KEMP - SaveKEMP Alternative Sites

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100-RG-ENG-PTH1X-900001 | June 2011

King EdwardMemorial ParkSaveKEMP alternatives

Thames Water response


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Thames Tunnel

SaveKEMP alternativesThames Water response

List of contents

Page number

1 Executive summary ......................................................................................... 11.1 Introduction .............................................................................................. 11.2 Thames Tunnel Preferred Scheme KEMP Foreshore .......................... 11.3 SaveKEMP proposed alternatives ........................................................... 21.4 Conclusion ............................................................................................... 2

2 Introduction ...................................................................................................... 43 Key features of schemes ................................................................................. 54 SaveKEMP Option 1 Main tunnel shaft north of The Highway .................. 6

4.2 Site 3 Heckford Street sites .................................................................. 64.3 Sites 4a and 4b Cemex and Studio sites .............................................. 64 4 Sites 4b and 4c Studio site and Cable Street site 7


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1 Executive summary

1 Executive summary

1.1 Introduction

1.1.1 The Thames Tunnel is urgently needed to help tackle the 39 million tonnesof untreated sewage which overflows into the River Thames in an averageyear, when Londons Victorian sewerage network becomes overloaded.

1.1.2 The North East Storm Relief (NESR) combined sewer overflow (CSO),which flows underneath King Edward Memorial Park (KEMP) in the

London Borough of Tower Hamlets, is the second largest gravity overflowto the River, discharging over 784,000m3 in a typical year.

1.1.3 The opportunity to intercept the flow of sewage before it spills into theRiver Thames is constrained by the need to make a connection to thislarge sewer at some point along its existing route. We have identified theKEMP Foreshore site as a preferred site to intercept the flows withoutpermanent intrusion in the park and minimising disruption to the

community who use it.1.1.4 The Report on Phase 1 Public Consultationwas published in March. We

are continuing to review and refine the scheme to achieve the optimumsolution with minimum disruption and least cost to our customers.

1.1.5 In March 2011, the SaveKEMP Campaign submitted a report Engineering Report Alternative Schemes to Preserve King Edward VIIMemorial Park (KEMP) document with two proposed alternative options.

1 1 6 F th t i iti l (100 CO CP1 OWNER 000792) h


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1 Executive summary

accommodate the tunnels and their flows, all within the limited spaceavailable at the Kings Stairs Gardens/Chambers Wharf site.

c. significant additional estimated cost of at least 30 million.

1.4.3 Option 1 compares favourably on cost with the Preferred Site at theForeshore. However, crucially, the proposed alternative Option 1 has agreater impact on residents, businesses and park users, among others,both in the short and long term. The key points are summarised below:

a. Direct impact on businesses in the area as a number of businesses

would require relocation on both a temporary and permanent basis,this may include Compulsory Purchase Orders

b. Construction would be concurrently over two sites and due to theirproximity would have a greater impact on traffic movements

c. The sites are inland and would provide no option for moving materialsby river, which we have said we will do as much as possible andwhere practical and cost effective to do so, to reduce impacts on local

roads and residents.

d. The impact on the central open parkland area is greater, although thepreferred scheme requires access to the foreshore across the westernpart of the park.

1.4.4 The KEMP Foreshore site will have some impact on the park duringconstruction but also offers a real opportunity to improve the park andfacilities for the local community in the London Borough of Tower Hamlets.W ill k ith th it t d t d h th t t th


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2 Introduction

2 Introduction

2.1.1 The North East Storm Relief (NESR) combined sewer overflow (CSO),which flows underneath King Edward Memorial Park (KEMP), is thesecond largest gravity overflow to the river, discharging over 784,000m3 ina typical year

2.1.2 This report presents an analysis of the viability, and relative meritscompared with the Preferred Scheme, of two alternative schemespresented by the SaveKEMP campaign group in their report Engineering

Report Alternative Schemes to Preserve King Edward VII MemorialPark.

