Roman Aqueducts


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Roman Aqueducts

  1. 1. The Roman Aqueducts An Engineering Wondersabato 2 febbraio 13
  2. 2. What have the Romans ever done for us? Monty Python Life of Brian, 1979 2 febbraio 13
  3. 3. Before the Romans Rome and Water How the Romans Built Aqueducts Lessons Learned Appendixsabato 2 febbraio 13
  4. 4. Water is essential to Life and the Development of Civilization Drinking Agricolture Sanitation Transportation Energysabato 2 febbraio 13
  5. 5. The First Civilizations appeared near abundant, easily accessible Water Supplies Ancient Egypt (The Nile) Mesopotamia (Tigris & Eufrates) India (Indus)sabato 2 febbraio 13
  6. 6. Water needs to be managed Control Inundations Distribute Fresh Water Collect waste waters Aqueduct in Segovia (Spain) Nilometer Cloaca Maximasabato 2 febbraio 13
  7. 7. Fresh water supply is essential especially in dry regions. Other civilizations built water transportation systems, before the Romans A qanat (Arabic ) or kareez (Persian) is a water management system used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates. The qanat technology was used most extensively in areas with the following characteristics: Water Table An absence of larger rivers with year-round flow sufficient to support irrigation. Proximity of potentially fertile areas to precipitation-rich mountains or mountain ranges. Arid climate with its high surface evaporation rates so that surface reservoirs and canals would result in high losses An aquifer at the potentially fertile area which is too deep for convenient use of simple wells.sabato 2 febbraio 13
  8. 8. The Qanat taps underground water and transports it using gravity. The underground course avoids loss by evaporation The investment and organization required by the construction and the maintenance of a qanat is typically provided by local merchants or landowners in small groups. The qanat system has the advantage of being relatively immune to natural disasters (earthquakes, floods…) and human destruction in war. Further it is relatively insensitive to the levels of precipitation; a qanat typically delivers a relatively constant flow with only gradual variations from wet to dry years. A typical town has more than one qanat. Fields and gardens are located both over the qanats a short distance before they emerge from the ground and after the surface outlet. Water from the qanats defines both the social regions in the city and the layout of the city. The water is freshest, cleanest, and coolest in the upper reaches and more prosperous people live at the outlet or immediately upstream of the outlet. When the qanat is still below grade, the water is drawn to the surface via Ater-wells or animal driven Persian wells. The lower reaches of the canals are less desirable for both residences and agriculture. The water grows progressively more polluted as it passes downstream. In dry years the lower reaches are the most likely to see substantial reductions in flow.sabato 2 febbraio 13
  9. 9. The construction method of the qanat is similar to that of the aqueduct Construction of a qanat is usually performed by a crew of 3-4 muqannis. For a shallow qanat, one worker typically digs the horizontal shaft, one raises the excavated earth from the shaft and one distributes the excavated earth at the top. The excavated material is usually transported by means of leather bags up the vertical shafts. It is mounded around the vertical shaft exit, providing a barrier that prevents windblown or rain driven debris from entering the shafts. From the air, these shafts look like a string of bomb craters. Traditionally qanats are built by a group of skilled laborers, muqannis, with hand labor. The profession historically paid well and was typically handed down from father to son. The critical, initial step in qanat construction is identification of an appropriate water source. The muqannis follow the track of the main water courses coming from the mountains or foothills to identify evidence of subsurface water such as deep-rooted vegetation or seasonal seeps.sabato 2 febbraio 13
  10. 10. Key facts Vertical shafts are excavated along the route, separated at a distance of 20-35 m. In general, the shallower the qanat, the closer the vertical shafts. Most qanats in Iran run less than 5 km. The overall length of the qanat often runs up to 16 km, while some have been measured at ~70 km in length near Kerman. The vertical shafts usually range from 20 to 200 meters in depth, although in Iran qanats in the province of Khorasan have been recorded with vertical shafts of up to 275 m. The vertical shafts support construction and maintenance of the underground channel as well as air interchange. Deep shafts require intermediate platforms to simplify the process of removing spoils. The qanats water-carrying channel is 50-100 cm wide and 90-150 cm high. The channel must have a sufficient downward slope that water flows easily. In shorter qanats the downward gradient varies between 1:1000 and 1:1500, while in longer qanats it may be almost horizontal. Such precision is routinely obtained with a spirit level and string. The construction speed depends on the depth. At 20 meters depth, a crew of 4 people can excavate a horizontal length of 40 meters per day. When the vertical shaft reaches 40 meters, they can only excavate 20 meters horizontally per day and at 60 meters in depth this drops below 5 horizontal meters per day. Deep, long qanats (which many are) require years and even decades to construct.sabato 2 febbraio 13
