Case Study. Erosion Control, Erosamat Type 3. Allermoor Spillway protection, Somerset. Key Project Information. Erosamat Type 3/20Z500M.

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1 Erosion Control, Erosamat Type 3 Allermoor Spillway protection, Somerset River Parrett The Somerset Levels is a coastal plain and wetland area of central Somerset running south between the Mendip and Blackdown HIlls, South West England. The Levels are low lying with an elevation around 3 to 4 m above mean sea level and have historically been prone to flooding from both fresh water and occasional salt water inundations. The Parrett and Sowy Flood Management Improvements were carried out in summer The work comprised the re-profiling of the River Parrett s bank aimed at improving flow onto the spillway ensuring that during periods of high-flow water is diverted onto the spillway and onwards into the River Sowy. River Sowy Key Project Information Project Location Client Products Installation of erosion control measures on overflow spillway between Rivers Parrett and Sowy Somerset, UK Environment Agency Erosamat Type 3/20Z500M Installed Summer 2013 Benefits Permanent erosion control Withstands high flow velocities Rapid installation The consultant s challenge was to design spillway that would withstand high velocity throughout prolonged flows during potential flooding on the Somerset levels whilst maintaining a natural vegetated appearance when not in use. The spillway is critical to the performance of the flood defence system; as a result it was important that the turf reinforcement matting (TRM) provides adequate tensile strength and reinforcement to maintain structural integrity of the spillway. Adequately pinning and correct installation of the TRM system was required to withstand the expected hydraulic loading during flood events. Erosamat Type 3 Three dimensional matrix allows for root interlock Contact ABG t

2 Table 1: Allermoor Spillway, River Parrett and River Sowy, January & February 2014 Flood Monitoring Data, (from Black & Veatch) Depth on crest (m) Discharge intensity (m 2 /s) On crest At edge of track (7m from crest) Erosamat was chosen for this application as it is specifically designed to provide both an effective surface erosion control and a vegetative root reinforcement layer. In total over 17,000m2 of Erosamat Type 3/20Z500M erosion control system was installed on the spillway, fixed using 400mm pins spaced at 1m centres (0.5m along the overlaps). As result of construction delays the system, whilst installed correctly, was not fully vegetated by the end of 2013 leaving areas exposed over the winter months when the Levels are most prone to flood events. Subsequently during January 2014 prolonged heavy rainfall led to extensive flooding across the levels affecting over 6,900 hectares of land. During this flood event the spillway experienced water flow for 62 days. Without vegetation being established, a key element of the full protection level offered by Erosamat, it was important to understand how, or if, the Erosamat system would withstand the high velocity flows experienced. Velocities (m/s) At change in gradient (9m from crest) 10m from crest 20m from crest 30m from crest »» Flow depth and velocities recorded on Allermoor Spillway during 62 days of flooding in January and February 2014.»» Erosamat installation completed in September There was only minor grass coverage in January 2014.»» Unvegetated Erosamat system provided the required level of spillway protection for the velocities exceeding 4m/s. Following the completion of the spillway construction, Black and Veatch, as clients consultant, constantly monitored the performance of the spillway collecting data, including through the flooding events of 2014 (see table 1). The results collected showed a maximum flow velocity of 4.33 m/s across the spillway, a velocity much better than on the published datasheet, derived from laboratory tests. Field data from this flooding event demonstrated that un-vegetated Erosamat Type 3/20Z500M erosion protection system provides sufficient spillway protection for the velocities exceeding 4.0 m/s. When fully vegetated, Erosamat Type 3/20Z500M system is capable of hydraulic loading in excess of 6.0m/s. About ABG ABG are a market leader in the development of high performance geosynthetics for use in a wide range of civil engineering, environmental and building applications. Flood monitoring data Maximum design velocity 4.3m/s River Sowy 30m Erosamat 400mm River Parrett CS-034-A This literature together with technical data, specifications, design guidance, technical advice, installation instructions or product samples can be obtained by contacting ABG Ltd. All information supplied in this brochure is supplied in good faith and without charge to enable reasonable assessment of the practical performance of ABG products. Final determination of the suitability of information or material for the use contemplated and the manner of the use is the sole responsibility of the user. As design and installation is beyond the control of ABG (unless specifically requested) no warranty is given or implied and the information does not form part of any contract. ABG reserve the right to update the information within at any time without prior notice ABG Ltd. E7 Meltham Mills Rd Meltham, Holmfirth West Yorkshire, HD9 4DS United Kingdom t

