlike the Counters Creek Tunnel, cable tunnels are not constrained to a constant gradient. They descend to the north of the Thames, to cross beneath the proposed Crossrail 2 tunnels and continue to descend to pass beneath the TW infrastructure further north. Utilising the deeper tunnel level from alignment L1 (-37.11m AOD at Lots Road) the direct interface with the power tunnel and/or Crossrail 2 can be eliminated. This is achieved by aligning the proposed new sewer to the north upon leaving Lots Road and then returning to the base alignment south of Earls Court before returning to the L1 alignment at Mund Street as shown in Figure 4.2. Key constraints Physical constraints in the north section of the alignment remain, with the TW Thames-Lee Valley tunnel remaining as a critical crossing constraining the alignment. Increasing the tunnel gradient to rise above this tunnel only creates further conflicts at a higher level as demonstrated by alignment L1 base option. Table 4.5: L2 revised clearances Lots Road to Mund Street Infrastructure Clearance (m) Above / below Category Proposed Crossrail 2 North Proposed Crossrail 2 South 5 A II 5 A II National Grid LPT 2.3 B II* Note: National Grid Power tunnels are crossed with a clearance of 2.3 m with the Counters Creek Sewer passing above. Whilst this places the crossing in Category III, it is considered that an engineered solution can be found to successfully mitigate the impact. The Category has therefore been reduced to Category II with caution that permissions from National Grid will be required It is concluded that in all cases the L1 is not feasible yet an element of mitigation can be applied by realigning the tunnel between Lots Road and Mund Street to alignment L2. 16

20 Alignment L3 Figure 4.3: L3 Alignment Schematic Description Following on from the L2 alignment, the L3 alignment was developed to further mitigate against constraints posed on the sewer. The concept is to split the tunnel at Mund Street with one leg maintaining the base alignment concept to the Swanscombe Road area and a separate leg being a tunnel to a site at Brook Green. A shaft is assumed to be located at Brook Green to intercept the Hammersmith Storm Relief Sewer Brook Green Branch. This is in preference to forming a connection at Shepherds Bush Green via the tight radius shown in the L1 alignment The L3 alignment between Mund Street and Swanscombe Road is heavily constrained as per the L1 and L2 alignments. The leg to Brook Green is not so severely constrained and is viable with a level change (step) in vertical profile to avoid clashes with Thames Water assets (Ring Main and Thames-Lee Valley Tunnel) further north. With this step assumed at Mund Street the interfaces on the L3 alignment between Mund Street and Brook Green are shown in Table 4.6. This option has been developed further to create alignment L4 to mitigate against the above issues. 17

21 Table 4.6: L3 alignment interfaces for connection Mund Street to Brook Green Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Low Level Sewer No. 2 Main line TW Thames-Lee Valley Tunnel TW Ring Main (Barnes- Barrowhill) 7.6 A II 7.6 A II 15.3 A I 11.2 B I 6.2 B II Alignment L4 Figure 4.4: L4 Alignment Schematic 18

