Industrial wastewater discharge approvals

Discharging wastewater from construction site dewatering to the King County sewage system

The King County Industrial Waste Program regulates wastewater discharges from construction sites and requires permits. A King County Public Rule regulates construction dewatering discharges to the sewer.

About construction dewatering discharges: 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.

Applying for permission to discharge to the King County sewer system: Use a Construction Dewatering Request form to apply for permission to discharge to the King County sewer system. Industrial Waste Program staff members are available to discuss regulations and requirements. Discharge approval will be issued to the owner of the site. As such, this form must be signed by the site owner, or their authorized representative as defined by King County Code (KCC) 28.82.050. The site owner may delegate signatory authority to an authorized representative by completing a Delegation of Signatory Authority form (PDF 26KB) and submitting it to KCIW with a Construction Dewatering Request form.

Sewer charges: Where applicable, sewer charges will be levied to those discharging construction dewatering to the KC sewer system. Billing procedures update - see Other Fees on the KCIW Fees Internet page.

Solids in construction site wastewater: 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.

Wet and dry months: Large-volume dischargers of construction water (those discharging more 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.