3290 196-222 Kings Road 17

WALL CONSTRUCTION TEMPORARY / PERMANENT SUPPORT

TYPICAL WALL DEPTH TYPICAL RETAINED HEIGHT USUAL INSTALLATION TOLERANCE: VERTICALITY

ADVANTAGES /DISADVANTAGES REMARKS SUITABILITY

?

?

3290 196-222 Kings Road 18

7.3.2 Foundations.A range of spread footing types are possible, the choice of which is related principally to the bearing capacity of the soil and the nature of the load to be transferred to the ground below. Given the likely allowable bearing pressures within the clay layer at the level at which the building is to be founded and the concentrated loads imposed by the columns of the typical 8.0 x 6.0m structural grid, a raft foundation appears to be the preferred structural solution.

Raft foundations have the benefit of minimising differential settlements, which is of particular benefit in the case of concrete framed structures, which are generally more susceptible to such effects than the equivalent steel frame. This is especially relevant where asymmetric or irregular column grids are utilised as in the case of this building. A raft slab has the benefit of spreading the building load over the largest possible area reducing the contact pressure at the interface with the soil. They are thus particularly suited to conditions of variable or relatively low bearing capacity. However, it should be noted also that raft foundations have the potential to stress the soil to a much greater depth than more localised footings, although the effect of this is tempered by the lower contact pressure.

Ground heave is expected to occur during the removal of overburden pressure on the underlying clay strata. Measures to mitigate the effects of heave on the raft foundation may be required in extreme cases, though no such measures are anticipated in this case. A more detailed assessment of the impact of heave movements on the existing adjacent structures will be undertaken in the next stage of design.

A preliminary study has also been undertaken to assess a suitable raft thickness, including a preliminary sensitivity analysis to assess the effect of variability in ground conditions. This study has identified that a thickness of 1000mm appears generally suitable with local 1500mm thickenings under the core and more heavily loaded columns. This will be confirmed following the more detailed assessment in the next stage and may be supplemented by further borehole investigations.

On the basis of the preliminary site investigations undertaken to date and historical knowledge of the ground in the Chelsea area, it is not currently thought necessary to adopt piled foundations for the support of the proposed building.

7.3.3 UnderpinningThe proposals have been developed to avoid the potential for undermining adjacent structures wherever possible. There remains however the need to form underpinning existing Waitrose and Friese Green House basements, and also potentially 194 Kings Road subject to further investigations. These works shall be subject to party wall awards as appropriate.

An appraisal of the condition of walls to be underpinned shall be undertaken prior to planning the work. It is assumed that underpinning would be undertaken in a 1:6 sequence with adjacent pins connected via dowels and shear key. The concrete mix design will achieve the necessary DC class.

To minimise movement the final bearing between the pin and the existing footing shall be dry packed tight. A provision for localised dewatering of any perched water has been made subject to the planned groundwater monitoring. If dewatering is required the methodology will need to make adequate provision to avoid the washing of fines from under the adjacent footings through the use of tight boarding or where flows are significant subsoil permeation or jet grouting. A full specification for the works shall be prepared in accordance with the NBS framework.

Fig. 7.3: Rendered basement volume

Cinema double height space

Liner walls around perimeter

Single storey basement

Double storey basement

3290 196-222 Kings Road 19

7.3.4 Assumed construction sequencesOutline construction sequences related to the formation of the basement as assumed in the development of the permanent works design to date are indicated in the adjacent figures. This information shall be resolved further in subsequent design stages. The Contractor will be responsible for devising the construction sequence and methodology together with the completion of the final design of any required temporary works.

CHECKEDBYDESCRIPTIONDATEREV

PROJECT

DATE

DRAWN CHECKED

SCALE

PROJECT No.

TITLE

CAD FILENAME

DRAWING No.

STATUS

REV

196-222 KINGS ROAD

DEC 2013 NTS

AW RH 3290

STABILITY: BLOCK A STABILITY SYSTEM

PRELIMINARY

P1P1 03.01.14 RH S-SK-H104a

-

AW

NOTES:

1.

