Pervious Concrete Cost Implications

 

Complying with the new regulations emerging from Phase II implementation of the Clean Water Act need not be especially costly when the proper choice of BMP (Best Management Practice) is chosen. Use of bio-swales and retention ponds is costly – there is the cost of creating these units, the cost of maintaining them, but especially the high cost of poor optimization of land use – the land area of the retention ponds and/or bioswales is needed as well as the land initially required. Use of exit filtration systems in storm drains have an initial cost factor, a high ongoing maintenance cost factor, and a strong potential for very expensive ongoing effluent monitoring.

Infiltration BMPs produce no runoff and no discharge. As such, they are often preferred by both landowners and regulators alike. No runoff and no discharge can reduce or eliminate ongoing monitoring of effluent (because there is no effluent!), and if there ever are catastrophic events, they remain contained where they are much more easily and inexpensively remediated than an event that overwhelms a storm drain filtration or separation system.

Pervious concrete provides an infiltration BMP by turning the entire parking area, pathway or other paved surface into a retention and treatment basin. When placed over a sandy soil or over a class II permeable sub-base, stormwater is retained, filtered and treated by the sub-base and/or underlying soil. Tree wells can be very small, as the pervious concrete allows water and air to the tree roots. Thus tree growth, which cools the parking area and improves air quality, and is required by many municipalities and counties, is encouraged without giving up usable parking area.

Pervious concrete is a durable material – it is expected that most parking areas properly constructed will last 20-40 years with little or no maintenance. Thus concrete, conventional or pervious, is widely recognized as the

• Reduced grading. With no storm drains there is no need to slope the parking area. Pervious concrete accepts the existing topography of the area.

• No storm sewer tie-ins. Eliminating the cost of underground piping and drain inverts can be substantial.F

For the city, county or village responsible for storm water in the area, use of pervious concrete provides a number of benefits:

• Reduced summer temperatures, providing increased comfort and reduced ozone levels.

• Groundwater recharge to keep aquifer levels maintained.

• Complete infiltration means that no new storm sewer facilities need be constructed, nor existing lines enlarged.

• Improved tree growth and reduced sidewalk maintenance.

• No hydrocarbon pollution from asphalt pavement and sealers.

• Reduced potential for legal problems (see below).

For the owner or developer:

• Brighter surface reduces lighting needs and costs.

• No need to close down sections of the parking lot for resealing.

• Drastically reduced maintenance costs.

• Reduced concerns over future effluent monitoring.

• Increased land use efficiency.

• Easier to comply with tree shading ordnances.

• Lower life-cycle cost.

• Potentially lower initial cost.

A recent California court case (Dec. 21, 2001) supports infiltration BMPs rather than allowing any stormwater discharge from one’s property. In

In summary, providing stormwater management and first flush pollution mitigation via pervious concrete can not only be the lower cost option when compared to other BMPs, it can also provide lower cost than traditional parking lot constructions, when the costs of eliminating storm sewer tie-ins is factored in. Pervious concrete will virtually be the lower cost option over the life of the parking area.

 

• Reduced land purchase. Compared to bioswales and retention ponds, pervious concrete allows 100% use of the land for the purposes desired. No additional land need be purchased.

No additional SWPP (stormwater pollution prevention) devices such as storm sewer invert filtration systems. Costs savings here are both upfront and long term. Lombard Acceptance Corp v. Town of San Anselmo, the 1st District Court of Appeals stated that an uphill landowner who knowingly alters the natural drainage of surface waters may be liable for damage caused by the discharge of the water onto adjacent property. The properties need not be continuous.