We are publishing the texts in the press kit distributed at the Press Conference on 18 June 2014.
DEFINITIVE PROJECT FOR THE REHABILITATION OF THE UPPER AREA OF THE DOMUS AUREA
The Soprintendenza has completed the Definitive Project for the rehabilitation of the area above the Domus Aurea. The Project represents a development of the outline set out in the Preliminary Project of March 2011, following the recommendations of the Committees for Archaeological Heritage and Architectural and Landscape Heritage at a joint meeting on 11 April 2011 and entailing various theoretical and practical test phases.
The SSBAR planning team, with the support of external specialists for physical/environmental, hydraulic and bio-botanical aspects has tested the monument’s physical/environmental responses to various technical solutions for a new sustainable park for the conservation of the Domus Aurea that will completely replace the current park.
The first phase of the project will see the complete removal of the current park, archaeological excavations to uncover the ancient surface of the monument and essential consolidation work, the repairing of lesions and filling of gaps.
The Integrated Protection System will be installed on the rehabilitated ancient surface, connecting the underground monument to the ground surface of the new park, lowering the current weight by 70%. The System, less than a metre thick, does not consist of a simple waterproof layer, but combines waterproofing with insulation to maintain higher humidity and thus ensure the vitality of the new park and with a complex drainage system to maintain optimal humidity levels in the underground structures. Finally, it will be possible to intervene beneath the deep layer of waterproofing in the event of variations in humidity. Given its properties, this System will lead to an intrinsic general increase in security and will be controlled by a Monitoring System for sensitive data.
The system will cover an area of about 16,000 m2, subdivided into 22 basins that function autonomously from a hydraulic and structural point of view. This design responds to a variety of needs dictated both by the very large area to be treated, making it necessary to stagger the implementation of the project (the time schedule specifies 7 phases over 4 years) and by the need for compartmentalization to ease management and the identification of any problems that might arise.
The project for the “Domus Aurea Park” on the Oppian Hill confirms the objective of recovering and integrating the perception of the two ancient monuments, the older underground structure (Domus Aurea) with the upper more recent one (Baths of Trajan) by visually underlining the architectural features of the Domus Aurea from the outside.
The need to avoid vertical plant features is compensated for by a careful choice of green and flowering plants arranged in these ample spaces in such a way as to support the reading of the ancient architectural features. As already described in the Preliminary Project, the park – though its management is conditioned by the security of the Integrated Protection System and its Monitoring System – aims to recreate the ancient functions of the vast terrace belonging to Trajan’s bath complex. This was a monumental development of the concept of the “multifunctional” public space, where culture and physical exercise were combined.
Any change in environmental conditions increases entropy and therefore the probability of decay.
Reducing the amount of earth above the structure will necessarily alter the thermal profile.
As the thickness of the material crossed increases, the annual thermal wave becomes attenuated and out of phase with the outside.
Tests and digital simulations have demonstrated that it is possible, from a thermal point of view, to replace part of the earth above the vault of the Domus with a thinner layer of a suitable insulating material. This allows us to create conditions similar to those of ancient times, thus eliminating structural risks and the danger of an increase of surface decay resulting from environmental change.
Decay of Environmental Origin
Chemical and physical environmental decay is linked to the intensity of exchanges between the materials and the surrounding environment. We can identify three types of system.
- Open systems where both exchanges of energy (heat) and matter (vapour, water) can occur
- Closed systems where only exchanges of energy can occur
- Isolated systems where no exchanges can occur
The lower the entity of the exchanges, the more conservative the system
Arianna Monitoring Project
Given the complexity of the intervention entailed by the project and the flexibility of its possible adaptations, a monitoring system is needed to control the various thermo-hygrometric parameters of the Integrated Protection System, capable of recording all events and issuing a warning in time for rapid intervention.
The monitoring system known as Arianna uses various acquisition systems adapted to the various situations and innovative smart sensors appropriately distributed within the Integrated Protection System.
