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Why Is There So Much Interest In Pervious Concrete? Pervious Concrete is a serious answer to a serious problem. That problem is that 35% to 70% of our construction sites are being covered by paved surfaces and roofs as urban sprawl continues to dominate the landscape. The result is that our aquifers are dying of thirst. What happens when it rains on impervious surfaces? The water that is badly needed by the aquifer turns into storm water, which is not only wasteful, but it can be destructive as well, when it results in flooding and the pollution of our streams and waterways. Those same impervious surfaces convert sunlight to heat and add to the air conditioning burden well into the night.
	THIS SHOPPING CENTER WHILE HAVING SOME GREEN AREAS HAS APPROXIMATELY 462,000 SQUARE FEET OF IMPERVIOUS SURFACE. IT CONVERTS ONE INCH OF RAINFALL INTO APPROXIMATELY 288,000 GALLONS OF STORM WATER. IF IT WERE PAVED WITH PERVIOUS CONCRETE THAT STORM WATER COULD HELP RECHARGE OUR AQUIFER.
When impervious surfaces are within a town house project, though the percentage of grass and trees may be greater, there is still much rain water that is turned into storm water. Even though a retention pond may be on site, in a heavy rain the pond will overflow, and the overflow will wind up wasted into the gulf or some other body of water.

THIS TOWN HOUSE DEVELOPMENT WITH 136 RESIDENCES CREATES ABOUT 344,600 SQUARE FEET OF IMPERVIOUS SURFACES INCLUDING ROADS, PARKING AND ROOFS. DURING A 1" RAIN EVENT APPROXIMATELY 212,000 GALLONS OF RAIN WATER WILL BE DIVERTED TO A RETENTION POND. DEPENDING UPON HOW QUICKLY THAT 1" FALLS, SOME OF THAT RAIN WATER WILL OVERFLOW INTO NEARBY ESTUARIES AND CHANGE THE CHEMESTRY OF THE WATER!

DURING A 1" RAIN EVENT THIS PERVIOUS CONCRETE STREET IN INDIAN SHORES, FLORIDA, DIRECTS MORE THAN 6,000 GALLONS OF RAIN WATER THROUGH A COMPACTED BASE OF SAND  INTO  THE AQUIFER BELOW RATHER THAN FLOODING SURROUNDING STREETS. THIS HELPS TO FIGHT SALT WATER INTRUSION.

WHY SHOULD YOU BE INTERESTED IN PERVIOUS CONCRETE?

WHY SHOULD YOU USE IT OR ENCOURAGE ITS USE?

Are you concerned about:

• Shrinking good water supplies?

• Contamination of our aquifer

• Damage from storm water?

• Global warming?

• Air Quality?

WATER:

If you enjoy drinking good water, washing your car or watering your lawn, you depend on the land’s aquifer. Food plants need irrigation which depend on the aquifer. Year after year its level is dropping, and more and more pollution, especially from parking lots and other paved areas is getting into it. Water use restrictions restrain more legitimate uses year after year. Pervious concrete is part of the solution. It allows the rain to recharge the aquifer, but in the process it filters’ out harmful pollutants.

If we don't capture that rainwater it will become polluted storm water which robs our aquifer and damages our environment.

DON'T WASTE RAINWATER BY TURNING IT INTO STORM WATER.
AS RAINWATER CLEANS STREETS AND  FLUSHES OUT GUTTERS AND IS THEN COLLECTED BY STORM SEWERS, IT TURNS INTO POLLUTED STORM WATER.

CONTAMINATION:

Drive-thrus, gas stations, parking lots and driveways catch the most oil and grease. Roads are next. They also collect heavy metals from engines and catalytic converters, and harmful components from rubber tires. When it rains, they become large polluters.

Most rain events produce one inch or less of rain. Too many impervious surfaces short-circuit nature’s design, preventing the earth from getting the water it needs, by diverting it into storm sewers, streams and other bodies of water. We needlessly waste a precious commodity. That first inch of rain becomes loaded with pollutants from roads, parking lots and driveways. It is often more toxic than sanitary sewer water.

THE PREVIOUS CONCRETE ABOVE, RIGHT; WITH ITS POROUS SURFACE TRAPS OIL AND GREASE AS WELL AS METAL PARTICLES.

DAMAGE FROM STORM WATER: If you enjoy fishing, conventional pavements are against your interests. Asphalt and conventional pavements absorb the sun’s rays and convert them to heat. When it rains, the temperatures of storm water run offs may be elevated 10° to 30°. That warm water can stress or kill marine life, water plants and helpful bacteria. Elevated temperatures decrease the amount of oxygen in streams and estuaries which in turn decreases development of fish eggs, young fish and plankton which are the first link in the marine food chain.