  11. 11. Qanats are also used in clever air conditioning systems called “Wind Catchers” First, a windcatcher is capped and has several directional ports at the top (T raditionally four). By closing all but the one facing away from the incoming wind, air is drawn upwards using the Coanda effect, similar to how opening the one facing the wind would push air down the shaft. The key to generating frigid temperatures seems to be that there are very few cracks at the base of the thick structure below, but there is a significant air gap above the qanat. The qanat below aggregates the cold, sinking air of the night, which is then trapped within, unable to rise up to the less dense surface air. A windcatcher can create a pressure gradient which sucks at least a small amount of air upwards through a house. This cool, dry night air, being pulled over a long passage of water, evaporates some of it and is cooled down further. When coupled with thick adobe that exhibits high heat transmission resistance qualities, the windcatcher is able to chill lower level spaces in mosques and houses (e.g. shabestan) in the middle of the day to frigid temperatures. So effective has been the windcatcher in Persian architecture that it has been routinely used as a refrigerating device (yakhchal) for ages. Many traditional water reservoirs (ab anbars) are built with windcatchers that are capable of storing water and even ice collected during the winter at near freezing temperatures for months in summer. High humidity environments destroy the evaporative cooling effect enjoyed in the dry conditions seen on the Iranian plateau;sabato 2 febbraio 13
  12. 12. The technology is known to have developed in ancient Persia, and then spread to other cultures, especially after the Muslim conquests, to the Iberian peninsula, southern Italy and North Africa Written records leave little doubt that ancient Iran (Persia) was the birthplace of the qanat. As early as the 7th century BC, the Assyrian king Sargon II reported that during a campaign in Persia he had found an underground system for tapping water. His son, King Sennacherib, applied the "secret" of using underground conduits in building an irrigation system around Nineveh. During the period 550-331 BC, when Persian rule extended from the Indus to the Nile, qanat technology spread throughout the empire. The Achaemenid rulers provided a major incentive for qanat builders and their heirs by allowing them to retain profits from newly-constructed qanats for five generations. During Roman-Byzantine era (64 BC to 660 AD), many qanats were constructed in Syria and Jordan. From here, the technology appears have to diffused north and west into Europe.sabato 2 febbraio 13
  13. 13. Palermo, in Sicily, is the home of qanats built during the arab domination In the early ages (Punic and Roman times) wter supply came from wells and natural springs just outside the city In the IXth century the growth of the city as a capital under arab rule sharply increased water needs for private and public use (hammam) Arabs resolved the problem importing and adapting the qanats technology. In Palermo there no single supply well tapping into the water bed but a “drainage gallery” were water seeps up to be gently conveyed downhill, with a less than 0,5% incline There were two types of wells along the course: those used to excavate the qanat and for maintenance, and others, larger, used to lift up the water using “persian wheels”, sometimes driven by animals. In coincidence of these wells the bottom of the qanat formed a “pool”. Arabs introduced also the “wind-catcher” technology, applied in various “Camere dello Scirocco” Borgata Villagrazia Qanat dell’Uscibene- Altarello “Scirocco’s Room Villa Naselli, Galleria della Sorgente di Baida (Palermo) Villa Savagnone - Altarello di Baida (PA)sabato 2 febbraio 13
  14. 14. Although famously associated with the Romans, aqueducts were devised much earlier in the Near East and Indian subcontinent, where peoples such as the Egyptians built sophisticated irrigation systems. Roman-style aqueducts were used as early as the 7th century BC, when the Assyrians built a limestone aqueduct 30 feet (10 m) high and 900 feet (300 m) long to carry water across a valley to their capital city, Nineveh. The full length of the aqueduct ran for 50 miles (80 km).In the new world, when the Aztec capital of Tenochtitlán was discovered in the middle of the second millennium, it was watered by two aqueducts. India:The Indian subcontinent witnessed the construction of some of the earliest aqueducts. Prominent evidence can be found at the sites of present day Hampi. The massive aqueducts near river Tungabhadra supplying irrigation water were once 15 miles (24 km) long[2]. The elegant water ways were designed to supply water to royal bath houses The Phoenicians are the most important among pre-classical Hampi, India engineers. In Cyprus water was supplied to temples by rock-cut subterranean conduits carried across intervening valleys in siphons. Such conduits have been found near Citium, Amathus,sabato 2 febbraio 13
  15. 15. The numerous conduits which have supplied Jerusalem probably go back to the times of the kings of Judah The principal reservoir consists of the three Pools of Solomon which supplied the old aqueduct. These pools collected the water from Ain Saleh and other springs, and sent it to the city by two conduits. The higher of these--probably the older--was partly a rock-cut canal, partly carried on masonry; the siphon-pipe system was adopted across the lower ground near Rachels T omb, where the pipe (15 in. wide) is formed of large pierced stones embedded in rubble masonry. The lower conduit is still complete; it winds so much as to be altogether some 20 miles long. Near the Birket-es-Sultan it passes over the valley of Hinnom on nine low arches and reaches the city on the hill above the Tyropeon valley. In the case of the underground tunnel which brought water from the Virgins Fountain to the pool of Siloam, the two boring parties had no certain means of keeping the line; there is evidence that they had to make shafts to discover their position, and that ultimately the parties almost passed one another. Though the direct distance is 1100 ft., the length of the conduit is over 1700 ft. Besides these conduits excavation has discovered traces of many other cisterns, tunnels and conduits of various kinds. Many of them point to periods of great prosperity and engineering enterprise which gave to the city a water-supply far superior to that which exists at present.sabato 2 febbraio 13
