Scope of delivery:

+ 4x Double plate penstock 1640 × 2850 mm
+ Stop gate

Double gate penstocks for improved controllability and operational reliability
Modernization under continuous operation

Hüttenteich reservoir in the Harz region (Germany) serves as an intermediate buffer for intermittently occurring discharge water from drinking water production as well as for stormwater runoff. During construction works, this buffering function had to be maintained at all times, and regulated discharge into the Grane receiving watercourse had to be ensured. At the same time, new shut-off devices were to be installed at the outlet structure to improve robustness, maintainability, and controllability of operation.

Structural solution:

• Installation of four side-by-side double gate penstocks (each 1640 × 2850 mm), with independently operable gates for flexible control and redundancy
• Design in accordance with DIN 19704 (steel hydraulic structures)
• Integrated stoplog frame for safe penstock inspection and maintenance
• Installation within the existing structure: bolted to a site-installed stainless steel support structure and laterally concreted into the existing wall – enabling precise installation, permanent load transfer, and watertightness

Operation during construction (bypass concept):

• Inflow to the Grane was ensured via a water main running parallel to the reservoir, conveying reservoir water
• Discharge water temporarily stored in the reservoir was conveyed via a DN 150 siphon line with downstream penstock (flow rate control) and blended into the reservoir water from the bypass pipeline
• This fully decoupled the Grane inflow from the construction site; in the event of potential turbidity development in the reservoir/construction area, the siphon line could be shut off immediately without impairing the water quality of the Grane

Schedule and environmental constraints:

• The time frame for the work on the Hüttenteich pond was very tight. For nature conservation reasons (amphibian migration), preparatory works outside the water body, such as site establishment, were permitted only from July onward. Works within the water body, e.g., for dewatering measures, were allowed only from August
• Weather risk in the Harz region (Germany) : concreting-critical temperatures are to be expected as early as November; therefore, a tight concreting window with assured curing measures was required to achieve final strength

Operational reliability and maintenance:

• Double gate penstocks provide fine control, redundancy during maintenance or fault conditions, and safe inspection via the stoplog frame

Conclusion:

Despite tight environmental and weather-related constraints, the outlet structure was successfully modernized under continuous operation. The combination of four double gate penstocks (1640 × 2850 mm), DIN 19704-compliant design, an integrated stoplog frame, and hybrid integration into the existing structure provides flexible, maintenance-friendly, and permanently reliable operating conditions. The bypass/siphon concept reliably decoupled the Grane inflow from the construction site while ensuring water quality and schedule compliance.