Building of a fish pass in the form of stone ramp
Jasiołka River – km 19+100
Planned term of start:
IInd quarter 2019
Planned term of end:
IVth quarter 2019
1 554 061 Polish zloty
Why do we interfere in a river?
The existing concrete weir was made as a water intake for industrial and socio-household purposes of oil refinery. Theoretically, it creates a barrier of the height of 0,5 m but because of the erosion of the riverbed below the weir its real height equals 1 m. This barrier makes it impossible for aquatic organisms to pass through. Therefore, its modernization is necessary.
The structure dams water to the height of about 0,5 m. The right bank above the weir is strengthened by concrete plates, while the left one by a retaining wall of the stepped shape. A riverbed near the banks is strengthened by small stones embedded into a concrete. This strengthening is now heavily destroyed. There was an erosion of the bottom below the weir.
A modernization includes building of a fish pass and a reconstruction of the existing weir by cutting of hole in overflow. A fish pass will consist of a stone ramp made by irregularly arranged boulders of various dimensions. An inlet to the fish pass will be created as an overflow cut in the existing concrete weir. This irregular shape of an overflow was designed in order to concentrate low flows. In the final part, a stilling basin was designed ending with a diaphragm wall of erratic boulders.
Banks on the length of the fish pass will be secured by a stone overlay stabilized in a concrete which will improve its stability in high flows.