proposal - london borough of merton · back garden has holly trees and magnolias. 2.2 the site is...

PLANNING APPLICATIONS COMMITTEE 20 June 2013 Item No: 05UPRN APPLICATION NO. DATE VALID 12/P3050 16/01/2013

Address/Site 16 Lansdowne Road, Wimbledon SW20 8AW

(Ward) Village

Proposal: Proposed construction of a two-storey annexe building link-attached to main house, enlargement to existing basement (including installation of new swimming pool) and construction of front boundary treatment including sliding gates

Drawing Nos D718/01D, /09E, /10F, 11E, /13D, /14D, Design and Access Statement, Construction Method Statement & Drainage Strategy Plan

Contact Officer: Kelly Howell (8545 3112) ___________________________________________________________________

RECOMMENDATION

GRANT Planning Permission subject to conditions___________________________________________________________________

CHECKLIST INFORMATION

� Is a screening opinion required: No � Is an Environmental statement required: No � Has and Environmental Statement been Submitted: No � Press notice: Yes � Site notice: Yes � Design Review Panel consulted: No � Number of neighbours consulted: 59 � External consultations: None � Controlled Parking Zone: Yes (W7) � Density: N/A� Number of jobs created: N/A

1 INTRODUCTION

1.1 The application is put before the Planning Applications Committee for determination due to the level of local interest in the scheme.

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2 SITE AND SURROUNDINGS

2.1 The application site is a three-storey, locally listed, hipped roof 5-bed dwellinghouse, with a butterfly roof feature to the rear, basement accommodation with associated lightwells to the front and rear of the building, an existing car port on the southern/side boundary, two existing crossovers and a close-boarded fence delineating the front boundary. There is a Lime tree in the front yard adjacent to the boundary with Number 16; and there are also Yew trees. The back garden has Holly trees and Magnolias.

2.2 The site is on the west of Lansdowne Road – a road that slopes downwards from north to south. The property is located in the Wimbledon West Conservation Area, is also in the Wimbledon Village Archaeological Priority Zone; and is within CPZ W7.

2.3 The immediate vicinity is characterised by large residential Victorian villas set on large plots such as the property to the north at Number 17 Lansdowne Road. The West Wimbledon Conservation Area Character Appraisal states that the majority of properties on the western side of Lansdowne Road, including the application site, make a positive contribution to the streetscene whilst the majority on the eastern side have been excluded from the conservation area.

2.4 Number 16A Lansdowne Road is the immediately adjacent property to the north of the application site. It is the former coach house of the application site and was converted to a separate dwelling in the 1950’s. The property bounding the site to the south at Number 15 is the former coach house of the original villa on that plot that was converted to a separate unit of residential accommodation.

2.5 There are some smaller houses on the road that have resulted from sub-division, extension and replacement of other villas at some stage. In addition several of the original villas have been replaced by large blocks of flats.

2.6 Both the original villas and most of the new blocks of flats have large basements.

2.7 Many front curtilages have been converted to off-street parking spaces with blocks of flats benefiting from parking to the rear of their plots.

3 CURRENT PROPOSAL

3.1 The proposal is made up of 2 main elements - a two-storey annexe structure linked to the main dwelling house and an enlarged basement to the main house going under the new annexe and extending beyond it which would provide an underground gym and swimming pool.

3.2 Annexe - The annexe would be located adjacent to on the southern side boundary with the neighbouring property at 15 Lansdowne Road. It would house

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a garage and playroom at ground floor level and a bedroom and bathroom above would replace the existing car port on the southern boundary. The 2-storey addition would be set back behind the front wall of the existing dwelling by 0.7m; and would be set back behind the building line set by the neighbouring properties at Numbers 15-15C Lansdowne Road by 1.2m. It would also be set away from the boundary with no. 15 by one metre.

3.3 Overall the addition would be 5.6m wide and 9.5m long; with a dual-pitched roof 5.06m at eaves and 7.05m tall at ridge height. The proposal includes the insertion of a door, an up-and-over garage door and a small window into the front elevation; a pair of French doors and a small window into the rear elevation; and a set of folding doors, a single door and five small windows into the northern side boundary facing the main house. The materials would be facing brick, slate roof tiles and painted timber window frames to match existing; with painted doors.

3.4 Basement extension - The existing basement currently follows the footprint of the existing house. It is proposed to extend it under the southern half of the existing garden with a 19m by 10m footprint and a maximum depth of 4.6m in the location of the pool, reducing in depth in other areas. It would be lit by a rooflight at the rear with a lightwell and rooflight at the front.

3.5 Communication between the original basement and the new basement would be achieved through the creation of a new interior door in what is currently used as a dining room; as well as access through the existing rear lightwell.

3.6 The link attachment between the house and the annexe building would contain a staircase connecting the new basement and garage. The link would be 4m long and 1.2m wide with a 2.5m high flat roof. The materials would be facing brick to the front elevation facing Lansdowne Road and glazing to the rear facing the back garden.

3.7 The application also seeks the erection of a front boundary treatment including sliding gates traversing both cross-overs. The boundary treatment would be a dwarf brick wall topped with railings with wrought metal gates flanked by brick piers. The height of the boundary treatment would be 1.8m tall; 2m to pier height.

3.8 The development would result in the loss of shrubs and immature trees to the southern side boundary due to the erection of the new building with replacement planting proposed. The trees on the front boundary and on the rear and northern boundaries will be retained.

3.9 A construction method statement has been submitted in connection with the basement. The applicant intends to underpin the application property and then to use a static load hydraulic piling process to insert sheet piles.. They advise that the insertion process would minimise noise and vibrations and disruption to the surrounding earth and neighbouring properties and promote stability during subsequent excavations. Excavated soil would be removed from the application

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site using slim-profile equipment in recognition of the narrowness of Lansdowne Road.

3.10 A Drainage Strategy Plan prepared by Consulting Engineers has been submitted, which sets out the measures proposed to deal with additional surfacewater run off which includes new soakaways, porous paving, water butts and sections of roof garden.

3.11 The proposal currently before committee has been amended since it was first submitted. The 2-storey annexe originally projected forward of both the front wall of the existing house and the building line set by Numbers 15-15C and was directly adjacent to no. 15 – it now sits behind both building lines and has been moved 1 metre away from the boundary.

4 PLANNING HISTORY

4.1 In November 1952 planning permission was granted under delegated powers for the conversion of the house into flats and the conversion of the coach house into a separate residential unit; limited until 30/09/1967 (LBM Ref. WIM1274).

4.2 In February 1954 planning permission was granted under delegated powers for the conversion of the house into flats and also the conversion of the coach house into a separate residential unit without restrictions (LBM Ref. WIM1790).

4.3 In November 2007 planning permission was granted under delegated powers for the construction of a 2-storey side extension that was link-attached to the main house (LBM Ref. 07/P2771).

5. CONSULTATION

5.1 The proposal has been advertised through the means of a conservation area press and site notice procedure; and individual letters have been sent to immediately neighbouring occupants.

5.2 The original site notice did not appear to have been displayed by Merton’s contractors so a second notice was displayed by the case officer.

5.3 Nine letters of objection have been received, summarised as follows:

� The basement will affect the water table and cause groundwater flooding further downhill;

� water from the swimming pool may leak into the ground and cause damage to neighbouring foundations;

� the proposal may increase surface water runoff; � the construction of the basement may result in local subsidence and may

affect the foundations of neighbouring properties; � no geological survey has been submitted to assess the impact of the

basement in terms of the two preceding items;

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� the design of the building is out of keeping with the area and would make Number 15 appear as a terraced dwelling thereby reducing the visual appeal and value of the property;

� the proposal is overbearing and will result in a loss of privacy for, and overshadow the garden of, Number 15;

� the proposal is, in effect, another dwelling and will increase the demand for parking on the road;

� the design of the boundary treatment is out of keeping with the area and the height is unacceptable;

� the wall and sliding gates are not in keeping with the boundary treatments in the area which are low wooden fences with foliage behind;

� the sliding gates will cause vehicles to wait on the road for access to the property and impede traffic;

� the trees on the property screen Number 15 from both the road and the application site;

� the loss of the trees will result in overlooking of Number 15; � the loss of the trees will result in a loss of views from Number 15; � the removal of the trees at the rear of the property will decrease the value

of views from neighbouring windows at Number 15; � construction will be disruptive particularly because of the degree of

excavation and the amount of earth to be removed from site, generate a lot of dirt and rubbish on kerbs and pavements that has caused problems for residents before, particularly those with impairments;

� highway safety will also be affected due to a high demand for vehicle access on a tight road and result in illegal parking as is happening now;

� the current renovations have been occurring on Saturdays after 1pm and all day on Sundays;

� the calibre of the contractors currently working on the site is such that they litter the highway, park their vehicles so that people cannot walk on the pavements and racially abused a parking enforcement officer;

� the drains cannot be replaced and so the proposal would put additional strain on the existing facilities;

� no site notice was displayed for the first application in 2007 or for this application in 2012;

� The Local Council has not protected the living conditions of residents for the last few months during the renovation of the application property because they have not policed out of hours work, illegal parking and littering and this proposal will exacerbate the situation.

5.4 The South Ridgway Residents’ Association was concerned with the knock-on effects of the subterranean swimming pool and stated that there should be a full geological survey; and that the amount of ground water running off the hill is considerable and will affect construction.

5.5 The Wimbledon Society stated that: � The extension as originally submitted did not respect street patterns

because it was forward of the building line;

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� the extension of the basement could affect groundwater courses and neighbouring properties;

� the loss of half of the rear and side garden should only be allowed if the proposed development outweighs the loss of amenity and if replacement foliage is provided in line with the policy in the draft Sites and Policies Development Plan Document;

� a schedule for the removal of trees and the protection of retained trees should be provided;

� a method statement detailing how lorries will remove the excavated soil should be required.

