The power house of the diversion power plant Hieflau is located on the Styrian Enns in Gesäuse on the western periphery of Hieflau. The Erzbach flows past the power house to the east and the railway line runs to the west below the plateau that accommodates the Wag reservoir. The access road to the power plant site, which branches off the main street in Hieflau, comes from the south.
The entrance in the south leading to the yard is flanked by the former gatehouse and a garage building. The elongated main building of the power plant ensemble comprises three adjoining wings arranged roughly in a north-south direction. The southern building is the switching facility, the middle building the control center and the northern building the machine hall. An outdoor switching station is built onto the uphill side of the machine hall, on the other side the Erzbach with the weir system of Hieflau-Erzbach power plant and the tailrace channel that flows into the Erzbach. Other auxiliary buildings such as the warehouse and garages are located south of the entrance.
General design features
The appearance of the building is shaped by the smooth facade surfaces, originally finished with a reddish facing plaster and openings framed with natural stone, artificial stone and fairfaced concrete edgings. The ridge plate with drip moulds and grooved subprofile are made of fairfaced concrete. The natural stone, artificial stone and fairfaced concrete elements display sophisticated finishing techniques with pointed or bush hammered surfaces. Haas also used conglomerate from the Hieflauer region for the window edgings.
The eastern, longitudinal side of the building, which faces the Erzbach and is visible from a distance, serves as the main facade.
The machine hall, erected over an area of 50.0 x 17,50 mm, 15,20 m above ground level with a flat hipped roof, is the largest part of the power plant and has a dominating accent: Three segmental arch-shaped turbine outlets are located between the half-round pillars in the downstream platform. The base of the external wall has a pointed fairfaced finish. Above the outlets, a row of nine rectangular openings separated only by pointed fairfaced pillars illuminate the machine hall that is situated in the background.
A surrounding edging transforms the openings into a horizontal rectangular element which covers most of the facade surface. The parking area is located further south behind two further openings. Four window groups, each comprising two high rectangular windows, between the crane track and the eaves break through the eastern longitudinal wall. A further group is located in the northern front wall above a high rectangular window. The low side wing with monopitch roof, which runs along the western longitudinal side of the machine hall, accommodates the 6-kV switching unit. Niches for the transformers, which conduct the electricity to the adjoining outdoor switching station, are located in front of the walls of the west facade. The operations building is built onto the southern front wall.
Access to the 49.50-metre long and 13.80-metre wide machine hall is gained via doors on the western longitudinal side and the southern front wall of the operations building. The supporting pillars are located on the western longitudinal side in front of the line of the closed wall and the spaces between the pillars on the eastern longitudinal side are completely filled with glass surfaces that extend from the ground to the crane track. The glass surfaces are divided with steel glazing bars. The crane track that rests on the pillars also has supports for a flat coffered ceiling. The interior of the machine hall is dominated by the towering, cylinder-shaped enclosures for the three generators of Hieflau power plant. These are accessed from a platform via curved staircases.
In the north-western corner of the machine hall, a quarter spiral staircase leads to the two lower-level floors which accommodate the vertically integrated turbines. The entrance to the machine hall of Hieflau-Erzbach power plant, which joins the basement of the machine hall at a right angle to the east of the basement, is located in the upper lower-level floor.
Control center with operations building
The three-storey control center building, which joins from the south and is transverse to the machine hall, has a flat hipped roof and accommodates the control station and the rooms of the operations building. Its smooth external surfaces are interrupted by windows of different formats framed with natural stone. The larger high rectangular windows are arranged on the upper floor. On the same floor, the glazed, fairfaced bay window of the control station protrudes on the west side and rests on two consoles. The machine hall, the workshops to the west and the foyer of the control center to the east, which has a two-armed staircase that leads to the upper floors, can be accessed via the entrance in the southern front wall with an overlying balcony. The balcony facing the machine hall is accessed from one level of the staircase.
Switching station and extension
The switching station, which accommodates a 30-kV switching unit, is built onto the operations building to the south of the two-storey wing and is covered with a flat hipped roof. A dense row of high rectangular openings is arranged between fairfaced concrete pillars on the east facade above a base area with smaller square windows. A two-storey, triaxial extension with personnel and storage rooms rounds off the main building to the south.
The former gatehouse is located to the west of the entrance gate: The single-storey building has a steep hipped roof and accommodates personnel rooms.
Similar to the gatehouse, the single-storey garage building to the east of the entrance gate and transverse to the power plant axis is rendered and covered with a steep hipped roof. The wall facing the Erzbach on the eastern frontal facade is finished with building stone and therefore harmonises with the adjoining stone finished embankment to the north.
A stone-finished embankment confines the tailrace channel and Erzbach, and also encloses the yard which features green areas and a circular fountain with a water-spouting seal sculpture.
A subsequently erected garage building southwest of the power plant entrance was built onto the remains of a blast furnace wall made of natural stone and features stone finished pillars. Parking areas with single-pitch roofs and garages for prefabricated parts are located to the southeast of the power plant ensemble.
Three former residential buildings for the workers are located on the right bank at power plant level. The house to the north, which was formerly occupied by the plant manager, is built onto the remains of the firing bridge of the former blast furnace of Hieflau.
Works water channel
After processing in Hieflau power plant, the works water flows through a 230-metre tailrace channel into the Erzbach.