2.1.3 Phase 1 public consultation looked at all the preferred and shortlisted sitesalong with the three tunnel route options. The analysis of the consultationresponses are set out in a report titled Thames Tunnel: Main Report onPhase 1 Consultation and is available on our website. The SaveKEMPproposal was received on 16 March 2011,

2.1.4 The Preferred Scheme has been further developed taking into accountfeedback from Phase 1 Consultation and ongoing design. Among otherdevelopments, alternatives to interception of the Holloway Storm Reliefsewer at Butcher Row, and the Shad Thames CSO at Druid Street, arebeing investigated. These alternatives are not yet fully approved, but theeffect of not requiring interception of the Holloway Storm Relief Sewer atButcher Row on the SaveKEMP options has been considered in thisreport.


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3 Key features of schemes

3 Key features of schemes

3.1.1 Drawing 100-DL-GEN-PTH1X-069010 and Table 2.1 illustrates the mainfeatures of the area and designates the site references used in thefollowing sections.

3.1.2 The report Site Selection Methodology Technical Background Paper,published on our website, sets out the sizes needed for different types ofconstruction site. A construction site for a drop shaft connected to themain tunnel should be approximately 7,500m2 in this part of London, and a

CSO interception site approximately 1,500m2.

Table 3.1 Key Features of Schemes

Element PreferredScheme

SaveKEMPOption 1

SaveKEMPOption 2

CSO drop shaft

to main tunnel

20m internal

diameter shaft atKEMP foreshore.

7,500m2 tempreclamation,2,000m2permanentreclamation

20m internal

diameter shaftnorth of TheHighway.

7,500m2 tempworking space,2,000m2permanent

Enlarged shaft

(from 25m to atleast 30minternaldiameter) atKings StairsGardens orChambersWharf.


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4 SaveKEMP Option 1

4 SaveKEMP Option 1 Main tunnel shaft north of TheHighway

4.1.1 The SaveKEMP proposal identifies several potential sites for a drop shaftto the main tunnel, north of The Highway. This option would also require aseparate CSO interception site within KEMP to construct the interceptionof the NESR sewer, and a connection tunnel to be driven from the maintunnel shaft site. The site numbers are indicated on the attached plan.

4.2 Site 3 Heckford Street sites

4.2.1 These are variously known as the Heckford Street Business Centre and asThe Highway Trading Centre and The Highway Business Park, but arereferred to as the Heckford Street sites in this document. They areaccessed from Heckford Street, which adjoins The Highway (A1203). Thesites are currently occupied by commercial buildings, warehouses andoffices of one to two storeys in height with associated parking areas. TheHeckford Street sites are bounded to the north by Cable Street, which is

lined by one of the Mayor of Londons strategic Cycle Superhighwayroutes, five-storey council-owned residential properties and a closed,rundown public house. To the east is a large warehouse buildingcomprising about 170 small units occupied by small businesses, includingartist and recording studios (Cable Street Studios). Also, to the east of thesite are Cranford Cottages, which are two-storey, terraced properties, andan eight-storey Holiday Inn Express hotel.

4 2 2 Th H kf d St t it b d d t th th b A1203 (Th


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4 SaveKEMP Option 1

London, and is accessed from Butcher Row. The Cable Street Studios siteis occupied by a Victorian brick built warehouse building, accessed off

Cable Street. The building has been converted and subdivided into about170 small units occupied by numerous small businesses including artistand recording studios. Cable Street is one-way traffic, eastbound andincludes the Mayor of Londons strategic Cycle Super highway routesimmediately adjacent to the site. To the north is a hoarded off partiallycleared site that was previously in industrial use (Site 4c). Adjoining Site4c, also north of this site, are recently built and occupied five-storey blocksof flats (on the corner of Ratcliffe Cross Street and Cable Street) and onthe junction of Caroline Street and Cable Street is older five-storey socialhousing.

4.3.2 The nature and number of current uses on these sites mean that it is likelyto be significantly more difficult to justify disruption to the existingbusinesses than the Heckford Street sites and, particularly in the case ofthe Cemex site, unlikely be able to be relocated in this area due to thenature of the business and proximity of residential and other sensitive

uses. The loss of these employment uses is also unlikely to be supportedin this area which the council has considered to be an industrial areawhere loss of any employment uses will be resisted as being contrary totheir statutory Development Plan, the recently adopted Core Strategy. Thedemolition of the Cable Street Studios building is also likely to be moresensitive than the buildings on the Heckford Street sites given the age andstyle of buildings.

