SECTION 18 Kingspan Environmental

SECTION 18 Kingspan Environmental Septic Tanks Page 314 Klargester BioDisc Treatment Plants Page 315 Class 1 & 2 Bypass and Full Retention Separators Page 317 Wash Down & Silt Separators Page 317 HillMaster Pump Station Range Page 321 Envireau Rainwater Harvesting Systems Page 323 Stormwater Attenuation Systems Page 325 www.burdens.co.uk 313

Alpha Septic Tank For domestic dwellings without mains drainage, Kingspan Environmental s Alpha septic tanks provide a reliable economic and efficient solution to your sewage disposal needs. Alpha is manufactured in durable GRP and comes in three sizes. It is suitable for individual domestic dwellings up to a large family house. Kingspan Environmental has always maintained that an adequate and properly designed effluent disposal system is vital to the effective performance of any septic tank system. Capacity No. of people No. of people Litres assuming a flow assuming a flow 180l/head/day 250l/head/day 2800 4 3 3800 10 7 4600 14 10 Manhole Covers and Frames Description Galvanised pedestrian duty manhole covers and frames fitted with cross piece for safety purposes. To suit 460mm neck. 314 www.burdens.co.uk

Klargester BioDisc - BA - BC High performance packaged sewage treatment plants for domestic applications. For domestic dwellings without mains drainage, Klargester BioDisc provides a reliable, efficient and environmentally safe solution to your sewage disposal needs. Unique Design BioDisc is the only packaged sewage treatment plant utilising Rotating Biological Contactor technology (RBC) which comprises banks of vacuum formed polypropylene media supported by a steel shaft. This is slowly rotated by a low energy consumption electric motor and drive assembly. Process Stability BioDisc is recognised for its process performance. This is further enhanced by a unique Managed Flow System, which ensures optimum performance by smoothing peak flows and buffering biological loads over the whole working day. Low Profile Covers Access for service and maintenance is provided via a durable, unobtrusive cover at ground level. Single House Mutiple Houses Unit Size BA BA-X BB BC Population Equivalent 1 House, 1 House, 1 House, 3/4 House, Max. 6 Max. 9 Max. 12 Max. 18 OA Diameter (A) mm 1995 1995 1995 2450 Standard Drain Invert Inlet (B) mm 750* 750* 750* 600** Standard Outlet (C) mm 835 835 820 685 Depth from Invert to Base (D) mm 1400 1400 1400 1820 Pipework Diameter (mm) 110 110 110 110 Sludge Storage (approx) 12 months 9 months 6 months 7 months Standard Power Supply single phase single phase single phase single phase Motor Rating 50 W 50W 50 W 75 W Weight (tonnes) std units 0.388 0.418 0.418 0.6 * Optional invert depths of 450mm and 1250mm are available ** Optional invert depth of 1100mm is available www.burdens.co.uk Rotating Biological Contactor (RBC) The RBC comprises banks of vacuum formed polypropylene media supported by a steel shaft. This is slowly rotated by a low energy consumption electric motor and drive assembly. Note: BioDisc is designed to deal with normal domestic sewage. If your application involves combined drainage or the sewage is likely to contain unusual substances, refer to Kingspan Environmental. 315

Klargester BioDisc - BD - BF High performance packaged sewage treatment plants for residential and commercial developments. Rotating Biological Contactor (RBC) The RBC comprises banks of vacuum formed polypropylene media supported by a steel shaft. This is slowly rotated by a low energy consumption electric motor and drive assembly. Deep Drain Invert This provides the flexibility to connect with most incoming drainage systems without the need for greater excavation depth. With the new improved range of Klargester BioDisc packaged waste water treatment plant, Kingspan Environmental has built on its existing high performance product to deliver a treatment plant with even greater all round benefits. Not only will it meet the ever more stringent standards of controlling authorities, but it has also been valueengineered to give short and long term cost savings. Unique Design BioDisc is the only packaged sewage treatment plant utilising Rotating Biological Contactor technology (RBC) which comprises banks of vacuum formed polypropylene media supported by a steel shaft. This is slowly rotated by a low energy consumption electric motor and drive assembly. Process Stability BioDisc is recognised for its process performance. This is further enhanced by a unique Managed Flow System, which ensures optimum performance by smoothing peak flows and buffering biological loads over the whole working day. Low Profile Covers Access for service and maintenance is provided via a durable, unobtrusive cover at ground level. Unit sizes 316 www.burdens.co.uk