  16. 16. The earliest attempts in Europe to solve the problems of water-supply were made by the Greeks, who perhaps derived their ideas from the Phoenicians Among the earliest examples of Greek work are the tunnels or emissaria which drained Lake Copais in Boeotia; these, though not strictly aqueducts, were undoubtedly the precursors of such works, consisting as they did of subterranean tunnels (ὑπονομοι) with vertical shafts (φρεατιαι), sixteen of which are still recognizable, the deepest being about 150 ft. The insufficiency of water, supplied by natural springs and cisterns hewn in the rock, which in an early age had satisfied the small communities of Greece, had become a pressing public question by the time of the Tyrants, Polycrates of Samos obtained the services of Eupalinus, an engineer celebrated for the skill with which he had carried out the works for the water-supply of Megara (c. 625 B.C.). At Samos the difficulty lay in a hill which rose between the town and the water source. Through this hill Eupalinus cut a tunnel 8 ft. broad, 8 ft. high and 4200 ft. long, building within the tunnel a channel 3 ft. broad and 11 ells deep. The water, flowing by an accurately reckoned declivity, and all along open to the fresh air, was received at the lower end by a conduit of masonry, and so led into the town, where it supplied fountains, pipes, baths, cloacae, &c., and ultimately passed into the harbour (Herod, iii. 60).sabato 2 febbraio 13
  17. 17. Before the Romans Rome and Water How the Romans Built Aqueducts Lessons Learned Appendixsabato 2 febbraio 13
  18. 18. Break Down of Water Allocation in Augustus’ Rome Lacus: Public Basins Munera (Display Fountain and Water games) Private; 32%  Public; 53%  Opera Publica: Construction and maintenance of public buildings including Ceasars; 15%  Termae Camps Public: Castra, Opera publica, munera, Lacus For General public use, included water made available in public basins for domestic use of “insulae” dwellings Private: Carried into private properties, usually rich/noble people Villae or Domus In nomine Caesaris: it is not clear on what principles water was distributed in nomine Caesaris – does this refer to distribution to the emperor’s properties (and those of the imperial family), or to other public or military destinations, or also to private individuals to whom the emperor had granted privileges? Source: Frontinus, De Aquaeductu Urbis Romaesabato 2 febbraio 13
  19. 19. It is Frontinus who gives us an idea of how water was used in Rome Uncertainties: Definition of Castra and Castellum What is included in Ceasar’s Namesabato 2 febbraio 13
  20. 20. ATotal of 11 Aqueducts were built to serve the Capital City of Romesabato 2 febbraio 13
  21. 21. Organizing the data on a scatter chart reveals a pattern... 100  90  Trajana Elevation arriving in Rome 80  Claudia 70  T Julia epula Anio Novus 60  Marcia Anio Vetus 50  Alexandrina 40  30  Virgo 20  Alsietina Appia 10  0  ‐400  300 b.c. ‐200  100 b.c. ‐300  ‐100  0  100 a.d. 100  200  300 a.d. 300 sabato 2 febbraio 13
  22. 22. With some exception, each new aqueduct arrived in Rome at a higher elevation 100  90  Trajana Elevation arriving in Rome 80  Claudia 70  T Julia epula Anio Novus 60  Marcia Anio Vetus 50  Alexandrina 40  30  Virgo 20  Alsietina Appia 10  0  ‐400  300 b.c. ‐200  100 b.c. ‐300  ‐100  0  100 a.d. 100  200  300 a.d. 300 sabato 2 febbraio 13
  23. 23. This “correlation” is even stronger not condidering the two “outliers” 90 80 Elevation arriving in Rome 70 60 50 40 30 20 Virgo Alsietina 10 0 ‐400  300 b.c. ‐300  ‐200  100 ‐100  b.c. 0  100 a.d. 100  300 a.d. 200  300 sabato 2 febbraio 13
  24. 24. Aqua Appia, the first aqueduct built in 312 b.c., originally served the entire city. It was followed over the next three centuries by the Anio Vetus, the Aqua Marcia, Tepula, Julia, and Virgo As a result of this increase in availability, it was no longer necessary for the Aqua Appia to supply all districts with water in the Augustan age. Frontinus provides us with a list of the wards served by each aqueduct, and it seems likely that the Appia’s distribution was refocused to serve the areas closest to its distribution point, particularly the Aventine and the Circus Maximussabato 2 febbraio 13
  25. 25. Six aqueducts provided water to districts inside the city in the last years of Augustus’ reign Quinaria: Unit of measure for water flow: 1 Quinaria=0,48 liter/sec 1 Quinaria=41,5 MQ/day Source: C. Di Fenizio, Sulla portata degli antichi acquedotti romani e determinazione della quinaria, Roma, 1916sabato 2 febbraio 13
  26. 26. Growth in Water Availability mirrored growth in population 1.600.000 Water Supply (Cubic Meters/day) 1.400.000 1500000  1.200.000 950000  1.000.000 800.000 600.000 400.000 Population 200.000 187000  30.000 0 312 b.c. 269 b.c. 140 b.c. 125 b.c. 33 b.c. 19 b.c. 2 a.d. 52 a.d. 109 a.d. 226 a.d. Appia Anio Vetus Marcia Tepula Julia Virgo Alsientina Claudia + Anio Novus Traiana Alexandrinasabato 2 febbraio 13
  27. 27. The availability of water was abundant even for today’s standards 600,0 500,0 Cubic Meters/Year 400,0 300,0 200,0 100,0 ,0 RepublicAugustus Imperial Milan Rome Torino Per Capita Per Capita Availability Domestic Consumption Ancient Rome Contemporarysabato 2 febbraio 13