5.6 Tree Officer - raises no objections to the loss of trees that would result from the proposal; but has asked that those trees that are to be retained be protected with the addition of standard tree protection, site supervision and two non-standard conditions relating to the design of the boundary treatment and foundations and the provision of an aboricultural report..

5.7 Transport Planning – require some changes to the sightlines and gate design in order to avoid obstructed views of the highway and any impact upon pedestrian safety but are satisfied that this can be dealt with by a condition relating to the amendment of the existing crossover sightlines and the design of the proposed gates.

5.8 The application was subject to a reconsultation exercise following the receipt of the aforementioned amended plans. Eight subsequent letters of objection were received. In addition to reiterating the points already raised during the first round of consultation the following additional points have been made:

� No material change has been made and the proposal is still garden-grabbing over-development for the pursuit of profit;

� The two-storey building remains the same - simply re-naming a building is not amending plans – there is still a bedroom on the first floor whatever the ground floor is named;

� The description of side extension or annexe is misleading as the proposal is essentially another house and is an unacceptable increase in housing density;

� Adjoining properties were purchased in good faith without additional buildings on boundaries;

� This is a family home in Wimbledon not an embassy in central London; � The drainage report is not independent as it was commissioned by the architects

and does nothing to allay fears as no amount of technical theory will able to compensate for damage done in practice;

� The rear extension plan does not state explicitly in metres how deep the basement will extend down into the ground;

� Subterranean pool, Jacuzzi and gym is out of keeping with the area; � Residents can use Kings College’s pool so no need for a horrifying underground

pool;

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� Despite the report commissioned by the Applicant the excavation and removal of earth will adversely affect the living conditions of many for a considerable time;

� The nature of the road means that it will be impossible to replace sewers, thereby placing stress on the Victorian sewerage system;

� The proposal will block out the sun and make the garden of Number 15 much darker;

� Trees are now named in the tweaked plans, which shows a Cedar tree that is actually a Leylandii and it is obvious from the plans that this tree will need to be removed;

� The length of time necessary to construct this proposal will cause significant disruption and the disruption will reduce the quality of life for residents who have already suffered through years of disturbance from building work and renovations;

� To state that a crane and power-driven piling will diminish the impact upon neighbours is to insult our intelligence;

� The Applicant does not put away litter or bins and doesn’t remove their driveway gravel from the pavement;

� The reality of the Applicant’s concern for neighbours is reflected in the fact that a lorry delivering turf to the application site reversed into one neighbour’s driveway then wrecked a public lamppost outside another neighbour’s property and the driver spat and swore when the damage was pointed out to him;

� Another and a lorry delivering a TV blocked the road – incidents that could have been avoided if consideration had been given to neighbours and the restricted nature of the road;

� Obstructions in the road could be life threatening if an ambulance or fire engine were unable to pass;

� The front boundary wall has been re-jigged to include railings but the height remains the same and the sliding gates still remain;

� Planners ignored the concerns of residents about sliding gates slowing traffic at The Terraces – perhaps this time we will be heard;

� The proposal will set a dangerous precedent; � If the development is approved legal redress will be sought and the impact upon

residents and the area shall be publicised.

6. POLICY CONTEXT

6.1 The NPPF (2012) states that planning should:

� Seek to secure high quality design and a good standard of amenity for all existing and future occupants of land and buildings by responding to local character and history, and reflect the identity of local surroundings and materials, while not preventing or discouraging appropriate innovation;

� Support the transition to a low carbon future in a changing climate, taking full account of flood risk;

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� Conserve heritage assets in a manner appropriate to their significance, so that they can be enjoyed for their contribution to the quality of life of this and future generations;

6.2 The relevant policies from the London Plan (July 2011) are as follows: 5.12 (Flood Risk Management), 6.13 (Parking), 7.3 (Local Character), 7.6 (Architecture).

6.3 The relevant policies from Merton's Core Planning Strategy (2011) are as follows: CS13 Open Space, Nature Conservation and Culture, CS.14 (Design), CS.16 (Flood Risk Management), CS.20 (Parking, Servicing and Delivery)

6.4 The relevant saved policies from Merton's UDP (October 2003) are as follows: BE.1 (Conservation Areas, New Development, Change of Use, Alterations and Extensions), BE.11 (Local List, Rehabilitation and Maintenance), BE.15 (New Buildings and Extensions; Daylight, Sunlight, Privacy, Visual Intrusion and Noise), BE.22 (Design of New Development), BE.23 (Alterations and New Extensions), NE.11 (Trees; Protection

6.5 The following Supplementary Planning Guidance (SPG) is also relevant: Residential Extensions, Alterations and Conversions (November 2001).

7. PLANNING CONSIDERATIONS

7.1 The key planning issues are considered to be design and the impact upon the character and amenity of the conservation area, residential amenity and concerns about the impact of the basement in respect of construction and drainage, highways and trees.

