|ENEL - HPP Los Cóndores||References_5507|
Los Cóndores is a 150 MW HPP, including a 12 km long headrace tunnel (4.6m diam, excavated by D&B and a DS hard rock TBM), a 120 m high surge shaft (6m diam), a 480 m high pressure shaft (2.6m diam), both being excavated using a raise borer machine RBM, and a 1.6 km long subhorizontal pressure tunnel leading to an underground powerhouse accommodating 2 Pelton units. The region is volcanic, with several active volcanoes in the recent geological eras. Maule Laguna volcanic complex is one of the major and the geological formation are essentially dacitic and rhyolitic lava field with rich tuff and volcanic breccia presence in subhorizonal sedimentation and several lava and basalt domes and dikes crossing these formations. Excavation of the upper waterway (HRT) is foreseen in two phases through a central adit by TBM, in order to shorten the time for accessing and execute the vertical works. During the excavation of the HRT lower reach, the TBM got stuck in a cohesionless material, likely the seat of a paleo-basin (syncline) or a paleo-canal within the lava and breccia banks. The services targeted the understanding of the situation, definition of the operations required for the TBM to be safely unlocked from the jammed conditions and option for realizing a bypass around the TBM in case no success was provided by other means. Because of the significant modification of the working program, the evaluation was required of the options for realizing the upper reach of the HRT by other mechanized means (second TBM) or other excavation method, given the logistic conditions at site. Possible optimization of vertical works, in terms of efficiency and realization concept was also part of the required services; in particular, a preliminary study considering 5 alternatives of the scheme combined with different excavation methods options (D&B and/or RBM) were carried out, in order to analyze the possibility to disassociate the construction of the vertical works from the TBM advance and to better manage the geological and construction risks associated with vertical works construction.
The existing Ritom hydroelectric plant, owned by the Swiss Federal Railways (SBB), has been using the gross head of more than 800 m between Lake Ritom and the powerhouse Piotta since 1920. The plant essentially consists of an intake, a penstock (L = 900 m, D = 1.7 m), a surge chamber and 2 pressure tunnels (L = 1400 m, D = 1.10 m) to the power house, where 4 Pelton units with horizontal axis and a total nominal capacity of 40 MW are installed.
The expiry of the concession in 2005, the age and wear of the electromechanical equipment as well as the continuing demand for electric power prompted SBB to study various options of renewal works and expansion of the plant.
The new project envisages an extension of the plant by replacing the existing turbines with new, more powerful turbines (2 Pelton turbines each with a capacity of 60 MW, Q = 2 x 8.5 m³/s) located in a new building next to the powerhouse Stalvedro owned by the Azienda Elettrica Ticinese (AET). In addition, a 60 MW pump unit (Q = 7.8 m³/s) will be installed to enable pumped storage operation of the system.
The existing headrace system will be abandoned, and the water will be fed to the machines through a new underground pressure tunnel (Q=20 m³/s).
In order to reduce the impact of fluctuating discharges into the Ticino river caused by the pumped storage operation, a new downstream compensating reservoir will be constructed.
The project also includes a series of environmental compensatory and landscape enhancement works in the Piora region and along the Ticino river.
The detailed design, with the common owners SBB and AET (Ritom SA) is scheduled to start at the end of 2019.
|Pamco Shura - Gilboa PSP, Expert assessment||References_5376|
Gilboa PSP is a pump storage plant in the Gilboa mountain in central-eastern Israel, at the border with the Cigiordania looking over the Jordan River valley.
Its scheme includes an upper reservoir at el. 427 m.a.s.l., an approx. 500 m deep shaft (dia 4.5 m), a 956 m long high pressure tunnel (dia 4 m, then 3 m at the feeder near the PH), a 2x150 MW turbines cavern with turbine el. -147.5 m.a.s.l. and relevant transformer cavern, a 1'512 m long low pressure tunnel (dia 3.6 m along the outlets from the PH and 5 m when unified) with a 95 m high surge shaft (lower dia 5 m H 21.5 m, with steel diaphragm, upper part dia 10 m H = 60 m) and the lower reservoir at el. -84 m.a.s.l.
After an initial construction phase assigned to a Korean contractor, the Client reassigned the finishing works (some excavation and the final lining of the shaft, the HP and LP tunnel and the concrete inlet and outlet) to the Israeli contractor (JV) Pamco-Shura already providing for the loose soil excavation portion and relevant lining and cut&cover portal at the lower reservoir.
Services to be provided to the Contractor are expert assessments regarding the water leakages and the head loss along the powerplant, and repair works on waterway concrete linings.
The hydropower plant is located in the Los Andes and Panama farms, in the municipalities of Patulul and Santa Bárbara, Department of Suchitepéquez, Guatemala, about 70 km from the Pacific Ocean and 130 km from Guatemala City.
The plant uses the water of the river Coralito and comprises two intake works, a 1 km long low-pressure conduction (Ø 0.8 m), a daily compensation tank (V = 3'350 m³), a 3.5 km long penstock (Ø 0-7 m), a powerhouse with a horizontal-axis Pelton turbine and a discharge channel to the Coralito river.
Both intake works are equipped with "Coanda" screens, with a capacity of 0.25 m³/s and 0.60 m³/s respectively; the design flood is 25 m³/s and 120 m³/s. Both the low-pressure conduction and the penstock are made of glass fiber reinforced pipes (GRP). The low-pressure conduction has diameters of 0.45 m (first stretch) and 0.75 m (following stretch), the penstock of 0.70 m; the pipes are buried over their entire length.