  28. 28. Aqueducts were often “celebrated” in coins The sestertius reading IMP CAES NERVAE TRAIANO AVG GER DAC P M TR P COS V PP in capitals representing the bust of emperor Traian (98 - 117 AD) looking to the right. During his reign both the aqueduct Aqua Traiana and the Baths of Traian were put into use. The text on the reverse reads SPQR OPTIMO PRINCIPI AQVA TRAIANA S C with an image that can be interpreted in different ways: the genius of the aqueduct, an image of the castellum aquae (the water Trajana distribution station) at the end of this Roman aqueduct, or a collection of general elements of the water supply of Rome. It was 60 years later - about 56 bc - that moneyer L. Marcius Philippus honored Q. Marcius Rex with a coin bearing the image of his aqueduct, the Aqua Marcia. The reverse side shows an equestrian statue based on five arches reaching to the rim and the name of the moneyer PHILIPPVS. Within the arches one reads AQVA MR (Aqua Marcia). One assumes that here the builder Q Marcius Rex is Marcia represented together with the aqueduct which is named after him. Note that the moneyer also belongs to the Marcia family. This nymphaeum is an ornamental fountain including a castellum (water distribution station) which was fed by a branch of the Aqua Julia aqueduct It is the only remaining example in Rome of a class of fountains which is called munera by Frontinus because of its double function (ornamental fountain and water distribution station). The coins may have been mint when the Aqua Alexandrina was put into use.sabato 2 febbraio 13
  29. 29. Before the Romans Rome and Water How the Romans Built Aqueducts Lessons Learned Appendixsabato 2 febbraio 13
  30. 30. Arches are the first things that comes to mind when thinking about aqueducts... Pont du Gard, near Nimes in France Aqua Appiasabato 2 febbraio 13
  31. 31. ...but most of the lenght of an aqueduct ran underground Lenght (Km) Anio Novus  Aqua Claudia  Aqua Alsie?na  Aqua Virgo  Aqua Julia  Aqua Tepula  Aqua Marcia  Anio Vetus  Aqua Appia  0  10  20  30  40  50  60  70  80  90  100  Nimes Aqueduct. Total Lenght Specus height 170 cm Aqua Marcia Underground Lenght in Vicovaro, near Romesabato 2 febbraio 13
  32. 32. Most Aqueducts had certain key components Construction & Inspection Wells Castle Inverted Piscina (Water Source Basement Syphon Specus Arches Limaria Tower) Fistule Watch Out! This design is an oversymplified example 1) Underground section covers 90/95% of total lenght 2) Arches are more common near the city than upstreamsabato 2 febbraio 13
  33. 33. In Roman aqueducts water moved mostly by gravity. In modern conduits it moves only by pressure Note: Pressurized inverted syphons were used only occasionally, to bridge minor gaps. Technology did not allow for high pressuressabato 2 febbraio 13
  34. 34. Organization of Building aqueducts Considering the amount of surveying, underground building, and bricklaying involved, a construction of this size could not be built all at once. Instead, the engineers divided the entire construction site into individual building areas. Through archaeological research, the boundaries of these building areas have been determined. It has further been demonstrated that the surveying took place separately from the building, as is in fact the rule today in large construction projects. Finding the spring Deciding the Route Getting the water Digging the Tunnels The Inverted Syphon The Viaducts The settling Basin The Castellum Domestic Usesabato 2 febbraio 13
  35. 35. Finding Water -springs -observing vapours rising at sunrise -nature of the place (clay,, black earth, gravel, red sands, red stone) - presence of certain vegetation (bulrush, the wild willow, the alder, the withy, reeds, ivy, and other plants of a similar sort, which neither spring up nor flourish without moisture)sabato 2 febbraio 13
  36. 36. Finding Water - Vitruvius Advice Marcus Vitruvius Pollio, a Roman architect and engineer, in the first century B.C. wrote his influential treatise entitled The T Books on Architecture, Vitruvius provided specific instructions on finding and selecting en springs to provide houses with water: This will be easily accomplished if the springs are open and flowing above ground. If that be not the case, their sources under ground are to be traced and examined. In order to discover these, before sunrise one must lie down prostrate in the spot where he seeks to find it, and with his chin placed on the ground and fixed, look around the place; for the chin being fixed, the eye cannot range upwards farther than it ought, and is confined to the level of the place. Then, where the vapours are seen curling together and rising into the air, there dig, because these appearances are not discovered in dry places. We should also consider the nature of the place when we search for water. In clay, the vein of water is small, the supply little, and not of the best flavour; and if in low places, it will be muddy and ill tasted. In black earth, only tricklings and small drops are found, which, collected from the winter rain, subside in compact hard places, and are of very excellent flavour. In gravel, the veins are small and variable, but they are exceeding well flavoured. In the strong, common and red sands, the supply is to be depended on with more certainty, and is of good taste. In red stone, abundance and that of good quality may be obtained, if it do not filter away and escape through the pores. At the feet of mountains, and about flinty rocks the supply is copious and abundant; it is there cold and more wholesome. In champaign countries, the springs are salt, gross, tepid, and unpleasant, except those, which percolating from the mountains beneath the surface, issue forth in the plains, where, especially when shadowed by trees, they are as delicious as those of the mountains themselves. 