22 Description The L4 alignment drives a tunnel to Mund Street using the route developed for the L2 alignment, continuing through the Mund Street site, and on to Brook Green. An intermediate change in tunnel level south of the Thames-Lee Valley Tunnel and north of the National Grid London Power Tunnel is require to optimise clearances with assets across the catchment. It is assumed for this assessment that this change in level occurs at Gwendwr Gardens to keep the sewer at a deep alignment when crossing the Earls Court area which has likely piled foundations. See Appendix C At Brook Green a spur is taken up to the Swanscombe Gardens area. Developments in hydraulic assessments and a detailed review of the TW network have identified the potential to move the interception of the Hammersmith SRS Duplication and Counters Creek Branch south from Swanscombe Road. This is only hydraulically feasible if combined with the interception of the existing Counters Creek and the North Kensington Storm Relief Sewers at Upper Addison Gardens. This has the advantage over the L1 alignment of eliminating one drop shaft connection to the Counters Creek Sewer. From an alignment viewpoint, it also eliminates the need to cross the Thames Water Ring Main north of Holland Park, where it is at a shallower depth, together with the associated risks. Therefore, the L4 alignment proposes a connection to the Lower Addison Gardens area to intercept the Hammersmith SRS Duplication and Counters Creek Branch and on to Upper Addison Gardens. Details of the proposed local connection requirements in this area are included in Section The Shepherds Bush Green connection to the Hammersmith Storm Relief Sewer Brook Green Branch can be made at Brook Green without affecting the hydraulic requirements. As a consequence, a Goldhawk Road connection will need to be routed from Goldhawk Road to Brook Green. It is suggested at this initial stage that this connection is made via a new pipe jack along Shepherds Bush Road The possibility of forming a connection into the Brook Green Branch in the vicinity of Shepherds Bush needs to be considered further as this would then eliminate the need for the pipe jack connection The L4 alignment option is considered feasible following the above assessment, but would require further development following the Site Suitability Reports. Key constraints The constraints are shown in Table

23 Table 4.7: Impacts Alignment L4 Lots Road to Brook Green section with a change in tunnel level at Mund Street Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Low Level Sewer No. 2 Main line Proposed Thames Water Ring Main TW Thames-Lee Valley Tunnel TW Ring Main (Barnes- Barrowhill) TW Walham Green Storm Relief Sewer Proposed Crossrail 2 North Proposed Crossrail 2 South 7.6 A II 7.6 A II 15.3 A I 12.1 A I 11.2 B I 6.2 B II 22 A I 5 A II 5.0 A II National Grid LPT 2.3 B III 20

24 4.3 Hammersmith options It is initially assumed for the alignment assessment that the Hammersmith alignment options start Fulham Reach Development. Demolition of the old pumping station building would be recommended for this option to provide sufficient working area and access to the site from A nominal internal diameter of 4.0m has been assumed It has been assumed for the Hammersmith alignment options that a local connection in the Lots Road area can be made to form the interception for the Walham Green and Low Level 1 sewers As discussed for the Lots Road L4 alignment (Section 4.2), the Hammersmith alignments North of the Brook Green area, all require further connections via: A connection north from the Brook Green area to a shaft for the interception of the Hammersmith SRS Duplication and Counters Creek Branch (assumed for alignment assessments in the road at Lower Addison Gardens) Pipe jack or bored connection to Upper Addison Gardens from Hammersmith SRS Duplication interception shaft to intercept the North Kensington SRS and existing Counters Creek sewer. Pipe jack from the Hammersmith SRS Brook Green Branch interception site (if in the Brook Green area) to Goldhawk Road along The two pipe jacked alignments are discussed in Section The tunnel interfaces for a connection between Brook Green and Lower Addison Gardens are shown in Table 4.8. Table 4.8: Tunnel infrastructure crossing alignments between Brook Green to Lower Addison Gardens Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Low Level Sewer No. 2 Main line TW Ring Main (Barnes- Barrowhill) 7.9 A II 13.5 A I 5 B II 21

25 Alignment H1 Figure 4.5: H1 Alignment Schematic Description The profile of the H1 (Hammersmith West) alignment is shown in Appendix D The H1 alignment assumes construction of a new pumping station in the Old Hammersmith Pumping Station site. The alignment would enter the pumping station shaft from the west at an invert level of approximately -40mAOD and a gradient of 0.15% up to Brook Green This low sewer level is required to cross under the Thames Water Ring Main with a minimal clearance of 4m, south of the Hammersmith Flyover. Placing the sewer at such a depth would increase the pumping requirements as well as pumping station construction size at Hammersmith On leaving Brook Green, the H1 alignment option is assumed to follow the Shepherds Bush Road south, before running south west down Blacks Road and the A306. It then follows the North Western Storm Relief Sewer under the Hammersmith Flyover before turning east to a new pumping station down Worlidge Street The alignment would tie into the Addison Gardens and Goldhawk Road connections north of Brook Green, discussed in Section 4.4. Key constraints The H1 alignment interfaces can be seen in Table