3 Erosion Control Channel and slope protection using Erosamat and Erosaweb The Taylor Wimpey Barratt Homes development on Henthorn Rd, Clitheroe presented the project consulting engineers with an interesting challenge. Running across the development was an existing water course which required realigning and reprofiling. Part of the watercourse was channeled through a culvert with the remainder left as an open channel to form a green amenity area within the development. Key Project Information Client Taylor Wimpey plc Consultant Betts Associates Contractor X&P McGuigan Products Erosaweb GWX100/300 (1000m2) Erosamat Type 3 (5000m2) Benefits Speed of installation Long-term protection In order to maximise the available land for the development of housing the slopes of the culvert bank were to be as steep as permissible whilst taking into account the safety of the new residents. The slopes of the channel were to be vegetated and in order to prevent erosion of the topsoil before the vegetation established Bett Associates deemed the inclusion of an erosion control mat necessary. During periods of heavy rainfall the water flow velocity down the face of the slope was considered a risk so the For further information on erosion control systems /erosion-control t e technical@abgltd.com

4 use of a short-term biodegradable mat was discounted, preferring instead a permanent installation. The long lengths of the slope mean that the erosion control mat also needed an inherent tensile strength to withstand the load applied by the top soil before the vegetation root structure was established. Having considered various options it was decided that Erosamat Type 3 offered the necessary performance requirements. Erosamat Type 3 comprises a three dimensional structure of entangled filaments to create a long lasting, environmentally friendly, flexible erosion control mat which, in combination with vegetation, forms both an effective erosion control surface and a vegetative root reinforcement layer. The bottom of the flow channel required a different solution, one capable of withstanding the high flows within the watercourse. Here the consultants specified Erosaweb infilled with graded crushed stone engineered to withstand wash out by running water. Erosaweb is a three dimensional honeycomb structure designed to strengthen infill materials by containing them within its open structure. In water flow channels it dissipates energy by containing the granular fill and producing a rip-rap type performance. A holistic design combining both ABG products allowed the engineers to achieve the desired visual effect for the channel whilst allowing the groundwork contractors to quickly and simply install the required protection. Contact ABG to discover how Erosamat and Erosaweb could help you deliver a sustainable, cost efficient and carbon neutral solution. About ABG ABG are a market leading developer of high performance geosynthetic solutions for use in a wide range of civil, environmental and building applications. Established for 25 years and based in the UK ABG pride themselves of delivering outstanding customer service along with innovative solutions.. E7 Meltham Mills Rd Meltham, Holmfirth W.Yorkshire, HD9 4DS United Kingdom ABG 2013 CS_019 t +44 (0) e technical@abgltd.com

5 Geomembrane Protection and Top Soil Retention on Steep Slopes, Great Island Power Station, County Wexford, Ireland Erosaweb has been used to contain topsoil on the inside faces of a secondary containment bund within the construction of a new 460MW Combined Cycle Gas Turbine Power Station on Great Island, County Wexford. Project Information Client Scottish Southern Energy (SSE) Main Contractor Balfour Beatty Sub-Contractor Lining Technology Products Abtex SG60P/60PL Looped Geotextile Erosaweb GWX 150/300 Abfix Ties Benefits Rapid installation Protects geomembrane from damage Allows vegetation to establish on steep slopes The inside faces are formed from very steep slopes of 45o and consists earth faces overlaid with a protection geotextile which sits beneath a LLDPE geomembrane which forms the barrier in event of a failure occurring within the bund. Over the geomembrane liner is a Abtex looped geotextile and then finally the Erosaweb which is fixed to the Abtex using Abfix ties rather than with fixing pins that would puncture the geomembrane. Erosaweb laid on over looped Abtex. The loops onto which the Abweb is fixed are clearly visible. Erosaweb is a three dimensional matrix that works by confining materials within its cellular structure. On steep slopes it prevents top soil slipping down the slope allowing vegetation to establish. In this project a perforated Erosaweb has been used, this allows root interlock to take place between adjacent cells and also allows lateral drainage to occur. For more information on Erosaweb visit /products/erosaweb Top Soil Retention