AS MORE AND MORE LAND IS COVERED BY IMPERVIOUS SERFACES, RAIN SUDDENLY BECOMES DESTRUCTIVE. UNCONSTRAINED STORM WATER FLOODS ADJECENT PROPERTIES, ROADS, STREAMS AND ESTUARIES ERODING EMBANKMENTS, DESTROYING PLANT LIFE AND CAUSING FLOODING DOWNSTREAM, SOMETIMES WITH RESULTING LOSS OF LIFE. STREAM EMBANKMENTS ARE ERODED AND HAVE TO BE REPAIRED WITH CEMENT OR CEMENT BADS. PERVIOUS CONCRETE DIVERTS RAIN WATER WHERE IT BELONGS, INTO THE SOIL AND THE AQUIFER.

DOWN STREAM, TOXIC SEDIMENT IS DEPOSITED AND HAS TO BE REGULARLY REMOVED AT SIGNIFICANT COST.

GLOBAL WARMING: Black pavements and hot impervious roofs are taking more and more natural planted surfaces out of doing what they do best. Natural surfaces like grass and trees absorb sunlight and through photosynthesis they remove that Global Warming gas, Carbon Dioxide, as well as other pollutants from the air we breathe. Also their roots and foliage help trap storm water and move it to the underground aquifer.

If you are concerned about global warming, consider this: Asphalt pavements absorb more of the heat of the sun. This adds to the problem. Because asphalt is so widely used it creates heat islands as its black or grey surface absorbs sunlight. In summer its temperature may climb to 140° F or more. That heat requires more air conditioning thus requiring more electricity. Most electricity is generated using fossil fuels. So not only does this waste money, but in making electricity, power plants create more greenhouse gasses.

Even Impervious concrete absorbs much heat from the sun. Of the three, pervious concrete is the coolest. When it rains on hot pavements, the rain evaporates more quickly. Less water reaches the aquifer or other runoff receptors. Without Pervious Pavements, what eventually reaches streams, estuaries, the bays, the Intracoastal Waterway and the Gulf of Mexico or ocean is warmer water. It affects everything living in those waters changing the balance of nature.

USE PERVIOUS CONCRETE PAVING INSTEAD!

1. It may reduce or eliminate the need for subterranean storm sewer drains. Pervious concrete not only eliminates much of the run off from pavements, but may also catch the runoff from roofs and return it to the aquifer.
2. Trees are great tools in fighting the greenhouse effect. Unlike impervious pavements Pervious Concrete lets water and oxygen enter the soil below. This allows tree roots to perform their tasks efficiently. Those tasks include cooling the surrounding air by the evaporation of the captured ground water. This helps reduce air conditioning costs.
3. And finally for the developer or engineer, it makes possible maximum land use for parking lots, roads, and structures. With certified engineering it can reduce the size of retention areas. Storm drains may be eliminated and some curbing as well. For watershed and estuary areas it is an environmental tool to keep these waters clean and cooler. These are ecological as well as dollars and cents issues.

TREES THRIVE AS PERVIOUS CONCRETE ALLOWS RAIN WATER TO REACH THEIR ROOTS AS THE WATER IS DRAWN UP TO THE LEAVES OR BLADES OF GRASS THE MIRACLE OF TRANSPIRATION CONVERTS IT BACK TO VAPOR WHICH HELPS CREATE MORE RAIN WHILE COOLING SURROUNDING AIR

Why is Pervious Concrete superior to other pervious pavement materials?

1. Pervious Asphalt

    a. Pervious asphalt is black or grey. It absorbs more of the suns rays and converts them into heat. This heat helps create urban heat islands, which encourages the formation of ozone, nitrogen oxide and smog.

    b. Pervious asphalt has a tendency to creep at high temperatures. This encourages the formation of ruts from vehicle weight and ridges from vehicle braking. It's asphalt binders will adhere to silt and pollutants and will soon lose porosity. To stabilize it, pervious asphalt is often placed over an impervious base, making its primary advantage noise reduction, not water conservation

    c. Pervious asphalt is dependent on oil as a feed stock. After placement oil, byproducts release V.O.C.s (Volatile Organic Chemicals) which pollute the air.

2. Pervious Concrete Paver Blocks.

    a. Though these function well in residential driveways, installation is labor intensive.

    b. The weight of heavy vehicles can cause cracking.

    c. The weight of heavy vehicles on roadways will also cause settling and shifting. Maintenance issues prohibit installation over sand. If installed over impervious surfaces, they will look better longer, but they will lose their function of channeling rain water to the aquifer.

    d. Oil and grease seem to be more of a problem than with Pervious Concrete.