INTEGRATED PROTECTION SYSTEM
The Integrated Protection System comprises the entire package to be installed between the outer surface of the ancient structure, identified by archaeological excavations, and the visible surface that forms the external environment of the Oppian Hill. It thus includes paths, irrigation and drainage systems, monitoring systems and all the facilities needed for visitors to enjoy the area above the Domus Aurea.
The sequence of layers forming the integrated protection system and aimed at contributing to the “improved conservation” of the Domus Aurea was designed bearing in mind the results of the recent experiments by Prof. Sandro Massa and studies and research over the past twenty years.
Future archaeological excavations will highlight specific problems; the solutions designed are therefore easy to adapt to unforeseen situations and have a broad safety margin.
The solution identified entails waterproofing the whole area above the Domus Aurea, about 16,000 m2, dividing it into 22 drainage basins identified on the basis of archaeological, hydraulic and structural criteria. These can be constructed separately and are hydraulically independent of one another; they will therefore become operational immediately when construction has ceased and they have been connected to the existing public sewer system.
The Integrated Protection System recreates the conditions of antiquity, creating a cavity between the outer surface of the vaults and the new waterproof layer. The cavity is filled with insulating material consisting of polystyrene pellets that allow air and water to pass through easily. It also has a communications route with the outside that can be activated voluntarily depending on the specific humidity of the environment and the inside and outside temperature.
This will allow us to control the humidity of the structure, since water or water vapour can be inserted into the cavity.
The aim is to reverse the direction in which humidity circulates. At present, rainwater falls on the ground, seeps into the structure and evaporates towards the inside, causing decay on the internal surfaces of the galleries. With the proposed integrated protection system, the rainwater will be blocked by a waterproof surface. Beneath this, the upper surface of the vaults will be aerated, and evaporation will take place from inside to outside, leaving any salt residues above the vaults rather than on the painted surfaces inside.
This cavity is aerated in a controlled way, allowing us to reduce or increase the exchange of air by closing entry routes or by introducing forced air.
This will allow us to manage the drying of the wall structures at the desired rate, in order to control the outcome.
The package comprises four layers, each of which consists of several materials. The function shared by all the layers is that of thermal insulation, but each layer also has the specific functions described below, from bottom to top.
The first layer forms a zone highly permeable to air (air chamber) whose circulation is regulated by drainage pipes. These may carry air (including treated air) in or out from above; channel water downwards and out if the waterproofing system breaks; and channel water deliberately in from above to increase the humidity of the walls of the ancient structure to maintain a hygrometric equilibrium inside the Domus.
The second layer has a waterproofing function. The impermeable membrane will be protected from shear stress, from concentrated loads above and below, from traction tearing due to deformation of the ground and the “system”, from rodents and roots. A series of geocomposites will thus protect the impermeable membrane and allow for elastic deformation without creating concentrated stresses.
This is the drainage layer for rain and irrigation water. It consists of washed granules of expanded clay contained within polypropylene cells to ensure that they stay compact and do not cause movements that might lead to traction in the impermeable sheath below. The drainage pipes transporting the water towards its final destination run through the expanded clay.
The fourth layer consists of the soil, the pedestrian paths and the little channels for the collection of surface waters. It will be separated from the drainage layer by a non-woven geotextile that will separate, filter, drain and stabilize. The irrigation system and the pipes belonging to the irrigation system and monitoring system will be in this layer.
SUSTAINABLE PARK FOR THE CONSERVATION OF THE DOMUS AUREA IN THE OPPIAN HILL ARCHAEOLOGICAL SITE
The arrangement of the vegetation in the area above the underground monumental complex of the Domus Aurea entails significant modifications to the current park. Unfortunately, its current aesthetic, morphological and functional state clashes with the need to safeguard and rehabilitate the underground monument over which it lies. The new park will not have the strong aesthetic and environmental value created by the presence of large trees; their root systems, the weight of the earth and their biomass cause significant problems for the structures beneath. Instead, the new park will facilitate the reading of the archaeological site that supports and conditions it by signalling it on the surface, thus transforming this limitation into a genius loci.
