What is a dry well?

A dry well, also sometimes called a dry well infiltration system or infiltration basin, is a subsurface structure designed to receive and slowly release stormwater runoff or other water. Unlike a traditional well that's designed to extract groundwater, a dry well doesn't store water; instead, it allows water to seep into the surrounding soil.

Here's a breakdown of key information:

• Purpose: The primary purpose is to manage excess stormwater and reduce runoff. This helps alleviate flooding, recharge groundwater (in suitable locations), and reduce the load on municipal stormwater systems. They can also be used for greywater disposal (though this requires careful consideration of local regulations and soil conditions).

• Construction: Dry wells are typically constructed from porous materials such as gravel, perforated pipe, or concrete with openings. They're usually located underground, often with a gravel-filled chamber to facilitate infiltration. The size and design vary based on the expected water volume and soil permeability.

• Soil Conditions: The success of a dry well depends critically on soil conditions. The soil must be permeable enough to allow the water to seep away. Clay soils or soils with high water tables are unsuitable. A soil permeability test is essential before installation.

• Limitations:

  • Soil Suitability: As mentioned, unsuitable soil conditions are a major limitation.
  • Water Quality: Dry wells should not be used for wastewater containing contaminants, as this can pollute groundwater. Greywater use requires careful filtering and treatment.
  • Groundwater Levels: High groundwater levels can impede infiltration.
  • Maintenance: While generally low-maintenance, they may require occasional cleaning or inspection to ensure proper functioning.
  • Potential for contamination: If not properly designed or maintained, they can potentially contaminate groundwater.

• Regulations: Local regulations regarding dry well installation vary widely. Permits are usually required, and strict guidelines often exist regarding location, size, and design to prevent environmental hazards.

In summary, dry wells offer a sustainable approach to stormwater management in suitable situations, but careful planning, site assessment, and adherence to regulations are crucial for successful and safe implementation.