Permeable Pavement -- A New Approach To Storm Water Control and Water Quality and Supply Issues
I have run across several articles on the topic of permeable pavement systems. As we all know, when land is paved with traditional concrete or asphalt, it becomes an Impervious surface which does not allow water to seep back into the earth below. This creates a major problem with storm water runoff, as well as not allowing for the natural recharge of the aquifer that supplies much of the drinking water in many areas.
Until only several months ago, I never realized that such product even existed. The first mentioning of this idea was at the November 30, 2009 meeting that the Rockland County Municipal Planning Federation held, in which a presenter briefly touched upon the idea.
This system will be of welcome to any designer or land-use planner dealing with a municipality that has a limit on the amount of allowable impervious surface. Obviously, the use of this system will allow for greater coverage for pavement than would be allowed for standard pavement.
After doing some research on my own, I have found that permeable pavement is now available in both concrete as well as asphalt. It has its major value in light traffic areas, such as parking lots, side walks and patios. This is due to the fact that both systems do not possess the strength needed to handle heavy highway or even secondary road traffic at this time.
In general, for both permeable concrete and asphalt, it is possible to achieve a permeability rate of not less than five gallons per square foot per minute. This is far greater than what would fall in a 100 year storm, the general standard by which storm water control must comply with.
In the case of permeable cement, it is the unique manufacturing process that allows for this to happen. First, there is a careful control of the amount of water and cement in the mix, so as to create a paste that forms a thick coating around the aggregate materials. Second, there is little or no sand in the mix. This now creates a highly permeable interconnected set of voids that allows for the fast rate of drainage through the pavement. In fact, the voids account for 15 to 25% of the product.
EcoCreto is an example of a permeable concrete system that now claims to have a hardened strength as high as 5000 pounds within 28 days, and is 100% permeable. In addition, EcoCreto claims to reduce storm water contaminates such as suspended solids by up to 90%. Also claimed, is the reduction of heavy metals by 40 to 90%, as well as the removal of 90% of mineral oils, and 60% of phosphorous. Obviously, this goes a long way in addressing a major issue -- storm water quality control. The LEED rating system deals with this as well as storm water quantity control. By pre treating the water contaminates prior to the water seeping back into the aquifer to this level, we provide for far better aquifer recharge protection in terms of both quality and quantity of the water. As a result of this, this product is recognized by the federal Environmental Protection Agency as a Best Management Practice (BMP) for the control and management of storm water runoff.
In addition to the advantages of the permeable pavement allowing for the water to penetrate into the soil below, the soil and adjacent sub-surface also further purify the water, via microbial activity.
We MUST note that the property in which permeable pavement is considered for use be evaluated for its ability to absorb the water; if the water table is already high, or there is the presence of heavy clay or solid bedrock, the system will have limited effectiveness.
In general, a 12 to 36 inch sub base is prepared under where the pavement will be laid. This will consist of gravel, and sometimes, a piping network to allow for the water to be either drained directly into the ground below, or if needed, re-directed to an alternative location for seepage into the aquifer.
Porous asphalt is created in a similar fashion, and has the same benefits as concrete.
In terms of cold weather performance, especially with snow and ice, I ran across a PDF of an article from Storm Water, (September, 2008) that said that these products can be used in cold climates; in fact, it was claimed up a 75% reduction in the need for salt application for de-icing -- a BIG help to the environment as well as a cost-saver. In addition, increased slip resistance was noted when permeable pavement was used. This is most likely due to two factors: the increased texture created by the voids at the surface, and the lack of sheet water flow, resulting in less ice formation. However, a designer needs to take into account the frequency of freeze-thaw cycles, as this can effect the performance of the permeability if the cycles are too quick. Under most cases, the system allows water to drain away to warmer ground below prior to the pores being clogged with ice.
In spite of the porous voids and stone-like surface, these products have seen no issues with pedestrian traffic, even with high heel shoe use.
When used with proper planning, it is quite possible to significantly reduce or possibly eliminate the need for actual storm water catch basins and piping, thus saving far more than what the initial additional cost of using permeable paving vs. conventional materials. Thus, we see the interconnection of trade-offs and synergies that I have mentioned elsewhere. The final result can be a lower life-cycle cost, especially given the fact that industry expectations for the permeable pavement products to have a longer service life than that of standard pavements.
We also will benefit from the reduction of standing pools of water in parking lots, which in summer, can breed mosquitoes and in winter, turn to slippery ice.
Even higher traffic areas can find a use for this product, as the entire shoulder area can be paved with permeable material, creating a continuous drain to the earth below, while the traffic lane is paved with stronger conventional pavement.
For light duty projects such as patios or side walks, a product known as PermaPave can be used. This has all the properties of the above mentioned products, but comes in pre-formed paver blocks similar to the standard blocks used in driveways that we see in almost all neighborhoods today. PermaPave comes in 12 colors and four different sizes, ranging from 16" x 16" down to 8" x 4". It is installed in a similar way as standard pavers, but one MUST pay attention to the proper preparation of the sub surface below, to allow for drainage into the aquifer.
In summary, we have MANY advantages to using porous pavement products, from the environmental point of view to reduced maintenance.
