Project Description
Wexham Park is a large NHS Trust hospital providing multi-disciplinary health and emergency services; including trauma and orthopaedic surgery, paediatric, coronary care and maternity care, amongst other services. Staff parking at this large facility was inadequate, so the Frimley Foundation Trust decided to develop an adjacent greenfield site to provide an increased number of parking spaces and to reduce the amount of on-road parking which was adversely affecting local residents.
The Challenge
The proposed new car park was subject to planning restrictions which stipulated that the new surface must be designed to allow surface water run-off rates to remain at the same level as pre-development. Site investigation reports indicated that the subgrade soils were suitable to allow surface water infiltration, but the costs of permeable asphalt or concrete block paving exceeded the available budget.
The site investigation also revealed variable ground conditions, including some very soft areas. In order to maintain structural integrity, as well as meeting the required rates of surface water infiltration and attenuation for the Planning Conditions, the subbase design thickness needed to increase and utilise a permeable DoT Type 3 stone. This presented a challenge for the structural design team, because it also meant that the increased subbase depth would require an increased number of deliveries of more expensive aggregates.
The Solution
ABG’s in-house Design Team proposed a subbase design which utilises their unique Abgrid geogrid to reduce the thickness of DoT Type 3 stone required to achieve structural stability. An ABG Terrex NW non-woven geotextile layer was also proposed, to provide an additional stage of treatment for the infiltrating water. Overall, the incorporation of ABG’s proposal provided a shallower construction profile which resulted in reductions in site excavation, off-site tipping, DoT 3 stone volumes, deliveries and associated costs.
ABG Sudspave 40 gravel-filled cellular permeable plastic paving was then installed to provide robust, sustainable and permeable retained gravel surfaces for traffic aisles and parking bays. Sudspave porous pavers enables rainwater to infiltrate directly into the surface and through to the subgrade, whilst also receiving surface water run-off from adjacent asphalt areas, fulfilling strict planning requirements for drainage.
The ABG Service
Full subbase design, taking into account structural, hydraulic and treatment requirements. Technical support for required design approvals and on-site installation guidance. Scheduled deliveries to meet site programme.
Contact ABG today to discuss your permeable paving project specific requirements and discover how ABG’s past experience and innovative products can help.
