SWPPP and construction erosion/sediment control

One-line orientation

A Stormwater Pollution Prevention Plan (SWPPP) describes temporary construction measures that keep sediment and other pollutants from leaving the site. It is separate from the finished site’s permanent stormwater system.

Key points

• What it is: a Stormwater Pollution Prevention Plan — documents how a construction project controls stormwater pollution.
• Components: site assessment, Best Management Practices (BMPs), plus maintenance and inspection procedures.
• A SWPPP is required when construction will disturb one acre or more. It is also required for a smaller site that is part of a larger common plan that will ultimately disturb at least one acre. The requirement comes from the Clean Water Act and NPDES.
• Purpose: prevent pollutants and sediment from entering water bodies during construction.
• Common construction-phase BMPs (erosion + sediment control):
  • Silt fences — fabric barriers that catch sediment in sheet flow.
  • Sediment basins / traps — hold runoff so soil settles out before water leaves.
  • Stabilized construction entrances — gravel pads that knock mud off tires.
  • Inlet protection — guards around storm drains to block sediment.

Confusions / comparison

	SWPPP / construction-phase	Permanent stormwater design
When active	During construction only	Life of the finished site
Typical measures	Silt fence, sediment basin, inlet protection, stabilized entrance	Detention/retention ponds, bioswales, permeable paving
Driver	EPA / Clean Water Act / NPDES; ≥1 acre disturbed or common-plan trigger	Local stormwater code + site design
Goal	Keep disturbed sediment on site	Manage post-development runoff quantity + quality

Related

→ Runoff strategies (this module): permanent steep/shallow controls · Low-impact development (this module): the permanent-design philosophy · Detention vs retention (this module): permanent storage options.