Class 1 & 2 Bypass and Full Retention Separators The use of an oil/water separator is required wherever there is the risk of hydrocarbon pollutants causing contamination at the point of discharge i.e. an open ditch, river, stream or groundwater. Klargester Separators are accepted by Local Authorities, and national environmental regulatory bodies. The drainage area served, or the calculated flow rate determines the size of unit. The drainage area and peak flow rate in the following charts assumes 50mm/hr rainfall intensity. Our designs are based on the assumption that interconnecting pipework provided and fitted elsewhere on site does not impede flow in or out of the separator. Run-off from low risk areas, such as roofs, should not be connected to a separator and if this cannot be avoided the separator must be sized accordingly. Klargester Class 1 and Class 2 Bypass & Full Retention Separators are designed to comply with the latest Environment Agency Pollution Prevention Guidelines (ref. PPG3) and have been tested and certified to British Standards EN 858-1. The units incorporate: Oil storage volume. Silt storage capacity. Coalescer. Class 1 units only. Closure device to prevent excess stored pollutants from contaminating the discharge (Class 1 and 2 Full Retention Unit). PPG3 requires the installation of an oil alarm system with the separator, which we can provide as an additional item. The required discharge standard will decide whether a Class 1 or Class 2 unit is required. Class 1 & 2 Bypass Separators Bypass Separators are used in low spillage risk areas: Surface car parks. Roadways. Lightly contaminated commercial areas. Class 1 & 2 Full Retention Separators Full Retention Separators are used in high spillage risk areas: Heavily contaminated commercial areas. Fuel distribution depots. Vehicle workshops. Garage forecourts, require the Klargester Enviroceptor. www.burdens.co.uk Wash Down & Silt Separators Separators serving wash down areas such as car washes and other cleaning facilities must discharge directly into a foul drain as they utilise emulsifiers, soaps and detergents, which can dissolve and disperse the oils. Kingspan Environmental have a dedicated range of units for this type of application. 317

