HYDRO INTERNATIONAL STORMWATER MANAGEMENT SYSTEMS STORMBLOC STORMWATER MANAGEMENT SYSTEM

Transcription

1 Hydro International PLC Shearwater House Clevedon Hall Estate Victoria Road Clevedon Somerset BS21 7RD Tel: Fax: website: APPROVAL INSPECTION TESTING CERTIFICATION TECHNICAL APPROVALS FOR CONSTRUCTION Agrément Certificate 10/4795 Product Sheet 1 HYDRO INTERNATIONAL STORMWATER MANAGEMENT SYSTEMS STORMBLOC STORMWATER MANAGEMENT SYSTEM PRODUCT SCOPE AND SUMMARY OF CERTIFICATE This relates to the Stormbloc Stormwater Management System, for use as sub-surface water storage or as a soakaway to manage run-off from impermeable surfaces. AGRÉMENT CERTIFICATION INCLUDES: factors relating to compliance with Building Regulations where applicable factors relating to additional non-regulatory information where applicable independently verified technical specification assessment criteria and technical investigations design considerations installation guidance regular surveillance of production formal three-yearly review. KEY FACTORS ASSESSED System design information is provided in the Certificate to assist in the design of a stormwater management system (see section 5). Strength the system has adequate strength and stiffness to resist long- and short-term loads when used in accordance with this Certificate (see section 6). Resistance to chemicals the system will have adequate resistance to the types and levels of chemicals likely to be found in rainwater and soils normally encountered in civil engineering practice (see section 9). Durability the system will have a service life in excess of 50 years when installed in accordance with this Certificate (see section 11). The BBA has awarded this Agrément Certificate to the company named above for the system described herein. This system has been assessed by the BBA as being fit for its intended use provided it is installed, used and maintained as set out in this Certificate. On behalf of the British Board of Agrément Date of First issue: 24 December 2010 Brian Chamberlain Greg Cooper Head of Approvals Engineering Chief Executive The BBA is a UKAS accredited certification body Number 113. The schedule of the current scope of accreditation for product certification is available in pdf format via the UKAS link on the BBA website at Readers are advised to check the validity and latest issue number of this Agrément Certificate by either referring to the BBA website or contacting the BBA direct. British Board of Agrément tel: Bucknalls Lane fax: Garston, Watford mail@bba.star.co.uk Herts WD25 9BA 2010 website: Page 1 of 16

2 Regulations In the opinion of the BBA, the Stormbloc Stormwater Management System, if used in accordance with the provisions of this Certificate, will meet or contribute to meeting the relevant requirements of the following Building Regulations: The Building Regulations 2010 (England and Wales) Requirement: H3(3) Comment: Requirement: Regulation 7 Comment: Rainwater drainage The system can be used in a construction to meet this Requirement. See sections 5.1 to 5.10 of this Certificate. Materials and Workmanship The system is acceptable. See section 11 and the Installation part of this Certificate. The Building (Scotland) Regulations 2004 (as amended) Regulation: 8(1)(2) Fitness and durability of materials and workmanship Comment: The use of the system satisfies the requirements of this Regulation. See sections 10 and 11 and the Installation part of this Certificate. Regulation: 9 Building standards construction Standard: 3.6(a) Surface water drainage Comment: The system can be used in a construction to satisfy this Standard, with reference to clauses (1)(2) to (1)(2). See sections 5.1 to 5.10 of this Certificate. (1) Technical Handbook (Domestic). (2) Technical Handbook (Non-Domestic). The Building Regulations (Northern Ireland) 2000 (as amended) Regulation: B2 Fitness of materials and workmanship Comment: The system is acceptable. See section 11 and the Installation part of this Certificate. Regulation: B3(2) Suitability of certain materials Comment: The system is acceptable. See section 10 of this Certificate. Regulation: N5 Rain-water drainage Comment: The system can be used in a construction to satisfy this Regulation. See sections 5.1 to 5.10 of this Certificate. Construction (Design and Management) Regulations 2007 Construction (Design and Management) Regulations (Northern Ireland) 2007 Information in this Certificate may assist the client, CDM co-ordinator, designer and contractors to address their obligations under these Regulations. See sections: 2 Delivery and site handling (2.3) and 13 Installation Procedure (13.1) of this Certificate. Non-regulatory Information NHBC Standards 2010 In the opinion of the BBA, the use of the Stormbloc Stormwater Management System, in relation to this Certificate, is not subject to the requirements of these Standards. General This Certificate relates to the Stormbloc Stormwater Management System, consisting of polypropylene units, end plates, connection pieces and polyethylene pipe adapters. This Certificate does not cover the collection or disposal of the surface water. Information relating to this can be obtained from the Certificate holder. Stormbloc is a registered trade mark of Hydro International PLC. Page 2 of 16

