The retention function is protection against high water and floods in the lower reaches of the Gradna stream, especially on the critical section of the passage through the built-up center of Samobor.
The Rudarska Gradna Dam is zoned with a downstream support zone that will be constructed with tailings from the quarry. A waterproof bentonite membrane is placed on the support zone created in this way. The bentonite membrane is anchored in the anchor trench on the crown of the dam and the clay wedge in the leg of the support zone of the dam. This clay wedge extends the entire length of this part of the dam in the valley and on the flanks. In addition to the function of anchoring the bentonite membrane, this wedge also has the task of achieving watertight contact between the body of the dam and the sides of the dam. The stone material for the upstream support zone is various unselected material from the quarry.
The length of the dam in the crown is 109.00 m. The height of the dam crown is 210.10 m a.s.l. The width of the dam crown is 4.0 m, the slope of the upstream and downstream slope of the dam is 1:2.5. The maximum height of the dam is 14.69 m.
The discharge structures can be divided into several interconnected components:
- Coarse trash rack
- Inlet settling basin
- Intake head with fine trash racks (horizontal and inclined)
- Bottom outlet
- Gate shaft with outlet head and downstream spillway
- Service passage with access shaft
- Common stilling basin for the bottom outlet and safety spillway, with a terminal sill
- Crest safety spillway and chute on the downstream dam slope