7.2 Design and appearance and Impact on the Character of the Conservation Area

London Plan Policy 7.4 (Local Character) states that development should have regard to the form, function, structure, scale and massing of an area and its buildings. London Plan Policy 7.6 states that architecture should have a design appropriate to its context. Merton’s Core Strategy Policy CS14 (Design) requires all development to be designed to respect and reinforce the local character of the area in which it is located and UDP Policy BE.1 requires it to complement the Conservation Area. Merton’s UDP Policy BE.11 demands that extensions to locally listed buildings be sympathetic to the scale, proportion character and materials of the original building.

7.2.1 A previous proposal for a two storey annexe style addition to the main house was approved in 2007 but not implemented. Although it differed in footprint and design it was in a broadly similar location and read as a sub-servient building to the main house. A similar approach is taken with the current application in that it is visually separate from the main house, much smaller in scale, with the appearance of a coachhouse. Officers consider this to be acceptable in terms of

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the impact on the streetscene and the Wimbledon West Conservation Area. It maintains the visual integrity of the main building and produces a pattern of development that is in character with its surroundings.

7.2.2 The proposal appears to be an outbuilding but the link attachment and the connection with the existing and expanded basement means that it is actually an extension of the existing dwellinghouse and not a separate unit of accommodation. However a standard condition requiring that the structure be used only for purposes ancillary to the existing dwellinghouse could be applied to ensure that the Council maintains control over future development.

7.2.3 The proposal has been amended during the life of the application such that the 2-storey addition now sits behind both the front wall of the existing house and the building line set by Numbers 15-15C Lansdowne Road. In addition the link attachment has been reduced in height; and the separation distance between the flank wall of the extension and Number 15 has been increased to 1 metre.. These alterations combine to produce a scheme that would appear to be subordinate to the existing dwellinghouse.

7.2.4 As such it is considered that the proposed addition would replicate the pattern of development on the western side of Lansdowne Road – that is large villas with subordinate side structures - in a manner that would not be detrimental to the character and appearance of the streetscene as a whole or the Wimbledon West Conservation Area in general.

7.2.5 The proposed front boundary treatment would be a dwarf brick wall topped with railings; and the gates would also be composed of see-through wrought metal. The existing flank wall of the car port to be removed is flush with the highway and is as tall as the proposed boundary treatment. As such the proposed boundary treatment would provide enhanced views into the site compared to the existing close-boarding. Transport Planning have requested the addition of a non-standard condition requiring that the existing crossovers and the proposed boundary treatment be amended in a manner that may affect the final height and/ or location of the gates.

7.2.6 The proposed basement would not be visible from the public domain and no additional lightwells are to be created. The rooflights that will be inserted into the ground above the back of the proposed swimming pool would be flush with the ground and would have no impact upon visual amenity. The link attachment will be glazed to the rear to provide further illumination above the front of the swimming pool but would be in matching brick facing the road. As such it is considered that this element of the proposal would have no impact upon the character and appearance of the original locally listed dwellinghouse as a whole or the Wimbledon West Conservation Area in general.

7.2.7 Considering the above, the proposal is considered to be acceptable in terms of its impact upon the character and appearance of the existing locally listed

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building, the Lansdowne Road streetscene and the Wimbledon West Conservation Area.

7.3 Residential amenity

7.4.1 London Plan Policy 7.6 (Architecture) states that structures should not cause unacceptable harm to residential buildings in terms of privacy and overshadowing. Merton’s UDP Policy BE.15 (New Buildings and Extensions; Daylight, Sunlight, Privacy, Visual Intrusion and Noise) requires that extensions must protect the amenities of neighbouring occupants including the levels of light and privacy and avoiding visual intrusion and noise disturbance.

7.4.2 The annexe building would sit behind the front and rear walls of the nearest neighbour at Number 15. The height of the structure would not exceed the height of Number 15. As such it is considered that the proposal would not be overbearing nor would it result in a loss of light to neighbouring windows or overshadow adjacent gardens.

7.4.3 No windows are proposed in the flank wall facing Number 15. The windows in the rear elevation would only afford oblique views towards the neighbouring garden and replacement screen planting is proposed along the southern boundary which would be required by condition. As such it is considered that the proposal would not result in an unacceptable increase in overlooking.

7.4.4 A condition is proposed in order to ensure that there is no adverse noise impact from any plant or machinery associated with the swimming pool.

7.4.5 The excavation of the basement would require that a large amount of soil be transported from the site and has the potential to cause noise and disruption from its construction. A construction management plan would therefore be required to relating to control of dust, construction and delivery hours, control of noise and vibration, method of soil removal as well as the accommodation of construction, site worker and visitor vehicles and loading/ unloading could also be applied.

7.4.6 Concern has been expressed about both groundwater flooding and surface water flooding. London Plan Policy 5.13 (Sustainable Drainage) seeks to reduce surface water flooding and Merton’s Core Strategy Policy CS16 (Flood Risk Management) also seeks to manage surface water flooding through the use of sustainable drainage.

