Concrete Block Permeable Pavement (CBPP) is a structural pavement that allows rainwater to infiltrate and build up prior to being released into either the ground, a watercourse or a drainage system. In recent years, the technology has become ingrained in planning guidance and building regulations, as well as the draft Code of Sustainable Housing.
CBPP is suitable for a wide variety of residential, commercial and industrial uses - including car parks, residential roads and substantial heavy duty uses such as ports. Its main advantage is that it can optimise land use by combining hard landscaping with the management of surface water and Sustainable Urban Drainage Systems (SUDS).
The philosophy of SUDS is to manage surface water by attenuation and filtration to reduce the environmental impact of urban development by simulating natural drainage.
The system usually involves combining and linking a number of different techniques as a 'management train'. CBPP can be used as part of a SUDS train or as a stand-alone system.
While the initial focus of CBPP and SUDS was flood prevention, a number of other functions are now being realised. Most notable is the role played by CBPP in handling polluted water. Microbes develop naturally in the pavement due to regular contamination and combine with air to help treat the water.
CBPP reduces the concentrations of pollutants further via filtration, retention, use of biodegrading hydrocarbons within the pavement and settlement and retention of solids (see box).
In addition, CBPP is able to handle catastrophic incidents such as spillages, removing the need for interceptors.
However, although the benefits of CBPP and SUDS are increasingly being recognised, there is still some way to go.
The government's draft Code for Sustainable Homes fails to recognise the issues of water quality and the potential for water harvesting that CBPP offers.
John Howe is general manager of Interpave.