Industrial wastewater permit for Enbridge Line 3

A National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) permit will be needed to cover waters associated with hydrostatic testing of new pipeline and buoyancy control. Hydrostatic testing is done to check the structural integrity of new pipelines. Buoyancy control water is used to temporarily maintain the pipe in place during installation.

Testing the structural integrity of pipelines involves filling the vessel with water to a desired pressure and then checking for leaks or fissures. Buoyancy control involves filling the pipeline segment with water and capping it so that the segment of pipeline stays in place during the installation process. Test and buoyancy control water is normally secured from a nearby water body, groundwater or a municipal supply.

Upon completion of the test and buoyancy control, the process wastewaters must be discharged. It is this discharge that the NPDES/SDS permit addresses. Enbridge must discharge in accordance with NPDES/SDS permit conditions which can include monitoring, limits, and best management practices. The amount of water to be discharged is predicated upon the length of pipeline segment being tested or installed and can vary between several thousand gallons to several million gallons. Discharge duration can last from one day to several days depending about the amount of water to be discharged and discharge velocity.

The MPCA follows the general process below for processing water quality permit applications. Steps in green indicate opportunities for public participation in the process.

Permitting process timeline showing a red "current status" arrow pointing at "Permit decision".

Current status

The public comment period for the draft water quality permit for Enbridge Energy’s Line 3 project closed on April 10, 2020. The MPCA reviewed all comments and information received and has finalized responses to comments and the final permit. The final permit is effective November 12, 2020.

Draft permit documents

Industrial wastewater NPDES/SDS application

Previous documents

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