Architecture et réfection des aqueducs d’Orléans/Cenabum (Loiret)

Abstract

During the Early Empire, the secondary settlement of Orléans/Cenabum (France), in the territory of the city of Carnutes, covered an area of about 125 ha. Because of its status as a commercial centre with a river port and a bridge crossing the Loire, the town benefited from public facilities typical of Gaul, including public baths. Since the 19th century, several remains of trench aqueducts have been uncovered to the north and north-east of Orléans. They have made it possible to reconstruct at least three water supply structures.The catchments of these aqueducts are not known. Several springs or water points recorded in the neighbouring villages might have been used from the ancient period, but the lack of knowledge about the upstream route of the structure means that there is no backing for a specific hypothesis. At the downstream end, the data also remain very incomplete. A thermal facility identified near the monumental centre of Orléans/Cenabum in the 19th century or a peri-urban domus in the eastern districts of the town constitute two potential candidates for the outlet of the aqueducts, but did not show how they fitted into the urban fabric.In the second half of the 19th century, local scholars reported the discovery of the remains of an underground aqueduct (aqueduct A) along the present rue du Faubourg Saint-Vincent. The discontinuous observation points show a structure running from north to south towards the town. Since then, this structure has not been observed, which leaves many uncertainties as to its implementation, dating or route.Further east, the area known as “la Fontaine de l’Étuvée” has been known since mediaeval times as the site of a spring. In 1823, test pits led to the discovery of a stele dedicated to the goddess Acionna, from which the presence of a water sanctuary was deduced. Since then, several scheduled and preventative archaeological operations, especially over the last fifty years, have revealed the sanctuary and remains linked to the passage of water. Two trench aqueducts have been discovered. The older one (aqueduct B) winds along the bottom of a north-south oriented talweg, but deviates slightly in order to avoid the sanctuary, whose foundation dates back to the Roman conquest. The second, more recent aqueduct (aqueduct C), initially runs east-west, but has been diverted to the south at the level of a masonry manhole. A long, interrupted trench void of masonry extends towards aqueduct B after the manhole, while the masonry aqueduct C continues southwards. It runs for about 200 m before branching off again to the west. This change in the layout of the structure was made during the construction phase. The empty trench consists of two deep, wide linear excavations separated by a small strip of earth. The 2007 excavation showed that the aqueduct was built in sections of around 60 m in length, separated by a strip of unterraced land around 1.80 m wide. This was used both as a traffic space on either side of the trench and as a demarcation zone between two sections at two different stages of the construction. This space could also have been used for the preparation of a masonry manhole, which was never built. This abandoned route thus offers a unique view of the construction of an aqueduct, the organisation of the construction site and the distribution of the work teams.Aqueducts B and C meet at two quadrangular masonry basins uncovered between the 1970s and 1990s in the Parc de la Fontaine de l’Étuvée. Downstream of these, the trench of aqueduct B and its masonry conduit were identified during development work and diagnostics over a distance of about 400 m. This structure most certainly continued further south but was never found during the various operations in the area between the last section uncovered and the ancient city and its suburbs.Where observation was possible, it revealed that the masonry conduits of the Fontaine de l’Etuvée aqueducts are built in the classical manner. At the bottom of the excavation, the channel is between 0.50 and 0.70 m wide and between 0.75 and 1.30 m high and consists of a footing and two masonry pedestals. This channel is surmounted by a maintenance and circulation space, with a vault of limestone rubble covering the whole. Most of the masonry has suffered considerable deterioration due to the omnipresence of water on the site. The altitude of the water course remains largely unknown, because of the difficulty of reaching the base of the masonry conduit (up to 4 m deep) and the general poor state of preservation of the structures. Five quadrangular masonry manholes were excavated on the different sections. The workings of the complex of two quadrangular basins are still poorly understood, in particular because of the heterogeneity of the field data. Their positioning at the intersection of aqueducts B and C suggests that they were used as settling or expansion basins.Aqueduct B of the Fontaine de l’Étuvée could have been built during the first half of the 2nd century AD, since its installation trench intersects a ditch in the sanctuary. Aqueduct C is later than the first one and could date from the second half of the 2nd century. The chronology of the two basins is poor, but they seem to post-date the construction of aqueduct B.The aqueduct continued to function during Late Antiquity, since a very special arrangement, dated to this period, was found at the foot of a manhole north of the Fontaine de l’Étuvée sanctuary. Above the masonry shaft, timber armouring consisting of three rows of props supporting flights of horizontal planks holds back the surrounding earth, allowing safe access to the bottom of the trench from the surface. The masonry of the manhole uprights in contact with the armouring appears to have been partially rebuilt, which could justify the installation of such an arrangement. The footprint of this timbering could suggest repairs to a section of aqueduct over a length of approximately 6 m. The radiocarbon analyses carried out on certain pieces of wood suggest a date for the felling of the wood during the autumn or winter of 345-346, thus confirming that this section of aqueduct was in use in the middle of the 4th century and that the route of the aqueduct and the location of the surface manholes were known at that time.