In a statement, it said that the Government of Gibraltar has submitted an application to build Gibraltar's first wastewater treatment plant.
The company contributed the preparatory works necessary for today's submission, collaborating with its joint venture partner NWG Commercial Services (a part of the Northumbrian Water group).
Subsequently, Modern Water will be carrying out the design and build works on behalf of the joint venture which was selected as the preferred bidder back in October 2014.
"This step marks the completion of our advance works contract,” said Simon Humphrey, Modern Water chief executive.
“Together with our partners at Northumbrian Water, we continue to work closely with the Government of Gibraltar to finalise the main Design, Build and Operate contract."
Modern Water shares rose 1.04p or 17.19% respectively to trade at 7.09p.