3 Technical Specification 1 Description 1.1 The Stormbloc Stormwater Management System (see Figure 1) consists of: individual green polypropylene modular units, incorporating integral inspection tunnels, in two sizes (see Table 1) black or green polypropylene horizontal and vertical connection pieces green polypropylene end plates black polyethylene pipe adapters stainless steel screws for fixing end plates and adapters (if required). Figure 1 Stormbloc components full block (800 mm x 800 mm x 660 mm) half block (800 mm x 800 mm x 350 mm) modules DN 150 socket DN200 socket DN225 socket pipe adapters single layer (horizontal) connector multi-layer connector ancillary items Page 3 of 16 Snap-Ioc end plate

4 Table 1 Characteristics of modular unit Unit Full Block Half Block Nominal dimensions (length x width x height) (mm) 800 x 800 x x 800 x 350 Nominal volume (m³) Nominal storage volume (m 3 ) Porosity (void ratio) (%) Nominal Mass (kg) Ultimate compressive strength at yield (kn m 2 ) Short-term deflection (1) Vertical loading on top face Lateral loading on side face Vertical loading on top face Lateral loading on side face mm per 28 kn m 2 1 mm per 9 kn m 2 Estimated long term deflection (ln) (2) (Ln) (3) (mm) (1) Applied load. (2) At up to 20 years at 20 C at 94 kn m 2 load. (3) Time in hours. 1.2 The units are used in multiples in a block formation and are installed underground. The system manages run-off from impermeable surfaces by means of: infiltration ie as a soakaway to infiltrate water back into the ground attenuation ie as temporary storage for excess flows and to control outflow to streams and rivers a combination of the above methods. 1.3 Connection to pipework may be effected either by pipe adapters inserted through or screwed to the polypropylene modular units or through the use of Stormbloc inspect chambers. All such connection methods are outside the scope of this Certificate. Self-tapping screws (where required) are supplied with the units. 1.4 Each assembled system is wrapped in either a permeable geotextile when used for infiltration or an impermeable geomembrane when used for attenuation. These are outside the scope of this Certificate. Information on the required specification for the geotextile and/or geomembrane can be obtained from the Certificate holder. 1.5 Adequate venting (using an air vent) to a manhole or to the atmosphere must be provided to the Stormbloc structure to enable the system to accommodate its maximum storage volume. The designer should determine the number and size of vent pipe connections required. Air vent connections and associated pipework for use with this system are outside the scope of this Certificate. 2 Delivery and site handling 2.1 The Stormbloc Stormwater Management System units are supplied to site in packs of four full blocks (two layers of two units) to create a pallet 1.6 m x 0.8 m x 1.32 m deep, or eight half blocks (four layers of two units) to create a pallet 1.6 m x 0.8 m x 1.4 m deep. The modules are secured with two straps. Each pack carries a label bearing the product identification, employee reference, date of manufacture, article number and size. 2.2 Connection pieces are packed in sealed, polyethylene bags of 100. Each bag carries a label bearing the product identification and article number. 2.3 End plates and adapters are either individually packed and labelled with product identification and article number or packed in cardboard boxes bearing the same information. 2.4 The packs of Stormbloc units should be carefully placed on level ground and should not be stacked on site. Loose individual units should not be stored more than two modules high and should be secured against high winds. 2.5 Stormbloc units contain an inhibitor to resist the effects of ultraviolet light for up to six months. However, prolonged exposure to direct sunlight should be avoided. 2.6 Stormbloc units should not be stored near sources of direct heat, fuel bowsers, fuel tanks or solvents. 2.7 Stormbloc units are resistant to the types of damage likely to occur during normal handling but should not be dropped or thrown, particularly in cold or frosty conditions. They should be stored in locations away from the possibility of impacts from vehicles and other construction plant. Assessment and Technical Investigations The following is a summary of the assessment and technical investigations carried out on the Stormbloc Stormwater Management System. Page 4 of 16

