Acquedotto del Fiora is the only managing body of the “Integrated Water Service” in 56 communities of the province of Grossetto and Siena of ‘ATO N.6’, which stands for Optimum Territorial Area number 6. The company operates in the largest ATO in Central Italy, carrying out activities such as the collection, transportation and distribution of water for civil use, sewerage services and purification of waste water, as well as the recycling of water for agricultural purposes, and the desalination of sea water.

ATO N.6 covers some 7,144km2 and has a resident population of some 379,000 people, which during the tourist season reaches over an estimated 600,000 people. It has more than 10 million metres of pipes and 1,500 plants to manage. The planned yearly water supply of ATO N.6 is 60 million cubic metres.

Since 1918, the city of Siena’s drinking water has been supplied by the Vivo aqueduct, which is provided by springs located on the mountain slopes of Amiata. The Vivo aqueduct, even today, exclusively supplies the water networks of the communities through 70 km long pipelines.

At the end of the 60s, the growing water demands of the city of Siena obliged the Council to use the aquifer on the Luco plain situated in the bordering territory of Sovicille, full of good quality water. From 1973, 4 wells were built between 60 and 100 metres deep, which allows water to flow at up to 350 litres per second.

From 1974, water was pumped to the Poggio Pigna Tank and from there, by means of gravity, it reached Siena. Since 1980, water has been transported to the new Montarioso Tank, where it is mixed with the water arriving from Mount Amiata and disinfected with a chlorine bioxide generator.

The two sources of provision of the Siena aqueduct have extremely different chemical characteristics. The mixture provides water of a high quality that does not require any treatment before drinking. Possible risks of the aqueduct system lay in the water collection system (springs and wells), treatment plants, pumping stations and the distribution network.

For the Siena Aqueduct, with regards to water collection, it can be stated that :

• The mount Amiata Springs are all adequately protected from external pollution contamination, because of their depth and distance from inhabited areas.
• The Luco Well presents a higher risk factor due to a limited surface impermeable flooding deposit that protects the aquifer. The proximity of the well to a road with a high level of traffic and the relative proximity of the airport make the aquifer vulnerable to possible incidents such as the dumping of polluted products. In order to reduce the threat of the well being affected by surrounding activity, canals were recently built to facilitate the natural evacuation of waters further from the road.

Currently, a serious pollution of the Luco aquifer would render the main source of provision to the Siena community useless for a long period of time. With regards to the distribution network, possible risks are related to tampering of the tanks, each one of which accumulates six thousand cubic metres of water, the equivalent of the daily requirements of approximately twenty thousand people. The tanks are all supplied with fencing, which prevents access to the relevant areas, and robust doors render breaking and entering unlikely.

Theoretically, all consumption points represent points of risk through which contaminated substances could enter the network. However, the presence of no-return valves and the elevated pressure necessary within the network mean that such “criminal” action could only affect a restricted area.

The Siena Aqueduct is equipped with a Remote Telecontrol System which allows the surveillance of many plants and the execution of the necessary regulations and controls at a distance, from the central headquarters or by the available operators. This remote control provides the values of the levels and volumes present in the system in real and continuous time. It also provides information on the working order of the pump and the chlorine bioxide generator, and transmits telephone alarm signals to available personnel within 24 hours to report possible functional abnormalities, breakdowns and the presence of intruders on the plants.

Acquedotto del Fiora is fitted with a modern analysis laboratory that enables the self-execution of many of the analyses required to control the quality of water distributed to the communities. For specific analyses that cannot be self-executed, the company collaborates with qualified analysis laboratories.

For the Siena community, in addition to the checks carried out weekly, periodic checks are carried out on the water quality in various phases of the productive cycle, using a plan that schedules monthly controls of the tanks and distribution system, and biannual controls of the collection system.

The greatest risk for the city of Siena is the fact that some 80% of its water supply is extracted from the vulnerable Luco aquifer, with consequential risks for water drinkability in the event of serious pollution.

To guarantee the continuation of the water supply in accordance with future qualitative and quantitative requirements of Siena and the bordering communities, it is necessary to diversify the provision sources as much as possible.

With this in mind, the “Dorsale sense” project was created, its initial objective being to offer Siena as much water originating from Amiata as possible and thus distribute water mixed with that of Luco. In the second phase, the project aims to introduce water originating from the Mount Doglio dam, situated on the Tevere river, to the Siena Aqueduct system.

The work required covers an area that is 62 kilometres long and will serve a population of some 110,000 inhabitants, distributing an annual volume of over 15 million cubic metres of water provided from current and future sources.

In Siena’s case, the diversification of water supply sources (Mount Amiata Springs, Luco wells plus surface water) is an important factor in overcoming risks connected to the vulnerability of aquifers. Should one of the city’s three water sources be polluted, the two remaining sources will still be able to satisfy the requirements of the city and bordering communities.