Recharge

BGwT Recharge Coordinator

The role of the BGwT Recharge Coordinator is to assist property owners by educating and encouraging them to recharge their surrounding property(s). This can be accomplished by installing a recharge structure (such as a dry well), porous pavement, and pervious pipes in yards or appropriate parking areas.

In addition to assisting property owners, the recharge coordinator also performs the following:

  • Works with the city of Boston to incorporate porous pavements in practical locations
  • Gather information on structures used for recharging
  • Gather information on recharging materials; such as porous pavements
  • Attempt to quantify the benefits of recharge systems installed
  • Work with the BGwT Executive Director on presenting the benefits of recharging to educate public entities

The Recharge Coordinator is Christian Simonelli. He can be reached at csimonelli@bgwt.org.

Types of Recharge

DRY WELLS

What is a Dry Well?

A dry well is an underground structure that captures runoff from roof tops and surrounding areas and diverts it to the local groundwater table.

How does a Dry Well Work?

Water flows through the dry well under the influence of gravity. A dry well receives water from one or more entry pipes or channels at its top. Roof leaders connect directly into the dry well, which may be either an excavated pit uniformly filled with gravel, riprap, or rubble, wrapped in geotextile or a prefabricated storage chamber or pipe segment. Dry wells then discharge the stored runoff via infiltration into the surrounding soils. In the event that the dry well is overwhelmed in an intense storm event, a surcharge pipe or a connection to larger infiltration area will ensure that additional runoff is safely removed. It is very important that the dry well be properly designed and installed, with careful consideration of the elevation of local groundwater. A dry well that is installed too close to the surface may freeze in very cold weather. One installed below the existing or anticipated groundwater level would tend to fill with groundwater and not contribute to raising groundwater levels.

What are the Advantages and Disadvantages of Dry Wells?

Advantages:

  • Increase groundwater recharge
  • Reduce volume of storm water
  • Underground structure that does not devalue property
  • Can last up to 30 yrs. with proper maintenance

Disadvantages:

  • Difficult to install in low permeable soils
  • If not properly maintained, clogged dry wells must be refurbished or replaced
  • If not properly engineered a dry well could do more harm than good. i.e. flood adjacent property(s)
What are some different types of Dry Wells?

There are many different types of dry wells. Here are some examples:

  • A plastic barrel with holes drilled through it and block stone (click here).
  • A simple blocked lined dry well (click here).
  • A prefabricated dry well (click here).
  • Precast dry well detail (click here).

OTHER RECHARGE SYSTEMS

Below are other types of recharge systems that property owners have used to comply with the Article 32 Groundwater Conservation Overlay District (GCOD). Each type is site specific and was designed based upon storage capacity that is calculated during design. These are examples only. They are intended to assist the property owner (or contractor) in selecting the most efficient system.

StormTech: Subsurface Stormwater Management
http://www.stormtech.com/
  • Lightweight polypropylene plastic chambers
  • Helps recharge groundwater resources by recapturing nature’s own process of infiltration
  • Useful site with links and design calculators for Engineers, Contractors, Developers, Regulators, and Homeowners
CULTEC Chambers
http://www.cultec.com/
  • High density/ high molecular weight polyethylene plastic chambers
  • May be installed in trench or bed configurations according to site restrictions or client preference
  • Large variety of chamber sizes to accommodate almost any size site
  • Useful site for Engineers with CULTEC Chambers modeled in many current design software programs
  • An example of a commercial use CULTEC Chamber (click here)
Invisible Structure’s, Inc.: Rainstore3
http://www.invisiblestructures.com/rainstore3.html
  • Made from injection molded plastic
  • Modular and stackable structure used to store stormwater underground
  • Rainstore3 units measure 40" x 40" x 4" and having a 94% void space provides nearly 25 gallons of water storage per unit
  • Useful site with links for Architects, Contractors & Installers, Engineers, and Homeowners

In addition to the systems listed above the following storage types have also been used by property owners:

  • Leaching Galleys or Chambers
    • Typically constructed of concrete or plastic
    • The concrete units are typically 4’ x 4’ x 4’. They are open on the sides and bottom to allow water to percolate into the soil, backfilled with crushed stone, and then covered in filter fabric (click here).
    • The plastic units are open bottom with feeds coming in from the top (click here).
  • Perforated Pipe
    • Typically constructed of concrete or plastic
    • Perforated Pipes are usually placed at the bottom of a pit, backfilled with crushed stone, and wrapped in filter fabric to allow percolation of water into the pipe for leaching out (click here).
  • Tank & Infiltration Wells
    • Typically constructed of concrete or plastic
    • Precipitation is temporarily stored in tanks and then slowly leaches out into infiltration wells (click here).

POROUS PAVEMENT

What is Porous Pavement?

Porous pavement is a hard surface that can support some vehicular activities, such as parking and light traffic, and which can also allow significant amounts of water to pass through. Porous pavement is widely used in parking lots, and allows water to drain through the pavement surface into a stone recharge bed and infiltrate into the soils below the pavement.

How does Porous Pavement Work?

There are many types of permeable materials such as pervious concrete, porous asphalt, porous paving stones or porous bricks. All of these permeable materials allow precipitation to percolate through areas that would traditionally be impervious. The precipitation infiltrates through to the soil below usually in the form of an underlying, open-graded stone bed. As the water drains through the porous surface and into the stone bed, it slowly infiltrates into the soil. The stone bed size and depth must be designed so that the water level never rises into the porous surface.

What are the Advantages and Disadvantages of Porous Pavement?

Advantages:

  • Increase groundwater recharge
  • Reduce volume of stormwater
  • High void space ratio that drains quickly
  • Depending on type used can be relatively low maintenance

Disadvantages:

  • Depending on type used, cost more than dry wells
  • Depending on type used, must be cleaned by using a high pressure washer or industrial vacuum cleaner to remove sediment that may build up over time
  • Used mostly in light traffic areas
  • Limited depending on total weight acceptance
What are some different types of Porous Pavements?

There are many different types of porous pavements. Here are some examples:

Porous Pavement Factsheets/Specifications

Here are some examples: