Works for the construction of the Seveso flood containment tank

The tank, with the end of November 2023, is operational and can be used in case of emergency.

In the next few weeks, the plantings in the pool area, the final greenery and benches will be completed, as well as the installation of the rafts for the birds to nest in the pool.

This is the first tank entirely built among the four planned for the system to contain the flooding of the Seveso river which floods the Milanese neighborhoods of Niguarda, Pratocentenaro, Ca' Granda, Istria, Zara, Maggiolina and sometimes Isola.

Video | THE SEVESO POOL: how it works

In the event of a meteorological alert, according to the procedures defined between the competent bodies, the pond is emptied in approximately three hours.
If there is a risk of flooding, the lake is then filled with excess water from the Seveso by opening the bulkheads, in a time varying between 3 and 10 hours.
Before entering the tank, the river water is cleaned of branches and other materials thanks to a system of grids. The water will remain in the reservoir for the entire duration of the flood and will then be reintroduced into the river using a system of pumps.
Once emptied of the river water, the tank will be cleaned of the residues of the flood and will be filled again with clean groundwater, constantly moved in order to oxygenate the water, avoid stagnation and the propagation of algae. Emptying, cleaning the tank and reintroducing clean water can take between four and six days, depending on the extent of the phenomenon.

For most of the year the pool is a real lake also suitable for the nesting and resting of water birds, thanks to the positioning of special planted rafts, hospitable to the fauna. There will be green areas around the pond and along the banks.
The pond is adjacent to an expanded forest with new trees.
Cycle-pedestrian paths have been built around it, connected to the northern park and the city.
All accesses to the pond are under video surveillance to ensure the safety of citizens. In the event of floods, an automatic barrier system prevents access to pedestrians and bicycles, giving warning communication via variable message panels.

To learn more, watch the video.
 

News from the construction site - November 2023

All the functional tests necessary to verify the correct functioning of the systems, pumps and bulkheads were carried out in the tank, with the various simulations.
On the occasion of the first meteorological event with significant rainfall, the last test of filling with water from the Seveso river, emptying the basin of river water and cleaning the basin will be carried out. During operations, monitoring and all environmental controls that have been planned will be carried out.

Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023
Seveso tub November 2023

The Milan basin to contain the floods of the Seveso, part of a complex system for managing the floods of the Seveso river, is almost ready.
The excavations and construction of the definitive banks of the pool are almost finished, residual activities remain for the reconstruction of the definitive banks as well as for the access track to the bottom of the pool on the Via Aldo Moro side.
The waterproofing of the bottom of the pool and the banks has been completed to prevent the Seveso mud from remaining in the ground or reaching the aquifer and to facilitate complete cleaning.
The civil works have been completed, such as the regulation structures and the cabin for the electricity supply. The shielding of the electrical substation is nearing completion, using wood and nets to allow the planting of climbing plants.
The gates for regulating the tank have been installed.
The wooden fence along the Seveso stream has been completed.
Work has begun for the installation of underground services along the service tracks located at the top of the banks of the basin as well as the superficial arrangements of the areas on the left bank of the Seveso stream.
The next works include the completion of the banks which, starting from the bottom, have a first concrete part approximately one meter high, permanently immersed in clean groundwater thanks to continuous recycling of the water in the lake. The second part of the banks is covered with stone boulders cemented together, to give a natural effect but to guarantee correct cleaning after each use with water and mud from the Seveso. Finally, the third and last part, towards the walking surface, is covered in greenery. It will be flooded by the waters of the Seveso only during the most significant floods and for a short time, when the basin can contain up to 250.000 cubic meters of water.