5 Design Considerations 3 General 3.1 The Stormbloc Stormwater Management System must be designed in accordance with the Certificate holder s instructions. Guidance on the application of sustainable drainage systems (SUDS) for new developments, such as the Stormbloc Stormwater Management System, can also be found in the Planning Policy Statement PPS25 Development and Flood Risk and The SUDS Manual C697 published by the Construction Industry Research and Information Association (CIRIA). 3.2 The system can be used for the control of run-off from impermeable surfaces in three main ways: infiltration water is collected in the units during rainfall and allowed to drain away by soaking into the surrounding ground over a period of time attenuation water is collected in the units during rainfall and released at a reduced flow rate through a flow control device into an appropriate outfall. This reduces peak flows in the watercourse, thereby minimising the risk of flooding combined a combination of the above two systems. 3.3 Design of the appropriate system (see Table 2 and Figure 2) for a specific project must always be preceded by a detailed audit of the proposed site to establish: existing factors and considerations applicable to the site predicted factors relating to the site s use following the planned development, and the parameters within which the installation will be required to function the type of function of application suggested by this audit. Table 2 Site audit factors/considerations. Design aspect Drainage area Space required (footprint) Location Site topography and stability Subsurface soils, environmental sensitivity and groundwater Future site use Considerations area to be drained and rainfall data the drainage area connected to a tank or soakaway should be as small as is practical in order to limit silt accumulation a system of several smaller tanks is preferable to one large tank the use of upstream pre-treatment, such as silt traps or hydrodynamic separation, is recommended to minimise silts reaching the tank. available area for siting tank or soakaway. consider possible effects of infiltrating water on building foundations or other structures such as roads. ground should be stable, especially where it is sloping; specialist assessment of soil and groundwater conditions may be necessary. seasonal groundwater levels must be at least one metre below a soakaway; consider flotation forces if above base of a tank an appropriate risk assessment should be undertaken for areas which may contain contaminated soils, groundwater or are environmentally sensitive soil properties, eg CBR value, stiffness, infiltration potential, etc. should be considered. future possible changes in site use should be considered. For example, landscaped areas may be paved over to provide additional parking. Tanks or soakaways should be sited away from areas likely to be subject to further development. Page 5 of 16

6 Figure 2 Flowchart of the design process Is roof drainage present? NO Consider Infilration YES Consider rainwater harvesting Is the soil infiltration rate suitable? NO Use Stormwater Attenuation YES Determine design criteria: rainwater yield, non-potable water usage Is development in a protected groundwater zone? YES Determinine Design Critria: Return period, Rainfall data, Catchment data, Discharge consent NO Is the groundwater level appropriate? NO Calculate tank size, filter and control system requirements YES Determine design criteria: Return period, rainfall data, catchment data Design Flow Control (Hydro-Brake Flow Control) (1) Calculate Storage Volume Required Consider overflow solution Design Soakaway to BRE Digest 365 or CIRIA Report 156 Detailed Design Detailed Design StormBank Rainwater Harvesting Stormbloc Infiltration System Stormbloc Attenuation System (1) (1) Consider stormwater treatment such as Hydro Filterra, Downstream Defender, Up-Flo Filter (1) Stormbank Rainwater Harvesting, Hydro Filterra Bioretention System, Downstream Defender Separator, Up-Flo Filter and Hydro-Brake Flow Control are other drainage products offered by the Certificate holder but which are outside the scope of this Certificate. Further information can be obtained from the Certificate holder. Hydro-Brake is covered by Agrément Certificate 08/4596. (2) Stormbank, Stormbloc, Hydro Filterra, Downstream Defender, Up-Flo and Hydro-Brake are registered trademarks of Hydro International plc. 3.3 Once the project criteria have been established from the site audit, there are two main parts to the design process, namely hydraulic design and structural design (see sections 5 and 6). Page 6 of 16