7.4.7 Lansdowne Road is not in a flood zone. Merton’s Surface Water Management Plan (2011) was produced in response to the requirements of London Plan Policy 5.13 (Sustainable Drainage); and includes geological survey data for the borough. This report indicates that Lansdowne Road’s bedrock geology is a Bagshot formation set above London Clay; with a superficial geology of Black Park Gravel. This geology is theoretically considered to be less prone to groundwater flooding. A Drainage Strategy Plan prepared by Consulting Engineers has been submitted, which sets out the measures proposed to deal

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with additional surfacewater run off which includes new soakaways, porous paving, water butts and sections of roof garden.

7.5 Transport issues

7.5.1 The proposed garage door has been amended to sit further into the site to provide space within the front curtilage for a car in front of the garage. The proposed electric sliding gates would generate a shorter waiting time than manually operated gates. By demolishing the un-used carport, which is difficult to access in and out from, and providing a larger garage set further away from the footpath the proposal will result in a greater capacity for off-street parking.

7.5.2 It is considered that the proposal would not impede waiting traffic more than the current conditions on the site or at other properties on the road. Transport Planning have no objection to the erection of the sliding gates subject to the imposition of a condition relating to the amendment of the existing crossovers to include sightlines that may affect the height and/ or location of the proposed gates. This requirement for highway safety can be controlled through the addition of a non-standard condition requiring that the existing crossovers be amended and that also controls the design of the boundary treatment.

7.5.3 It is considered that this condition would improve the safety of highway users and, as such, the proposal is considered to be acceptable in terms of its impact upon local traffic, highway safety and parking.

7.6 Trees

7.6.1 The Tree Officer has raised no objections to the loss of immature trees and shrubs along the southern boundary that would result from the proposal; but has asked that those trees that are to be retained be protected by use of standard arboricultural report, tree protection and site supervision conditions and a non-standard condition relating to the design of the boundary treatment and its foundations.

7.6.1 Replacement planting is proposed to the southern side boundary with Number 15.

7.6.2 The trees to the front of the site consist of a Lime tree and three Yews. There are no Leylandii or Cedars. The construction of the dwarf boundary wall and railings will require some foundations but the Applicant intends to retain all trees at the front of the site. Conditions about tree protection and supervision during construction will be applied; as will a condition requiring full details of the front boundary treatment including any foundations.

7.6.3 It is considered that the proposal’s impact upon trees would be acceptable.

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8 SUSTAINABILITY AND ENVIRONMENTAL IMPACT ASSESSMENT REQUIREMENTS

8.1 The application does not constitute Schedule 1 or Schedule 2 development. Accordingly, there are no requirements in terms of EIA submission.

9 LOCAL FINANCIAL CONSIDERATIONS

9.1 The proposed development would result in a net gain in gross floor space and, as such, could be liable to pay the Mayoral Community Infrastructure Levy; the funds for which will be applied by the Mayor towards Crossrail.

10 CONCLUSION The proposal would result in the extension of a dwellinghouse with no undue impact upon visual or residential amenity, traffic and highway conditions or trees. The proposal is considered to accord with local and regional development plans; and is also in line with national policy guidance.

RECOMMENDATION Grant planning permission subject to the following conditions

A1 Commencement of Development A7 Construction in accordance with plans B1 External Materials to be approved

Non-standard condition - Details of boundary treatment No development shall take place until details of all boundary walls, fences or gates, including height, design, materials, location, foundations and method of construction, are submitted in writing for approval to the Local Planning Authority. No works which are the subject of this condition shall be carried out until the details are approved, and the works shall be carried out in accordance with the approved details and maintained as such thereafter. Such details relating to the construction of the dwarf wall, piers and gates along the frontage shall have regard to the BS 5837:2012 and shall be included in the Aboricultural Method Statement and Tree Protection Plan Reason: To ensure a satisfactory and safe development in accordance with policies BE.16 and BE.22 of the Adopted Merton Unitary Development Plan; and to protect and safeguard the existing retained trees in accordance with policy CS13 of the AMSPS 2011.

B8 Piling Condition

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C2 No Permitted Development (Windows and Doors) D4 Soundproofing of Building Control of noise from plant and machinery D11 Construction times E6 Ancillary Residential Accommodation F5P Tree Protection F8 Site Supervision (Trees)

Non-standard condition: Amendment to crossovers/location and design of gate. Reason: In the interests of the safety of vehicles and pedestrians and to comply with Local Development Framework Core Strategy policy CS20

H9P Construction Vehicles

Non-Standard condition: Construction management plan Reason: To ensure a satisfactory and safe development and to protect neighbouring amenity during construction.

Reason for Approval: It is considered that the proposed extensions and alterations would be sympathetic to the form, scale, bulk and proportions of the original locally listed building and would preserve or enhance the character and appearance of the Merton (West Wimbledon) Conservation Area, whilst not having a detrimental impact on neighbour amenity. The proposal accords with the Council's Adopted Unitary Development Plan, Core Strategy and London Plan Policies. The policies listed below were relevant to the determination of this proposal. London Plan (July 2011): 3.5 (Quality and Design of Housing Developments), 5.12 (Flood Risk Management).