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4 SaveKEMP Option 1

owned by the the Royal Foundation of St Katherine) which is a strategicred route.

4.6 General assessment

4.6.1 Site 3, Heckford Street sites, are considered the most practical of the sitesnorth of The Highway, with both the Cemex and the Cable Street Studiosites having a more significant detrimental impact on existing employmentuses.

4.6.2 Use of any of the sites north of The Highway for a tunnel shaft would

require realignment of the main tunnel inland from the river, passing undernumerous residential and business properties, with potential albeit minorimpacts on a large number of people. There would also need to be anadditional connection tunnel with potentially greater impacts. The preferredforeshore shaft site allows an alignment which is almost all under the river,passing under very few buildings in the London Borough of TowerHamlets, especially if the Butcher Row interception is not required..

4.6.3 The site required at Butcher Row for a connection to the Holloway StormRelief sewer would be the same as for the Preferred Scheme. A site wouldbe required within KEMP adjacent the North East Storm Relief sewer toconstruct a connection tunnel reception shaft, and sewer interceptionchambers, but this would be smaller than a foreshore site and would berequired for a shorter period; estimated to be about half the time requiredon the foreshore.


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5 SaveKEMP Option 2

5 SaveKEMP Option 2 No main tunnel shaft at KEMP

5.1.1 This option would comprise a 3.6m internal diameter connection tunnel,more than 1,840m long, from Butcher Row, through KEMP, anddischarging into the main shaft south of the river at Kings Stairs Gardensor Chambers Wharf. Because of limited site space at Butcher Row, thisconnection tunnel would have to be driven from Kings StairsGardens/Chambers Wharf.

5.1.2 CSO worksites would be needed at both KEMP and Butcher Row to allow

construction of interception chambers and drop shafts, and to remove thetunnelling machine.

5.1.3 The Kings Stairs Gardens/Chambers Wharf main shaft is also theconnection point for the Greenwich connection tunnel. The total inflow(including the North East Storm Relief and Holloway Storm Relief flows) tothe main tunnel at Kings Stairs Gardens/Wharf would amount to some95m3/s, which presents a number of significant design challenges.

5.1.4 Moving large volumes of water generates large hydraulic forces andturbulence that must be safely controlled. If only the Greenwich flows areconnected at Kings Stairs Gardens/Wharf, the shaft would have to be25m internal diameter. To cater for the additional NESR flows, this shaftwould have to be duplicated or made significantly larger, initially assumedto be 30m internal diameter, but, even then there would be a high risk ofinadequate performance. Furthermore construction health and safety riskswould increase due to the need to construct vortex approach chambers at

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5 SaveKEMP Option 2

space required for the associated slurry handling plant, the two drivescould not be carried out at the same time. While receiving a TBM requires

much less equipment and time than driving, a clear window needs to beprogrammed for each of the incoming drives, during which the shaftcannot be used for other activities. Shaft fit-out, including the constructionof the vortex drop shaft and roof, cannot be undertaken until all the tunneldrives to/from the shaft have been completed. Consequently there isinsufficient time within the available programme to safely undertake alltunnelling and shaft construction from Kings Stairs Gardens/ChambersWharf site.

5.1.7 It is concluded that the SaveKEMP Option 2 is not technically feasible atthe Kings Stairs Gardens/Chambers Wharf site and the need to makeadequate provision for ventilation of the main tunnel, and it cannot becompleted within the time available. Even if the hydro-pneumatic problemscould be overcome, the cost of this option would be significantly higher,estimated to be at least 30 million, than the Preferred Scheme.

5.2 Comparison of Preferred Scheme and SaveKEMP Option 15.2.1 Of the potential sites north of The Highway, the Heckford Street sites are

considered the most suitable and have been used for the assessment.Using the Cemex site would effectively close a strategic businessimportant to construction in the east side of the city. Using the CableStreet Studio site would result in the loss of a building of some localarchitectural or historical merit and displace some 170 small businesses in

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5 SaveKEMP Option 2

5.3.4 The Preferred Scheme would have amenity impacts on a number ofresidential properties particularly along the western edge of park.

