BenefitsAllow water to filter through hard surface to increase soil moisture and sustain adjacent vegetation
- Infiltration rates in permeable interlocking concrete paving (PICP) after 8-10 years of service have been reported at or above 100 mm/hour (Beecham, et al., 2009)
- After about 10 years of service, PICP would be 18% of its value when constructed (Borgwardt, 2006)
- The majority of permeable pavements have a design life of 15 (Mullaney & Lucke, 2014) to 20 years (Shackel, et al., 2008)
Decrease excess stormwater runoff
- Catchment outflow reductions of 67% are possible for rainfall events of less than 50 mm by using permeable paving built over clay subgrades (Collins, Hunt & Hathaway, 2008)
- Permeable pavement appears to be an effective tool for hydrologic mitigation of storms from “every day events” up to the 10-year, 24-h average recurrence interval (ARI) or now referred to as 10% AEP (Fassman & Blackbourn, 2010)
Avoid downstream drainage system upgrades
Stormwater management solution when no underground drainage system exists
Case study: Kegworth Road, Melrose Park permeable paving project cost $30,000 more than resurfacing the road with asphalt. The project cost $200,000 in total, including permeable paving, leaky wells, and soakage and distributions systems in the nearby reserve. This was in comparison with the estimated $1.2 million cost of upgrading the conventional pit and pipe network to address a local flooding issue (Johnson & King, 2020)
Support maintenance of pre-development run-off rates and/or more natural hydrological cycle
Reduce stormwater ponding on surface of carpark, road or footpath
Reduce the need for stormwater pits and pipes (and associated cost)
Design tipsTIP 1 – Geofabric between bedding course and base layer almost redundant
If ratio of diameter of bedding layer to base course layer aggregate is less than 1:10, then no geofabric is required between the layers.
Why? The materials are close enough in size, ensuring that migration of smaller bedding course material into the voids of base course does not occur.
TIP 2 - To avoid clogging of permeable pavers
Ratio of contributing impervious areas to permeable paving area – no greater than 4:1
TIP 3 – Avoid recycled concrete basecourse
Why? The limestone leaches out of the material and clogs the system.
TIP 4 – Always install an edge restraint or a concrete kerb
TIP 5 – When design is close to a footing or structure
ensure no water enters the subgrade by:
- ensuring a minimum 1% grade of pavement to draw the water away from the structure/wall
- installing an impermeable liner that redirects water away from the footing.
TIP 6 – Use permeable paving to protect significant trees
even if the tree is on an adjacent property.
TIP 7 – To preserve infiltration capacity
pervious pavement subgrades should not be compacted (Drake, Bradford & Marsalek, 2013).