6 The inclusion of Erosaweb offers a couple of key benefits for the project: 1. Using Erosaweb allows the formation of a protective layer over the geomembrane protecting it from damage and also from degradation as a result of exposure to UV. 2. By filling the Erosaweb with a top soil it is possible to establish vegetation on the steep slopes minimising the visual impact of the bund on the surrounding environment. Contact ABG to explore how Erosaweb can help your client achieve a sustainable, cost effective and carbon neutral solution on their project. About ABG ABG are a market leading developer of high performance geosynthetic solutions for use in a wide range of civil, environmental and building applications. Established for 25 years and based in the UK ABG pride themselves of delivering outstanding customer service along with innovative solutions. ABG Ltd 2013 CS_013_A abg Ltd E7 Meltham Mills Rd Meltham, Holmfirth West Yorkshire HD9 4DS t +44 (0) e geo@abgltd.com

7 Highway Drainage SuDS Balancing Pond Erosaweb, A1 Elkesley Improvement, UK Project Description This Highways England project comprises a new grade separated junction and a new local link road which means that road users will not have to use the busy trunk route to access the village of Elkesley. The scheme has improved safety and makes it easier to join or leave the A1, eventually allowing the national speed limit to be restored. Carillion was awarded this design and build scheme and carried out the 1.5 mile (2.5km) upgrade with associated link roads. The Challenge Highway drainage, in line with the Sustainable Drainage System (SuDS) regulations, requires proper control of surface water runoff preventing flooding and pollutants from road surfaces flowing straight into watercourses. In flat countryside, such as the area around Elkesley, flooding can easily occur and so balancing attenuation ponds are necessary. These require lining to prevent infiltration into ground water reserves. Lining is normally achieved with polymeric sheeting which has a low friction angle susceptable to UV degredation and vandalism. Water flows into the balancing pond via an inlet from the highway drainage system and the outlet is regulated to attentuate the water thus balancing the flow following a storm event. The challenge was to create an environmentally acceptable, stable,lined balancing pond at optimum cost. Project Information Client Highways England Contractor Carillion Consultant AECOM Products Erosaweb GWX 100/300 Quantity 10,000m 2 Sustainable solution Re-use of site soils Quick and easy installation Benefits Folds flat for easy handling Material cost savings Assists protection of liner Erosaweb is manufactured in the UK by ABG. abg ltd. E7 Meltham Mills Rd, Meltham, West Yorkshire, HD9 4DS UK t e geo@abgltd.com Export t +44(0) e export@abgltd.com

8 Highway Drainage SuDS Balancing Pond Erosaweb, A1 Elkesley Improvement, UK The Solution The contractor chose a soil retention and erosion control geocellular containment system to hold a suitable amount of topsoil in place on top of the slippery liner. The honeycomb structure is anchored in a trench at the top of the slope beyond the liner edge and hangs down the slope. The panels are jointed together around the pond to form a continuous curtain. Topsoil is placed into the cells from the bottom up. The topsoil retained on the slope by the Erosaweb allows drainage through holes in the cell walls to prevent puddling within the cells. The result is a naturally planted SuDS pond which deals with surface runoff to national standards lined with the minimum thickness liner. The ABG Service Assistance with cost comparisons, installation suggestions and advice on topsoil quality requirements. Deliveries were palletised and the folded flat Erosaweb panels were easily handled on site. ABG Erosaweb accelerates the growth of indigenous plants by creating ideal growing conditions. Plants need stable, moist topsoil to encourage early growth. The plant growth binds the surface layer through root growth. The 100mm thick layer of topsoil also protects the liner from puncture during maintenance visits. Web is just overfilled with topsoil and left to self seed The result a protected lined balancing pond Contact ABG today to discuss your project specific requirements and discover how ABG past experience and innovative products can help on your project. abg ltd. E7 Meltham Mills Rd, Meltham, West Yorkshire, HD9 4DS UK t e geo@abgltd.com Export t +44(0) e export@abgltd.com