Until only several months ago, I never realized that such product even existed. The first mentioning of this idea was at the November 30, 2009 meeting that the Rockland County Municipal Planning Federation held, in which a presenter briefly touched upon the idea.
This system will be of welcome to any designer or land-use planner dealing with a municipality that has a limit on the amount of allowable impervious surface. Obviously, the use of this system will allow for greater coverage for pavement than would be allowed for standard pavement.
After doing some research on my own, I have found that permeable pavement is now available in both concrete as well as asphalt. It has its major value in light traffic areas, such as parking lots, side walks and patios. This is due to the fact that both systems do not possess the strength needed to handle heavy highway or even secondary road traffic at this time.
In general, for both permeable concrete and asphalt, it is possible to achieve a permeability rate of not less than five gallons per square foot per minute. This is far greater than what would fall in a 100 year storm, the general standard by which storm water control must comply with.
In the case of permeable cement, it is the unique manufacturing process that allows for this to happen. First, there is a careful control of the amount of water and cement in the mix, so as to create a paste that forms a thick coating around the aggregate materials. Second, there is little or no sand in the mix. This now creates a highly permeable interconnected set of voids that allows for the fast rate of drainage through the pavement. In fact, the voids account for 15 to 25% of the product.
EcoCreto is an example of a permeable concrete system that now claims to have a hardened strength as high as 5000 pounds within 28 days, and is 100% permeable. In addition, EcoCreto claims to reduce storm water contaminates such as suspended solids by up to 90%. Also claimed, is the reduction of heavy metals by 40 to 90%, as well as the removal of 90% of mineral oils, and 60% of phosphorous. Obviously, this goes a long way in addressing a major issue -- storm water quality control. The LEED rating system deals with this as well as storm water quantity control. By pre treating the water contaminates prior to the water seeping back into the aquifer to this level, we provide for far better aquifer recharge protection in terms of both quality and quantity of the water. As a result of this, this product is recognized by the federal Environmental Protection Agency as a Best Management Practice (BMP) for the control and management of storm water runoff.
In addition to the advantages of the permeable pavement allowing for the water to penetrate into the soil below, the soil and adjacent sub-surface also further purify the water, via microbial activity.
We MUST note that the property in which permeable pavement is considered for use be evaluated for its ability to absorb the water; if the water table is already high, or there is the presence of heavy clay or solid bedrock, the system will have limited effectiveness.
In general, a 12 to 36 inch sub base is prepared under where the pavement will be laid. This will consist of gravel, and sometimes, a piping network to allow for the water to be either drained directly into the ground below, or if needed, re-directed to an alternative location for seepage into the aquifer.
Porous asphalt is created in a similar fashion, and has the same benefits as concrete.
In terms of cold weather performance, especially with snow and ice, I ran across a PDF of an article from Storm Water, (September, 2008) that said that these products can be used in cold climates; in fact, it was claimed up a 75% reduction in the need for salt application for de-icing -- a BIG help to the environment as well as a cost-saver. In addition, increased slip resistance was noted when permeable pavement was used. This is most likely due to two factors: the increased texture created by the voids at the surface, and the lack of sheet water flow, resulting in less ice formation. However, a designer needs to take into account the frequency of freeze-thaw cycles, as this can effect the performance of the permeability if the cycles are too quick. Under most cases, the system allows water to drain away to warmer ground below prior to the pores being clogged with ice.
In spite of the porous voids and stone-like surface, these products have seen no issues with pedestrian traffic, even with high heel shoe use.
When used with proper planning, it is quite possible to significantly reduce or possibly eliminate the need for actual storm water catch basins and piping, thus saving far more than what the initial additional cost of using permeable paving vs. conventional materials. Thus, we see the interconnection of trade-offs and synergies that I have mentioned elsewhere. The final result can be a lower life-cycle cost, especially given the fact that industry expectations for the permeable pavement products to have a longer service life than that of standard pavements.
We also will benefit from the reduction of standing pools of water in parking lots, which in summer, can breed mosquitoes and in winter, turn to slippery ice.
Even higher traffic areas can find a use for this product, as the entire shoulder area can be paved with permeable material, creating a continuous drain to the earth below, while the traffic lane is paved with stronger conventional pavement.
For light duty projects such as patios or side walks, a product known as PermaPave can be used. This has all the properties of the above mentioned products, but comes in pre-formed paver blocks similar to the standard blocks used in driveways that we see in almost all neighborhoods today. PermaPave comes in 12 colors and four different sizes, ranging from 16" x 16" down to 8" x 4". It is installed in a similar way as standard pavers, but one MUST pay attention to the proper preparation of the sub surface below, to allow for drainage into the aquifer.
In summary, we have MANY advantages to using porous pavement products, from the environmental point of view to reduced maintenance.
Posted by Alan L. Englander at 2/2/2010 9:38 PM 
Categories: Aquifer Recharge, Storm Water Control, Best Management Practice, Water Quality, Permeable Concrete, Permeable Asphalt
Categories: Aquifer Recharge, Storm Water Control, Best Management Practice, Water Quality, Permeable Concrete, Permeable Asphalt
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