FOR INFORMATION

BLOCK A STABILITY: BASEMENT FLOOR LEVEL PLAN

FIGURE A: ERECTION OF FACADE RETENTION STRUCTURE, SITECLEARANCE AND DEMOLITION OF BUILDINGS, UNDERPINNING TOFRIESE GREEN HOUSE, WAITROSE, 194 KINGS ROAD AND FACADE.

FIGURE B: CONSTRUCTION OF PILE MAT AND PILING AT HIGH LEVEL.POTENTIAL ACCESS ROUTE FROM CHELSEA MANOR STREET

FIGURE C: BERM AGAINST CHELSEA MANOR STREET AND KINGS ROADALLOWING PILING AT LOW LEVEL FOR B2 BASEMENT AREA.CONSTRUCTION OF CAPPING BEAMS IN SEQUENCE

FIGURE D: INSTALLATION OF TEMPORARY PROPPING TO ALLELEVATIONS. UNDERPINING BELOW RETAINED FACADE PROPPED FROMLOW LEVEL PILES.

FIGURE E: TEMPORARY GANTRY INSTALLED EITHER ON CHELSEAMANOR STREET OR HEMUS PLACE PRIOR TO DEEP EXCAVATION.CONCURRENT B1 RAFT, LINER WALLS CONSTRUCTION IN SINGLESTOREY BASEMENT.

FIGURE F: CONSTRUCTION OF RAFT, LINER WALLS AND B1 RC SLAB.REMOVAL OF PROPPING TO THE TOP OF THE PILES IN SEQUENCE

Current best available record information suggests that the boundary walls with the adjacent properties are structurally independent. This would allow the existing buildings to be demolished without the need for wall retention or propping. It is possible however that while not initially designed to provide mutual support, the existing buildings have adopted such a condition over time. The presence of such conditions will be determined through suitable investigations during the next stage of design. An allowance has been made for repair works to the adjacent walls following demolition works and temporary localised shoring or reinforcement works.

Fig. 7.4: Indicative construction sequence

Temporary support to embedded retaining walls and underpinning will be required to allow excavation to proceed until the permanent structure has been constructed to provide support. The location and size of the temporary props is to be determined by the contractor.

Access to the site will likely be from Chelsea Manor Street or Hemus Place which restricts the site organisation. Once the excavation extends towards formation the site would no longer be accessible direct from the road, therefore a temporary gantry may be erected to achieve the full dig.

3290 196-222 Kings Road 20

7.3.5 WaterproofingThe design will proceed in accordance with BS 8102 (1990) Protection of Structures against water from the ground. The grade of environment to which the respective areas of the basement are to be designed informs the determination of suitable waterproofing strategy. This decision is taken by the Client in consultation with the design team as the grade of protection chosen influences the architectural treatment of the basement and also the active measures necessary to control the environment. It is currently determined that the occupied areas of the basement shall achieve a Grade 3 environment with the option to downgrade to Grade 2 in areas containing plant or secondary usage.

Forms of construction

BS 8102 Protection of structures against water from the ground, identifies three specific methods of water-resisting construction:

•• Tanked Protection

•• Structurally Integral Protection

•• Drained ProtectionAt this stage an allowance has been made for a full cavity drained solution with the water resistance of the liner wall enhanced by the addition of a waterproofing admixture in the case of the new structure. It is not assumed that the reinforcement will be designed to satisfy water-retaining requirements in these areas. Allowance is made for double waterbars at all construction joints and the provision of waterproofing admixture in the capping beam and first 1.5m of any slabs or beams taking support from the liner wall.

In plant areas a structurally integral or externally tanked solution may be substituted subject to the acceptance of a Grade 2 environment. In the retained buildings waterproofing is likely to be enhanced via the use of internal tanking systems where necessary, most likely render based. The final waterproofing strategy will need to be determined in consultation with the wider design team, Client and waterproofing specialist (as defined under BS 8102) during the next stage of design.

Structural durability

The necessary level of chemical resistance will be achieved through the specification of suitable concrete mixes achieving the relevant Design Chemical (DC) class in accordance with the requirements of BS 8500-1:2006 and associated Euronorms and the provision of adequate cover to reinforcement.

