Underground Detention

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Traditional BMP

Detention storage located in underground tanks or vaults designed to provide water quantity control through temporary storage of stormwater runoff. They also remove heavy sediments to improve water quality. 
 

Maintaining Underground Detention

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Routine maintenance should be performed on underground detention areas. This includes the removal of debris from inlet and outlet structures and cleaning sediment built up inside the structure. Generally, inspections can be conducted through an access opening. Sometimes, maintenance requires an individual who is certified in OSHA confined space entry.

After a large rainstorm, inspect the underground detention area. If the underground detention area is not draining properly, check the inlet and outlet structures to make sure they are not clogged.

Underground Detention Maintenance Issues

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Here are some of the common problems to be aware of when maintaining a vegetated filter strip. They include, but are not limited to, the following:

  • Sediment build-up
  • Clogging in the inlet and outlet structure
  • Requirement to have Occupational Safety and Health Administration (OSHA) confined space entry training

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Underground Detention Areas

Routine Maintenance Schedule
Schedule
Activity

As needed

  • Remove any trash/debris and sediment buildup in the underground trash racks, vaults or tanks.
    Check drainage areas for trash, erosion, and debris.
    Clean underground detention if hazardous or foreign substances are spilled in the contributing drainage area.
    Perform structural repairs to inlet and outlets.
Annually
  • Follow manufacturer’s guidelines and develop/adjust plan for the underground detention.
  • Clean out underground detentions with vacuum or boom trucks.
  • Clean sediment or oil chambers