Class 1 & Class 2 Bypass Separators NSBD18-NSBD36 NSBD55-NSBD130 NSBD3-NSBD15 Nom size Flow l/s Peak flow rate (l/s) Drainage area (m 2 ) Silt Oil storage capacity litres storage capacity litres Length (L) Dia (D) Access shaft Dia (D1) Base to inlet invert (A) Base to outlet invert (B) Std Fall Across Unit Min inlet invert (E) Std. pipe wk. dia. DIN (C) NSBD3 3 30 1670 300 45 1765 1225 750 1450 1350 100 500 315 NSBD4 4.5 45 2500 450 68 1765 1225 750 1450 1350 100 500 315 NSBD6 6 60 3335 600 90 1765 1225 750 1450 1350 100 500 315 NSBD8 8 80 4445 800 120 3065 1225 750 1450 1350 100 500 315 NSBD10 10 100 5560 1000 150 3065 1225 750 1450 1350 100 500 315 NSBD12 12 120 6670 1200 180 3915 1225 750 1450 1350 100 500 315 NSBD15 15 150 8335 1500 225 3915 1225 750 1450 1350 100 500 315 NSBD18 18 180 10000 1800 270 3200 2012 600 2110 2010 100 1000 375 NSBD24 24 240 13340 2400 360 3200 2012 600 2110 2010 100 1000 375 NSBD30 30 300 16670 3000 450 3915 2012 600 2110 2010 100 1000 450 NSBD36 36 360 20000 3600 540 3915 2012 600 2110 2010 100 1000 525 NSBD55 55 550 30560 5500 825 5085 2820 600 2310 2060 250 1000 750 NSBD72 72 720 40000 7200 1080 5820 2820 600 2310 2060 250 1500 750 NSBD84 84 840 46670 8400 1260 6200 2820 600 2310 2010 300 1500 750 NSBD96 96 960 53340 9600 1440 7375 2820 600 2310 2010 300 1500 825 NSBD110 110 1100 61110 11000 1650 7925 2820 600 2360 2010 350 1500 825 NSBD130 130 1300 72225 13000 1950 8725 2820 600 2360 2010 350 1500 825 All dimensions are in millimetres. *Some units have more than one access shaft - diameter of largest given. To specify a Nominal Size Klargester Bypass Separator, the following information is needed: The calculated flow rate(ns) or the drainage area served. Our designs are based on the assumption that any interconnecting pipework fitted elsewhere on site does not impede flow into or out of the separator. Run-off from low risk areas, such as roofs, should not be connected to a separator. When this cannot be avoided, the separator must be re-sized accordingly. The required discharge standard. When performance tested under lab conditions Class 1 produced <5mg/l oil, Class 2 <100 mg/l oil. The drain invert inlet depth. The difference between the drain invert depth and the minimum invert (F) above rounded up to the nearest half metre, is the length of extension shaft(s) needed. Extension shafts, for site fitting, are available in 0.5 metre increments. The maximum recommended extension is 1.5m above the standard i.e. 2 or 2.5m total. Units may be installed at greater depths with an appropriate civil engineering design which must include access for coalescer removal. Oil Alarm System. See separate data sheet for full details and available options. Pipework type, size and orientation. Unless specified otherwise, units are supplied with the standard (minimum) invert depth and pipework size and orientation shown in the above table. Pipework internal diameter less than 315 will be PVCu. Larger sizes are GRP connectors. 318 www.burdens.co.uk

Class 1 & Class 2 Full Retention Separators Unit Flow nom. l/s size Drainage area (m 2 ) PPG3-3 (0.018) Silt storage capacity litres Oil storage capacity litres Length (L) Unit dia (D) Manhole cover dim. (D1) Base to inlet invert (A) Base to outlet invert (B) Min inlet invert (E) Std. pipe wk. dia. (C) NSFA3 3 170 300 30 1760 1225 600x900 1050 1000 500 200 NSFA6 6 335 600 60 1760 1225 600x900 1050 1000 500 200 NSFA10 10 555 1000 100 2610 1225 600x900 1050 1000 500 200 NSFA15 15 835 1500 150 3910 1225 600x900 1050 1000 500 200 NSFA20 20 1115 2000 200 3200 2010 600 1850 1800 1000 315 NSFA30 30 1670 3000 300 3915 2010 600 1850 1800 1000 315 NSFA40 40 2225 4000 400 4640 2010 600 1850 1800 1000 315 NSFA50 50 2780 5000 500 5425 2010 600 1810 1760 1000 315 NSFA65 65 3610 6500 650 6850 2010 600 1810 1760 1000 315 NSFA80 80 4445 8000 800 5700 2820 600 2500 2450 1000 315 NSFA100 100 5560 10000 1000 6200 2820 600 2500 2450 1000 400 NSFA125 125 6945 12500 1250 7365 2820 600 2500 2450 1000 450 NSFA150 150 8335 15000 1500 8675 2820 600 2550 2450 1000 525 NSFA175 175 9725 17500 1750 9975 2820 600 2550 2450 1000 525 NSFA200 200 11110 20000 2000 11280 2820 600 2550 2450 1000 600 All dimensions are in millimetres. Units>NSFA 20 have multiple necks fitted. Units >NSFA 80 have multiple coalescers. To specify a Klargester Class 1 or 2 Full Retention Separator, the following information is needed: The calculated flow rate (NS) or the drainage area served. Our designs are based on the assumption that any interconnecting pipework fitted elsewhere on site does not impede flow into or out of the separator. Run-off from low risk areas, such as roofs, should not be connected to a separator. If this cannot be avoided, the separator must be re-sized to take into account the additional flow. Influent must not be pumped. The required discharge standard. i.e. a unit to meet Class 1 (<5 mg/l) or Class 2(<100 mg/1) oil - as demonstrated during the test procedure. The drain inlet invert depth. The difference between the drain invert depth and the minimum invert (E), rounded up to the nearest half metre, is the length of extension shaft(s) needed. Extension shaft kits, for site fitting are available in 0.5 metre increments. The maximum recommended invert depth for these separators is 2.0/2.5m total. The kit includes coalescer extension handles. Units may be installed at greater depths with an appropriate civil engineering design and you must make suitable provision for coalescer removal and maintenance. With or without an Oil Probe tube. Oil Alarm System. See separate data sheet for available options. Pipework type & sizes. The table indicates the standard pipework fitted. Up to and including 315mm ID, the pipe is PVCu spigot. >450mm are GRP connectors. The standard size stated are generally those required by EN 858. By request, alternate sizes can be fitted however, please note we do not alter internal pipework dimensions and alternate pipework selections will generally be fitted external to the standard. www.burdens.co.uk 319

