pioneering projects: doing it differently and new ways of
TRANSCRIPT
TOM PALMER FdSc BSc (Hons) Project Design Engineer Essex County Council [email protected] 03330 139511
SMALL PROJECT OF THE YEAR British Construction Industry Awards 2018
Pioneering Projects: Doing it Differently and New Ways of Working Kingsmoor, Harlow Pluvial Flood Alleviation Scheme
• 5 year, £19m programme
• Individual schemes funded from programme and topped up with grants from the EA
• Projects selected by prioritising Critical Drainage Areas identified within SWMP’s and s19 report locations
• Feasibility and Option Optimisation studies undertaken with gate reviews prior to design and delivery stage
5 year capital programme scheme locations within Essex
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Essex Capital Programme
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Location and Problem
• Kingsmoor is an area in the south west of Harlow, Essex
• Heavily developed between 1950 and 1980
• Rural upstream, developed downstream
• Recorded internal property flooding to 20 properties from surface water and 20 from sewers, most from a single storm event in 2006
• Residential estate access road frequently made impassable due to flooding
• Issues with silt and debris from farmland upstream entering piped systems
• Modelled risk to 179 properties and 9 businesses from a 1% AEP event
Kingsmoor Critical Drainage Area (CDA)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Kingsmoor Area Flooding Photos
Photographs courtesy of Harlow DC
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Development
• Feasibility and Option Optimisation studies undertaken by Jacobs
• Determined that a large earth bund and storage area provided the greatest benefits
• Reviewed in conjunction with Harlow District Council and leaky dams and pond de-silting aspects were proposed to better mitigate against silt
• The number and positioning of dams changed after discussions with Harlow DC based on known flood flow routes
• Potential dam locations identified and finalised following site meetings
Location of proposed measures
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Constraints and Considerations
Key site constraints
Site Constraints:
• Local Nature Reserve (LNR) • Ancient Woodlands • SSSI’s (pedunculate woodland) • Crematorium • Footpaths and public access • Proximity to residential areas • Local ecology (hedges, trees, wildlife)
Considerations:
• Use and type of machinery • Working methods • Noise and working hours • Vehicle movements and re-use of spoil • Sustainability (design and construction)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Mitigation Measures
• Early engagement with stakeholders and partners
• Dam positions adjusted to reduce impact to woodland and utilise existing morphology and features
• Use of volunteer group to help clear woodland areas
• Use of wood sourced from within woodlands as part of existing management plan
• Use of heavy horses to move materials into position and dams installed by hand
• Footpath diverted with unadopted path on bund crest
• Work stopped for funeral processions
• Grassland Management Plan created for Local Nature Reserve area
Photo courtesy of Place Services
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Opportunities and Wider Benefits
• Woodland clearances chance to improve wider area (in line with SSSI status)
• Ecology and biodiversity in woodland and ponds
• Local amenity, promotion of woodland, awareness raising
• Education: woodlands frequently visited by schools
• Footpath inconsistencies, chance to correct
• Earth bund seeded with grasses and wildflowers
• Innovative Grassland Management Plan for whole LNR rather than compensatory like for like area replacement
• Improved wildlife corridors Site boundary (red) and Local Nature Reserve (blue)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Photos: Leaky Dams During Construction
Photos courtesy of Harlow DC
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Photos: Dams and Ponds Post Construction
Leaky dams and pond de-silting works immediately after completion (November 2017)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Photos: Leaky Dams and Ponds
Leaky dams and ponds (June 2019)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Photos: Earth Bund During Construction
Top and bottom far left photos courtesy of TopBond PLC.
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Photos: Earth Bund Post Construction
(June 2019)
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Scheme Summary and Key Outcomes
• Leaky dams completed November 2017, bund completed July 2018
• Total scheme costs £440k, pond de-silting and leaky dam aspects £42.8k
• Flood protection to 43 properties from a 5% AEP event, depth reductions to over 110 others
• Carbon assessment: 94.4t of CO2 saved
• Flood mitigation measures can be delivered in sensitive areas!
• Flood alleviation works as an opportunity for wider benefits to ecology, biodiversity, water quality and amenity, and for raising flood awareness
• Partnership working essential to project success Toads and mint returning to a pond
Harlow, Kingsmoor Pluvial Flood Alleviation Scheme
Thank You
TOM PALMER FdSc BSc (Hons) Project Design Engineer Essex County Council Flood and Water Management Team [email protected] 03330 139511
Kingsmoor Flood Alleviation Scheme SMALL PROJECT OF THE YEAR British Construction Industry Awards 2018