Written by: Samantha Justice, P.E. Green infrastructure incentive programs have become commonplace for new construction and redevelopment regulations. Five of the most common incentives include: Development incentives such as expedited permitting, decreased fees, zoning upgrades, and stormwater requirement reductions. Grants. Rebates and installation financing. Awards and recognition programs. Stormwater fee discounts. A subset of green infrastructure, stormwater management usually includes the consideration of pervious/porous pavements. Traditional asphalt and concrete parking lot surfaces create significant stormwater runoff, and many municipalities do not allow them in expansion or new build situations. When the entire parking area is constructed using a porous pavement system, stormwater concerns are greatly reduced. Depending on the type chosen, pavements that return rainwater to the aquifer nearly eliminate stormwater runoff and reduce sheet flow and point load erosion problems at the pavement edges. They also reduce the need for additional stormwater infrastructure to convey the water away from the area. Integrating porous pavement systems with asphalt and concrete surfaces can reduce such failures and reduce or eliminate the need for stormwater conveyance channels, pipes, and swales. As a result, downstream stormwater pipe systems see less silt and water, which requires less maintenance and less capital expenditure for upsizing stormwater pipes…. Read more »
Posts Tagged: GeoPave
Porous Pavements Myth Busters: Cost
Written By: William G Handlos, P.E. Does a porous pavement solution cost more? Porous pavements are less expensive to install than impervious concrete or asphalt when you consider total project costs. When evaluating parking lot construction costs for porous pavements vs. impervious alternatives, you must consider the following cost “buckets.” Traditional pavements such as bituminous asphalt or Portland cement concrete enjoy low cost and ubiquitous installation contractors. This information may lead one to think that choosing a porous pavement would lead to higher overall project costs, but that is a myth because almost everything else about traditional parking lot construction is far more expensive than the porous pavement alternative. Traditional hard-surface pavements require inlet structures, castings, and covers for inlets and manholes, underground pipes, outfall structures, and detention ponds. Costs & Maintenance of Stormwater Ponds Detention ponds have three major cost drivers. Land costs to locate a pond can vary wildly depending upon commercial real estate values, but it is not unusual for land to be upwards of $250,000/acre even in small markets. The impact of the land utilized for detention ponds does not end there. Lost rental or income value is another cost consideration. Ponds take up valuable commercial… Read more »
Porous Pavements Myth Buster: Clogging
Written By: Bill Handlos, P.E. Not All Porous Pavements Clog Well-designed porous pavement systems resist clogging When designing porous pavement systems, it is important to consider the effects of silt, grit, sand, and other fine material that can slow or stop water from infiltrating. However, it is a common myth that all porous pavement systems eventually clog. A good PPS system design, simple but effective site design, and careful construction inspection and field guidance can all but eliminate the clogging threat. System Design Do’s and Don’ts Cross-sections will vary according to the porous pavement selected, but following some simple practices can ensure a successful system with long-lasting percolation. Never place filter fabric immediately below the porous pavement surface. Whether you are using pervious concrete, porous asphalt, polyethylene injection-molded paving block (such as GEOBLOCK vegetated or GEOPAVE aggregate PPS), or concrete paving stone, your cross-section should allow free flow from the paving layer to the base and storage layers. The last thing you want is to trap water in your pavement layer. Surprisingly, at least one aggregate PPS manufacturer sells their product with a filter fabric attached to the bottom of the units. Always use a filter fabric or other separator at the bottom of… Read more »
Porous Pavements Myth Buster: Winter Durability
Written By: Bill Handlos, P.E. Properly designed porous pavement systems will not be damaged by the dynamics of freeze-thaw cycles. For decades, civil engineering roadway designers have been trained to use positive drainage, crack sealing, and sealcoating to keep the area under pavement dry. The prevailing mentality was to use a well-graded, tightly compacted base under impervious concrete or asphalt wearing surfaces. When water gets between the well-graded base and the impervious surface, frost conditions would lift pavements, weaken the base structure, create potholes and, in general, wreak havoc with the life of the pavement. So, it is not surprising that age-old tenets related to moisture, seepage, and freeze-thaw cycles get mistakenly applied to porous pavement systems. What makes well-designed porous pavement cross-sections so resistant to the power of freezing and expanding water? The answer is space. Poorly graded crushed aggregate offers up to a 40% void ratio, which gives water a place to move and expand upon freezing, and a network of pathways to drain. High void ratio systems allow the Earth’s natural warmth to move up from below the frost line into and through the open-air system just as water and ice-melt move through the system. If… Read more »
Porous Pavements Myth Buster: Winter Maintenance
Winter Maintenance for Porous & Pervious Pavements Porous pavement systems are a great way to reduce the amount of stormwater runoff on your site and incorporate Low Impact Development (LID) practices. One of the simplest ways of creating a porous pavement area is to confine unbound aggregate in a rigid paving unit such as the GEOPAVE® Aggregate Porous Paver. The GEOPAVE system is similar to pervious concrete and porous asphalt solutions, but is usually both less expensive and easier to install. Porous Pavements Are Difficult to Maintain in Winter Weather Conditions. NOT TRUE! The GEOPAVE Gravel Pavers are easy to maintain, and requires no special equipment. GEOPAVE parking lots or low volume roadways can be maintained in much the same way as a regular concrete or asphalt surface. An unbound aggregate system has many maintenance benefits over other porous pavement systems. Look at the table below and you’ll see how the GEOPAVE system beats pervious concrete and porous asphalt every time. (Click Chart to Zoom) The GEOPAVE rigid porous pavement system is comparable to standard paving materials, and a cut above other porous pavement systems. GEOPAVE systems have all of the benefits of hard surface porous pavements—fast… Read more »
How long does it take to install geosynthetic construction products?
How long does it take to install? It is a question we hear every day. When it comes to cost and installation rates for geosynthetic construction products, there are no simple answers to what seems like simple questions. In fact, beware of those who try to simplify determination of installation costs for their products with quick answers or charts and tables to determine construction rates. Experienced project managers and site supervisors of the crews charged with installation are in the best position to estimate productivity rates. They know best their crew’s capability and the characteristics of the site involved. The variables that need to be considered include: Crew size, talent, work ethic and workday length Temperature, precipitation and length of day (sunlight) Experience with product class Size of the project Site Access Site Conditions (see weather) Crew The optimum crew size is important. Too small and you may lose the benefits of assembly line productivity. Too large and you will find that you fall over each other and pay for extra “inspectors”. All crews are not created equally. The familiarity with tools and techniques vary greatly as does the work ethic both between crews and by region and country. Weather… Read more »
Impervious Gravel vs. Porous Aggregate Paving Systems
Written by William G. Handlos, P.E. For two decades, I held the position of City Engineer and frequently had to explain to disbelieving homeowners, developers and elected officials – that gravel driveways and parking lots were not porous. I would explain that for purposes of stormwater runoff, such gravel pavements must be treated exactly as we would concrete and asphaltic pavements. They often bristled at the idea that gravel did not percolate water and were upset to find that their gravel driveway, lots and roadways were assumed to shed 100% of rainwater. So it is with more than a dose of irony that I now have found myself in the position of regularly explaining to local and state officials that aggregate pavements are not necessarily impervious. Stakeholders are so accustomed to repeating the impervious gravel mantra…that they forget to notice that porous aggregate is not the same thing as gravel. I think it is best to start with a primer on the vernacular. A “good” gravel (Image 1) should have 40 to 70% stone, well-graded from 1/4” to 2-1/2” diameter; 20 to 50% sand; and 10% +/- fines. It should resist abrasion, shed water and be capable of being compacted. A… Read more »
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