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Construction Best Management Practices (BMPs)

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The potential for storm water pollution exists on any construction project. Developers, contractors and property owners are expected to prevent erosion and the release of sediment and other pollutants through Best Management Practices (BMPs). BMPs include scheduling construction activities, employing prevention measures and installing control devices. The goal is to keep pollutants out of storm drains, waterways and adjacent properties. Pollutants should be contained on-site until appropriate disposal is possible.

Common pollutants at construction sites

  • Sediment from grading operations
  • Concrete wash from tools and trucks
  • Sanitary waste and pathogens from temporary restrooms
  • Debris from discarded building materials
  • Oil and grease from equipment and vehicles
  • Paint, chemicals and solvents
  • Litter

Recommended Best Management Practices

  • Schedule construction activities during dry weather. Keep grading operations to a minimum during the rainy season (October 15 through April 15). You can properly protect an exposed slope once before rain arrives or send out a crew to repair a wet, muddy and slippery slope every time it rains.
  • Protect and establish vegetation. The root structures of plants and trees help keep soil in place while leaves and canopies help dissipate rainfall energy to prevent dislodging and transporting of soil.
  • Train and educate construction crews and personnel to better understand the effects of storm water pollution from construction projects and learn ways to prevent or minimize pollution on the job.
  • Stabilize construction entrances and exits to prevent tracking onto roadways. As vehicles enter and leave construction sites, pollutants such as sediment, gravel and other loose particles are spread onto adjacent roads. Those pollutants can get washed into roadside ditches and are a nuisance to drivers when damage to vehicle paint or windshields occurs.
  • Protect exposed slopes from erosion through preventative measures. Cover the slopes to avoid contact with storm water by hydroseeding, applying mulch or using plastic sheeting.
  • Install straw wattles (fiber rolls) and silt fences on contour to prevent concentrated flow. Straw wattles should be buried 3 to 4 inches into the soil, staked every 4 feet, and limited to use on slopes that are no steeper than 3 units horizontal to 1 unit vertical. Silt fences should be trenched 6 inches by 6 inches into the soil, staked every 6 feet, and placed 2 to 5 feet from any toe of slope. Avoid the use of hay bales as sediment control devices. They have high failure rates and the hay is better suited as ground cover.
  • Use brooms and shovels whenever possible to maintain a clean site instead of a hose. Introducing more water than necessary only adds to water pollution.
  • Designate a concrete washout area to avoid wash water from concrete tools or trucks from entering gutters, inlets or storm drains. Maintain washout area and dispose concrete waste on a regular basis.
  • Establish a vehicle storage, maintenance and refueling area to minimize the spread of oil, gas and engine fluids. The use of oil pans under stationary vehicles is strongly recommended.
  • Protect drainage inlets from receiving polluted storm water through the use of filters such as fabrics, gravel bags or straw wattles.
  • Check the weather forecast and be prepared for rain by having necessary materials onsite before the rainy season.
  • Inspect all BMPs before and after a storm event. Maintain BMPs on a regular basis and replace as necessary.

All recommended BMPs are suggestions only. Each construction project should employ site specific BMPs. Property owners and project applicants are encouraged to enlist professional services to ensure appropriate and effective BMPs are used during and after the construction process.


The County of Sonoma and the Regional Water Quality Control Boards are responsible for enforcing violations of storm water quality. Failure to prevent discharges of polluted runoff are violations of the Sonoma County Code, the California Water Code and the Clean Water Act.

Civil penalties up to $10,000 per day plus $10 per gallon of polluted runoff may be administratively imposed by the RWQCBs. Fines up to $25,000 per day for each violation may be assessed if imposed by the Superior Court.