Nacka municipality has two parallel lake pipes for drains located in Skurusundet in Stockholm, at the outlet to the Baltic Sea. At one point one of the pipes four valves was stuck in closed position and blocked thereby the flow in one line. This had the consequence that the second line became overloaded. One solution could be to close the main line, thereby allowing the wastewater to flow into the bay. With such a solution, however, the risk of coliform emission in the drinking water had been high.
Instead, the municipality hired Proco Services, who adjusted their tools to perform a line stopping in a bend of the drain pipe and then replace the valve. Proco’s engineers shut down one line at a time for the replacement of the valves on the non-operating line. It was put into operation while, as a precaution, Proco even changed the valves on the still-functioning line. This prevents hopefully that future outages may occur. The work could be carried out without the sewage flowing into the Baltic Sea and a possible contamination with harmful coliform could be avoided.