7 4 Practicability of installation The system is designed to be installed by a competent general builder, or a contractor, experienced with this type of system. 5 Hydraulic design Infiltration Calculation principles 5.1 Either the Construction Industry Research and Information Association (CIRIA) method, as given in Report 156 Infiltration Drainage Manual of Good Practice, or the Building Research Establishment method, as given in BRE Digest 365 Soakaway Design, may be adopted. 5.2 A simplified approximate approach can be used on a very small site (eg a single-house development) where detailed site infiltration rate information may not be required nor available (see Table 3). From Approved Document H of the England and Wales Building Regulations, for areas up to 25 m 2, a storage volume equal to 10 mm of rainfall over the area to be drained may be used. Beyond this size, design should be carried out in accordance with BS EN 752 : 2008 or BRE Digest 365. It is suggested in BS EN 752 : 2008 that a storage volume equal to 20 mm of rainfall over the area to be drained may be used. In Scotland, guidance for the design of single-house soakaways is given in Mandatory Standard 3.6, clause (1). (1) Technical Handbook (Domestic) Table 3 Sizing guide for individual plot soakaways Number of Stormbloc units Nominal storage volume (m³) Maximum impermeable catchment area to be drained (m²) Full block Half block Full blocks Half blocks (1) 21.1 (1) (2) 25 (1) (2) 31.6 (2) (2) 42.2 (2) (2) 52.7 (2) (2) (2) (1) In accordance with Approved Document H (2) In accordance with BS EN 752 : 2008, clause NA The design volumes and areas for trench or cuboid type installations when using the CIRIA or BRE approach can be found in Tables 4 and 5. Table 4 Volumetric data per linear metre for 1 full size unit wide (0.8 m) trench configuration Number of units deep Storage volume (m 3 ) Surface area of ends (m 2 ) Surface area of sides (m 2 ) Surface area of base (m 2 ) Table 5 Volumetric data for 3D usage one full size unit high (0.66 m) Units Long 2 Units wide 4 units wide 8 units wide Volume (m³) Side and ends area (m²) Base area (m²) Volume (m³) Side and ends area (m²) Base area (m²) Volume (m³) Side and ends area (m²) Base area (m²) For calculations, the size and volume of the units are given in Table 1. The total surface areas of the base and sides are required as water is absorbed through the geotextile soil interface. Storage volume is 95% of the total volume. As an example, using Table 4, for a typical linear trench 40 m long and 2 units deep, the volume is 1 m 3 by 40 = 40 m 3, the side area is 2.7 m 2 x 40 = 108 m 2, the end area is 2.1 m 2 and the base area is 0.8 m 2 by 40 = 32 m 2. Page 7 of 16

8 Attenuation Calculation principles 5.5 The anticipated run-off volume (A) from the site must be estimated. The most commonly used method for evaluating storm rainfall events in the UK is the Wallingford Procedure, by which the total rainfall level of storms over defined time periods ranging from five minutes up to 48 hours is assessed. The depth of water (mm) found can be multiplied by the catchment area to assess the size of attenuation systems and is normally based upon a two-hour storm of a return period appropriate for the catchment. The allowable discharge rate from the site to an appropriate outfall is established but will normally be set by the Environment Agency, the Scottish Environment Protection Agency or Planning Authorities. The outflow volume (B) to be discharged at this rate over the two-hour period is calculated and subtracted from the run-off volume (A B). This defines the excess volume (C) to be stored in Stormbloc units constructed as an underground tank. The number of Stormbloc units needed to contain this excess is calculated on the basis that the storage volume is equal to 95% of the total volume of the tank. Pipe connections 5.6 Pipe connections are made to Stormbloc units using either a pipe adapter or an integral Stormbloc Inspect access chamber. These both allow various sizes of pipe to be connected but are outside the scope of this Certificate (see Figure 3 for connection options). 5.7 When connecting pipes for storage applications (using a geomembrane), care must be taken to ensure a watertight seal. It is recommended that connections are made using a flange adapter. Adhesive or double-sided tape should be used between the geomembrane and flange adapter to ensure a watertight seal. Manifold design 5.8 The Stormbloc modules are manufactured to allow connection of pipes (via an adapter) up to 225 mm internal diameter, although connection of pipes up to 500 mm internal diameter is possible via a Stormbloc Inspect access chamber (outside the scope of this Certificate). If the anticipated design flow is greater than the hydraulic capacity of a single connection pipe, then the flow may be split between a number of pipes from an adjacent manhole. The system designer should ensure that the number and size of the pipe connections is sufficient to convey the anticipated design flow without restriction. Figure 3 Pipe connection options 5.9 Where the system has an outflow or overflow connection, the flow will generally need to be controlled in order to comply with the discharge rate consent of the site (see Figure 5). A number of methods of flow control are available. Comparative features and performance of these flow control devices should be considered prior to selection. Such devices are outside the scope of this Certificate. Outflow positioning and head calculations 5.10 The invert level of the outflow pipe should be flush with the bottom of the lowest unit to allow the tank to drain. The Stormbloc units may be laid to a gradient to assist free draining, but this will affect the loads that can be carried by the system as the units are manufactured to have the greatest strength in the vertical plane. Generally, gradients of Page 8 of 16

