Pervious Pavement

Practical Solution

The “How To”

PPppppdddssasdafs All three forms of pavement work in similar fashion. The topgrade surface is made of either pervious concrete, asphalt, or permeable interlocking pavers. The former two pavements are a slight variation of the traditional pavement which produces gaps in the pavement allowing water to seep down. Interlocking pavers have small openings that allow the water to percolate underneath the pavement. Immediately below the pavement is a layer of crushed rock, and immediatley below that is uncompacted soil. The idea is for the water to reach the soil as it would if there were no pavement. The layer of crushed rock forms a reservoir to store water as it permeates into the soil.

The Metropolitan St. Louis Sewer District (MSD) has information on all three forms of pavement. Additional resources are available online for pervious concrete, permeable interlocking concrete and pervious asphalt. The Federal Highway Administration has a good wepage on pervious concrete as well.

All three pavements are suitable for low traffic areas, such as parking lots, alleys and residential streets. Pervious pavement has not proven effective in high traffic areas. The trade off is that the pavement can be up to a hundred percent permeable.

 

Planning & Zoning

Pervious pavement is not much different from traditional pavement, so it does not require a major change to zoning ordinances. Some cities such as St. Ann (Section 500.480) and Ellisville (Section 400.490) encourage the use of pervious pavement when constucting parking lots. Jefferson County (Section 400.4020), on the other hand, mentions the installation of pervious pavement parking space when there is an increase in "dwelling units, guest rooms, seats or floor area" of a building.

Dollars & Cents

If you are looking to install pervious pavement, it is recommended you consult a construction company that specializes in pervious pavement. The Center for Neighorhood Technology published a document that on page 10 has a good summary of the benefits associated with pervious pavement. Some of the unlikely benefits include reduced salt (from salting streets before a snow storm) and improved air quality.

The Metropolitan St. Louis Sewer District (MSD) offers rainscaping grants, which may be able to used for permeable pavers, as well as other projects that manage and filter rainwater.

Measuring Success

An indicator of pervious pavement's impact is water quality, which can be measured by the percentage of assessed streams, rivers and lakes that are polluted. The desired trend is for this percentage to go down.  

Pervious pavement systems can last more than 20 years while providing an initial high level of infiltration even as the surface takes in moderate amounts of sediment. Where applicable, reduced impervious area can result in lower fees for areas with stormwater fees based on impervious cover.

Environmental benefits such as alleviating flooding and reducing stormwater runoff can be associated with this Best Management Practice (BMP). LEED credits are also possible for construction using it. According to the Metropolitan St. Louis Sewer District, well-designed permeable pavement projects should remove 80% of total suspended solids and prevent these pollutants from entering streams. 

Case Studies

Ranken Jordan - Pediatric Specialty Hospital - Paver

• Contact

  David Kersten
  Maintenance Contact
  314-872-6400

  Address

  11365 Dorsett Road - Maryland Heights, MO 63043

  Description

  Project increased impervious area greater than 1 acre, with the installation of a parking lot at the hospital. A combination of systems were employed to help spread the need for a BMP. The project included the installation of pervious pavers and a rain garden. Per the owner, permeable pavers had the best track record with the most contractor acceptance and installation knowledge. If system clogged, pavers would be easier to pickup and repair BMP if needed in lieu of permeable concrete or asphalt.

  Cost

  Permeable Paver Cost - $180,000

  Quarterly inspections. Annual Cost - $2,000

  Vacuum rest of parking lot to reduce debris to pavers. Annual Cost - $940

  Permeable Pavers are vacuumed annually or on an as needed basis to help reduce fine partial infiltration. Trap rock chip is checked and reapplied. Annual Cost - estimate $1,200 - $3,600

  Lessons Learned

  Silt control is critical throughout construction and growing period of project to keep structures clean.

  Settling of pavers and up-keep, needs to be considered when designing a maintenance program.

  Keeping upstream areas of pavers clean and limiting activities, that that can potentially produce debris that can clog pavers to a minimum, may aid in reducing overall maintenance costs.

  Porous concrete and asphalt was dismissed as a viable BMP do to cost, lack of contractors to install, concern for silt clogging thus possibly hard to maintain and poor aesthetic value.

  It is expected that the permeable pavers to last 50-70 years but may require maintenance of the joint filler to be removed and reinstalled every 5 years.

St. Louis City Pervious Alleys Pilot Project

• Contact

  Dr. Jianpeng Zhou P.E. DEE
  Associate Professor and Graduate Program Director - Southern Illinois University Edwardsville
  618-650-3221
  This email address is being protected from spambots. You need JavaScript enabled to view it.

  Description

  The City of St. Louis is served by a combined sewer system. Reduction of combined sewer overflows that pollute the tributaries of the Mississippi River is a major effort underway. In 2008, a pilot project was developed to evaluate the use of pervious pavement in the St. Louis Area to deter the overloading of the system during wet weather. This study aimed to evaluate the effectiveness of porous pavement on flow reduction and water quality improvement in combined sewers. Total Nitrogen, Total Phosphorous, Zinc, Copper, and Total Suspended Solids were the parameter monitored.

  Lessons Learned

  The project consists of three phases: Phase I was to monitor and characterize the flows and water quality under existing conditions; Phase II is to design and construct porous pavement; and Phase III is to monitor and characterize the flows and water quality under improved conditions where LID is implemented. Results of Phase II and Phase III were not available.

Discover More

Education should be provided to residents in areas with pervious pavements projects and maintenance personnel. Signage is important as well. The Metropolitan St. Louis Sewer District (MSD)'s BMP toolbox was developed to help those implementing stormwater management BMPs to successfully navigate the technical and procedural path to post-construction stormwater BMPs design, installation and maintenance. Planning for installation is critical and it is important to consider drainage areas and area of implementation. MSD's Permeable Pavement Design and Construction Details and the WERF SELECT model are two great tools to use for planning and understanding best fit. The WERF SELECT Model is a planning tool that simulates BMP selection for stormwater management.