Corrosion protection of any steel structures will generally be achieved by means of a suitable paint system, which will be specified to provide a life to first major maintenance of 10 to 15 years. The choice of protection level will be influenced by location and aesthetics. Where steelwork is exposed to the external environment, a galvanized coating will improve durability and reduce maintenance periods. The existing masonry and stone facades will generally be subject to re-pointing with matched mortars and crack stitching as necessary.

Fig. 7.5: Indicative construction sequence for the basement below the facade retention

1. Installation of retention system and demolition of the existing building

2. Install piles with king postthrough berm

3. Underpin facade in 1:6 sequence down to formation level. Underpins require propping during excavation. 4. Construction of raft slab and internal retaining structure.

3290 196-222 Kings Road 21

8 Design Standards

8.1 Proposed structureSince March 2010 Eurocodes and their associated National Annexes (providing country-specific design parameters), have superseded British Standards as the principle design codes for structural elements in the United Kingdom. Reference will be made to British Standards and other technical guidance where topics are not adequately addressed in the Eurocodes. It is of note that while no longer current, the superseded British Standards generally remain cited within UK Building Regulations.

The following codes and design guides will be used principally in preparing the structural design for the project. For the sake of brevity National Annexes are not listed:

Eurocode 0: Basis of structural design

BS EN 1990:2002

Eurocode 1: Actions on structures

BS EN 1991-1-1:2002, BS EN 1991-1-2:2002, BS EN 1991-1-3:2003, BS EN 1991-1-4:2005, BS EN 1991-1-5:2003, BS EN 1991-1-6:2005 and BS EN 1991-1-7:2006, (BS EN 1991-3:2006)

Eurocode 2: Design of concrete structures

BS EN 1992-1-1:2004 and BS EN 1992-1-2:2004, (BS EN 1992-3:2006)

Eurocode 3: Design of steel structures

BS EN 1993-1-1:2005, BS EN 1993-1-3:2006, BS EN 1993-1-4:2006, BS EN 1993-1-5:2006, BS EN 1993-1-7:2007, BS EN 1993-1-8:2005, BS EN 1993-1-10:2005, BS EN 1993-1-11:2006, BS EN 1993-5:2007 and BS EN 1993-6:2007

Eurocode 6: Design of masonry structures

BS EN 1996-1-1:2005, BS EN 1996-1-2:2005, BS EN 1996-2:2006 and BS EN 1996-3:2006.

Eurocode 7: Geotechnical design

BS EN 1997-1:2004, BS EN 1997-2:2007

BS8102 2009 Protection of below ground structures against water from the ground

SCI P354 Design of floors for vibration: A new approach

BS6472-1:2008 Evaluation of human exposure to vibration in buildings

The Concrete Centre: A design guide for footfall induced vibration of structures

CIRIA C579 Retention of masonry facades – best practice guide

CIRIA C580 Embedded retaining walls – guidance for economic design

Building Regulations: all relevant sections, including Approved documents A & B concerning structure and fire safety

8.2 Existing structureAppraisal of the existing structure shall be undertaken where there is a proposed structural alteration. This appraisal shall generally follow the principles outline in the IStructE publication entitled The Appraisal of Existing Structures, the appraisal. The three stages outlined below, which represent increasing degrees of refinement and complexity shall be employed as necessary with the assessment proceeding from stage to stage until verification is achieved:

Stage 1 analysis:

A preliminary assessment of the structure and its intended use, its apparent physical condition and its strength, including simple calculations where necessary. If this check is not satisfied immediately, it may be required to undertake further investigations. For this stage of assessment, it is assumed that checking the model using a working stress method will be adequate. This will generally be undertaken according to the code current at the time of construction. In the case of the cast and wrought iron the guidance current in 1879 shall be utilised, as set out in the BCSA Historical Structural Steelwork Handbook. In the case of timber construction the relevant code shall be CP112 The Structural Use of Timber.

Stage 2 analysis

If the structure cannot be verified on this basis of a Stage 1 analysis, a more detailed assessment is to be carried out checking the strength, capacity and deflections of the structure. Conventional limit state calculations are to be used during these checks. In the case cast and wrought iron structures the more modern Highways Agency document BD21/02 shall be used for these calculations. In the case of timber structure BS5268 shall be used. Necessary allowances for the material quality and manufacturing defects shall be made, especially where these vary from the assumptions inherent within the formulation of the codes of practice (eg buckling curves for steel elements). Loadings may be assessed in accordance with BS6399. If these checks are not satisfied, then a further more in-depth analysis is required.

Stage 3 analysis

This final most intensive analysis should be based on the best knowledge of loads and material strengths that can practically be obtained. This more precise knowledge may justify a reduction in the factors of safety used in the calculations. The following recommended ranges are set out in the annex to the IStructE publication The Appraisal of Existing Structures, the choice of which is dependent on the certainty that can be applied to the variable in question:

m 1.05 – 1.15f1(DL) 1.05 – 1.15f3(LL) 1.15 – 1.20 (Primary) 1.05 – 1.25 (Secondary)

3290 196-222 Kings Road 22

9.0 Impact assessment Detailed assessments as outlined below will generally be undertaken at the appropriate stage of design by AKTII Limited, the project structural and civil engineers with support from external geotechnical specialists such as Geotechnical Consulting Group (GCG) and A-Squared Studio as necessary. AKTII Limited have extensive experience in the development of designs for deep basements in London and throughout the world. Given the size and importance of the project, construction will be undertaken by an established main contractor and associated supply chain with significant experience of such ground works. Comprehensive calculation packages will be prepared by AKTII Limited for Building Control approval at the relevant stage of design.

9.1.2 Construction phasingThe construction phasing shall be considered in the assessment of time dependency effects. At this stage of design development the following stages have been identified as critical to one or all of the structures that may be affected to by the proposed development.

•• Stage 1a: Short term heave due to demolition

•• Stage 1b: Short term heave due to excavation

•• Stage 2a: Short term settlement due to construction before application of brittle finishes

•• Stage 2b: Short term settlement due to construction after application of brittle finishes

•• Stage 3a: Consolidation settlement due to building occurring during 100 year design life

•• Stage 3b: Consolidation settlement due to building occurring after 100 year design life

•• Stage 4a: Long term heave due to gross unload occurring during 100 year design life

•• Stage 4b: Long term heave due to gross unload occurring after 100 year design life

Through the use of superposition the relevant design conditions for the affected structures may be determined. The table below provides a summary of the ground movement components relevant to the various structure types.

9.1.3 Time dependency effectsWith reference to Tomlinson (2001) and Brien & Sharp (2001), where relevant the following apportioning of the total ground movement into short- and long-term response with regard to settlement and heave are assumed as follows: With reference to Tomlinson (2001), the rate of consolidation settlement will been assumed to conform to drainage model type 1 using the coefficient of consolidation (Cv) value as determined by relevant soil tests to be undertaken. Consolidation curves shall be derived for the London Clay deposits. It will be assumed that the rate of long term heave development follows the same progression through time.

9.1.4 Design standardsDesign will be undertaken in accordance with Eurocode 7 with load factors taken from Eurocode 1. All relevant ULS and SLS cases shall be considered, which in the case of this design are likely to comprise structural (STR), geotechnical (GEO) and uplift (UPL) cases. The partial safety factors to be utilised in design together with the relevant load case combinations are listed below:

i. Load factors

Demolition

Case 1: 1.00ψ2Gk,existing + 0.30ψ2Qk,existingwhere all loads are assumed to be uniformly distributed over the site and the weight of buildings and imposed loads are estimated from record information

Excavation

Case 1: 1.00ψ2Gk,soilwhere Gk,soil is equal to the weight of soil in accordance with the recommendations of the SI report

Proposed building

Short term effects Load from proposed building at end of construction Ref: EN1990:2002 Quasi-permanent combination (6.16a)Case 1: 1.00ψ2Gk,proposed + 1.00ψ2Qk,proposedCase 2: 0.90ψ2Gkwhere Qk,proposed is determined considering live load reduction by factor αn (Ref: EN 1991-1-1:2002 eq. NA.2)

Long term effects Load from proposed buildingRef: EN1990:2002 Quasi-permanent combination eq. 6.16aCase 1: 1.00ψ2Gk,proposed + 0.30ψ2Qk,proposedCase 2: 0.90ψ2Gkwhere Qk,proposed is determined considering live load reduction by factor αn (Ref: EN 1991-1-1:2002 eq. NA.2)

ii. Material factors

Soil parameters

For the purpose of ultimate limit state design using Type 1 combinations, encompassing the structural design of the raft, retaining walls and assessment of any secondary effects generated from tilt of cores, etc. the undrained shear strength will be modified by the factor γcu = 1.4 in accordance with EN1997-1:2004 Annex A. It follows that the Young’s modulus values derived from the undrained shear strength will be subject to the same partial safety factor. When considering serviceability effects the soil parameters will be utilised without the application of partial safety factors.