9 1:100 should not be exceeded. Systems laid to a gradient are outside the scope of this Certificate. As the tank fills, a depth of water develops on the upstream side of the outflow control, creating a driving head to push the flow through the control device. For a tank with two layers of Stormbloc units, the maximum depth is 1.32 m when the units are full. For design purposes, the head used in calculations is taken as that at the invert level of the outflow device. 6 Structural design 6.1 Stormbloc units can be placed under a wide variety of landscaped, amenity or trafficked areas. Design procedures for heavily-trafficked applications are outside the scope of this Certificate. If the proposed application of the Stormbloc is in areas subject to high-intensity traffic, commercial vehicles or other heavy loads, advice should be sought from the Certificate holder. 6.2 The short-term ultimate compressive strength at yield for the Stormbloc units, as derived from independent test data, is 400 kn m 2 for vertical loading on the top face and 130 kn m 2 for lateral loading on the side face. A partial safety factor for materials (f m ) of 2.75 for ultimate limit state and 1.5 for serviceability limit state should be applied to these values for a design life of 20 years. The short and long-term deflections are given in Table Creep tests indicate that the long-term deflection may be estimated from the following expression. This is valid for vertical loads up to 94 kn m 2 for durations of up to 20 years at 20 C. In locations where settlement is not a concern, designs of up to 50 years can be considered: deflection (mm) = Ln (time in hours) For small-scale applications such as soakaways for individual house roof drainage and where it is assumed that there will be no traffic loads, it is recommended that: the minimum distance from the building should be 5 m the maximum depth to the base of the units should be 5.1 m. This assumes a minimum value (which should be confirmed from site investigation) for the angle of shearing resistance of the surrounding ground to be 29 and groundwater to be at least one metre below the base of the units the minimum cover depth over a completed installation to be 0.5 m to avoid damage by landscaping, agricultural or gardening equipment. 6.5 Stormbloc units used for large-scale storage or infiltration must be designed to carry all loads that will be applied, including dead and imposed loads. Design parameters and estimated loads should be used to determine the maximum depth of installation and the maximum and minimum cover depths. 6.6 The criteria provided in Tables 6 and 7 can be used to design the Stormbloc units for installation below lightlyand non-trafficked areas. These design tables are only applicable in temperate climate conditions such as the UK. The following partial safety factors for loads have been applied: ultimate limit state vertical dead load (f dl ) 1.40, earth pressure (horizontal) dead load (f ep ) 1.35, imposed live load (f ll ) 1.60 serviceability limit state vertical dead load (f dl ) 1.00, earth pressure (horizontal) dead load (f ep ) 1.00, imposed live load (f ll ) Partial safety factors for materials (f m ) of 2.75 for the ultimate limit state and 1.5 for the serviceability limit state have been applied. The Stormbloc system can be used for areas where greater loads are anticipated but these applications are outside the scope of this Certificate and specific advice should be sought from the Certificate holder. Table 6 Maximum Installation depths (to base of units) (1) Typical soil type Typical angle of shearing resistance Page 9 of 16 Maximum depth of installation (to base of units) (m) Groundwater level 1 m below ground level. Units installed in fully encapsulated membrane liner (attenuation) Trafficked area Non-trafficked area No groundwater present (below base of units) normal case Trafficked area Non-trafficked area Stiff over consolidated clay, eg London Clay Normally consolidated silty sandy clay eg alluvium, made ground Loose sand and gravel Medium dense sand and gravel Dense sand and gravel (1) The following assumptions apply: trafficked areas are accessible only to cars and occasional refuse or emergency vehicles (typically once per week) ground surface is horizontal shear planes or other weaknesses/defects are not present in the soil structure shear angle is confirmed by site survey figures are calculated in accordance with CIRIA C680 for a design life of 20 years where groundwater is present or the cover depth is greater than 4 m a detailed site survey and design assessment will be required; contact the Certificate holder for further details.

