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Renovation of the Mazzè facilities on the Dora Baltea

Renovation of the Mazzè facilities on the Dora Baltea

The Mazzè facilities located on the Dora Baltea are undergoing a major reconfiguration and renovation project by Itinera Spa (Gavio Group) to eliminate serious hydraulic and structural problems, thereby improving both the functionality and safety of the spillway.  To accomplish this, the entire dam had to be demolished once the existing sluices and hydraulic system had been dismantled and landfilled.  

Overall view of the old and new dam:

The first phase of the work consisted of completely demolishing four buttresses, the existing vehicle deck and the overhead footbridge, the right and left abutments, and the foundation bed.  The demolition took place in two phases following the construction of the surface infrastructure (new spillway) and execution of special operations for the foundation to ensure that it is sufficiently stable and safe.  Below is a description of the work performed. 

Overall diagram of the construction work:

SPECIAL FOUNDATION CONSTRUCTION

FOUNDATION – SPILLWAY

  1. Upstream screen:  consists of three parallel rows of earthen columns injected with cementitious mixtures.  The two exterior rows were injected with a fine bifluid cementitious mixture (produced with 52.5 R type I from Buzzi Unicem’s Robilante plant), while the middle row was injected with a silica mixture with a high saturation capacity.  The treated earthen columns have a diameter of 1.80 meters and a depth of 24 meters, with an overall area of approximately 73 meters. 
  1. Downstream screen: consists of two rows of earthen columns treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant).  The exterior row is reinforced and equipped with a header curb, while the interior row with a diameter of 1.20 meters has not been reinforced.  The reinforcement rods have a diameter of 889 mm and the reinforced header curb measures 60 x 60 cm.  
  1. Buttresses: consist of rows of unreinforced earthen columns with a diameter of 1.20 meters treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant)
  1. Left bank: consists of two rows of earthen columns with a diameter of 0.80 meters treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant).  The interior row is not reinforced while the exterior row is reinforced with rods with a diameter of 889 mm, on top of which a header curb measuring 60 x 60 cm will be built.
  1. Right bank: consists of 0.80 meter thick sluice panels, stabilized during excavation with four series of stay rods. 
  1. Spillway bottom plugs: consist of rows of unreinforced earthen columns with a diameter of 1.20 meters treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant).

ICHTHYOFAUNA - FISH LADDER

Perimeter: consists of two rows of earthen columns with a diameter of 0.80 meters treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant).  The interior row is not reinforced while the exterior row is reinforced with rods with a diameter of 889 mm, on top of which a header curb measuring 60 x 60 cm will be built.

Fish ladder bottom plugs: consist of rows of unreinforced earthen columns with a diameter of 1.20 meters treated with bifluid jetgrouting (produced with 32.5 R type II/B-LL from Buzzi Unicem’s Trino Vercellese plant).

Once the special works for the foundation is complete, the construction that will use concrete supplied by UNICAL Spa will begin, including the following:

  1. 1.       Construction of the spillway foundation

The spillway foundation bed will be poured in two phases, the first of which with consistency class S5 concrete and the second with SCC (as shown in the diagram).  The foundation will measure 59.79 meters long with a gross width of 48.80 meters in the sections under the abutments and buttresses.   The net width of the spans between the abutments and buttresses will be 12.80 meters.
RcK30 concrete will be used for the above-ground construction, namely the left and right abutments and buttresses 2 and 3.

Once the above-ground work is complete, a deck will be built to connect the operator’s house with the existing power plant, and house the new metal sluices to regulate the water flow. 

Concrete walls on both the right and left sides will be built to protect the new spillway.  A 170.00 meter long protective stone bank will be built downstream up to the Mazzè highway bridge.

A bank with an escarpment of 66% (3:2), average thickness of 1.80 meters, 6 meters high, and foundation berm measuring 2 meters wide and 1.5 meters deep will also be built.   

The fish ladder will be built at the same time.

  1. Construction of the fish ladder

The fish ladder was the subject of a detailed study done by the Dipartimento di Ingegneria del Territorio, dell’Ambiente e delle Geotecnologie – Settore Ecologia Applicata (Department of Regional, Environmental and Geotechnical Engineering – Applied Ecology Sector) of the Polytechnic University of Turin.  Because the fish ladder is going to be located between the new left abutment of the spillway and the old power station building, a technical fish pass must be built to reduce the size of the passage as much as possible but still remain usable by the fish.  The solution chosen among the many available was the vertical slot, which allows the fish to pass easily and is already widely used in other international projects.  The fish ladder will be built in concrete and stone.  A 170.00 meter long protective stone bank (photo 3) will be built downstream up to the Mazzè highway bridge.     

Bank with an escarpment of 66% (3:2), average thickness of 1.80 meters, 6 meters high, and foundation berm measuring 2 meters wide and 1.5 meters deep 

 

  • Commissioning authority: CAUTENZA CANALI CAVOUR NOVARA – VERCELLI
  • Net amount of work contracted: € 6,364,978.61
  • Health and safety costs: € 112,508.00
  • Net construction amount awarded: € 6,477,486.61
  • Contract addendum: € 8,470,183.00
  • Health and safety costs: € 149,922.24
  • Total construction costs: € 8,620,105.24
  • Planner and planning safety coordinator:  Giorgio Massara, Engineer (Associazione Irrigazione Est Sesia – Novara)
  • Construction manager and construction safety coordinator: Gian Enrico Grieco, Engineer (Associazione Irrigazione Est Sesia – Novara)
  • Site operations manager:  Cristiano Zanellato, Surveyor (Associazione Irrigazione Est Sesia – Novara)
  • General contractor: A.T.I. ITINERA S.p.A. /CO.GE.FA s.p.A.
  • Site engineer: Gianni Gavotti, Engineer
  • Site manager: Riccardo Berrone, Surveyor

VENICE 2020