9.1 Ground movements

9.1.1 Soil parameters and design approachFurther deep boreholes are required in order to determine the soil parameters necessary to complete detailed assessment of ground movements for comparison against relevant acceptance criteria. The procedure for implementing this analysis is outlined below for review. Preliminary assessments of likely ground movements have been made on the basis of the site investigation results obtained to date benchmarked against typical stiffness parameters for the London Clay deposits. These preliminary analyses have formed the basis of the assessment of the viability of a raft foundation and retaining wall proposals, which are to be verified in the next stage of design. A detailed design philosophy shall be developed in preparing the Geotechnical Design Report as required under the provisions of Eurocode 7. Ground modelling for the assessment of ground movements shall principally comprise the following analyses addressing both vertical and lateral movements:

•• Elastic halfspace analysis of the proposed raft foundation considering short and long term conditions accounting for variation in pore water pressure and considering time dependency of movements; use of halfspace model to assess vertical ground movements below and adjacent to the excavation with consideration of rebound heave effects in both short and long term conditions

•• Elastic plane-strain 2D section cut analyses for assessment of lateral and vertical ground movements in regions adjacent to the excavation including the effects of basal heave

•• Review of predicted ground movements against empirical derivations and case study data (eg CIRIA C580 data). The results will be assessed against relevant acceptance criteria as outlined below in order to secure the relevant formal approvals for the works to be undertaken. Any resulting requirements with regard to the Contractors’ methodology will be detailed and enforced through the project specifications and preliminaries.

3290 196-222 Kings Road 23

Concrete

To account for cracking in concrete elements in the short-term the Young’s modulus for the concrete will be modified to 0.75Ecm. To account for the combined effects of creep, shrinkage and cracking in concrete elements in the long-term the Young’s modulus will be modified to 0.60Ecm.

9.2 Ground water flowOn the basis of the findings from previous site investigations as outlined in section 4.0 above a perched water table is thought to exist on the site overlying the relatively impermeable London Clay deposit. Perched water levels can vary seasonally and are prone to rapid changes through heavy rain events on permeable surfaces, accidental events (such as burst water mains) and the introduction of new underground construction causing blockages to natural perched water flow. The River Thames is located 0.5km to the South and it is assumed that the ground water flow would be in this direction. The presence of open green space in nearby St Luke’s Gardens may also impact on the prevailing groundwater flow regime. The new basement will extend down to a level just above and in some instances within the relatively impermeable London Clay deposits. In order to assess the potential impact of interruption of flow within the gravel strata and the need for any resulting mitigation measures, continuous groundwater monitoring will be undertaken. Further details of the surrounding basements will also be required to inform the assessment. It is noted however that the impact of the proposed development is not anticipated to be significant and that any effects are likely to be mitigated through the provision of free-draining layers surrounding the proposed substructure.

Groundwater levels for design

The design philosophy in relation to ground water levels to be assumed in design of the permanent works is outlined below for reference. Analysis will be completed upon receipt of the outstanding site investigation information.

BS EN1997-1:2004 & National Annex

The 196-222 Kings Road project will be designed to Eurocode 7 (BS EN1997-1:2004 & National Annex) and as such the following limit states shall be considered:1. Ultimate Limit State (ULS): Design values shall be the most

unfavourable design conditions that could occur during the lifetime of a structure during an extreme or accidental event.

2. Serviceability Limit State (SLS): Design (characteristic) values shall be the most unfavourable design conditions that could occur in normal circumstances. The option is given to the designer to determine design values for ground water by either “applying partial factors to the characteristic water pressures or by applying a safety margin to the characteristic water level” cl.2.4.6.1(8). Partial safety factors for use under normal conditions are noted within the code, guidance for accidental conditions comes from 2.4.7.1(3) & the National

Annex. For the uplift design condition UK NA Appendix A Table A.NA.15 can be used.