The expected annual power generation amounts to about 12 GWh, with a design flow of 0.85 m³s, a net head of 291 m and an installed capacity of 2.1 MW.
Lombardi services for the project consisted of the prefeasibility study, the feasibility study, the preparation of the tender documents, owner's support during the awarding of contracts, the final design, the technical site supervision, the detailed design (constructive) and the project administration of the project.
The plant is in operation since 2014 and Lombardi continues to provide management services for the operation and maintenance of the plant.
|Frankonedou and Kogbedou HPP||References_5113|
The hydroeletric complex of Frankonédou and Kogbédou will be built on the river Milo, approx. 70 km from Kankan in eastern Guinea.
The 37 m high Frankonédou dam (upstream) will impound a reservoir of 1'300 hm³, which will regulate the discharge downstream. The powerhouse, located at the dam toe, will exploit a max. gross head of 26 m. it is equipped with 2 Kaplan unit.
The Kogbédou scheme, located approx. 30 km downstream of Frankonédou dam, will include a 10 m weir, an headrace channel ending with a concrete forebay, 2x 5.5m diameter penstock, an open air powerhouse equipped with two Francis units. The max. gross head is 29 m.
The total installed capacity of the complex is 102 MW with a design discharge of 160 m³/s for Frankonédou and 200 m³/s for Kogbédou. The expected total power generation is 468 GWh/year.
Both dams will include a concrete structure in the central part with the intake and outlet works and embankments on the banks.
|Solu Khola HPP (86MW)||References_5903|
The Solu Khola Hydropower Project is of the Run-Of-River (ROR) type.
The project comprises an ungated 15m high and 31.80 m long concrete weir with a horizontal floor stilling basin built across the Solu river. The weir crest is located at elevation 1262 m a.s.l. A concrete intake is located on the left bank of the Solu river, formed by 3 orifices equipped with intake gates of 4.0 m x 2.0 m each. A gravel trap 5.0 x 5.0 m is provided behind the intake.
Three underground concrete desilting basins (L x H x W = 85.0 m x 9.0 m x 5m), achieve a trap efficiency of 90% for particles larger than 0.15mm and include a S4 flushing system for cleaning of the basins.
A 4500 m long partially concrete lined headrace tunnel (Inlet to Valve Chamber), D-shape (section 4.3 m x 4.5 m) and a 1850 m long steel penstock pipe (2.5 to 2.1 m diameter, including drop shafts and horizontal underground stretches) convey the water to the powerhouse located at the right bank of Dudh Koshi River at Maiku Besi. The powerhouse, housing 3 Pelton turbines is located about 1 km upstream of the suspension bridge across the Dudh Koshi River.
A 375.0 m long inclined surge tunnel (D-shape 4.0 m x 4.0 m) is provided to reduce hydraulic transients in the pressure waterways. Between the surge tunnel and the penstock, a valve chamber equipped with a safety shut-off butterfly valve is provided.
The project also includes 4 construction adits.
In autumn 2017, the canton of Zurich, after a positive decision for the concession renewal for a further 60 years, granted building permission for the refurbishment of the historical Dietikon run-of-river power plant.
Construction works started in early 2018, whereby in the existing main power plant, both Kaplan turbines dating back to the years 1931/32 were replaced (new Q = 2 × 47.5 m3/s, HN = 3.4 m, P = 2 × 1.7 MW) and an ecological discharge power plant (Q = 25 m3/s, HN = 3.1 m, P = 770 kW) was built nearby the existing weir. Compared to the previous plant layout, from 2019, the new scheme generates 19.70 GWh/a, about 14% more than before.
Particular attention was given to ancillary works that facilitate the free fish migration and ensure their protection. For the upstream migration, two new fish ladders were built, while the downstream migration is ensured through a trash rack with horizontal bars (B x H = 22.8 x 5.9 m, clearance 20 mm) before the main powerhouse and the adjustment of an existing ice channel into a bypass. The existing boat ladder was also replaced.
|Gere HPP - Lot 2||References_5374|
The Gere HPP was conceived in previous design phases as a traditional high-head scheme with a nearly horizontal, approx. 2 km long low-pressure headrace and an 800 m long buried penstock. The low-pressure headrace was designed as a tunnel with an exposed pressure line inside, being the tunnel intended also for acceding the headworks in the winter season.
During the offer preparation for engineering services including tender, detail design, site supervision and commissioning, Lombardi as a member of the JV IGSL proposed a scheme modification with a 2.6 km long inclined tunnel from the powerhouse area up to the desander facilities and the Tirolean intake. The winter access function of the tunnel was maintained as in the original layout. The project was awarded to IGSL adopting this layout optimization.
Drill-and-blast underground excavation is carried out from the d/s portal only. The tunnel portal is located close to the powerhouse, easily accessible and just approx. 300 m from the designated dumping area. After excavation completion, the GRP-line is installed in the tunnel from u/s to d/s. Site logistics could be dramatically simplified compared to the original project layout: the two cableways for conveyance of the excavation material to the dumping area and for penstock installation are no more needed and the project environmental impact could be further reduced.
Lombardi has been in charge of all conceptual and design project issues whereas our JV partner is responsible for project management and site supervision.