The atomic plant ceased power generation in 2004 and its cooling towers were demolished in 2007 with the lengthy decommissioning process ongoing.
Now a joint project involving the Nuclear Decommissioning Authority, Magnox Ltd, Scottish Environment Protection Agency and Scottish Water aims to improve the eco-system in the area with the eel pass part of that effort.
It is hoped it can upgrade the majority of the catchment from “poor” to “good” ecological status.
Euan Innes, Scottish Water asset planner, said it was delighted to help the “globally rare and declining species” get access to more of the River Annan.
Chapelcross site director Richard Murray said the project was an “excellent example” of how it could improve the environment in which it operates.