Russian energy giant JSC RusHydro has completed stabilization work on the Zagorskaya 2 pumped-storage plant.
HydroWorld.com reported that erosion of foundation soil under the 840 MW plant was caused by the "inefficient performance" of its impervious system this past Decemeber after workers noticed water seeping into Zagorskaya 2's turbine room in last September.
The turbine room and other areas were flooded during the next several hours via broken expansion joints and intakes of unfinished water pipes, caused by the erosion of soil that made the building sag.
RusHydro (LSE: HYDR) said the stabilization work began immediately after with the erection of an earth-fill dam on the tailrace side of the building. The area adjacent to the building was completely drained by June, while a temporary support was formed beneath the basement plate to prevent further subsiding.
The support was formed by drilling holes and injecting more than 20,000 cubic meters of "special fluid", RusHydro said, while the turbine room was also cleared of sand drifts.
"The stabilization of the powerhouse lays ground to the next phase of rehabilitation -- eventual restoration of the plant," the company said in a statement.
RusHydro is currently considering several options for the project's rehabilitation. The plans are being developed by the group's JSC Hydroproject Institute in conjunction with engineering firm Lahmeyer International and other industry experts. The final plan will be chosen by the company jointly with external experts before being presented for approval to respective government agencies.
Zagorskaya 2 is unique, RusHydro said, in that the plant is built on soft soil instead of hard rock as is preferable. Such foundations are not typical in Russia's central region, however, and the company said its designers did not properly account for the soil around the plant's base.
The utility had wanted to put the plant's first pair of turbines into operation earlier this year, though the delayed completion of a transmission line by the Federal Grid Company (FCG) have moved Zagorskaya 2's commissioning date back.
Work on the pumped-storage plant began in July 2007.