THESE CONCRETE PAVER BLOCKS WERE INITIALLY USED AT AN INTERSECTION IN BELLEAIR, FLORIDA. THEY HAVE SINCE BEEN REINSTALLED AFTER A FEW YEARS DUE TO THE FORMATION OF RUTS, ACCUMULATION OF GREASE AND CRACKING.

3. Masonry Grass Blocks

    a. Grass blocks do not allow as much rainwater through because the concrete they are made from is impervious.

    b. Oil and grease droppings kill grass.

    c. Mowing and fertilizing are needed. Maintenance cost is higher. Many times grass is replaced with sand.

MAINTAINING GRASS WITHIN GRASS PAVER BLOCKS IS EXPENSIVE. THE RESULT IS THAT SAND EVENTUALLY TAKES OVER AND THE SURFACE IS MUCH LESS POROUS THAN PERVIOUS CONCRETE.

Is Pervious Concrete Strong enough?

Thus far it has been difficult to quantify the strength of pervious concrete. We have installed thicknesses of 6" through 10", and have found that with the correct mix and placement it has lasted for many years. We offer a 10 year limited warranty.

Ultimate endurance of Pervious Concrete is dependant upon a well compacted porous base, fast, but controlled placement, uniform compaction and correct control joints. These factors control raveling and cracking. (At present Pervious Concrete is not recommended for high speed, high traffic roads.)

To understand why Pervious Concrete it is so strong, consider that the aggregate used is crushed, not round. This means that under compaction there is more contact between surfaces. The voids are like a honeycomb that creates unusual structural strength. And finally, it is believed that a chemical bond forms between the silicates in cement, some of which are part of its limestone component, and the chemicals in lime rock. (River gravel is not a suitable aggregate in pervious concrete.) Also, since lime rock is somewhat porous it allows penetration by the cement paste. With over 25 years working with Pervious Concrete, that is why we know it stands up when properly engineered and installed for its intended end use.

PROPERLY INSTALLED  PERVIOUS CONCRETE (RIGHT) WILL RESIST RAVELING, PROVIDE MUCH GREATER STRENGTH AND WILL LAST! WORK ON LEFT BY COMPETITOR WAS NOT PROPERLY SCREENED AND COMPACTED

New Possible Applications For Pervious Concrete

1.  Airport Tarmac and Terminal Edge Strips. So much rain water is converted to storm water at airports because of the vast amount of paving for runways, ramps, tarmacs and gate areas. If some of that can be paved with Pervious Concrete, much rain water will reach the aquifer.

2.  Curbs, Gutters and Bicycle Path Strips. This is a way that could divert a tremendous amount of water from the storm water sewers. Consider: a three ft. wide strip of pervious concrete, 150' long upstream from a catch basin could return over 25,000 gallons of water per hour to the aquifer, diverting it from surrounding bodies of water. This estimate is based upon percolation rate of 1 gallon per minute per square foot.

3.  Playground Bases. A well constructed Pervious Concrete system covered with shredded tire mulch can provide a well drained easily maintained playground surface.

4.  Drainage Ditch Linings.

5.  Sound Absorption Walls For Highways.

References:

Bellnet
http://bellnetweb.brc.tamas.edu/evaluati.htm

Charger Web Page: Storm Water Control
http://perviousconcrete.com/stormwatercontrol.htm

Cool Communities
http://www.CoolCommunities.org/cool_pavements.htm

EPA
http://www.epa.gov/owow/estuaries/monitor/chptr13.html

EPA
http://www.eetd.lbl.gov/heatisland/

EPA Urban Heat: Island Mitigation Initiative
http://satellite,zodiak.com/destination/frames_version/EPA-UHI.htm

Mississippi Concrete Industries Association
http://www.mississippiconcrete.com/pervious.cfm

McGraw Hill Construction, Industry Headlines
http://www.construction.com/NewsCenter/headlines/ENR/20011010b.asp

National Resources Defense Council
http://www.nrdc.org/water/pollution/storm/execsum.asp

Pathfinder Science
http://pathfinderscience.net/stream/cbg4temp.cfm

Rinker Materials
http://www.rinker.com/Florida/PerviousPavement.htm

City of Santa Monica
http://santa-monica.org/engineering/projects/pcpcp/pervious_gutters.htm

Sacramento Bee, October 3, 2000 (Heat Island)
http://www.fraqmd.org/Heat%/20Island.htm

Third World Network

http://twnside.org.sg/title/marine-cn.htm

Washington Aggregates & Concrete Association
http://www.washingtonconcrete.org/industry/pervious_pavement.htm

For More Information Contact:

Member aci international (American Concrete Institute International) aci Certified Flatwork Installers Certified Green Builders  Personal Membership (CW) in ICC (International Code Counsel)

Charger Enterprises, Inc. a Women Owned Corporation