Dounreay Site Restoration Limited (DSRL) have developed a design and scope for the Optimisation Works to upgrade the existing Non-Active Drain Installation at the Dounreay Nuclear Decommissioning Site which requires construction and when constructed, will deliver several capital maintenance items identified as required to be addressed following repeated non-compliances with SEPA waste management license. The objective of the project is to provide a passive and non-intrusive solution which will provide robust and reliant compliance with the suspended solids limits set by SEPA by modifying four existing CSOs and constructing two new treatment plants, both capable of treating greater than Formula A / 6DWF before discharging to the Atlantic Ocean through existing outfall pipes.