Wash Down & Silt Separators Ref. Total capacity (litres) Maximum rec. silt volume Maximum flow rate Length (l/s) (L) Dia. (D) Main Dimensions mm Access Base to Base to Std. fall shaft inlet outlet across dia. (D1) invert (A) invert (B) unit Min. inlet invert (E) Std. Approx. pipework empty dia. (C) weight (Kg) W1/012 1200 600 3 1310 1225 460 1120 1070 50 500 160 60 W1/020 2000 1000 5 2210 1225 460 1120 1070 50 500 160 120 W1/030 3000 1500 8 3060 1225 460 1120 1070 50 500 160 150 W1/040 4000 2000 11 3910 1225 460 1120 1070 50 500 160 180 W1/060 6000 3000 16 4530 1440 600 1360 1310 50 500 160 320 W1/080 8000 4000 22 3200 2020 600 2005 1955 50 500 160 585 W1/100 10000 5000 27 3915 2020 600 2005 1955 50 500 160 680 W1/120 12000 6000 33 4640 2020 600 2005 1955 50 500 160 770 W1/150 15000 7500 41 5435 2075 600 1940 1890 50 500 160 965 W1/190 19000 9500 52 6865 2075 600 1940 1890 50 500 160 1200 The units above all include a single chamber, (W1) but on request, we may be able to provide 2 or 3 chambers. If you require larger units, these are also available. Please contact us to discuss your specific application. Invert depths (E) can be supplied in additional increments of 500mm from the minimum stated above. Please indicate the inlet drain invert required when specifying units. Maximum 2.0 m. To purchase or specify the Klargester separator you require, the following information is needed. The number of chambers and type of separator. Prefix Reference (see table) with: W1 If you require a single chamber oil/water separator W2 If you require a 2 chamber oil/water separator (1200 litre not available) W3 If you require a 3 chamber oil/water separator (1200 litre not available) The capacity of the separator in litres (see table) Drain inlet invert depth Inlet & outlet pipework size if not the standard 160 mm PVCu. PLEASE NOTE: We will assume that you require the standard unit unless you have specified differently. Additional charges may apply to alternate specifications. Non-standard inlet/outlet pipe sizes and reduced falls across the unit may be provided but please note we do not alter internal pipework dimensions. 320 www.burdens.co.uk