10 Table 7 Minimum cover depths (1) Load Conditions Minimum Cover Depth (m) Non-trafficked areas, e.g. landscaped, amenity areas, etc. 0.5 (2) Car Parks, vehicle mass 2500 kg 0.6 Car Parks, occasional vehicle mass > 2500 kg (3) 0.8 (1) Assumes 27 load distribution through fill material and overlying surface of asphalt or block paving (2) Minimum cover depth to avoid accidental damage from gardening/landscaping work (3) Occasional trafficking by refuse collection trucks or similar vehicles (typically one per week). 6.7 For lightly-loaded applications, the bearing capacity of the underlying soils should not be exceeded by the Stormbloc System. Therefore settlement of the underlying soils should be negligible. On weak or compressible soils, the bearing capacity and settlement characteristics should be confirmed by a geotechnical engineer. 6.8 Care should be taken when the Stormbloc system is used for infiltration below trafficked areas and close to structures. It is important to ensure that the infiltrating water will not soften the soils or cause loss of fines and settlement. 6.9 When the units are wrapped in a geomembrane and placed below the groundwater table, flotation may occur. To prevent this, the weight of the soil over the top of the units must be greater than the uplift force caused by the units buoyancy in the water. This can be achieved with most types of fill if the depth of cover fill is equal to, or greater than, the depth of penetration of the units below groundwater level. 7 Geotextiles and geomembranes 7.1 In infiltration applications a geotextile is wrapped around the Stormbloc system to prevent the silt that may be contained in surface water run-off from contaminating the surrounding soil, in addition to reducing its permeability and to prevent surrounding soil from entering the Stormbloc units. In storage applications the purpose of the geotextile is to protect the geomembrane. 7.2 The selection of an appropriate geotextile for a specific Stormbloc infiltration installation should be considered carefully, particularly with reference to the surrounding soil properties and required performance. Points to consider are: pore size this should be designed and specified to assist infiltration and prevent migration of fine soil particles permeability and breakthrough head the geotextile should not limit flow of water in the system, and should have a similar or greater permeability than the surrounding ground puncture resistance the geotextile must be able to resist piercing by potentially sharp objects, eg stones in the soil tensile strength the geotextile should have sufficient strength to resist any imposed forces (eg from traffic). 7.3 The geotextile should be selected according to specific site conditions. Typical characteristics of a geotextile for infiltration systems are shown in Table 8. Geotextiles are outside the scope of this Certificate and the system designer should be satisfied that the chosen geotextile is suitable for the particular application. Specialist advice should be sought if surrounding soil characteristics exhibit a high degree of fines/low infiltration capacity and/or there is risk of damage from ground contaminants. Table 8 Geotextile typical specification Material Property (units) Test Method Nominal Value CBR Puncture Resistance (N) BS EN ISO : Water Permeability (1) (m s 1 ) BS EN ISO : x 10 3 Water flow normal to the plane (l m 2 s 1 ) BS EN ISO : Elongation (%) MD CD Tensile Strength (kn m 1 ) MD CD BS EN ISO : 2008 BS EN ISO : 2008 Characteristic opening size (AOS) (2) (µm) EN ISO : Thickness (under 2 kpa) (mm) BS EN ISO : Mass per unit area (g m 2 ) BS EN ISO 9864 : Fibre bonding Needled/thermally bonded Material Polypropylene (PP) (3) (1) Geotextile must be sufficiently permeable to allow free discharge of water and must be greater than the permeability of the surrounding soil (2) The pore opening size should not be so large as to enable soil migration into the tank (3) A white/light coloured geotextile is recommended to assist with CCTV inspection. 7.4 In attenuation/storage applications where infiltration is not possible or permitted, a geomembrane is wrapped around the Stormbloc system to: prevent release of attenuated/stored water to surrounding ground prevent the inflow of pollutants from contaminated subsoil into the storage reservoir prevent loss of storage volume due to inflow from groundwater and to prevent contamination of the groundwater. Page 10 of

11 7.5 The specification and selection of the impermeable geomembrane must be correct for the proposed installation, to ensure it performs to the level required. It is essential that the specified material: withstands the rigours of installation resists puncture resists multi-axial elongation stress and strains associated with settlement resists environmental stress cracking resists damage from ground contaminants remains intact for the full design life. Geomembranes less than 1 mm thick are unlikely to meet these criteria (except in shallow, domestic installations), and are not recommended for use with the Stormbloc system. For further details the Certificate holder s advice should be sought. A specification for a typical polypropylene geomembrane is shown in Table 9. Table 9 Typical geomembrane characteristics Material Property (units) Test Method Nominal Value Thickness (mm) EN : Mass per unit area (g m 2 ) EN : Tensile stress at break (MPa) BS EN ISO : 1996 > 18 Elongation at break (%) BS EN ISO : 1996 > 750 Tear propagation resistance (N mm 1 ) DIN : 1977 (with cut) > 45 Piercing resistance (N) FTMS 101C > 150 Water absorption after 7 days (%) BS EN ISO 62 : 2008 < 0.2 Stress cracking resistance (h) ASTM D5397 > 1150 Dimensional changes after heat ageing (%) DIN : 2007 (1h/140ºC) ± To ensure total impermeability, joints between adjacent sheets of impermeable geomembranes should be sealed correctly using proprietary welding techniques. The integrity of joints should be demonstrated by non-destructive testing, advice on which is given in CIRIA SP124 : 1996 Barriers, liners and cover systems for containment and control of land contamination. 8 Venting 8.1 Adequate venting must be provided to the Stormbloc structure, either through high level pipe connections between the units, through direct venting to the atmosphere or via Stormbloc Inspect chambers which render separate venting systems unnecessary. Venting systems are outside the scope of the Certificate. Typical options are shown in Figure 4. Figure 4 Ventilation options 8.2 It is recommended that all air vent installations in storage applications (using a geomembrane) are made using a flange adapter. Adhesive or double-sided tape should be used between the geomembrane and flange adapter to ensure a watertight seal. 9 Resistance to chemicals 9.1 An assessment by the BBA indicates that the components of the system will resist the types and quantities of chemicals likely to be found in rainwater. 9.2 An assessment of the suitability of Stormbloc units for use on brownfield sites should be made only after a site investigation to determine the possibility of chemical contamination has been carried out. Particular care must be taken where acids and organic solvents are present in high concentrations. For further information contact the Certificate holder. Page 11 of 16