Merton's Core Strategy (2011): CS13, CS.14 (Design), CS.16 (Flood Risk Management), CS.20 (Parking, Servicing and Delivery)

Merton's UDP (October 2003): BE.1 (Conservation Areas, New Development, Change of Use, Alterations and Extensions), BE.11 (Local List, Rehabilitation and Maintenance), BE.15 (New Buildings and Extensions; Daylight, Sunlight, Privacy, Visual Intrusion and Noise), BE.22 (Design of New Development), BE.23 (Alterations and New Extensions), NE.11 (Trees; Protection), NE.12 (Trees, Hedges and Landscape Features),

SPG: Residential Extensions, Alterations and Conversions (November 2001).

INF11 Drainage INF15 Discharge conditions prior to commencement of work INF26 Community Infrastructure Levy

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Non-standard informative about the need to comply with the building regulations and contact details of Merton’s Building Control Team

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Construction Method statement

1. Introduction.

This Construction Method Statement has been prepared by Marek Jasinski Design Marek Jasinski BA Hons Dip Arch RIBA has had over 20 years experience in building on site and has built many basements in the London area and also many pools in surrey.

His experience in overseeing basement construction as both site architect and director allows him to write this report.

2. Soil report.

Lansdowne Road is situated on a hill and the British Geological Survey bore hole ref 589285. This is detailed in the drainage report prepared by The Stilwell Partnership

Building control has also confirmed that the general make up is of about 3m of ballast-i.e. sands and gravels sitting on clay but no exact detail has been confirmed.It is also possible to assume that the makeup of the clay will be similar to those found in Arterberry road – see planning application 09/P129.

3. Drainage report.

A separate drainage report is being prepared by The Stilwell Partnership which is attached to our application as a separate document.

4. Construction methodology.

In order to avoid disturbance to adjoining neighbours, we are proposing to use either contiguous concrete piles or sheet piles using a relatively silent process know as static load hydraulic piling. Please see details attached at back of method statement. These piling methods would be a quiet, clean and near vibration free operation and therefore would have reduced impact on neighbours.

The area where the basement is proposed does not affect any existing drainage or services. It is unlikely that the works will initiate slope instability that will affect neighbours as the and is relatively level. Further down the hill as shown in the report for Arterberry Road some failures have occurred due to the slope of the land. In recent cases this has been overcome.

Steel sheet pi le can be of numerous shapes, thickness and sizes. Most of them can be water-tighted and for some heavy sections they can be driven down to 15m

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depth. To erect and install a series of sheet piles and keep them vertical in all directions a guide frame may be required. The piles are lifted by a crane, using the lifting holes near the top of each pile, and positioning them between the guide walling of the guide. A hydraulic hammer can be used to reduce noise.

The advantage of sheet piles is that they form a waterproof barrier and can be laid relatively easily without taking up much space. It would also be possible to allow some movement of water across the site by setting out the sheet piles way from the adjoining property 15 Lansdowne Road.

The existing house would be underpinned as normal under pinning works. The rest of the extension would be sheet piles

Once the existing house has been underpinned and the site enclosed in piles then the remaining earth enclosed will be removed from site.

It is noted that the width of the road and the size of the site will require all construction machinery/vehicles (including piling rigs, dumpers and excavation equipment) to be of a suitably slim profile in order to manoeuvre properly

It is planned that that waste would be transported by mini-dumpers to a skip located on the drive or to lorries parked on the drive. It may be possible subject to agreement by neighbours that we may use a conveyor system that would be located on the driveway itself, which could be less disruptive to the residents, due to the absence of mobilised traffic.

Once the soil has been excavated the concrete slab etc will be poured including drainage etc subject to approval by Thames Water and Building Control. The pool walls and roof will then be cast allowing the construction of the courtyard and the garage extension.

The sheet piles will retain the soil adjacent to the existing buildings and therefore without vibration will not affect the structures. Any works will confirm and exceed the British Standards for temporary works. Before works start a full report will be prepared by the contractor and checked by the Structural Engineer acting for the client . The engineer will be either a Chartered Civil Engineer (MICE) or Chartered Structural Engineer (MI Struct.E),

Party wall Act.

It will be necessary to agree party wall awards with the adjoining owner of 15 Lansdowne Road with an agreement to monitor and control the affects of the constriction.

Conclusion

1. The site can be piled using silent and vibration free methods. 2. Extraction of soil cab be executed by using small machines and kept very quiet using conveyor belts to help with the process.

152

3. A party wall agreement will be entered into with the adjoining owners to ensure that no works damage the property and that it is fully monitored during the construction process. 4. The design of the structural works will be carried out by a qualified structural engineer.