In summary:

ULS (STR & GEO) Design Cases: normal conditions γf = 1.35 accidental conditions γf = 1.00

ULS (UPL) Design Cases: normal conditions γf = 1.10

SLS (ALL) Design Case: normal conditions γf = 1.00

It is expected that the upper layers of the London Clay deposits will contain fissures, leading to penetration of the perched water in the long run and the potential to form an increased head of water. The depth of penetration is subject to engineering judgement based on knowledge of the surrounding ground conditions and on site investigation results.

Concrete Basements – Guidance on the design and construction of in-situ concrete basement structures (Narayanan & Goodchild)

With reference to BS EN1991-4, the use of a partial factor of 1.2 on the most unfavourable or accidental ULS design case is recommended, this level being taken as ground level unless there is high confidence in the water table. The factor of 1.2 is in accordance also with the provisions of BS81101:1997 Table 2.1 for water retaining structures. This additional provision shall be adopted in design as the only variation to the Eurocode 7 design procedure, with the exception that the accidental groundwater level will be taken as 1m below ground level as per BS8102, which has been the adopted figure in UK construction for many years. It is considered that taking the accidental level at the ground surface would be unduly conservative.

9.3 Surface water flowWith reference to section 4.0, according to the Environment Agency flood map, the site is not at risk of flooding and consequently lies in flood zone 1 with a return period of event of 1 in 1000 years. No change or increase to the extent of hard-standing over the site is proposed. New surface drainage will be installed in areas of hardstanding within the proposed development discharging to the public sewer with consent via new below ground drainage installations. Given the surrounding public sewer invert levels it is anticipated that the surface water can be disharged by gravity through the basement at high level into the public sewers.

In order to meet the BREEAM and Code for Sustainable Homes requirements, at least a 30% reduction in surface water run-off from the existing rate will be required. Storage tanks are being located within the site boundary to attenuate surface water prior to being discharged into existing sewers in Kings Road or Chelsea Manor Street.

CHECKEDBYDESCRIPTIONDATEREV

PROJECT

DATE

DRAWN CHECKED

SCALE

PROJECT No.

TITLE

CAD FILENAME

DRAWING No.

STATUS

REV

196-222 KINGS ROAD

MAR 2014 NTS

AW RH 3290

GROUND WATER FLOW: FLOWS AROUND THE SITEFOLLOWING DOUBLE BASEMENT CONSTRUCTION

PRELIMINARY

P1P1 21.03.14 RH S-SK-H110

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AW

NOTES:

1.

FOR INFORMATION

BLOCK A STABILITY: BASEMENT FLOOR LEVEL PLAN

FIGURE E: TEMPORARY GANTRY INSTALLED EITHER ON CHELSEAMANOR STREET OR HEMUS PLACE PRIOR TO DEEP EXCAVATION.CONCURRENT B1 RAFT, LINER WALLS CONSTRUCTION IN SINGLESTOREY BASEMENT.

228-232 KING'S ROAD 224-226 KING'S ROADING'S ROAD

CHELSEA MANOR STREET

206 KING'S ROAD 200-204 KING'S ROAD208 KING'S ROAD 196-198 KING'S ROAD

BURNSALL STREET

228-232 KING'S ROAD 224-226 KING'S ROADING'S ROAD

CHELSEA MANOR STREET

206 KING'S ROAD 200-204 KING'S ROAD208 KING'S ROAD 196-198 KING'S ROAD

BURNSALL STREET

DOUBLEBASEMENT

SINGLE EXISTINGBASEMENT

SINGLE EXISTINGBASEMENT

SINGLE BASEMENT

SINGLE EXISTINGBASEMENT

SINGLE EXISTINGBASEMENT

SINGLE EXISTINGBASEMENT

GROUNDWATER FLOW AROUND DOUBLEBASEMENT. POTENTIAL LOCAL MINORINCREASE IN GROUND WATER LEVEL.

