Discharges from Construction Sites

The King County Industrial Waste Program regulates wastewater discharges from construction sites and requires permits. Call 206-263-3000.

A King County Public Rule covers construction dewatering to the sewer.

Read a Construction Dewatering Fact Sheet (72 KB).

Use a Construction Dewatering Request Form to apply for permission to discharge to the King County sewer system.

During construction, workers may pump groundwater or stormwater away from the site. This process is called dewatering. Usually this water is clear, but sometimes it can be contaminated. Discharging it to a stream or lake may harm water quality. This water may be discharged into the sewer only if authorized by King County.

Wastewater that goes into the sewer must contain less than 7 milliliters per liter of solids capable of settling. This prevents restricting or blocking flow in sewer lines. A company discharging solids is liable for any damages caused by sewage backups. Discharge of materials such as ashes, sand, grass, and gravel is prohibited.

Large-volume dischargers of construction water (larger than 25,000 gallons per day) must find other means of disposal than sewers during the "wet months" (November through April) when the hydraulic capacity of sewerage systems is a concern. Discharges of construction water to the sewer are not prohibited during the "dry months" (May through October). Regardless of discharge volumes and period of discharge, dewatering dischargers must meet King County permitting requirements.