As you may already know, one of the main activities of the FishForLife project is making migration passages for fish, in Albeni and Targu Carbunesti. For the first set of works to be carried out at the spillway threshold in the area of DJ675B bridge in Albeni, EPA Gorj received and approved the technical project for this objective. It provides a rock ramp fish passage solution, but also a series of measures to recalibrate the riverbed, in order to reduce the flow rate and eliminate the existing hydraulic jump (waterfall).
At present, the existing overflow threshold is provided with a ramp in the middle with a length of approx. 9 m and a height of 1.30 m, which makes it impossible for fish to pass. Works that will be carried out according to the technical project are divided into four categories:
- Works upstream the existing threshold, where three rows of boulders (approx. 450 kg / piece) will be installed, acting as energy dissipators, arranged interax at 1.50 m, with spacing at length of 1.70 - 2.00 m, on foundations of concrete. Also, at the connection with the banks, boulders with a weight of 200 - 300 kg / piece will be installed, to direct water to the central area.
- Works on the existing threshold, which include bringing the existing ramp of the threshold, but also of the two adjacent areas, at the projected elevation (3% slope) through successive layers of concrete, in which large boulders will be installed (450 kg / pcs, diameters 50 - 70cm). Among rows of big boulders (every two rows) will be fitted smaller boulders (approx. 100 kg / piece).
- Works downstream the existing passage, consisting of riverbed recalibration activities with local materials (blocks and ballast) and will continue the arrangement of the passage by installing in line the large boulders (450kg / piece, diameters between 50 and 70 cm), embedded in a concrete spur on the central area. Selected boulders measuring between 10 and 15 cm will be placed along the entire ramp designed in the space between the rows of boulders. At the downstream end of the passage, a reinforced concrete relief basin will be built, at the upstream limit, boulders will be installed to ensure a continuous slope.
- Riverbanks consolidation, Prevention (reducing) riverbanks erosion (L = 35m) downstream of existing gabion walls will be achieved by installing massive boulders, which ensure consolidation and protection for erosion of the riverbank slope base, and some twig fences continuing the boulders massifs, on the banks slopes. The spaces between the fences will be filled with local material, and at the upper part with vegetal soil (h = 20 cm) which will be artificially grassed on the lower terraces, and on the upper terraces will be planted seedlings of alder (Alnus glutinosa).
- Establishing access road and deviate riverbed in the works area. The roads will be provided with a ballast thickness of 40 cm, a width of 4 m and a total length of 100 m. Riverded deviation in the works area shall be executed step by step, ensuring to be carried out under optimum conditions.
In the next period, EPA Gorj will obtain the necessary authorizations based on the documents provided by the draftsman. It is estimated that the works will start between June and July and will last about 6 months (depending on weather conditions).