12 10 Maintenance 10.1 The customer is responsible for maintenance. Recommendations for maintenance of SUDS systems are given in CIRIA C697. Integral inspection/maintenance tunnels in each unit allow the use of CCTV equipment for inspection and jetting or rodding equipment for maintenance For soakaways to individual houses, the only necessary maintenance of the system is to keep gullies clear of debris such as leaves For large installations or where the receiving waters are environmentally sensitive, a system of regular inspections should be established to prevent siltation of the system which, if allowed to develop, would reduce effectiveness. They should also be inspected after every major storm event It is recommended that a silt trap or hydro-dynamic vortex separator is incorporated into the pipework at the inlet to the tank (see Figure 5). There must be a maintenance plan that ensures regular cleaning of the trap to ensure correct performance. Silt traps and hydro-dynamic vortex separators for use with this system are outside the scope of this Certificate. Figure 5 Typical attenuation layout including hydro-dynamic vortex separator and vortex flow control 10.5 For all flow control devices it is good practice to incorporate access (via a manhole or similar) to the location of the pipe entry, orifice or vortex control. This will enable easy removal of any blockage. The flow control itself may be protected by a debris screen and may incorporate devices to allow drain down of the chamber should a blockage occur Paved surface areas above an installation should be inspected at the same time to ensure the units continue to provide the required structural support. 11 Durability The structural properties of polypropylene used in the components of the system will deteriorate with time and should be taken into account at the design stage by the application of suitable safety factors. In the opinion of the BBA, the Stormbloc Stormwater Management System, when used in accordance with this Certificate, will have a life in excess of 50 years. Installation 12 General The Stormbloc Stormwater Management System should be installed in accordance with the Certificate holder s installation instructions and relevant legislation. 13 Procedure 13.1 The hole or trench is excavated to the required depth, dimensions and levels. Sufficient area (300 mm minimum) must be left around the sides to allow access for plant to compact backfill material. The base of the excavation must be smooth and level without sharp drops or humps. Slopes must be cut to a safe angle or adequately supported and safe access must be provided to allow personnel to enter the excavation. Page 12 of 16

13 13.2 The base must be inspected for soft spots in the formation. Any present must be excavated and replaced with compacted granular fill material A 100 mm thick bedding layer of coarse sand or gravel is laid on the base and sides of the excavation. In an attenuation system, the protective geotextile fleece is laid The geomembrane (or geotextile, if an infiltration system) is laid over the bedding layer and up the sides of the excavation. The geomembrane is inspected for damage and all welds are tested as required. Joints between adjacent sheets of impermeable membrane should be sealed correctly using proprietary techniques with a minimum lap of 50 mm. Generally jointing with tape is not recommended as the system becomes reliant on the mechanical properties of the tape to maintain its integrity The Stormbloc units are installed in accordance with the installation schedule for correct orientation. The units are arranged so that the tunnels are in line, giving access through the system. For single-layer applications, horizontal connection pieces are used and for multiple layer systems, multi-layer connection pieces are used The ends of the tunnel are fitted with the appropriate end plate The geotextile or geomembrane enclosure of the base, sides and top of installation, including protective geotextile (where required), is completed. Geomembranes should be welded with double seams. The geomembrane is inspected for damage and all welds are tested as required Inlet and outlet connections are made to the installation using pipe adapters The installation is backfilled with type 1 or 2 sub-base or Class 6P (side fill only) selected granular material in accordance with the Manual of Contract Documents for Highway Works, Volume 1. The backfill is compacted in 150 mm thick layers. The side fill and the first 300 mm of compacted material above the tank should be compacted using laminar working devices only A 100 mm thick coarse sand or gravel protection layer should be placed over the top of the units that are wrapped in either a geotextile (infiltration system) or a geomembrane with protective geotextile (attenuation system). Backfilling is continued with: trafficked areas (eg car parks) type 1 or 2 sub-base material compacted in 150 mm layers in accordance with the Manual of Contract Documents for Highway Works, Volume 1. Compaction of the first 300 mm of cover should be carried out using laminar working devices. Thereafter compaction plant over the top of the system should not exceed 2300 kg per metre width landscaped and non-trafficked areas selected as-dug material with size of pieces less than 75 mm, compacted to 90% maximum dry density vehicle movement over the top of the system should be performed in straight passes only The pavement construction or landscaping is completed over the Stormbloc system It is recommended that CCTV inspection of the system is carried out following the installation to ensure that the membrane/geotextile liner has been installed correctly and has not been punctured or torn during construction. This inspection can also serve to ensure that no debris has entered the storage volume. Technical Investigations The following is a summary of the technical investigations carried out on the Stormbloc Stormwater Management System. 14 Tests Tests were carried out on the system to determine: long-term and short-term resistance to loading volumetric capacity. 15 Investigations 15.1 The manufacturing process was examined including the method adopted for quality control, and details obtained on the quality and composition of the material used An assessment of the system was made in relation to: material properties design procedures geotextile and geomembrane specifications A site visit was made to assess the practicability and ease of installation and connection. Page 13 of 16