Jobs May 2023 - download the video

Seveso tub
tub with Seveso
Seveso tub taken
Seveso bathtub ramps
Complete Seveso tub

The state of play in November 2022
The work carried out in the months of September and October brought the overall state of progress of the works to approximately 79%.
The bottom of the pool has been entirely finished, as has the intake and discharge structure, of which the slide has recently been completed, which will allow the controlled entry of torrential water into the pool basin
the installation of the sliding guides of the additional removable gates (benches) is almost completed, as are all the civil works near the intake structure. In particular, the construction of the Unareti/MM SpA cabin has been completed, already finished with a green roof, and also the installation of the walkway connecting the two banks of the stream
the definitive sides of the pool are being built. In some short stretches, to the north, the cliffs are already finished and even grassed. On the remaining part of the perimeter of the pool, however, work is being carried out relating to the construction of the banks, including the laying of waterproofing sheets, stones to finish the cliffs, preparation of the final geometry of the land, and finally modeling of the cultivation land.
Earthworks are also entering their final phase, currently underway in the portion of the basin near which the access ramp for maintenance vehicles will be built.
the floating rafts have been delivered to the construction site - the installation of which is expected at the end of the works - which will allow the birds to have a safe landing on the artificial body of water.
 

The state of play in February 2022
60% of the work has been completed.
Earthworks to create the volume of the tank are approximately 80%.
The bulk of the reinforced concrete structures for regulating the tank such as the intake structure, the drainage structure, the groundwater intake wells are completed. 
The redevelopment of the banks of the Seveso, excluding planting and finishing works such as fences, is completed. 
Earthmoving work is currently underway, as is the construction of the bottom slab of the tank and the definitive banks with the creation of concrete cliffs.

The rolling tank in July 2021
The preliminary works, excavations for the tank and for the groundwater collection wells have been carried out. The civil works of the tank regulation structure have begun.
The Seveso torrent was reprofiled with the construction of the cliff.
The waterproofing of the bottom of the tank has begun.
Monitoring of all environmental components (noise, atmosphere, water) is being carried out.

Situation as of April 2021
Excavation activities and the removal of material from the construction site continued in the months of March and April. In the last week of April the bottom of the excavation was reached on the west side of the basin.
The construction of the groundwater collection wells and the works for the construction of the tank regulation structure continued.
The reprofiling works of the Seveso torrent have begun with the construction of the cliff.
In April, monitoring of the avifauna present within the construction site areas began in order to analyze the impact of the felling of trees and the presence of the construction site on it. At the same time as the monitoring, the installation of the 15 birdhouses was carried out. Intervention that plays an important role for the partial compensation of tall trees cut in the woodland.

Footnotes
Between the end of February and the beginning of March 2021, thanks to the collaboration between Parco Nord, MM SpA and the Contractor, a campaign was organized to collect herbs of naturalistic value (scilla bifoglia) present on the construction site along the banks of the Seveso. 
The campaign had a positive outcome, managing to collect and preserve almost all of the double-leaved squills present in the area. 
All recovered materials (earth and rocks) were disposed of according to the project, in compliance with the excavated earth and rock management plan presented by the Contractor and approved by the competent bodies. 
Excavation activities require the movement of trucks to transport the earth to the locations identified and authorized by the Lombardy Region. All trucks move covered with tarpaulins, except during loading operations, before leaving the construction site they pass through an automatic tire washing system, they exit and enter exclusively from via Aldo Moro in the Municipality of Milan, on the two-lane road in each direction of march. A vehicle is in service on the construction site that constantly wets the tracks traveled by the trucks to reduce the dispersion of dust, a system that will be integrated in the coming weeks with an automatic track irrigation system.
The overall plan to combat the Seveso floods continues with the simultaneous activation of 6 construction sites currently in operation, after the start of work on 18 March on two other construction sites: 

  • the redevelopment by MM of the Redefossi in the stretch along the Cerchia dei Bastioni, an underground route where the waters of the Seveso flow under a part of the city of Milan
  • the redevelopment by MM of the stretch of the Martesana under via Melchiorre Gioia where the waters of the Seveso flow under a part of the city of Milan
  • the construction of the Senago tank by AIPO
  • the construction of the Lentate sul Seveso tank by AIPO
  • the creation by AIPO of the floodplain areas north of Lentate sul Seveso to accommodate the waters of the Seveso during floods.