153

��

DRAINAGE STRATEGY PLANProposed Development at 16 Lansdowne Road Wimbledon

For Nathalie Ridge

MAY 2013

Stilwell LimitedConsulting Engineers Satelliet House,2 Nexus Park,Lysons Avenue,Ash Vale,GU12 5QE

Telephone: 01276 700 400Fax: 01252 544 934E-mail: [email protected] Site: www.stilwell-ltd.co.uk

Version No: 2.0

Stilwell Partnership ISO 9001:2008Certificate No: LRQ 4004624

154

Nathalie Ridge Drainage Strategy Plan16 Lansdowne Road, Wimbledon

Document LocationEnsure that this document is current. Printed documents and locally copied files may become obsolete

due to changes to the master document.

This is a controlled document.

The source of the document can be found on the file server at location:

S:\Clients\Nathalie Ridge\16 Lansdowne Road, Wimbledon - P2432\Reports\Drainage Strategy Plan V2.0.docx

Revision HistoryThis document has the following history:

Version No. Version Date Summary of Changes Changes marked

1.0 26/04/2013 N/A N/A

2.0 03/05/2013 Detail added No

ApprovalsThis document requires the following approvals:

Name Title & Organisation

David Brooke Author – Stilwell Limited

DistributionThis document has also been distributed to:

Name Organisation

Marek Jasinski Marek Jasinski Design

Kelly Howell Merton Council

Nathalie Ridge Client

Version 2.0 Page 2 Version Date: 03/05/2013 Date Printed: 03/05/2013 14:54Author: David Brooke Owner: The Stilwell Partnership

S:\Clients\Nathalie Ridge\16 Landsdowne Road, Wimbledon - P2432\Reports\Drainage Strategy Plan V2.0.docx155


CONTENTS

1.0 INTRODUCTION ................................................................................................ 4 2.0 LOCATION OF SITE .......................................................................................... 4 3.0 SITE DESCRIPTION AND CONTENT................................................................ 5 4.0 DEVELOPMENT PROPOSAL............................................................................ 7 5.0 SUMMARY AND CONCLUSIONS ..................................................................... 9

APPENDICES

A Site Location PlanB Topographical SurveyC Borehole RecordD Bedrock and Superficial Geology MapE Contour MapF Existing Drainage FeaturesG Sewer RecordsH Proposed Site Layout PlansJ Drainage Strategy Plan




1.0 INTRODUCTION

1.1 The Stilwell Partnership has been instructed by Nathalie Ridge, to provide a Drainage Strategy

Plan to support a Planning Application for the proposed development at 16 Lansdowne Road

Wimbledon.

1.2 This report aims to demonstrate that the surface water can be handled adequately and also

mitigate and reduce the risk of ground water contamination, by providing adequate sustainable

urban drainage systems.

1.3 Marek Jasinski Design on behalf Nathalie Ridge is in the process of submitting a Planning

Application for an extension, on land adjacent to 16 Lansdowne Road.

2.0 LOCATION OF SITE

2.1 The site is located to the west of Lansdowne Road Wimbledon and is located generally in a

residential setting. Lansdowne Road is a quiet residential road which links to the B281

Ridgeway to the north. The town centre is located approximately a few hundred metres from

the site. A Site Location Plan is included at Appendix A.

2.2 The Local Authority is Merton Council.




3.0 SITE DESCRIPTION AND CONTEXT

Site Description

3.1 The proposed development site encompasses the existing garden of 16 Lansdowne Road,

south of the building. The topography of the site is generally flat. A series of domestic drainage

features exists within the curtilage of the site. A Topographical Survey is attached at Appendix

B.

3.2 The existing detached house has a lower basement and a detached garage.

Geological Setting3.3 A borehole record (BGS ID 589285) at No:8 The Drive, which is located 184.3m to the southeast

of the site, has been gained from the British Geological Survey website. The borehole is 9.14m

deep. According to the borehole the ground formation is as follows:

The topsoil is approximately 600mm thick. Next 1.7m consists of sandy gravelly strata. This

section sits onto the firm to stiff grey laminated silty clay containing layers of sand and sandy silt.

This section is approximately 5.6m. The last section of the borehole is approximately 2.1m and

containing stiff dark grey laminated silty clay containing layers and pockets of sand and sandy

silt. The detail of the borehole record is included in Appendix C.

3.4 London Borough of Merton provides some geological information in their Surface Water

Management Plan (SWMP). According to the maps, figure 1 & 2 of the SWMP, the bedrock and

superficial geology of the area is as stated;

Bedrock and Superficial geology: The site is located in ‘Black Park Gravel Member’. The

generic description of ‘Black Park Gravel Member’ is defined on BGS website as "Sand and

gravel, with possible lenses of silt, clay or peat. Similar soil classification is provided with BGS

borehole record.

The bedrock and superficial geology is attached at Appendix D.

Hydrogeology Setting

3.5 Although according to the BGS borehole there is an indication of water presence within the

borehole at 2.28m, the depth is minimal. This is likely due to the lower ground having reduced

permeability properties.