3. Besides the above signs for ascertaining in what places water may be found, are the following: when a place abounds with the slender bulrush, the wild willow, the alder, the withy, reeds, ivy, and other plants of a similar sort, which neither spring up nor flourish without moisture. For these plants usually grow about lakes, which, being lower than the other parts of a country, receive both the rain water and that of the district, through the winter, and, from their size, preserve the moisture for a longer period. On these, however, we must not rely. But in those districts and lands, no lakes being near, where the plants in question grow spontaneously, there we may search.sabato 2 febbraio 13
  37. 37. Choosing the Spring - Vitruvius Advice Springs should be tested and proved in advance in the following Expertiones autem et probationes eorum sic sunt providendae. si ways. If they run free and open, inspect and observe the erunt profluentes et aperti, antequam duci incipiantur, physique of the people who dwell in the vicinity before aspiciantur animoque advertantur qua membratura sint qui beginning to conduct the water, and if their frames are circa eos fontes habitant homines, et si erunt corporibus strong, their complexion fresh, legs sound, and eyes clear, valentibus coloribus nitidis, cruribus non vitiosis, non lippis the spring deserves complete approval. oculis, erunt probatissimi. item si fons novus fossus fuerit et in vas corinthium sive alterius generis quod erit ex aere bono ea If it is a spring just dug out, its water is excellent if it can be aqua sparsa maculam non fecerit, optima est. itemque in sprinkled into a Corinthian vase or into any other sort made aeneo si ea aqua defervefacta et postea requieta et defusa of good bronze without leaving a spot on it. Again, if such fuerit neque in eius aenei fundo harena aut limus invenietur, ea water is boiled in a bronze cauldron, afterwards left for a aqua erit item probata. time, and then poured off without sand or mud being found 2. item si legumina in vas cum ea aqua coniecta ad ignem posita at the bottom of the cauldron, that water also will have celeriter percocta fuerint, indicabunt aquam esse bonam et proved its excellence. salubrem. non minus etiam ipsa aqua quae erit in fonte si fuerit limpida et perlucida, quoque pervenerit aut profluxerit muscus And if green vegetables cook quickly when put into a vessel of non nascetur neque iuncus, neque inquinatus ab aliquo such water and set over a fire, it will be proof that the water is inquinamento is locus fuerit sed puram habuerit speciem, good and wholesome. Likewise if the water in the spring is innuitur his signis esse tenuis et in summa salubritate. itself limped and clear, if there is no growth of moss or reeds where it spreads and flows, and if its bed is not polluted by filth of any sort but has a clean appearance, these signs indicate that the water is light and wholesome in the highest degree.1sabato 2 febbraio 13
  38. 38. There are many ways to get (ground)water into an aqueduct. Springs were the commonest source for roman aqueducts. River intakes were used occasionally. Spring boxes and Well intakes Collect water in a rectangular chamber; the water was supplied through numerous splits or specially created, sometimes arched, openings. A single outlet discharges the water into the aqueduct conduit. Infiltration galleries Infiltration galleries were sections of aqueduct gallery, 20 - 100 m long which ran along a hill side to intercept the flow of water that trickled out of the splits in the wall into the gallery. At one side the water was collected into a settling basin to get rid of the debris and sediments: the start of the aqueduct. River intakes A river as a source for an aqueduct was not very popular in Roman times Dams Artificial created lakes as a source were rare although they could have been used to equilize the variations in the seasonal flow rates of the feeding spring(s)sabato 2 febbraio 13
  39. 39. While different in shape, spring boxes shared the purpose of protecting the water source Bingen (Germany) Kalmuth, Cologne (Germany) Emmaus / Nicopolis (Israel) Spring Boxes often included a settling basinsabato 2 febbraio 13
  40. 40. Infiltration Galleries could be built into a web of tunnels for better yield Different types of infiltration Grune Putz, Germany Sens (France) areas in one system, Gigen (infiltration galleryand (Bulgaria settling basin)sabato 2 febbraio 13
  41. 41. River intakes led usually to poor quality of water, dependent on meteo conditions. The Anio Vetus waters muddied each time it rained Alcabideque, start of the Conimbriga aqueduct (Portugal)sabato 2 febbraio 13
  42. 42. Dams were sometimes built to improve water quality (acting as settling basin) and to stabilize the seasonal water flow Emperor Nero (AD 54-68) had a 40 m high, 13.5 m wide, and 80 m long dam built for a pleasure lake near his villa at Subiaco, Italy. The dam was one of the earliest Roman dams and remained the highest the Romans ever built. Moreover, the Subiaco dam and two smaller dams nearby are the only Roman dams in Italy. Although the dam was too thin, it remained intact until it failed in 1305. Records blace the blame on two monks who took it upon themselves to remove stones from the dam, apparently in an attempt to lower the level of the lake which was flooding their fields. Inside a monastary near the dam hangs a painting from 1428 showing St. Benedict fishing from the crest of the Subiaco Dam. Incedentally, this painting is the oldest surviving illustration of a dam. he record height of the Roman Subiaco dam wasnt broken until 1594 with the construction of the 46 m high Tibi dam in Spain. However, the Roman concept of a rectangular wall was mostly maintained, with only a few, hesitant attempts to use trapezoidal, let alone the correct triangular, cross sections. The use of concrete by the Romans for the dams interior or as a building material in general, fell into oblivion, while the construction techniques essentially remained the same: pick and shovel. Sant Bemedict fishing from the damsabato 2 febbraio 13