The ground level of the new park will differ from that of the present due to the removal of earth entailed by the rehabilitation and protection project for the Domus Aurea. Furthermore, the prevalently sandy soil that currently covers the Trajanic terrace and facilitates the seepage of rainwater into the Domus Aurea will be completely replaced by the new soil layer of the integrated protection system. Its composition will contribute to retaining water and increasing evaporation and transpiration rates, helping to regulate the microclimate.
In terms of design, the layout of the park will present outlines and forms that recall the geometrical design of ancient gardens. Its structure is inextricably linked to the water drainage system of which it forms the first layer. The overall surface can be described as flat since the slight changes in altitude are invisible to the naked eye but the careful ‘humpback’ modelling of each zone will help surface waters to drain away; the positioning of drainage channels and drains has been designed in accordance with the form of the 22 drainage basins and the preassembled panels of the technological package.
The routes taken by the terracotta channels on the south side visually recall the location of the Trajanic galleries; this device, at once functional and aesthetic, highlights an important feature of the underground archaeological sites: the different orientation of Nero’s Domus and the Trajanic galleries.
The overground location of the sensors belonging to the monitoring system for humidity and temperature levels that, as already noted, must be kept constant to safeguard the wall decorations of the Domus Aurea, situated both inside the monument and in the technological package, has determined or influenced some design choices in the layout of the park.
Overall, the project is unique, a functional system whose various components guarantee the practicality and efficiency of the structure.
In choosing plants for the park, we took into consideration the development and vigour of their root systems to avoid any interference with the primary objective of safeguarding the monument. We have preferred historically significant species typical of the local area and, last but not least, plants that entail low ordinary maintenance costs.
The overall design, though homogeneous, is subdivided into various areas: lawns, flower gardens, a large paved leisure area, a path to the south-east shaded by a pergola that recreates the line of the ancient portico, placed on the sunniest side of the monument.
The north-western area, where the pilot worksite is located, hosts the garden whose outline and vegetation is based on information about Roman gardens, geometrically subdivided by a central path and straight avenues as shown in pictorial representations or described in ancient texts.
The use of containment elements in sheets of corten steel, light and extremely long lasting, will allow us to prevent any interference from roots below the desired depth and to carry out all the gardening operations needed for the plants to survive in so little earth without any danger of damage or alteration to the technological package beneath.
A pergola will be installed along a stretch of the path running along the front of the south-east side, the sunniest and least exposed to the prevailing winds from north-northeast. This pergola recreates the route of the ancient portico, traces of which emerged during archaeological investigations in around 1970.
An extremely interesting viewing point can be found in the centre of the park, highlighting the area’s archaeological importance and the “hanging” nature of the garden: at park level, an area will be left open allowing visitors to see into the courtyard of room 51 from above, at a height of about 10 m.
What archaeologists refer to as the “pentagonal courtyard” is a room in the Domus Aurea that has never been excavated and is currently occupied by the substructures of Trajan’s baths.
The rooms of the pavilion faced onto this architectural feature; a large leisure area will be created above it, replicating the geometry beneath.
THE PROJECT IN NUMBERS
AREA AFFECTED (ABOVE THE MONUMENT) 16,000 M2
PRELIMINARY ARCHAEOLOGICAL EXCAVATION C. 36,000 M2
22 INDEPENDENTLY FUNCTIONING BASINS
7 WORK PHASES
DURATION OF THE PROJECT: 4 YEARS
TOTAL COST: EURO 31,000,000.00 (INCLUDING 22% VAT)
COST PER M2: C. EURO 2000.00
AVERAGE COST PER FUNCTIONAL ZONE: EURO 4,500,000
ANNUAL FUNDING: EURO 7/ 8,000,000.00