HillMaster 24 Range The HillMaster 24 range has been specifically designed to meet the requirements of Building Regulations Document H1 Foul Drainage. This regulation recognises the need for pump stations to have 24hr storage capacity in case of a disruption in service (such as a power failure). This comprehensive range offers an advanced solution to larger domestic and industrial applications. For large-capacity flows (such as stormwater run-off from hard-standing areas), horizontal holding chambers are available in a comprehensive range of sizes. High-level alarm fitted as standard Various invert depths Internal lifting chains and guardrails fitted as standard Wide range of pump options including grinders/macerators Combined chamber capacity up to 90,000 litres Pumping distances up to 1000 metres Pedestrian/vehicle covers HillMaster24 1.25m x 3.0m GRP 1.8m x 3.0m GRP 2.6m diameter pump chambers GRP SEWAGE STANDARD MODEL SEWAGE SPECIAL ORDER MODEL SURFACE WATER STANDARD MODEL SURFACE WATER SPECIAL ORDER MODEL EFFLUENT STANDARD MODEL EFFLUENT SPECIAL ORDER MODEL HillMaster Range The HillMaster range offers a competitive solution to the pumping requirements of both domestic and industrial applications. Often it can be preferable to keep civil work and costs down to a minimum but such economy should not mean any shortfall in quality. The 1.0 diameter units are manufactured in tough polyethylene using advanced rotational-moulding technology, while the 1.25, 1.8 and 2.6m units are made from maintenance-free GRP. All units are engineered with the highest quality parts and fittings. High-level alarm fitted as standard (optional as marked*) Various invert depths Internal lifting chains and guardrails (as specified) Wide range of pump options including grinders/macerators Pedestrian/vehicle covers HillMaster Range 1.0m x 2.0m 1.25m x 2.0m 1.25m x 3.0m 1.25m x 3.5m 1.8m x 4.0m Roto-moulded GRP GRP GRP GRP STANDARD SEWAGE SINGLE PUMP SPECIAL ORDER SEWAGE TWIN PUMP STANDARD SURFACE WATER SINGLE PUMP SPECIAL ORDER SURFACE WATER TWIN PUMP STANDARD EFFLUENT SINGLE PUMP * * SPECIAL ORDER EFFLUENT TWIN PUMP *Optional High-level alarm www.burdens.co.uk 321

Domestic Sewage Pumpsets If the main sewer is accessible but at a higher level to (or some distance from) the domestic foul drain, then a domestic sewage pumpset may be used to pump unsettled sewage directly to the main. Whilst single pump units are acceptable for individual houses, it is recommended that twin pumping systems be used for multiple dwellings. Effluent Pumpsets A septic tank or treatment system pumpset can be used to disperse settled effluent when a site has a high water table or adverse invert levels. Installed after the septic tank or treatment system and pumping settled effluent up to an inspection chamber, flow to the drainage system then takes place by gravity in the normal way. Surface Water Pumpsets Due to the amount of rainwater that can fall in a short time period, surface water run-off is often the most demanding of all applications, whether hardstanding or roof areas. Klargester offers a comprehensive range of packaged pump systems in both standard form or manufactured to bespoke specifications. Careful calculation of the run-off areas is essential when sizing these pump systems. Applications Developments where foul drainage by gravity is not possible, including: Domestic sewage pumping Effluent pumpsets for sewage treatment plants Surface water pumping systems Septic tank pumpsets 24 hour storage chambers Bespoke systems Features Complete package systems delivered direct to site Ready for immediate and simple installation Factory built and quality assured Maintenance free GRP and polyethylene chambers Full Klargester after sales maintenance available All Klargester products are manufactured under the quality procedures of BS ISO 9001: 2000 Design All standard Klargester package pump systems are supplied with GRP/ polyethelene chambers, pump(s), high-level alarm, pre-set automatic level control, non-return valve, discharge pipe and all connections. Options Wide range of emergency overflow tanks 110mm or 160mm inlet connections Various invert depths Standby replacement pumps Bespoke Systems Klargester manufactures pumping chambers of various diameter and depths, with pumps, guide rail and control equipment fitted as per the client s specification. Delivery and installation Units are normally delivered by flat bed vehicle and cranage facilities should be available on-site for off loading. Installation is quick and economical, the unit requiring only a concrete base and surround. Comprehensive installation instructions are supplied with every unit. Maintenance Klargester package pump systems are designed for minimum maintenance. Legal Requirements Prior to installation, there is a legal requirement to obtain permission from the appropriate agencies (including connection to a public sewer). 322 www.burdens.co.uk

