German potash producer K+S and the state of Hesse have agreed on a new plant for permanent disposal of saline wastewater in the mining area bordering the rivers Werra and Weser.

Initial plans for construction of a 400-km underground pipeline to transport the water to the North Sea have been abandoned, due in part to the opposition from the coastal state of Lower Saxony but also because construction costs would have exceeded K+S' budget and the €2.4 billion cost nearly matched the company's capitalization of €2.5 billion.

An expert opinion commissioned by the state government concluded that even if the wastes were diverted, the river water would not revert to its natural state, in part because of the tailings piles of mining waste that dot the shores. However, fresh water quality could be achieved with the help of certain remediation measures.

The political sector also feared that a shutdown of the mines to avoid further pollution in a structurally weak region could cost the company's 5,000 local jobs.

Under the current four-step plan agreed with the state environment ministry, K+S will foot the bill for farther-reaching water protection measures expected to cost around €400 million between 2018 and 2021.

Injection of wastes into the subsoil is planned to end in 2021, at which time local disposal is to be supplemented by a pipeline leading to the Upper Weser river, which is expected to be in use until 2060. This will be supplemented by retention basins designed to hold up to 750,000 cbm.

A new treatment facility is to be built to reduce the occurrence of saline wastewater by 1.5 million cbm/y starting from the end of 2017.

Tailings piles are to be covered for the long term and pile wastewater considerably reduced.

The Weser and Werra rivers are expected to attain fresh water quality by the end of the fourth phase.