Surface Water Management Program for DGR Sites

Abstract

The management of surface water at the NWMO Deep Geological Repository is being developed to meet the needs of the facility while also minimizing its environmental footprint. Namely, the program aims to ensure water taken from the environment is minimized, water on-site is recycled to the greatest extent possible, and water discharged to the environment is of suitable quality. The water management program consists of the following systems:

• Water Storage, Treatment, and Distribution Systems, and
• Service and Stormwater Management.

As a component of this development, the following has been assessed to minimize off-site impact; total daily facility service and domestic water demands for the surface and underground during the construction and operations phase; sewage treatment; raw water supply; water storage facilities; distribution systems; and the recycling of used service water and underground water.

The NWMO has begun to advance the development of the water management programs for the unique site-specific geosphere and surface conditions, based upon an established set of guidelines.

The following have been considered in the design of the service water and stormwater management systems: post-development catchment areas and associated peak flows based on meteorologic data; the site framework layout; finished grading design; and preliminary road design. Hydraulic calculations for the sizing of drainage infrastructure (i.e., stormwater management ponds, ditches, culverts, storm sewers, catch basins) are based on a 1-in-500-year storm event. In addition to the stormwater management ponds for the protected area, the balance of site, and the excavated rock management area; there are the DGR water settling pond and the service water settling pond, along with engineered wetlands to hold treated water prior to release.