  43. 43. Roman gravity dams abound in the Iberian peninsula, North Africa, and the Middle East. Proserpinadam (Merida - Spain) The largest reservoir impounded by the Romans was created by a dam located near Homs, Syria in 284 AD. The dam had the extraordinary length of 2000 m and impounded approximately 90 million m3 of water. The main body of the dam consisted of concrete lined by masonry on both slightly inclined faces and on the crest. It was also grossly overdesigned: in its central part, the dam was 7 m high and 14 m wide . The crest width was smaller, but still measured 6.6 m for the upper 1.3 m of height.sabato 2 febbraio 13
  44. 44. The course of the aqueduct usually followed the contour of the terrain in order to maintain the incline while minimizing expensive construction work Example: Anio Novussabato 2 febbraio 13
  45. 45. Roman’s method and tool to determine direction is very similar to that still in use today Groma Dioptra Allowed a perfect alignment. Could trace Older than the Groma, already known to only square angles the Greeks,could measure anglessabato 2 febbraio 13
  46. 46. Most of Romes aqueducts run underground, in covered trenches or tunnels Advantages of underground constructions - dont disturb surface activities such as farming or traffic. - less vulnerable to wind erosion, the weather, and earthquakes. - not vulnerable to enemies. Above ground arches were like advertising to the enemy: “Here is our aqueduct. “ - labour to dig was abundant and “cheap”, construction material and technology scarce and expensivesabato 2 febbraio 13
  47. 47. Trenches are used when the aqueduct follows the contours of the land. They are quick and easy to build as they require neither the construction of arches nor the burrowing of tunnels. The conduit’s cover coud have different shape. Every 70 meters a big stone determined the course of the aqueduct and marked a “no activity” strip of 1,45 meters each side. When running near the surface, a low wall above ground delimited a larger area of respect (4,4 meters) It was necessary to provide a vent for the air, which otherwise would have been compressed to such a degree as to burst the walls or roof of the specus.sabato 2 febbraio 13
  48. 48. A number of carefully planned detailed ensured centuries of functionality even after maintenance stopped A structure way stronger than required for its use could be caused by lack of knowledge? “melius est abundare quam deficere”sabato 2 febbraio 13
  49. 49. The internal lining ensured the conduit was absolutely water proof and it can still be seen in perfect conditions 20 centuries afterwards Hydraulic cement was called “opus signinum” or “cocciopesto”, because it was made by crushed pottery and even glass It was “crushed” a second time while being laid down, to ensure perfect adherence and smooth surface. The lining went up to 150/170 cm. The brownish deposits confirm water level never exceeded 50/90 cm Aqua Marcia in Vicovaro, near Romesabato 2 febbraio 13
  50. 50. Opus Signinum Opus signinum, ( cocciopesto) is a cement finishing made of lime mixed to china fragments (terracotta) and even glass, utilized in the roman times as watertight lining for pools, water reservoirs or in house floors. The term comes from the city of Segni (Signa), near Rome where was allegedly invented. Vitruvius describes the way it was made: In the first place, procure the cleanest and sharpest sand, break up lava into bits of not more than a pound in weight, and mix the sand in a mortar trough with the strongest lime in the proportion of five parts of sand to two of lime. The trench for the signinum work, down to the level of the proposed depth of the cistern, should be beaten with wooden beetles covered with iron. Then after having beaten the walls, let all the earth between them be cleared out to a level with the very bottom of the walls. Having evened this off, let the ground be beaten to the proper density. If such constructions are in two compartments or in three so as to insure clearing by changing from one to another, they will make the water much more wholesome and sweeter to use. For it will become more limpid, and keep its taste without any smell, if the mud has somewhere to settle; otherwise it will be necessary to clear it by adding salt.sabato 2 febbraio 13
  51. 51. Tunnels were dug in both directions from vertical shafts aligned with the intended path of the aqueduct. This way, many teams could work at the same time, shortening time needed to completion Key Facts The course was divided in sections, each of 15.000 roman feet(4.400 meters)each managed by separate teams. Each linear meter of the aqueduct required excavating 3-4 cubic meter of soil, the construction of 1,5 cubic meters of brick structures and 2,2 square meters of surface finishing.sabato 2 febbraio 13
  52. 52. Determining and maintaining the right direction was crucial, even more so when digging tunnels Heron described methods how to produce tunnels with his Dioptra. So the ancient Greeks must have a sufficient advanced geometric knowledge and the corresponding measuring devices to produce the Eupalinos channel. Example by Heron how to use the Dioptra to construct a tunnel through two opposite points in a mountain. Take a point close to the first entrance B and another point E. Then use the Dioptra to obtain the perpendicular line EF and through a set of other perpendicular segments get line segment KL the point M for which DM is perpendicular to KL, where D is the other opposite entrance point. Using DN and NB estimate the angle alpha necessary to connect points B and D.sabato 2 febbraio 13