Finally, the project coordinated by the Lombardy Region and carried out with the 3 water service managers of the Provinces of Como and Monza and the Metropolitan City of Milan began, for the census and control of all discharges on the Seveso river through the use of drones.

In the month of February 2021 excavation activities continued in the lamination area and drilling activities began on the groundwater collection wells that will feed the permanent lake.
In the central week of the month, the last felling of some trees present along the banks of the Seveso stream was carried out, a necessary intervention as the trees had a critical position in the Seveso riverbed and were incompatible with the arrangement of the banks, so the work continued of excavating the tank.

In the early days of January 2021 the left bank of the Seveso torrent has been consolidated where the structure for regulating the pool will be built, work on which began at the end of January.
Also in January, the temporary diversion of the Seveso torrent was activated, along which a temporary bridge was built for construction site traffic.

At the beginning November 2020 the first compensation areas for approximately 48.000 m44 have been assigned to the North Park, equal to approximately XNUMX% of the total areas that will be assigned to the park as per the project. The Park has begun redevelopment and planting interventions through new wooded areas, rows, meadows and paths accessible in these new areas which have become an integral part of the North Park.
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  1. Construction of a boundary wall on the left bank of the Seveso stream.
  2. Scotico of the Northern area. 
  3. Transfer of stumps to landfill.
  4. Driving of sheet piles for the temporary diversion of the Seveso torrent.
  5. Arrangement of the exit for construction site vehicles along Via Aldo Moro.
  6. The noise barrier has been installed near the Aler condominium in the municipality of Bresso, on the left bank of the Seveso stream.
  7. Installation surface and abutments of the bridge in correspondence with the temporary deviation of the riverbed.
  8. Transfer of excavated soil to landfill as planned.

Work carried out in October 2020

  • Completion of War Ordnance Clearance in the area and obtaining the relevant certificate from the Military Engineers
  • execution of the 14 exploratory excavations requested by the Superintendency of Archaeology, Fine Arts and Landscape with the assistance of a technician specialized in archaeological excavations
  • felling of trees on the left bank of the Seveso stream, up to the area of ​​the former Judicial Depository and on the right bank, up to the pedestrian bridge
  • boundary wall on the left bank of the Seveso, in the municipality of Bresso, in the areas of the Civil Protection, 2 Gas Networks and the former Judicial Depot
  • supplementary surveys requested in the decree of via n. 4186 of 12.05.2016 in the three wooded areas where it was not possible to carry them out in the design phase
  • the removal of a surface layer of soil has begun.

Project and description of works

For almost the entire year the pool is a recreational place, with cycle and pedestrian paths at different heights, spaces equipped for rest and green areas.

Only in cases of exceptional rainfall and flooding, on average 6 times a year, the basin fills with river water which, before entering the artificial basin, is cleaned of branches and other materials thanks to a system of grates.

The water remains in the basin for the duration of the flood and is then released back into the Seveso, the basin is cleaned and filled with clean water, to return to being a lake.

This process lasts two to five days. For the safety of citizens, all accesses are under video surveillance; furthermore, during floods, a system of automatic barriers prevents access to pedestrians and bicycles, giving warning communication via variable message panels.

This tank is part of a system designed to prevent the floods of the Seveso from damaging inhabited centers and neighborhoods, causing risks to people and extensive material damage.

The containment project includes:

  • the adaptation of the floodplain areas (areas where the stream naturally flows out when it floods) of Cantù, Carimate and Vertemate with Minoprio
  • tub 1 - Slow down
  • pool 2 - Paderno Dugnano
  • pool 3 - Senago
  • tub 4 - Milan.

The filling of the tanks will take place in relation to the trend of meteorological phenomena and the consequent creation of flood waves.

Tank 4 - Milan is close to the entrance to the Seveso river burial. It is used to contain the floods that form south of the North West Scolmatore Canal and prevents water from escaping from the manholes, flooding the neighborhoods of Niguarda, Pratocentenaro, Ca' Granda, Istria, Zara, Maggiolina and Isola.

