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Instructions & Forms

NPD-002 Protection of Stormwater Quality on Construction Sites

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Version 03/06/2023

Information for owners and contractors regarding their responsibility to protect stormwater quality during construction and recommendations for how to protect stormwater quality. Responsible and proper construction management at the job site is essential for the protection of stormwater quality.

Property owners and contractors have an obligation to protect stormwater quality, pursuant to the County Code and the County’s Stormwater Management Plan. 

Stormwater

Stormwater runoff is the water that collects on your property and runs off during rain storms. This stormwater runoff might enter a storm drain in an urban area but eventually the water will enter a creek or stream. As rain strikes the earth it can become polluted and transport this pollution to storm drains and creeks. Stormwater runoff that enters the stormwater drainage system is not treated nor cleaned before it enters a creek or stream.

It is your responsibility to keep the stormwater on your construction site clean as it leaves your site. The most effective method is to control stormwater at the source before it becomes polluted. However, treating polluted runoff before it leaves the property is also an option.

Common Pollutants

Construction includes projects such as home construction, commercial construction, new garage and shed construction, general home repair, roof replacements, and the installation and replacement of plumbing, electrical and mechanical work. Common types of pollution at building job sites are sediment from disturbed soil, litter or debris, concrete, paint, oil or fuel, and pathogens.

Stormwater and Quality Protection

Protect stormwater quality by using best management practices (BMPs) on the job site. A BMP is defined as a program, technology, process, siting criteria, operational method or measure, or engineering system, you can use to prevent, control, remove, or reduce pollution on your job site.

The following are some common pollutants and the BMPs that you can use to protect stormwater quality during construction.

Pollutant Origin BMP
Sediment Exposed soil, debris piles, excavations, or other earth disturbances.
  1. Store materials under a roof to reduce exposure to rainfall. Alternatively, use plastic sheeting to cover piles or excavations prior to rain and during the rainy season (October 15 through April 15). Keep all debris away from the street and storm drains.
  2. Schedule excavation projects during the dry weather; generally April 16 through October 14.
  3. Prevent erosion by planting fast-growing native grasses that shield and bind soil.
  4. Re-contour disturbed areas to return the ground to its previous shape.
  5. Spray water, without causing runoff, to prevent dust from entering stream systems.
  6. Use course gravel or steel shaker plates to limit the amount of sediment and pollution  that vehicles track out offsite.
Litter of Debris Trash at messy job site
  1. Clean up and sweep job sites.
  2. Pick up debris and place in covered cans.
Concrete Pouring new or breaking up pavement or foundations.
  1. Mix correct amounts of concrete so no waste is left. Never bury waste material nor dump it into a storm drain.
  2. Store concrete bags under cover protected from rainfall & away from storm drains.
  3. Designate a concrete wash-out area for containment, drying and removal. Use a berm or plastic sheet to collect and contain liquid material.
  4. Transport small amounts of concrete to a landfill.
  5. Transport large amounts of concrete to a crushing company to recycle
  6. NEVER dispose of concrete washout into driveways, streets, gutters, storm drains or drainage ditches.
Paint Application and cleanup during new construction and remodeling
  1. Avoid spills by careful use and placement of paint cans. Keep all liquid paint away from streets and storm drains. Use water-based paints when possible.
  2. When thoroughly dry, dispose of used brushes, rags, drop clothes, and empty paint cans (lids off) into trash.
  3. Do not use paint manufactured prior to 1980 as lead levels are likely elevated.
  4. Paint chips and dust from non-hazardous dry stripping of paints may be disposed of as trash. Chips and dust from paints containing lead or tributyl tin are hazardous wastes and must be disposed of properly.
  5. If you do use high-pressure water, block nearby storm drains and allow cleaning
    water to flow into grass, soil, or gravel area.
  6. Paint out brushes to the extent possible. Rinse water-based paints in the sink. Clean oil-based paints with thinner, reuse thinner, and dispose of residue as hazardous waste. Reuse leftover paint for touch-ups.
  7. NEVER clean or rinse paint equipment into a street, gutter or storm drain.
Oil or fuel

Refueling spills.

Fuel and/or oil leaks
  1. Refuel at one location away from streams or streets. Use drip pans to catch spills.
  2. Have absorbent pads in the cabs of machinery ready to collect spills.
  3. Repair equipment such that there are no leaks. Check frequently for leaks.
Pathogens Human or animal waste.
  1. Use appropriate waste disposal systems. Make sure portable toilets are in good working order and are serviced regularly.
  2. Secondary containment trays are required for all portable toilets.
  3. Never stage portable toilet in the street, gutter or nearby storm drains.
  4. Clean up dog or other animal waste

More Information on Protecting Stormwater

Please call Permit Sonoma at (707) 565-1900 and ask for the Stormwater Coordinator for additional information about protecting stormwater. There is much that can be done to help reduce the amount of pollutants entering Sonoma County’s waterways. By incorporating stormwater BMPs on your site you can have a project that preserves and protects stormwater water quality in our neighborhoods and in Sonoma County.

Hazardous Waste Drop Off

Hazardous waste can be dropped off at the County’s Household Toxic Facility located at the Central Disposal Site, 500 Meecham Road, Petaluma.

The facility is open every week for free drop-off of toxics from Sonoma County residents, no appointment necessary. Contact the Eco-Desk Hotline at (707) 565-3375 or www.ZeroWasteSonoma.gov for more details.

Services are also available for certain businesses every week by appointment (call toll free 877-747-1870).