Envireau Rainwater Harvesting System Designed as a low-cost installation for both residential and commercial applications. BBA certified, it works by taking the rain from your roof gutters, filtering out leaves and debris and storing the water in an underground tank. This is then pumped into the house to be used for non-portable applications such as toilet flushing and washing machines. If the tank runs empty, the system automatically switches to mains supply. For use within: Homes and gardens Schools and public buildings Commercial offices Warehouses and factories Housing Associations Farms and agriculture Plant nurseries and garden centres Key benefits of using Rainwater Harvesting Sustainability Rainwater Harvesting can be a cost effective way of incorporating sustainability in to the fabric of a new construction project. Planning The specification of sustainable products at the planning stage can assist the process. Many sites now have restrictions on the volume of water run off, therefore the incorporation of Rainwater Harvesting can assist by greatly reducing the volume of water going to waste from new developments. SUDS (Sustainable Urban Drainage Systems) The major benefit of Rainwater Harvesting in this process is its ability to take most or even all of the roof water out of the surface water system. Cost Saving A reduction in use of mains water will obviously provide the user with a reduction in water charges. Rain harvesting can replace up to 50% of a household mains water consumption, and up to 85% on commercial installations. The payback period can be as quick as 3 years on buildings with large roofs and a high non-portable water demand. The Envireau system can supply over 50%* of domestic needs Mains Water % of domestic use Rain Water % of domestic use Personal Washing 32 Garden & Car 13 Drinking Water 2 Laundry 12 Washing Up 8 WC Flush 33 *Dependent on precipitation levels. Gardening Rainwater caught straight from the sky is the best water you can give to your garden. Captured before it hits the ground, rainwater is free of many pollutants that plague surface and underground water supplies and almost always exceeds the quality of ground or surface water. Lawn and garden watering typically consume 40% of total household water use in the summer. Re-use of rainwater is not subject to hosepipe bans. www.burdens.co.uk 323

Business Funding Businesses investing in the Envireau rainwater products may be able to claim tax relief through the Enhanced Capital Allowance (ECA) scheme, as the products are on the approved Water Technology List. Businesses may be able to offset 100% of the cost of products on the Water Technology List against their taxable profits. All businesses that pay corporation and income tax in the UK are eligible for tax allowance. Envireau Direct System The Direct System is suitable for both domestic and commercial applications. This system is used where it is impractical to have a header tank and therefore filtered rainwater is pumped direct from the holding tank to the various appliances. When the holding tank is running dry there is a small automatic charge of mains water into the storage tank to ensure the system never runs completely dry. The main advantage of this system is that rainwater is delivered to the appliances at mains pressure (3.5 bar). Envireau Gravity System The Gravity System is ideal for both domestic and commercial applications. It has a major advantage in that in the event of a power failure on site (or the rain stocks running dry) the system will automatically switch to mains water supply to ensure a continuity of service. The header tank contains two independent valves operating both the mains and rainwater supply. The system will always draw on rainwater first. Envireau Multi User System The Multi User System is used where one Envireau Gravity System is used to service up to 5 properties from one tank. This system is used most often on Housing Association Developments where the roof areas are small and cannot justify a system for each property. A landlord s electricity supply must be available for this system. Raintrap Garden Watering System Raintrap is an easy to install underground rainwater storage and delivery system designed specifically for garden irrigation. Raintrap collects rainwater from the roof via the existing guttering and downpipe system on the property. The integral leaf filter will remove unwanted debris washed down from the roof thus ensuring good quality stored water. The system is connected to the integral water pump. A simple on/off switch will operate the pump, allowing it to deliver the stored water under pressure to where it is needed. Simple on/off operation Suitable for existing and new homes Automatic rainwater diversion when tank reaches capacity 2800, 3800 & 4600ltr capacities Internal self-cleaning leaf filter Designed and manufactured in the UK Automatic pump shut off when empty Raintrap Capacity Overall diameter Height to inlet/outlet Weight ltr mm mm kg 2800 1905 1565 125 3800 2070 1795 180 4600 2080 2035 210 324 www.burdens.co.uk

