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Permeable Pavement

Permeable pavements are made of material that is itself impermeable to water but the material is laid so that space is provided where water can infiltrate into the underlying structure. They reduce peak flows and effects of pollution. They require no additional land take and are therefore highly valuable interventions in dense areas, especially because they are easily accepted by the community around. An aggregate subbase allows water quality improvements and attenuation of flows, while a geotextile layer improves pollutant removal and performance.

Access

Can be used in multifunctional areas but does not provide same benefits as greenspace. Can provide area for recreational use. (8,15, 14)

Air Quality

Not given.

Pluvial Flooding

40% more effective peak flow reduction than conventional pavements, other studies have found runoff reductions of up to 100%, treating the paved area and to an extent even runoff from adjacent areas. Runoff generation can be eliminated. (1, 2, 3, 6, 9, 10, 13, 14)

Fluvial Flooding

Can provide flood prevention downstream by reducing runoff into rivers.

Climate Regulation

Potential to mitigate UHI through evaporation and storage of water but this depends on various factors. If combined with other technologies (see below) may help to reduce emissions. (11, 12, 14)

Habitat Provision

Not given.

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Low Flows

Permeable pavements can potentially allow groundwater recharge and combined with rainwater harvesting reduce pressure on mains water. (8)

U

Water Quality

Pollutant reductions are very high but can depend on maintenance. TSS reductions of >60% (58-94), motor oil, diesel and metals (20-99) can be (nearly) completely removed. N and P have varying degrees of removal, dependent on the design of the structure (below ground infiltration). (1, 2, 6, 10, 12)

Aesthetics

May allow grass to grow, creating attractive green area where otherwise only paving would be present. Depends on type of pavement used. (7,15)

Cultural Activities

Not given.

Property Values

Depending on type and quality may add value. (14)

Flood Damage

Taking up water from their own area and surrounding areas can help reduce the risk of flooding and the extent of flooding on a larger scale.

Position in the Catchment

Permeable Pavings provide source control and infiltration and can be combined with storage systems. They are the first stage the water passes through. Where runoff cannot be completely eliminated, conveyance to a storage area should be designed.

 

Costs

27-40£/m2 (high). Depends on whether replacement or new development and type of paving. No need for connection to sewer system (saves additional costs). If all costs are taken into account, they are lower than for traditional surfacing and drainage. (4, 7)

Feasibility

Industrial and Domestic. Retrofit possible. The type of pavement used depends on expected traffic load and aesthetic requirements. Only gentle slopes. Adjacent areas need to be stabilised to prevent sediment flow into the paved area. Sand or sediment input can happen especially during construction; contractors have to be made aware of this. (5, 7, 8, 14)


Maintenance

0.5-1£/m3 of water stored/treated. Brushing/vacuuming every 6 months – to prevent the clogging and accumulation of metals in the top layers is likely necessary to maintain good water quality performance. Clogging however is more an issue with porous than permeable pavements. Unlimited design life. (4,5, 7, 8, 14)

Additional Benefits

 

 

Trade-offs and Potential Dis-services

Water Re-Use

There is high potential of combination with RWH systems that allow using the water for non-potable uses. The combination with geothermal heat pumps (GHPs) enables re-use of water (e.g. for gardening) along with energy efficient heating/cooling of buildings. This of course depends on the site context but can provide sustainable heating without need for fossil fuels (therefore reducing emissions) that compares with other residential GHP schemes in terms of efficiency.

Multifunctionality

Paved surface enables safe and comfortable use for vehicles and pedestrians while allowing infiltration and benefitting vegetation, providing treatment and flow management. While it is not a greenspace itself, it can improve the accessibility of greenspaces by providing convenient, safe paths through existing green infrastructure that integrate well with the landscape.

References:

  1. Ahiablame, L. M., Engel, B. A. and Chaubey, I. (2012) ‘Effectiveness of Low Impact Development Practices: Literature Review and Suggestions for Future Research’, Water, Air, & Soil Pollution, 223(7), pp. 4253–4273 Studies show runoff reductions by 50-93%, with pollutant removal for various substances ranging from 20-99%(metals), 58-94%(TSS), 75-85%(N) and 10-78%(P). Runoff generation can be eliminated, PPS are therefore a valuable source control system.
  2. Ashley, R. M., Nowell, R., Gersonius, B. and Walker, L. (2011) ‘Surface Water Management and Urban Green Infrastructure’, 44(0), pp. 1–76.
  3. Booth, D.B. & Leavitt, J., (1999) Field Evaluation of Permeable Pavement Systems for Improved Stormwater Management. Journal of the American Planning Association, 65(3), pp.314–325.
  4. Environment Agency (2015) Cost estimation for SUDS – summary of evidence. Bristol.
  5. Harley, M. & Jenkins, C., (2014). Research to ascertain the proportion of block paving sales in England that are permeable, Report for the Sub-Committee of the Committee on Climate Change.
  6. Imran, H.M., Akib, S. & Karim, M.R., (2013). Permeable pavement and stormwater management systems: a review. Environmental technology, 34(17-20), pp.2649–56.
  7. Interpave, (2008). Understanding Permeable Paving, Leicester.
  8. Design guidance and description of various available systems and performances.
  9. Kellagher, R., Martin, P., Jefferies, C., Bray, R., Shaffer, P., Wallingford, H. R., Woods-Ballard, B., Woods Ballard, B. (2015) The SUDS manual, CIRIA. London.
  10. Qin, H., Li, Z. & Fu, G., (2013). The effects of low impact development on urban flooding under different rainfall characteristics. Journal of environmental management, 129, pp.577–85. Runoff reduction of 75% on average through permeable pavement. Best for smaller storms with short durations, with peaks in the middle of the event.
  11. Scholz, M. & Grabowiecki, P., (2007). Review of permeable pavement systems. Building and Environment, 42(11), pp.3830–3836. Permeable and porous pavements provide 10-42% more effective peak flow reduction compared to conventional asphalts. They provide good water quality treatment with TSS reductions of about 60% and nearly complete removal of motor oil, diesel and metals.
  12. Starke, P., Goebel, P. & Coldewey, W., (2010). Urban evaporation rates for water-permeable pavements. Water Sci Technol, 62(5), pp.1161–9.
  13. Tota‐Maharaj, K. et al., (2010). The synergy of permeable pavements and geothermal heat pumps for stormwater treatment and reuse. Environmental Technology, 31 (14), pp. 1517-31.
  14. S. Environmental Protection Agency (2013). Stormwater to Street Trees. Washington: USEPA.
  15. Royal Horticultural Society (2016): Front gardens: permeable paving.
  16. http://www.susdrain.org/delivering-suds/using-suds/suds-components/source-control/pervious-surfaces/pervious-surfaces-overview.html