In 2015, Bouygues Energies and Services Limited invited Enviromesh to the Forest Hill School site in Lewisham. The meeting consisted of us proposing a number of design solutions to the school’s representatives. Enviromesh were approached following an initial enquiry via our website.
The project involved two 50-metre long, five-metre wide Mass Gravity Gabion Retaining Walls. The wall installation is part of an earlier landscaping scheme, by a previous contractor. The walls were to retain two raised-beds containing ground cover vegetation and taller shrubs. Both walls situated in the main playground and recreational area inside the school’s grounds.
The rather well-worn (and damaged) gabion walls were in urgent need of either repair or replacement. Initial site surveys revealed a number of defects in the original installation. We addressed this as part of our overall package to replace the walls with a more durable and effective specification. A combination of poor installation and incorrect mesh specification, as well as damage caused by the removal of stone and excessive voids in the filling material, had resulted in distortions and in places, mesh failure.
Enviromesh presented a number of options to repair the existing wall. We were then invited back in July 2016 to carry out the works during the school’s summer holidays.
REPAIRS
The project would involve the removal of the existing walls next to the clean tarmac surface of the playground. Therefore one of the first challenges here would be to take surface protection measures to avoid damage. By limiting the use of heavy machinery and through careful planning of deliveries.
The existing planting scheme was a high priority for ensuring limited disturbance. Particularly to the larger roots that would be exposed during the removal works. Inspection of both the wall’s foundations and existing geotextile membranes could occur following the removal of the existing baskets. A final decision chose to replace all the baskets and membranes. This ensured the completed structure complied with our ISO accreditation and installation warranty.
INSTALLATION
Protection of both the existing tarmac surrounding the walls in addition to the plants and shrubs took primary consideration before any work could start. A lighter weight mini excavator employed to minimise the risk of damage. Coupled with surface preparation and a thorough briefing on the matter to all personnel involved. The replacement mesh baskets were specified as 5mm on all faces to provide the required strength. Along with rigorous clipping together to prevent inquisitive youngsters from opening them. By adding helical spirals to run the length of all exposed joints. Security of the rock fill material would be enhanced along with providing a ‘rounded’ surface rather than a sharper corner or edge. This would make for a safer solution, given the situation and health and safety considerations.
Completion of the project within the six-week school holidays was a key part of the contract and schedule of works. The limited, 48 hours notice given to commence works condensed the time frames. However, Enviromesh employs a national network of specialist gabion installers. We were able to mobilise both our team in the South-East and materials to site within a few days’ notice.
