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Example: Bishop's Waltham Moors, Hampshire - A Wetland and Fenland Site
A31 Picket Post Junction in the New Forest, Hampshire - Remedial Works to Drainage Outfall. The Problem
A new two level interchange on the A31 at Picket Post was causing concern to various organisations because of interrupted spring flow and erosion from a drainage outfall. This was causing landscape and wildlife habitat degradation and potential damage to an internationally important valley mire. The Environmental Project Consulting Group was approached initially by English Nature and Hampshire County Council Surveyors Department to explore various engineering options to deal with hydro-ecological problems. The interchange is on the edge of a gravel terrace aquifer feeding valley head springs. These springs saturate peaty ground supporting acidic bog vegetation rich in increasingly rare plants and the wildlife dependent on such habitats and for which the New Forest is internationally renowned. The problem was two fold. Firstly, construction of the interchange was very likely to have cut off groundwater supply to the springs and secondly, because all surface water off the interchange entered the forest at a single point, there was considerable water erosion to the heathland landscape, loss of a bridleway and of Commoners grazing land. The Solution
Our design solution (based on detailed soil, peat, ecological and hydrological sensitivity studies), was to pipe surface water flows underground to a chamber at spring level from where horizontal porous pipes in stone filled trenches contoured around the valley head recharging springs, maintaining wetland habitats and at the same time removing erosion and allowing habitat recovery. The Result
The project has protected part of the New Forest landscape and ecology by removing the cause of water erosion that had led to landscape, habitat and bridleway degradation. This scheme has allowed recharge of springs feeding an internationally important valley mire habitat, revegetation of heathland, restoration of a bridleway and all to the satisfaction of English Nature, Forestry Commission, New Forest Commoners Association, the horse riding interests and Hampshire County Council as agents for the Department of Transport. |
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