Maintaining pervious surfaces

Permcon permeable concrete provides a hardwearing course for vehicular and pedestrian traffic, while acting as filter system for stormwater. As with any filtration system, maintenance is key to performance – and with Permcon it is more than manageable, as outlined below

Permcon permeable concrete is a specialised type of concrete – primarily used for rigid pavements – that allows stormwater to pass through it into an open-graded basecourse beneath it for detention purposes. From there, it can recharge groundwaters, evaporate, or be managed into the stormwater network.

As such, permeable concrete pavements help reduce street flooding, improve the health of receiving streams and rivers by filtering debris and pollutants from the stormwater, and cool water as it infiltrates the permeable base system.

Maintenance matters

As with any filter, there is an element of maintenance required to ensure Permcon permeable concrete performs at its best.

Debris such as leaves, grass clippings, dust and soil can accumulate on the pavement surface and, over time, will break down and wash into the voids of the concrete, plugging the wearing course and inhibiting the flow of stormwater to the open-graded basecourse below.

The best type of maintenance is preventative. Stockpiling mulch, soils or other organic materials directly onto the pavement surface should be avoided at all costs. It is also preferred that Permcon concrete is kept slightly proud of surrounding landscaped areas to mitigate stormwater runoff from these areas.

Drainage of upstream pavements onto the Permcon concrete will also accelerate the accumulation of debris in its voids, as the stormwater ‘washes’ across them. So, if clients are considering mixing impermeable and permeable concrete areas, it is better design practice to put the permeable areas at the high end.

Routine maintenance

Routine maintenance should start with a visual inspection. If there are leaves, grasses or other solid debris on the pavement, these can be removed by sweeping, a leaf blower or similar. On larger areas, using a regen sweep truck is recommended. The pavement should also be reviewed after a storm event to assess its state. If there is standing water or puddles that are not draining, it is a sign that the voids in the Permcon concrete are plugged.

This might be due to moss in the voids (particularly if the pavement is in a shaded area or on the dark side of the house). In these instances, a light power wash or stiff broom can dislodge the materials.

If using a chemical wash to remove moss or moulds, it is important to check for environmental impacts. Residue will wash through the permeable basecourse into the sub grade, which could harm the bacteria that assists with removing pollutants from the stormwater, and filter into the water table itself, harming local plant life or impacting on receiving streams and rivers.

Exceptional maintenance

If the plugging is severe or routine maintenance has been missed and the debris has worked past the surface voids deeper into the pavement, a light wash or sweep may not be enough to reestablish permeability rates. In this case, a deep clean might be necessary.

The best method for this is to simultaneously power wash and vacuum. Once the pavement is saturated, the water will come up through the concrete, bringing the lodged debris with it, when it can be vacuumed out. There are companies in New Zealand that have specifically designed equipment to provide this service.