26 Table 4.9: Tunnel infrastructure crossing H1 Alignment and its impact Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW North Western Storm Relief Sewer TW Ring Main (Barnes- Barrowhill) 27.8 A I 28.3 A I 4.0 A II UKPN Tunnel 15.8 A I The Thames Water Ring Main (TWRM) is a 2.59m ID tunnel of wedge block construction and sits with an invert level at approximately 32m AOD at the point of crossing to the west of the Old Hammersmith Pumping Station The n Road. The UKPN tunnel has an invert level of approximately 20m AOD and is a 2.54m ID tunnel of wedge block construction The wedge block construction method makes both tunnels highly sensitive to settlements, especially when running beneath and or parallel to existing assets. Therefore, both the TWRM and UKPN tunnels are likely to require strengthening works for any crossings in close proximity An alternative vertical alignment within the 9m zone between the UKPN tunnel and the Ring Main was considered to raise the tunnel level and minimise risk, impacts and costs. Using a nominal 4.6m external diameter Counters Creek Sewer provides 3.2m (0.7D) clearance to each of the existing assets. This solution is not recommended due to the sensitivity of both assets to ground movement, especially when constructing the sewer in parallel to and beneath the UKPN tunnel The North Western SRS is at high level, preventing a shallow alignment for the Counters Creek Sewer above the UKPN tunnel between the Brook Green area and the Hammersmith Flyover. The Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch also interface with the H1 alignment at high level, further restricting a shallow profile Therefore it is concluded that the vertical profile of the H1 alignment is only feasible at the deeper level. This is not a preferred option as it will increase construction size, cost and programme. 23

27 Alignment H2 Figure 4.6: H2 Alignment Schematic Description The H2 alignment investigates the option of connecting into the Old Hammersmith Pumping Station from the east as an alternative to the H1 alignment. The vertical profile of this route is shown in Appendix D.2. An invert level at Hammersmith of -21m AOD, and a 0.15% gradient up to Brook Green has been assumed From Brook Green the H2 option runs south east, down Rowan Road and Shortlands before passing under the Hammersmith Flyover with the Hammersmith SRS Duplication and Counters Creek and Mainline Branches. The alignment then passes round the West London Magistrates Court, following the shallow Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch alignment to the Hammersmith Site. Key constraints The H2 alignment interfaces with several existing underground structures as summarised in Table Table 4.10: Tunnel infrastructure crossing H2 Alignment and its impact Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch 8.8/8.2/6.79 A/A/A I/I/II 7.6/7.5/7.5/7.1 A/A/A/A II/II/II/II TW Thames-Lee Valley Tunnel 12.0/11.6 B/B I/I TW Ring Main (TWRM) (Barnes- 6.4 B II 24

28 Infrastructure Clearance (m) Above / below Category Barrowhill) The H2 alignment option crosses over the Thames Water Thames-Lee Valley Tunnel twice near Hammersmith and Brook Green The Thames-Lee Valley Tunnel is a 2.56m ID tunnel of wedge block construction and has an invert level of approximately -36 and -34m AOD at the points of crossing. The H2 alignment also crosses over the wedge block constructed TWRM close to the Brook Green site, with an invert level of approximately -29m AOD This alignment only crosses directly over the sensitive TWRM and Thames-Lee Valley Tunnel, and does not run parallel to either, reducing settlement impacts and requirements for strengthening works The H2 alignment runs at a shallower depth than the H1 option. This reduces the shaft depth, pumping requirements and construction costs for a new Hammersmith Pumping Station Site and therefore H2 is preferable to H1. However, a clearance of only 6m exists to the TWRM and therefore 2 diameters clearance is not achievable. Due to its sensitivity, the asset would require further assessment before this option was progressed Originally, for the Hammersmith outfall alignments H1 and H2, the Mund Street interception has been assumed to be a local sewer upgrade with additional storage. However, further hydraulic assessment indicated that the required storage volume could not be provided by this arrangement and a sewer interception at Mund Street is necessary. Therefore, an additional tunnel drive to this interception point has been developed in alignments H3 and H4. Alignment H3 Figure 4.7: H3 Alignment Schematic 25