Stormwater Attenuation Systems Managing the Stormwater Challenge As more river valleys become developed with hard surfaces (paths, roads and roofed areas) the volume of rainwater that runs off the land increases. This can have a severe effect in a watercourse where flash floods can occur downstream where the volume of water entering the system can be extremely high due to a cumulative effect of development upstream. Global warming has also had an impact on the level of rainfall, which has gradually increased over the past few decades. This has accentuated the problem of stormwater entering waterways. Flash floods along with rising sea levels have been responsible for some severe flooding in the UK in recent years. This has led to rising insurance claims and leaving some areas as blackspots where insurance against flood damage cannot be obtained. Sustainable Urban Drainage Systems (SUDS) To address this problem, the drainage systems of towns, cities and developments have been surveyed and a policy of Sustainable Urban Drainage Systems (SUDS) has been developed to counteract the problems being encountered. SUDS addresses issues of quantity and quality of the water run-off from sites. Attenuation systems (tanks and rainwater harvesting systems) and separators (to remove oil contaminants from discharges) are required. To size the systems required, the flow rate from the development is calculated from rainfall records and the run-off rate for a particular type of surface, i.e. roadway, roofed area, grassed area, all of which allow surface water to run off at different rate. The design is normally based on the highest recorded rainfall in the previous 30 years, but this can vary. Most authorities limit the amount of rainfall run-off from a development to a level where the rate does not exceed the rate of discharge from a green field site (5 litres/sec/acre approx.) but this must be specified by the local authorities. A technical engineer should provide the design calculations for the surface water run-off in order to size a system. This should also include the flow rate allowed for discharge to a watercourse, and the required storage volume. How does an Attenuation System work? When the peak inflow rate in a storm exceeds the allowed discharge into the watercourse, the excess flow has to be attenuated on the site for the duration of the storm. This is then released at, or less than, the allowed discharge rate after the storm. To store the excess volume and allow the correct discharge rate to go to the watercourse, a flow regulator is installed to bleed off the correct maximum flow rate. The flow regulator can be a vortex type system or a simple orifice plate system. The remainder of the water is stored either in-line or off-line, depending on the design. www.burdens.co.uk 325

In-Line Attenuation Tanks In-line systems allow water to back up through the tank and drain by gravity through the flow regulator. This system is normally used for installations where a fall through the system of 2.5-2.6 metres (on a sloped site) can be accommodated. In-line Orifice Tank System V.1 An orifice plate system works on the principle that the pressure created at a particular head will result in a particular flow based on the head versus hole size. This is a simple and inexpensive system. In-line Vortex Tank System V.2 A vortex flow regulator works on the principle of inducing a rotating flow around an opening at a high speed to limit the outflow of the liquid. This is the same principle that can be seen in a bath as it empties; the vortex reduces the flow from the bath even though there is a high head. 326 www.burdens.co.uk

Off-Line Attenuation Tanks Off-line tank systems have the flow regulator in a separate chamber and allow the flow to build up and overspill into a storage tank, adjacent to the chamber. Off-line Tank System V.3 The storage tank is emptied using pumps which are activated when the level in the regulating chamber recedes after the storm. This system gives a shallow inlet to outlet dimension and can cater for larger flows. www.burdens.co.uk 327

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