Fig. 9.3: Indicative sketch showing direction of ground water flow around basement

3290 196-222 Kings Road 24

9.4 Impact on adjacent buildingsThe impact of the proposed development on the adjacent buildings will be assessed and approvals secured via party wall awards. The assessment will be based principally on movement, vibration and other non-structural issues such as noise limitation.

A package of relevant drawings, calculations and reports shall be prepared for review by the adjacent owners appointed structural engineer and relevant third parties. Assumed temporary works designs shall be prepared prior to the Contractor completing the final design.

9.4.1 Damage criteria assessmentThe ground movements predicted through the halfspace modelling shall be combined with those resulting from the retaining wall analysis as appropriate in order to develop predicted vertical and lateral ground movement contouring. This contouring shall be used to assess the impact on the adjacent buildings. This analysis shall be made available to the party wall surveyors upon request as part of the party wall awards process.

The applicable components of ground movements will be as defined above. It is proposed to use the classification of visible damage to walls scheme as outlined in CIRIA C580 with reference to Burland et al, 1977, Boscardin and Cording, 1989; and Burland, 2001. Subject to the approval of adjacent owners’ party wall surveyor and relevant LBC, Damage Category 1 (very slight) shall be assumed acceptable. In the case of listed buildings Damage Category 0 (negligible) may be enforced. This will need to be determined through consultation early in the next stage of design.

Vibrations limits shall be defined in accordance with BS ISO 4866:2010, which addresses the recommended vibration limits for buildings. Reference will also be made to the related CIRIA Technical Note 142 Ground-borne vibrations arising from piling, in particular chapter 5. On the basis of the current information the adjacent buildings would appear to fall under Category 7 type Cc in the worst case as defined under BS ISO 4866:2010. This classification may be improved if evidence of adjacent basements is confirmed. Peak particle velocity limits shall be defined and monitored as deemed necessary during the works.

9.4.2 GroundwaterA regime of inspection has been defined, further details will be sought to allow an assessment to be made of the potential impact from variation in the perched water regime resulting from the proposed basement.

No fundamental alteration of the groundwater regime is proposed or is expected to occur as a result of the proposals. Provided sufficient means of permeation is maintained adjacent to the boundaries to relieve any water pressure that might otherwise occur (either through retention of the existing gravel material or provision of permeable material) the proposed development is not anticipated to present a significant impact on surrounding properties.

9.4.3 MonitoringA regime of monitoring of the surrounding buildings and the proposed retaining walls and adjacent pavements will be specified. Pre-condition surveys and appraisals will be undertaken for all adjacent buildings as part of the party wall awards process. Drawings and specifications will be prepared in line with best practice for agreement within the party wall award. Appropriate green, amber and red trigger levels shall be set with reference to relevant CIRIA guidance documents on the observational methodology.

The scope of monitoring is likely to include the follow:

•• Movement monitoring of party walls via targets surveyed using electronic levels

•• Vibration monitoring using transducers placed on the foundations of the adjacent buildings

•• Crack monitoring via the use of graduated tell-tales

•• Movement monitoring of retaining wall/capping beams via targets surveyed using electronic levels

•• Monitoring of adjacent pavement levels via studs surveyed using electronic levels

•• Monitoring of retaining wall movements via use of Inclinometers cast in secant piles

•• Potential use of extensometer bored in place to monitor heave movements in clay

9.5 Highways approvalsThe proposed basement construction adjacent to the public highway along Kings Road, Chelsea Manor Street and Hemus Place will be subject to Highways Agency and Local Authority approval.

An approval in principle (AIP) document shall be prepared in accordance with the provisions of Highways Agency BD2/12 Technical Approval Of Highway Structures. Full calculations will be subsequently issued for building control approval. Temporary works assumed in the design of the permanent works will be outlined within the AIP. The Contractor will be expected to liaise with the third parties as necessary to obtain the necessary licenses for temporary works supporting adjacent highway structures.

An additional approval will be sought to allow the facade retention temporary works to be placed externally to the site on Kings Road. Full calculations will subsequently be submitted by the Contractor.

9.6 Utilities approvalsA desk study has been undertaken as recorded in section 4.0. Full statutory searches were undertaken as part of this study. On the basis of these findings it is expected that the following third party approvals will be required prior to commencing the relevant construction activities.