14 Bibliography ASTM D 5397 : 1999 Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using Notched Constant Tensile Load Test BS EN 752 : 2008 Drain and sewer systems outside buildings BS EN ISO 62 : 2008 Plastics Determination of water absorption BS EN ISO : 1996 Plastics Determination of tensile properties Test conditions for films and sheets BS EN ISO : 2005 Geosynthetics Determination of thickness at specified pressures Single layers BS EN ISO 9864 : 2005 Geosynthetics Test method for the determination of mass per unit area of geotextiles and geotextile-related products BS EN ISO : 2008 Geotextiles Wide-width tensile test BS EN ISO : 2010 Geotextiles and geotextile-related products Determination of water permeability characteristics normal to the plane, without load BS EN ISO : 2006 Geosynthetics Static puncture test (CBR-test) DIN : 2007 Testing of plastic films; Determination of dimensional stability DIN : 1977 Determination of tear strength of rubber, elastomers and plastic film using Graves angle test piece with nick EN : 2001 Flexible sheets for waterproofing Determination of thickness and mass per unit area Plastic and rubber sheets for roof waterproofing EN ISO : 1999 Geotextiles and geotextile-related products Determination of the characteristic opening size FTMS 101C : Method 2065 Puncture test Manual of Contract Documents for Highway Works, Volume 1 Specification for Highway Works, Series 900 Road pavements bituminous bound materials Manual of Contract Documents for Highway Works, Volume 2 Notes for Guidance on the Specification for Highway Works, Series 900 Road pavements bituminous bound materials Page 14 of 16

15 Conditions of Certification 16 Conditions 16.1 This Certificate: relates only to the product/system that is named and described on the front page is granted only to the company, firm or person named on the front page no other company, firm or person may hold or claim any entitlement to this Certificate is valid only within the UK has to be read, considered and used as a whole document it may be misleading and will be incomplete to be selective is copyright of the BBA is subject to English law Publications and documents referred to in this Certificate are those that the BBA deems to be relevant at the date of issue or re-issue of this Certificate and include any: Act of Parliament; Statutory Instrument; Directive; Regulation; British, European or International Standard; Code of Practice; manufacturers instructions; or any other publication or document similar or related to the aforementioned This Certificate will remain valid for an unlimited period provided that the product/system and the manufacture and/or fabrication including all related and relevant processes thereof: are maintained at or above the levels which have been assessed and found to be satisfactory by the BBA continue to be checked as and when deemed appropriate by the BBA under arrangements that it will determine are reviewed by the BBA as and when it considers appropriate In granting this Certificate, the BBA is not responsible for: the presence or absence of any patent, intellectual property or similar rights subsisting in the product/system or any other product/system the right of the Certificate holder to manufacture, supply, install, maintain or market the product/system individual installations of the product/system, including the nature, design, methods and workmanship of or related to the installation the actual works in which the product/system is installed, used and maintained, including the nature, design, methods and workmanship of such works Any information relating to the manufacture, supply, installation, use and maintenance of this product/system which is contained or referred to in this Certificate is the minimum required to be met when the product/system is manufactured, supplied, installed, used and maintained. It does not purport in any way to restate the requirements of the Health & Safety at Work etc Act 1974, or of any other statutory, common law or other duty which may exist at the date of this Certificate; nor is conformity with such information to be taken as satisfying the requirements of the 1974 Act or of any statutory, common law or other duty of care. In granting this Certificate, the BBA does not accept responsibility to any person or body for any loss or damage, including personal injury, arising as a direct or indirect result of the manufacture, supply, installation, use and maintenance of this product/system. Page 15 of 16

16 British Board of Agrément tel: Bucknalls Lane fax: Garston, Watford Herts WD25 9BA 2010 website: Page 16 of 16