29 Description Street. This option can follow either alignment H1 or H2 up to Brook Green, and runs a second connection between Hammersmith and a site to intercept the North End Road Sewer (assumed for this assessment at Mund Street). This alignment requires a reception shaft at Mund Street, where the site area is highly restricted The assumed H3 connection between Hammersmith and Mund Street runs east out of the Old Mund Street. to Key constraints The H3 alignment interfaces between Hammersmith and Mund Street can be seen in Table These are in addition to those for the H1 or H2 alignments to Brook Green shown in Table 4.9 and Table Table 4.11: Tunnel infrastructure crossing H3 Alignment connection from Hammersmith to Mund Street Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch TW Thames-Lee Valley Tunnel 9.2 A I 8 A I 11.7 B I From this assessment it is noted that although there are no interface issues with the alignment option between the Hammersmith and Mund Street areas, the alignments from Hammersmith to the Brook Green area require further alignment development. 26

30 Alignment H4 Figure 4.8: H4 Alignment Schematic Description presents an alternative connection to Mund Street. The alignment follows either H1 or H2 up to Brook Green, and then runs a connection between the Brook Green area and Mund Street (assumed site for the interception of the North End Road Sewer as per H3) The H4 route between Hammersmith and Mund Street runs down Brook Green, Edith Road and North End Road to a shaft at the junction between Mund Street and North End Road. Key constraints The H4 alignment interfaces are the same as H1 or H2 between Hammersmith and Brook Green. Interfaces between Mund Street and Brook Green are as per the L3 alignments as shown in Table

31 Alignment H4a Figure 4.9: H4a Alignment Schematic Description The H4a alignment plan and profile can be seen in Appendix D.3. This option was created to further reduce the impacts from the H1 and H2 alignments, whilst maintaining a connection to intercept the North End RoadSewer (assumed at Mund Street). The option built on the H4 and L4 alignments, to reduce interfaces with existing subsurface assets. It is based around an additional central site assumed at Gwendwr Gardens on the junction between: Talgarth Road, Trevanion Road and Gwendwr Road H4a comprises 3 drives between the Gwendwr Gardens site and: North End Road Sewer interception (assumed Mund Street) Hammersmith SRS Brook Green Branch (assumed Brook Green) New pumping station at Hammersmith (assumed Hammersmith Old Pumping Station) This requires an additional site to the H3 and H4 alignment proposals, and therefore increased land purchase costs, but also reduces impacts on the Thames Water Ring Main, UKPN and Thames-Lee Valley Tunnel To the north of Brook Green, as per the other Hammersmith alignments, connections are also required to Goldhawk Road and Addison Gardens. Key constraints The H4a alignment interfaces between Mund Street and Brook Green are as per the H4 and L3 alignment, shown in Table 4.6. Those new interfaces between Gwendwr Gardens and 28