9.6.1 UKPNIt is expected that structural builderswork drawings will be provided by UKPN during the next stage of design. The requirements outlined will be included within the structural design including inherent structural fire resistance requirements.

9.6.2 Crossrail 2As part of the site lies withing the Crossrail 2 safeguarding zone, the structure will require approval and conditions may be placed on the scheme. The extent of the conditions will be determined during negotiations with Crossrail 2 during the next design stages.

9.6.3 National Grid Gas (NGG)A number of NGG installations are located within Kings Road. As such discussions will be started with the NGG Asset Protection team with a view to defining relevant retaining wall movement limits and securing the necessary approvals and easements.

9.6.4 Thames WaterThames Water developer services will be consulted to confirm whether Buildover agreements will be required for the proposals. It is noted that public sewers under Kings Road and Chelsea Manor Street appear to be at a distance less than 6m from the site boundary. As such it is anticipated that an impact assessment will need to be undertaken for both sewers prior to gaining approval.

3290 196-222 Kings Road 25

9.6.5 Other bodiesThe site lies greater than 25m from the nearest LUL tunnel installations. As such no consultation is likely to be necessary. Other minor services providers indicated as affected in searches undertaken while completing the desk study shall be consulted following notification of the project.

9.7 ArchaeologyAn archaeological assessment of the site has been carried out by MOLA which concludes that there is a low potential for the site to contain significant archaeological assets.

It is also noted that a watching brief during the preliminary ground works could be requested during planning.

9.8 Tree protectionIt is not anticipated that the proposed basement works will present particular risk to the existing trees adjacent to the site given the clearance between the proposed works and the extent of the retaining walls.

9.9 Demolition & construction impact Reference is drawn to the draft Construction Management Plan (CMP) included with the submission and the notes regarding assumptions related to phasing contained within this report. The CMP will be developed during subsequent stages of design and planning of the works following the appointment of a main contractor to include amongst other items detailed consideration of:

•• Noise and vibration

•• Dust

•• Visual impact

•• Obstruction of pavements

•• Bringing excavated spoil up to awaiting skips / vehicles

•• Transporting the spoil away from site, using local roads

•• Delivery of construction material to site

Demolition

All demolition work will be planned and undertaken in accordance with BS 6187:2011 Code of Practice for Full and Partial Demolition. The Contractor will devise an appropriate demolition methodology and safe method of work to be documented within the demolition plan. The demolition plan will include (but not necessarily be limited to):

•• Statements addressing the planning & management of site work to include:

•• Details of any structural surveys required, if any

•• Sequence of works, logistics & detailed methodology

•• Details of supervision, monitoring & site management

•• Description of how the structural stability of the building and adjacent structures is to be maintained during the works and upon completion. Details of auxiliary and temporary support designs to be provided.

•• Description of measures to be taken to protect the public and site operatives including details of exclusion zones, control and protection measures. The Contractor will be required to consider less vibratory methods of demolition (eg hydraulic bursting, chemical fracturing, etc.) and the use of pre-weakening and isolation to limit transmission of vibration to adjacent structures. A discussion of the impact on adjacent buildings is included.

9.10 SustainabilityThe proposed scheme shall be subject to assessment under the BREEAM framework and the Code for Sustainable Homes. It is intended that secondary or recycled aggregate content within the substructure concrete construction shall confirm to the BREEAM requirements for the relevant credit. This availability of appropriate sources locally have been confirmed and shall be controlled through the structural specification.

9.10.1 Removal of wasteReference is made to the draft CMP included within the planning application. This document will be subject to development upon the appointment of the main contractor.

9.10.2 Construction materialsReference is made to the draft CMP included within the planning application. This document will be subject to development upon the appointment of the main contractor.

3290 196-222 Kings Road 26

10.0 Conclusions

This document presents the preliminary basement impact assessment, which records the process undertaken to demonstrate the feasibility of the proposed subterranean development in accordance with items raised within the subterranean development SPD. As noted above, the design philosophy and procedures set out above will form the basis for the detailed analysis and assessment works that will subsequently be required to secure the necessary third party approvals prior to commencing works on site.