A30 Dualling – Chiverton to Carland Cross Earthworks subcontract, 2022
The footprint of the A30 Chiverton to Carland Cross scheme passes through a small, isolated area of existing dwarf shrub heathland and lowland heathland, approximately 0.5 Ha in area, which is designated as a habitat of principal importance for the conservation of biodiversity in the UK.
The heathland habitat has intrinsic biodiversity value, providing habitat for key terrestrial invertebrates such as common lizards, adders, and common newts. Without mitigation measures, unavoidable loss of heathland habitat will occur during the construction phase. This area is also of key archaeological importance with known features of interest present such as the Two Bowls Barrows. As part of the biodiversity net gain plan the heathland is planned to be retained and translocated to a donor site, located approximately 375m northeast.
To date 4 No. trials have been undertaken, testing various methodologies to determine the most effective and efficient way to translocate heathland turfs whilst causing minimum damage to the soil structure and vegetation. Previous trials have indicated the optimum size for each turf is 2.50 m (L) x 1.50 m (W) by 0.30 – 0.40 m (H), which allows the turf / soil structure to be retained when translocated.
Trial No. 4 was undertaken on 5th September 2022 and comprised the translocation of two turfs. Ecological and archaeological watching briefs were undertaken throughout the works. The first step was to create a vertical face at the front of the heathland to allow the bucket to be inserted into the ground at the correct depth. The next step, using an open bucket to cut the rear of the proposed heathland turf, allowing material to come away easily. After this, the bucket is pushed horizontally into the ground at the required depth and the turf is lifted up.
The turf is then gently placed on a steel plate (with guiding rails on the base) with the aid of a second excavator’s bucket with minimum shaking as the bucket is withdrawn. The turf was then inspected by ecologists to confirm the absence of terrestrial invertebrates. A bog mat was then placed on top of the turf, secured using ratchet straps and wrapped in clingfilm to ensure no material is lost during transport. The turf was then lifted onto a flatbed trailer and transported to the donor site, which involves a short 15-minute journey on the public highway.
At the donor site, the turf was lifted off the trailer via forks and placed on the required surface by dropping the forks at a suitable angle.
Generally, the trial was deemed a success. The structural integrity of the soil was generally maintained and key heathland flora was retained. Some loss of subsoil occurred at the front edge, but this would be covered by the next turf to be placed. The trial highlighted that the use of clingfilm would not be feasible in terms of labour required and the volume of single use plastic used.