  53. 53. Determining and maintaining the right direction was crucial, even more so when digging tunnels The Groma was used by the Agrimensori for Using a Groma to measure non accessible measuring and dividing the territories in points (example the width of a river before “centuries” (centuratio) crossing itsabato 2 febbraio 13
  54. 54. Horizontal Alignment - How to make ends meet... Shafts (spiramen) , one every 35 or 70 meters along the Special gromas, connected to pointers down the tunnel, intended path greatly reduce the margin of error allowed the digging team a reference directionsabato 2 febbraio 13
  55. 55. Horizontal Alignment - How to make ends meet... In digging tunnels, external light, when available, could be used to ensure alignment. By deliberatly narrowing the beam of light ,it would act as a pointer that the workers needed to maintain at the center of the digging frontsabato 2 febbraio 13
  56. 56. ...and correct mistakes Team 1 B Team 2 A Team 1 Correcting Mistakes in case the two tunnels do not meet head to head both teams turn in the same direction. This will certainly make the two intersect either in point A (if team 1 has team 2 to its Evidence of course correction left) or point B (if team 1 has team 2 to its right) Warning!! This works only if the two tunnels are at the same elevation (that is, are on the same plane.sabato 2 febbraio 13
  57. 57. Elevation was maintained through “coltellatio” Use of the Dioptra (at B) and two leveling rods for determining the height of A bove B Sighting over a mountain to determine the line of an aqueduct channel through the base of a mountainsabato 2 febbraio 13
  58. 58. T ensure horizontal alignment and build the needed gradient Romans o used mainly the Chorobatessabato 2 febbraio 13
  59. 59. Short steep sections were introduced to connect aqueduct sections built by different gangs, as a remedy for misalignment....and correct mistakessabato 2 febbraio 13
  60. 60. Archeological Analysis gives evidence of construction methods Left or Right handed Excavating tunnels workers needed the light supplied bu oil lamps. The niches in the rock Work Shifts Sense of Excavation where these lamps stayed are ridges like these mark the progress of Pickaxe marks on the rock tells us the still visible. Considering the each shift team. Progress is more in soft sense in which the tunnel has been dug sense of excavation, if the niche rock and slowed down when passing is on le left, the worker was right through hard rock handed, if on the right, he was left handedsabato 2 febbraio 13
  61. 61. Sometimes the building shafts tunnels also acted as inspection manholes after the construction work was done. Manhole with a broad base Manhole on an arcaded Manhole on a siphon basin Manhole with a small base and settling basin aqueduct Their main purpose was for cleaning and repairs and/or to air the water.sabato 2 febbraio 13
  62. 62. Settling basins (Piscina Limaria) were built to get rid of all kinds of pollution and were mostly situated near the source of an aqueduct and / or near the end, just before the terminal castellum divisorium, the water distribution centre of a town or villa Some basins had a special outlet to discharge the dirt, in other cases the debris had to be removed periodically by hand. The best known examples were at the aqueduct of Cologne, also an infiltration gallery, (Grune Putz, Germany) and Rome (Aqua Virgo tanks)sabato 2 febbraio 13
  63. 63. Some settling basins were quite complex in construction Settling Basin Aqua Virgo in Romasabato 2 febbraio 13
  64. 64. Most Aqueducts came from the Appennines East of Rome. Many were build next to each other Building acueducts next to each other: - Saved time in measuring - save space and avoided having to buy/confiscate new space - Reduced the need for construction (e.g. used the same service road) - allowed to switch water from one another during maintenance, thus avpoiding a reduction of supplysabato 2 febbraio 13
  65. 65. During Maintenance water was diverted from one aqueduct to another In order to switch water from one aqueduct to another, they needed to cross each other in elevation. An aqueduct could be at one point above and one point underneath another following the same route. There were no pumps, so again water moved only by gravity. Of cource each tract was a decline (since water cannot move uphill)This was accomplished by varying the gradient.sabato 2 febbraio 13
  66. 66. Most important example is the last tract of the Aqua Marcia, Tepula, Iulia Porta Maggiore Porta Tiburtinasabato 2 febbraio 13
  67. 67. Libramentum or censura declivitatis: the right gradient was key to proper water transportation Water flows along gradients, and its velocity depends on a number of factors. Water flows more quickly along steeper gradients, but wear and tear on such pipes is greater, The right incline according to some authors resulting in the need for more frequent repair. More gradual sloping pipes result in slower-flowing water with greater sludge deposits; hence, these pipes require more cleaning with less repair. Water velocity along conduits is also greater in larger, smoother pipes. Pipes or canals that have rough surfaces disrupt water flow, slowing it down. In addition, larger diameter passageways provide less resistance, because a smaller percentage of the flowing water is retarded by the surface friction of the conduit. Thus, smaller diameter pipes slow the flow of water compared to larger diameter pipes.sabato 2 febbraio 13
