WET News

16 WET NEWS MARCH 2016 ONSITE Flood risk management 3D was used to develop the solution, and grading tools and clash detection to optimise the design. MWH used visualisations, created using the 3D model and landscape plan, at customer events and as interactive educational tools. The contractor was able to avoid double handling of data by inputting the 3D ground model to an Automated Machine Control system (Trimble 3D GPS) in order to form SuDS features. This improved accuracy and saved time on site. Passing data from initial concept e.g. data collection and modelling, to design, construction and back to the end user like this forms a basic Building Information Model for infrastructure schemes. Approach By using SuDS, the project scheme opened the door to more than just flood risk reduction. The project was also able to include biodiversity features such as new ponds for two primary schools, planting of wildflower meadows in detention basins and the extension of an existing wooded area with native trees and shrubs. The benefits from these features include reducing pollution, providing new habitats, creating community spaces and improving health and wellbeing. By adopting this approach, less concrete was needed than for conventional drainage by creating so† engineered structures such as detention basins and swales from native soils. Additionally, the 3D TECHKNOW • Civil 3D was used to develop the solution • Grading tools and clash detection helped optimise the design • Spoil from excavations was reused to form flood defence bunds or landscaping bunds • Using SuDS meant the scheme could also include biodiversity features • Less concrete was needed than for conventional drainage by creating soft engineered structures NEED TO KNOW 1 Overall project costs were reduced by 36% through working as partners, sharing the same consultant and contractor 2 SuDS costs were judged to have been more than £2M lower 3 The scheme was constructed within programme and business budgets 4 Reduced working hours helped minimise disruption and improve safety 5 The project used the partnering and sustainability philosophies from Defra's SWMP THE VERDICT The Fellgate flood alleviation scheme has paved the way for further surface water management schemes, and NWG and STC now have a number of partnership working projects in their investment programmes. The detention basin during heavy rainfall this winter Ponds provide ecological and educational benefits Construction of the detention basin design approach provided the necessary tools to optimise SuDS. For example, using cut and fill assessments they were able to reuse spoil from excavations to form flood defence bunds or landscaping bunds. This project also demonstrated that SuDS are safer to build, needing less construction plant and people. Finally, compared to delivery of a traditional piped solution construction costs, SuDS costs were judged to have been more than £2M lower. But not only are they cheaper than conventional drainage they bring additional benefits as identified in an economic impact assessment used to evaluate the full range of benefits. The most significant were identified as property damage avoided, educational opportunities, habitat creation and amenity value, resulting in a benefit to cost ratio of 2.9. This clearly demonstrated the business case and helped secure funding for the project. Relationships Building on the SuDS biodiversity enhancements the project team achieved further benefits working with local schools. For example, they provided outdoor classroom space, education sessions and a tree planting event supported by the Wildfowl and Wetlands Trust and held local school workshops on the construction process and water cycle. From early in the project a number of events were held to build relationships with and inform the local community,

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