The planning of the construction works of the lamination tank was carried out following the monitoring and census of the presence of bird species in the affected area.

The use of multiple survey methodologies, the evaluation of the methods of carrying out cuts in the forest and the identification of the reproductive season and the progress of the nesting season have made it possible to direct the carrying out of the works with respect for the local avifauna.

Furthermore, the document suggests ways of safeguarding and protecting trees not subject to cutting: all aimed at promoting a more rapid repopulation of birds in the area affected by the intervention.

The details of Ornithological report they can be consulted among Attachments of this page.

Further clarifications on the intervention and its implementation methods can be found in the FAQ, which can also be consulted among Attachments of this page.

The Parco Nord Milano acquires 109.000 square meters of new surface area (almost 11 hectares) which in the coming months will be covered by wooded areas, rows, meadows and usable paths to compensate for an area on the border with the Municipality of Bresso intended for the construction of the containment tank for the floods of the Seveso, necessary to secure the inhabited areas systematically damaged by the flooding of the stream.

The green area that the North Park acquires in compensation is approximately three times larger than the area in which the pool will be built.

The new areas that become part of the Park's heritage are located in the Municipalities of Bresso and Cormano (ex-Item area, Ca' Granda Foundation area and Alfonso Pini Foundation area) are spaces that are now partly disused and concreted over, on which Parco Nord Milano will intervene with redevelopment projects, increasing the natural capital according to the naturalistic criteria that have always characterized the Park's projects.

Among these there are also areas that are currently cemented and therefore waterproof which will be transformed into green and permeable areas, contributing to increasing the infiltration of water into the soil and therefore limiting the flow of rainwater in the Seveso basin. Particular attention will be paid to redeveloping part of the riverbed and banks of the Seveso to make them safe from erosive phenomena which affect their stability especially during flood phenomena.

Up to 2.500 plants per hectare will be planted in the planned wooded areas, including native trees and shrubs, to further reinvigorate the green lung of Milan. Green surfaces in fact bring benefits to the territory effectively when they arise in highly urbanized contexts such as the city of Milan, both in terms of air quality, thanks to the absorption of carbon dioxide, and mitigation of the urban heat island, helping to reduce summer temperatures in the surrounding areas and counteracting the effects of climate change in the city.

Cleaning and planting in some of the areas delivered to Parco Nord Milano in compensation for the hydraulic work for the Seveso torrent 

In the summer months of 2020, the procedures for the acquisition and delivery of the first compensation areas of the hydraulic work for the Seveso torrent to the Parco Nord Milano were carried out. In the acquired areas - approximately 11 hectares in total, redevelopment and planting interventions have begun through new wooded areas, rows, meadows and usable paths.

In particular, in the area of ​​approximately 4,8 hectares of the former "Alfonso Pini Foundation", the Park has started with the cleaning, arrangement and preparation of the land for the planting of new trees and shrubs. In fact, in recent weeks, both the lake and the canal to the north of the area have been cleaned, the rows already present have been pruned and the seedlings have been sown to create a new flowering meadow to the south of the area which for 200 meters The Apistrada dei Fiori, already present in the Park, will continue in length towards the velodrome.

The redevelopment project of the area also involves the creation of a meadow of approximately 3 hectares open to use through pedestrian paths, cycle paths and bodies of water to accommodate the green toad - a protected species widely spread in the Park - and will host a "decorative snail ” made up of around fifty tall trees including limes and hackberries.

Over one hectare of surface area will also be forested, the Park has already begun the planting of around three thousand native forest plants such as English oaks, white hornbeams, maples, ash trees, cherry trees, alders, poplars, apple trees, pears and among the shrubby plants the hazelnut, the rose, the hawthorn, the dogwood, the blackthorn and the dogwood.

For information write to: Comunicazione@mmspa.eu

Updated: 01/12/2023