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Dewatering Bags for Erosion and Sediment Control

Q&A: GMA Techline | April 1, 2023 | By:

Q: How does a dewatering bag (Dirt Bag, sediment container, Siltsack, etc.) work on a construction site to help you with your erosion and sediment control plan? 

A: Temporary construction erosion and sediment control is the practice of preventing or reducing the movement of sediment from a site during construction. Soil erosion and sediment runoff to waterways are significant problems and regulated in most states. In general, you need:

  • carefully crafted sediment and erosion control plans designed to reduce polluted runoff
  • implementation and updating of the plan
  • operation and maintenance of runoff reduction measures until the site is stabilized
  • significant penalties for negligence and willful violations

The progression of activities at a construction site is as follows. 

  • Evaluate and assess the construction site:

Collect site information (size, slopes, soils, drainage patterns). 

  • Identify sensitive areas—waters, vegetation, slopes, etc. 
    • Produce map or drawing of the existing site. 
    • Create the final project design map or drawing. 
    • Characterize the sequence of major construction activities. 
    • Calculate area, infiltration, runoff and drainage system sizing. 
  • Select site-specific erosion, sediment and housekeeping controls: 
    • Review local and state permit requirements. 
    • Identify erosion prevention field practices and site locations. 
    • Select sediment control practices and field locations. 
    • Determine housekeeping and pollution prevention practices. 
    • Indicate location of best management practices (BMPs). 
    • Prepare a plan for inspecting and maintaining BMPs. 
  • Complete permitting and notification tasks: 
    • Identify all contractors and subcontractors. 
    • Develop stormwater pollution prevention plan (SWPPP). 
    • Submit notice of intent to agency. 
    • Apply for and obtain other local/state/federal permits. 
    • Familiarize contractors and others with SWPPP requirements. 
  • Construction and SWPPP implementation: 
    • Install stabilized exit and initial downgradient perimeter controls. 
    • Install and stabilize initial drainage system, traps and basins. 
    • Proceed with phased clearing and grading work. 
    • Implement phased erosion/sediment BMPs as needed. 
    • Stabilize disturbed areas within 14 days or as required. 
    • Inspect and maintain BMPs; document activities. 
  • Final stabilization and permit termination: 
    • Stabilize all disturbed areas, slopes and drainage systems. 
    • Remove waste and unused materials. 
    • Remove all temporary BMPs; stabilize BMP locations. 
    • File notice of termination and other required notices. 

I know this is a lot so, to answer your question directly, dewatering bags offer a means to jump on the source of the problem early. For example, if you are pumping water (sediment) from an evacuation with a mud pump, direct it into a dewatering bag before discharging. They are small temporary sediment traps to treat runoff water by allowing sediment particles to settle out of the water. Typically lying in a drainageway or other point of discharge from a construction site, dewatering bags capture runoff water laden with sediment before it flows into the watershed. It is best to manage sediment at the source ASAP.

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