32 Hammersmith are shown in Table It is noted that construction on an additional intermediate site (assumed here as Gwendwr Gardens) increases the potential for both construction cost and disruption. Table 4.12: Tunnel infrastructure crossing H4a Alignment Gwendwr Gardens to Hammersmith Infrastructure Clearance (m) Above / below Category TW Hammersmith Storm Relief Sewer Main Line TW Hammersmith Storm Relief Sewer Duplication and Counters Creek Branch 17.0 A I 15.8 A I TW Thames-Lee Valley Tunnel 4.0 B II 4.4 Sewer connections Upper Addison Gardens As discussed in Section 2.1, hydraulic analysis developed a requirement for a connection at Upper Addison Gardens to intercept the North Kensington Storm Relief Sewer and existing Counters Creek Sewer. In developing the potential alignments, the concept of a smaller pipe jack connection between the interception shaft for the Hammersmith SRS Duplication and Counters Creek Branch and Upper Addison Gardens was formed This short pipe jack will be restricted in alignment by the existing sewers in the Upper Addison Gardens area and requires further development following location of the Hammersmith SRS Duplication and Counters Creek Branch site. Goldhawk Road Alignment options L3, L4 and all of the Hammersmith options require a connection between the Goldhawk Road Local Sewer interception point and the interception site for the Hammersmith SRS Brook Green Branch (assumed in this section to be at Brook Green). A schematic alignment option for this connection, which is proposed as a pipe jack, is shown in Figure The likely alignment for the connection follows Shepherds Bush Road. This provides the opportunity for minimal numbers of straight line connections and reduces risk to third party properties, enabling a shallow pipe jack connection. Goldhawk Road and Shepherds Bush Roads are generally very busy with high levels of traffic, and use of a pipe jack technique enables impact reduction in comparison to an open cut connection Although the diameter of this sewer has not yet been decided, an external diameter of 2m has been assumed in producing this alignment study. A maximum drive length of 300m has been assumed due to the friction loading of pipe jacking through London Clay, and risk of requiring 29

33 additional construction should the pipe jack require recovery. This limits the spacing of the pits To limit disruption to traffic, it is suggested that the construction pits are placed within the northbound road lanes as there are generally 2 lanes for traffic going northbound and one lane for southbound traffic. The pavements are also generally wider on the northbound side of the road, providing more space for construction Assuming a tunnel diameter of 2m means that the construction pits would be roughly 6m x 4m in plan where there are no sharp turns in the alignment. However, where there are sharp turns in the alignment, a larger and squarer construction pit is necessary (6m x 6m). Figure 4.10: Goldhawk Road to Brook Green alignment 4.5 Conclusion on alignment options investigated This alignment assessment has sought to develop the baseline alignment between hydraulic interception points, developing the route to optimise the vertical profile and reduce impacts on third party assets. Alignments to new pumping stations at both Hammersmith and Lots Road locations have been considered. The study has concluded that the L1 alignment is not feasible for any of the three vertical profiles investigated Alternative plan alignments have been developed and studied and these have identified other constraints which are present in the project area and need to be overcome. 30

34 4.5.3 The assessment of the alignments that were presented in this report was carried out with the results shown in Table Assessments have been made on a qualitative basis with assessment made between individual assessment grades for each alignment option This high level assessment concludes the alignments showing the least impact using the above criteria were L4 and H4a. These should be carried forward for further consideration and will need to be refined to mitigate impacts. Those alignments which have been rejected are ruled out on the basis of conflict with other infrastructure or lack of connectivity to required Thames Water network. Recommendations The following is a list of items to be carried forward to the next phase of the project delivery For each of the viable alignments: Finalise acceptable shaft sites Confirm outfall location viability and assess impacts Consider straight line alignments Confirm tunnel diameter Confirm deep foundation risk for preferred alignment Consider innovation and how this could aid project delivery Assess construction impacts Confirm pumping station design at each location with respect to physical constraints Confirm pumping station constructability and assess impacts Consider potential CC TTT interfaces in detail Assess preferred alignment through public consultation efforts to be concentrated on viable alignments. ent will allow 31