3.6 The Environment Agency’s website shows aquifers and provides designations which are in line

with the Water Framework Directive and are based on maps produced by the BGS. The

Superficial Deposits and bedrock designation beneath the site are classified as Secondary A.

This suggests that the soil below the site is permeable to certain extent and these layers are

capable of water supplies at local level. However, borehole records show no signs that there is

groundwater around the site.

Contour plan for the area shows that the site is located at the high level (50m), this contour plan

is attached at Appendix E.

Existing Drainage Situation

3.7 As stated previously, the site is an existing house with a garden. There are private drains within

the site as shown in Appendix F. In Lansdowne Road there is a 150mm diameter foul sewer

and a 300mm diameter surface water sewer. A copy of the sewer records is attached in

Appendix G.

3.8 The majority of the existing surface water drainage discharges into two soakaways, one in the

rear garden and the other in the side garden as shown in Appendix F. There is also one

rainwater pipe connecting to the foul system.

3.9 All foul drainage discharges into the public foul sewer in Lansdowne Road.




4.0 DEVELOPMENT PROPOSAL

4.1 The proposal is to build an extension to the house with a basement and indoor swimming pool.

4.2 The proposed Site Layout Plan is included in Appendix H. The proposed site will obviously

increase the amount of hard surfacing and, therefore measures to reduce surface water runoff

will be introduced. These include a number of sustainable drainage techniques for the proposed

site.

� Aquacell units (soakaways) for the roof areas only

� Porous paving for private driveway and parking area

� Water Butts

� Sections of roof garden

4.3 It is proposed to use sustainable infiltration measures on site to accommodate the surface water

run-off. However, it should be noted that we are not increasing the amount of rainwater entering

the ground, but concentrating water into one point. The surface water from the roof will be piped

to a soakaway in the rear garden. All these measures will be explained in detail later in the

report.

Surface Water4.4 The underlying soil strata of the site is gravel overlaying clay. The exact depth of the gravel is

unknown but the local building control office believes it to be about 3m in the area. Therefore,

the site is suitable for infiltration.

4.5 The surface water from any roofs will be discharged into Aquacells (soakaways). All

soakaways, where practicable, should be located 5m away from buildings. If it is not possible to

provide soakaways in rear garden for any reason, then permission will be sort to discharge the

surface water into a Thames water Surface Water Sewer. Any additional water would be

attenuated before its enters the public sewer. At present the existing surface water discharges

into soakaways (see existing drainage features in Appendix F).

4.6 The new soakaway will be designed to accommodate a 1 in 100 year plus 30% climate change

event. It will replace the two existing soakaways which were most likely designed to

accommodate a 1 in 2 year storm event. It is possible to locate an Aquacell style soakaway at

least 5m from any structure, as shown in Appendix J. The Calculations would be submitted as

part of the building control submission.




4.7 Any surface water runoff from the small driveway will infiltrate the ground through porous

surfacing. The runoff will flow through the clean stone, where pollutants are captured and

immobilised. The treated water is then conveyed to the underlying gravel.

4.8 For parts of the surface water system it will be necessary due to levels and site constraints to

pump surface water to higher level before entering the conventional drainage system. This is

similar to the existing arrangement where rainwater from the lower basement is pumped. A

regular maintenance system will need to be in place.

Foul Drainage

4.9 The foul water discharge will be to the existing 150m diameter pipe in Lansdowne Road (see the

Drainage Strategy Plan in Appendix J). The internal foul drainage will need to improved and

re-routed in places subject to building control approval.

4.10 Due to the basement and swimming pool there will be the need to pump foul water from these

areas up to ground level before the foul waste gravitates to the system.

4.11 Any discharge required from the pool when cleaning or general maintenance will be directed into

the foul system.




5.0 SUMMARY AND CONCLUSIONS

5.1 The Stilwell Partnership has been instructed by Nathalie Ridge to produce a Drainage Strategy

to accompany a Planning Application seeking permission for a new extension.

5.2 The report has shown that the site surface water will be adequately drained and treated before

any infiltration into the ground.

5.3 The development will not be increasing the runoff from the site by introducing soakaways,

porous paving, water butts, therefore not increasing the likelihood of flooding.

5.4 The development by introducing a new soakaway designed to accommodate a 1 in 100 year

storm event plus climate change will improve the drainage for the site.

5.5 The foul drainage will connect into a public sewer in Lansdowne Road, as likely to be agreed by

Thames Water.

5.6 This drainage strategy has confirmed that the systems proposed for the development are

appropriate and sustainable.



APPENDIX A

Site Location Plan

163

APPENDIX B

Topographical Survey

165

APPENDIX C

Borehole Record

167

APPENDIX D

Bedrock and Superficial Geology Map

170

APPENDIX E

Contour Map

172

APPENDIX F

Existing Drainage Features

174

APPENDIX G

Sewer Records

176

APPENDIX H

Proposed Site Layout Plans

179

APPENDIX J

Drainage Strategy Plan

182

proposal - london borough of merton · back garden has holly trees and magnolias. 2.2 the site is...

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