Roads and parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic. Stabilizing roads, parking areas, and other on-site vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or stormwater runoff. 

*The contents of this guide are to provide a general overview only. It is the users responsibility to ensure all BMPs utilized on their project meet the requirements of their state and local jurisdictions.

Find it in the Stormwater Management Manual:

Eastern WA          Western WA

Installation:

• On areas that will receive asphalt as part of the project, install the first lift as soon as possible 

• Install 6 inch depth of 2-4 inch crushed rock, gravel base, crushed surfacing base course immediately after grading or utility installation. A 4 inch course of asphalt treated base may also be used, or the area may be paved.  
• Roadways should be carefully graded to drain into drainage ditches directed into a sediment control bmp 
• In some cases roadways can drain into an area of > 50feet of heavy vegetation.  
• Protect storm drain inlets from sediment laden water 

Maintenance:

• Inspect stabilized areas regularly, especially after large storm events 
• Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded 
• Following construction, these areas shall be restored to preconstruction condition or better to prevent future erosion.  
•  Perform street cleaning on paved areas at the end of each day or more often if necessary