35

36 5 Further Assessment of Options 5.1 Lots Road area options The L4 alignment is a preferred alignment with an outfall at Cremorne Wharf emerging from Section 4. A schematic of this alignment is shown in Figure 4.4. The L4 alignment was qualitatively assessed as shown in Table Sites The L4 alignment has 6 sites at: Lots Road, Mund Street, Gwendwr Gardens, Brook Green Common, Upper Addison Gardens and Lower Addison Gardens. It connects to Goldhawk Road sewer via a pipe jack from Brook Green Common. Access and spoil transportation Using Lots Road as a drive site, barge transportation for spoil removal can be considered, reducing the volume of lorry movements required at this site. The use of a drive site at Brook Green could only use road transportation. Lots Road area outfall and pumping station The L4 alignment requires one new pumping station in the Lots Road area. A pumping station in the Lots Road area would mean that flows from all interception points could be taken to one new pumping station Works are proposed for the Thames Tideway Tunnel on the Cremorne Wharf site. Should this site be selected for a Counters Creek pumping station and outfall further assessment and coordination would be required. 5.2 Hammersmith options The site selection process resulted in Mund Street being concluded as the only suitable site for the interception of the North End Road Sewer. This would require a Hammersmith alignment to connect into Mund Street. This additional short tunnel drive was assessed as high impact and cost due to the short length of the drive and the restricted site at Mund Street. It is further noted that these options also do not intercept the Walham Green and Low Level 1 sewers and would therefore still require an interception and connection to a pumping station in the Lots Road area. The H4a alignment was identified as the preferred option for a Hammersmith outfall emerging from the assessments in Section 4. A schematic of the alignment is shown in Figure

37 Sites The H4a alignment has 7 sites. For assessment sites have been assumed at: Old Hammersmith Pumping Station, Gwendwr Gardens, Mund Street, Brook Green Common, Lower Addison Gardens and Upper Addison Gardens with a pipe jack connection from Brook Green Common to Goldhawk Road. Access and spoil transportation A Hammersmith outfall site would potentially require a large conveyor system to enable barge transportation to be used for spoil removal. Transportation and access to Hammersmith as a drive site would be predominantly by road, which would be restricted by the TTT and St Georges Development works which would share the access roads. Use of Gwendwr Gardens or Brook Green Common as drive sites would rely solely on road transportation. Hammersmith outfall and pumping station In addition to the requirement for a new pumping station for an outfall option at Hammersmith, further assessment has shown that a new pumping station is also required at Lots Road. This is due to the requirement to intercept the Walham Green and Low Level 1 sewers along the hydraulic interception adjacent to Lots Road. Therefore, the use of an outfall at Hammersmith requires two new pumping stations compared to one, larger pumping station if the outfall is located at Lots Road At Hammersmith a proposed Thames Tideway Tunnel shaft is located within the piled St Georges Development, now under construction. Should a connection be developed at a later stage, the piling would restrict tunnel access to the Thames Tideway Tunnel drop shaft, making an interface at this location problematic. If a connection was required this option may require redesign of the pile foundations and subsequent compensation Several locations were considered for a new pumping station at Hammersmith as discussed in Section Conclusion of further assessment Following these further assessments for alignments options, it has been concluded that an alignment to Hammersmith is not optimal for several reasons: Two pumping stations would be required for a Hammersmith option Works would still be required in the Lots Road area in the form of a local scheme for a Hammersmith option Alignment connections to sites at Hammersmith are highly constrained for both options H1 and H2 by existing assets at the downstream end of a sewer alignment 34

38 5.3.2 Therefore, the alignment options for an outfall and pumping station at Lots Road have been carried forward for further development and assessment. The site selection area has been refined to reflect this conclusion, and this has been used in development of the Site Selection Short List report. 35