SaveKEMP Option 1 would use two construction sites and is likely to haveresidential amenity impacts on a greater number of residential properties,as well as other sensitive uses such as the Shadwell Centre and CableStreet Studios, in addition to impacts on residents adjacent to the park.The Heckford Street sites are adjacent, on three sides, to a predominatelyresidential area.

5.3.5 The alignment of the main tunnel and the construction sites for the

Preferred Scheme minimises the number of potential residential propertiespassed under. The Heckford Street sites are immediately adjacent to asite allocated in Schedule 3 of the UDP relating to arts and entertainment.The SaveKEMP Option 1 tunnel alignment would be under moreproperties including a number of sensitive uses such as recording studios,library and residential properties.

5.4 Property comparison

5.4.1 All of the SaveKEMP Option 1 sites will cause disruption, principally to thebusinesses on the sites, and the acquisition and compensation costs willbe significantly higher than those expected for the Preferred Scheme. It isassumed that any of the sites could be acquired under reasonablebusiness terms, but it should be noted that should Compulsory PurchaseOrders be required, it may be difficult to justify the land acquisition sincethe foreshore is a feasible alternative.

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5 SaveKEMP Option 2

5.6 Environmental comparisons

5.6.1 The significant environmental considerations include the following:a. The Preferred Scheme foreshore location provides the opportunity for

river transport, as barges can moor alongside the site, whereas noneof the SaveKEMP Option 1 sites would permit river transport.Otherwise, there is no clear preference.

b. There is no clear preference between the options regarding builtheritage and townscape, as both proposals are likely to affect the

character of the park and the conservation area, albeit in differentways.

c. The SaveKEMP Option 1 is preferable regarding water resources dueto its lower risk of spillage, scour, etc, impacts on the River Thames.

d. The SaveKEMP Option 1 is preferable regarding aquatic ecology sinceit has no adverse impacts on foreshore habitats.

e. The Preferred Scheme is preferable regarding construction impactsincluding air quality and noise, given that more people are likely to beaffected under SaveKEMP Option 1 (notably in the environs ofHeckford Street sites).

f. The SaveKEMP Option 1 results in double the duration of constructionimpacts when the time taken to build on two sites is compared withone site for the Preferred Scheme.

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6 Costs

6 Costs

6.1.1 The estimated overall scheme costs of the Preferred Scheme andSaveKEMP Option 1 are similar, within estimating accuracy at this stageof design, and so direct costs are not a significant factor in the selection ofoptions. Indirect costs associated with business disruption due toincreased traffic on The Highway have not been calculated but would behigher for the SaveKEMP Option 1.

a. The SaveKEMP Option 2 is estimated cost at least 30 million more

than the Preferred Scheme.7 Conclusion

7.1.1 Following our review, KEMP Foreshore remains our preferred site. It wasoriginally selected following the professional judgement of our engineering,property, planning, community and environment teams. These sameprinciples have been applied to the proposed alternative sites and onfurther examination the two alternatives do not conform to our

requirements or our objectives.

7.1.2 We have discounted Option 2 for a number of reasons outlined in the mainreport, including:

a. It presents new and complex engineering challenges to the ThamesTunnel scheme, both hydraulic and pneumatic concerns introducingtoo much flow at a single location which add unacceptable risks to theproject.


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6 Costs

7.1.4 The KEMP Foreshore site will have some impact on the park duringconstruction but also offers a real opportunity to improve the park and their

facilities for the local community in the London Borough of Tower Hamlets.We will work with the community to understand how they want to use thenewly created area; benefits would include improved access to theThames Path and recreational facilities for those who use the park and theriver.

7.1.5 We have stressed throughout our site selection that the park is importantto the local community and as there is a limited area of open space in the

neighbourhood, we proposed the foreshore site. This decision was nottaken lightly and we are still refining our proposals to ensure we minimisedisruption to all those residents potentially affected by our works.

7.1.6 We believe that our ongoing review to refine our proposals at the KEMPForeshore site ensures that we meet the objectives of the Thames Tunnel,and we continue to take into account information from the local communityand stakeholders as we continue to refine the scheme.

7.1.7 The conclusion has been tested for the scenario without the proposedHolloway Storm Relief interception at Butcher Row site and does notchange. Similarly, the conclusion would not change if the Southwark andBermondsey Relief Sewer is not intercepted at Druid Street.


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