39 6 Review and Redefinition of Route Corridor 6.1 Vertical alignment level change Further development of the alignment and vertical profiles (Sections 4 and 5) identified that to provide sufficient clearance to existing assets, a high level tunnel is required in the north of the catchment whilst a low level tunnel is required in the south of the catchment. The crossing of the Thames Water Thames-Lee Valley Tunnel was determined as the boundary between these two zones and therefore a constraint on the alignment. Therefore a change in vertical alignment of the sewer is required to the South of the Thames-Lee Valley Tunnel and to the north of the National Grid London Power Tunnels. 6.2 Site selection zones To enable the alignment options to be further developed and to assist with site selection, a GIS plan (Drawing Number C680-A DR, Appendix E ) was prepared. This plan enabled the route corridor to be better defined, considering the revised interception locations and the constraints identified in Sections 2.1, 2.2 and 2.3 above. This was carried out as follows: The revised, hydraulically defined, interception limits were marked on the drawing. These were then connected together (the dotted red lines on the drawing), thus identifying the general route of the tunnel. By super imposing a 400m wide corridor (from stage 2a) over the red lines, a more defined zone was identified for a drive site search in comparison with the initial corridor identified in the Site Selection Report Stage 2a (Long List of Sites). The line of the National Grid London Power Tunnel was also marked on the drawing. The proposed sewer can only cross over the National Grid London Power Tunnel from the Brompton Cemetery (south of ) northward, where the cable tunnel dives down to a greater depth of -40mAOD. This enables the sewer to be shallow enough for a potential gravity connection into the Thames Tideway Tunnel (should that interface arrangement be selected following further technical analysis) whilst maintaining a clearance of more than 1x the tunnels diameter to the proposed Crossrail 2 alignment. This meant that all the areas to the west of the National Grid London Power Tunnel from Lots Road to the Cemetery could not be reached by the sewer without significant engineering difficulties. The area to the west of the cable tunnel was therefore shown hatched. The engineering difficulties of connecting to Lots Road (Cremorne Wharf) would entail either: construction at a greater depth with a larger pumped connection to the outfall; or construction of a large pumping station to the west of the cable tunnel and laying a new, shallow, large diameter rising main to the terminal pumping station. ourt and the high rise buildings with piled foundations in this area and at the Westfield shopping centre (in the north of the catchment) were also marked onto the drawing. It was decided to avoid both of these areas for site locations if possible. Construction within the area could lead to potential compensation claims by the developer for reconfiguration of the proposed buildings and pile foundation designs on the line of the new sewer. 36

40 The above exercise enabled identification of a more defined route alignment corridor and a site search area for tunnel drive The GIS plan was then further developed to better define the interception/drop shaft sites: The existing sewers to be intercepted generally run under highways or buildings. In order to avoid construction of major structures in highways and their closure for considerable periods of time, innovative construction techniques are being considered. It is envisaged that (subject to ground conditions and depth of the sewer), it may be possible to locate the interception chamber and the drop shaft some 10-15m off the existing sewer line on land adjacent to the road. An underground connection into the existing sewer could be made through a short tunnel excavated in a heading. This may then allow any available area next to the highway to be utilised, minimising periods of highway closure. Interception and diversion of flows in a heading is unprecedented and will very much depend on safety considerations, ground conditions, depth, and sewer diameter. For these reasons, the length of the heading must be kept to a minimum (no further than any space or land available adjacent to the highway where the existing sewer is located). If at a later stage this is not considered practical, then road closure would become necessary. The drawing C680-A DR (Appendix E) was therefore marked with a 15m zone around the limits of interception locations to search for suitable sites. 37

41 7 Emerging Preferred Option Following the results of the Site Suitability Reports (SSRs) the L4 alignment was further developed with the preferred site options to develop the preferred L6 alignment option It is noted that the L5 alignment was derived as a revision of the L4 alignment with the level change moved to an additional site at Gwendwr Gardens to avoid the Thames-Lee Valley Tunnel and reduce construction works at Mund Street. This was further optimised by the L6 alignment and as such the L5 alignment is not discussed. 7.2 Site Suitability Reports outputs The Site Suitability Reports concluded that the preferred 5 sites for use on the project were: Cremorne Wharf Mund Street Kensington Olympia Car Park Upper Addison Gardens Shepherds Bush 5* Car Wash (with an open cut connection to intercept the Goldhawk Road local sewer) 7.3 L6 Alignment Figure 7.1 shows a schematic of the L6 alignment, proposed to connect the 5 preferred sites and developed from the L4 vertical alignment. The plan and profile drawing is shown in Appendix F. Figure 7.1: Proposed L6 alignment 38