  68. 68. The average incline varied Average Gradient (m/Km) The Nimes Appia aqueduct in the 0,61 Anio Vetus Pont du Gard re 3,64 section has a e Marcia d 2,83 gradient of only ve Tepula 34 cm per Km i 5,07 Julia a R Virgo 12,51 (1:3000), dropping only 17 D 0,19 Alsientina meters in its 50 5,85 Claudia km lenght 3,68 Anio Novus Some “steep 3,79 Traiana chutes” have an 2,63 Alexandrina incline of up to 23,50 78%sabato 2 febbraio 13
  69. 69. ...but within the same aqueduct “flat” sections were often broken by “steep chutes” Besides being a method of correcting elevation mistakes, steep chutes acted as -energy dissipators - aereators of the water - sedimentation basins Smooth chutes and stepped chutes were used for shorter portions. Dropshaft cascade for longer onessabato 2 febbraio 13
  70. 70. Some “steep chutes” DH=drop in Height L= Lenght of the chute So= Slope (angle of incline) Q/Max = Max water flow in M3/secsabato 2 febbraio 13
  71. 71. The Great crossing of “T Fiscale” or More of this later...sabato 2 febbraio 13
  72. 72. T bridge a gap in the terrain and to prevent a long o detour, especially to cross a valley or a river, a bridge for the aqueduct conduit was built. The arched arcades require less material than walls and dont interfere with the passage of water or people through the environment.sabato 2 febbraio 13
  73. 73. Bridges used one, two or three tiers of arches The highest bridge almost 50 meters above the river Gardon is the Segovia Aqueduct famous Pont du Gard, part of the aqueduct op Nîmes (France),sabato 2 febbraio 13
  74. 74. The Arch: terminology and technology The arch stands due to compression and attritionsabato 2 febbraio 13
  75. 75. The Arch: Construction Wooden forms are used to keep pieces in place until the keystone was placed. At that time the arch is complete and able resist high pressuressabato 2 febbraio 13
  76. 76. Where a valley to be crossed was too deep or too big for a bridge, a siphon was built Where a valley to be crossed was too deep or too big for a bridge, a siphon was built. The aqueduct water ran into a distribution tank, often called header basin. A The basis of a syphon is the principle of conduit left the other side of the tank and descended into the valley, crossed the communicating vessels bottom on a so called venter bridge and climbed up to the other side to the receiving basin from which the water continued in a masonry channel to its destination.sabato 2 febbraio 13
  77. 77. Communicating Vessels When water is poured into a U-shaped water-hose, the water reaches the same height on both sides.sabato 2 febbraio 13
  78. 78. Communicating Vessels When water is poured into a U-shaped water-hose, the water reaches the same height on both sides.sabato 2 febbraio 13
  79. 79. Components of an inverted Siphon HT = Header T ank H = Height VB = Venter Bridge HG = Hydraulic Gradient RT = Receiving T ank G = Geniculus (bend)sabato 2 febbraio 13
  80. 80. Remains of siphons in Lyon Headertank and ramp of the The receiving tank and ramp of Yzeron siphon in the Gier the siphon of the Brévenne aqueduct of Lyon (France) aqueduct of Lyon (France)sabato 2 febbraio 13
  81. 81. The Greeks often used cut-stone or terracotta pipes. The same applies for the Romans in Spain, while in France they used lead pipes. In France in particular the Romans used lead pipes. These pipes had a small diameter which were easier to produce than the bigger ones: commonly a series of pipes were applied in siphons with lead pipes. The most striking example is the 8 - 10 pipes parallel in the nine (!) siphons in the four aqueducts of Lyon (France). Section of the Cadiz Roman aqueduct, rebuilt along the highway IV between Puerto Real and San Fernandosabato 2 febbraio 13
  82. 82. The technology for making (lead) pipes did not make them strong enough to withstand high pressures Pipes were also very prone to clogging because of mineral sediments. This is why syphons using pipes were more used in France than in Rome, where water is very rich in calciumsabato 2 febbraio 13
  83. 83. Some aqueducts with Inverted Syphonssabato 2 febbraio 13
  84. 84. Distribution basins in the city: from gravity to pressurized system Closed system (Pressurized) Open system (Gravity) Public Fountains Spas Homes, Homes, labs (Munera) (Termae) labs Ground Secondary Main Level Castellum Castellum Underground pipes Water outlet in the city took the form of a “castellum” (castle), a structure of viable size that contained one or more pools, similar to the “piscina limaria”, where the flow slowed down and the last impurities could sediment. Water exited through pipes (fistulae) or cup shaped outlets. These buildings were protected by armed guards, to prevent tampering and pollution of the watersabato 2 febbraio 13
  85. 85. Water was never tapped directly from the aqueduct but from special structures: the Castellum Secondary Castellum Users Hydraulic gradient Public Fountain From Previous A: Main Conduct Castellum B: Settling Tank C: Secondary Conduct T next o D: Outlet Castellumsabato 2 febbraio 13
  86. 86. Castellum Nimes Aqueductsabato 2 febbraio 13
  87. 87. Castellum in Pompeiisabato 2 febbraio 13
  88. 88. Domestic water in Pompeiisabato 2 febbraio 13
  89. 89. Lead Pipes were called Fistulae Lead pipes in the Roman baths in Bath (UK) Pipes and faucets in Roman Sicilysabato 2 febbraio 13
  90. 90. Lead Pipes And Health From the Antiquity it is known the harmful character of lead that could cause evident pathologies – probably in some emperor- and intoxications along the Roman history and that caused illnesses to the miners and lead workers and to everyone that used frequently lead –through lead fistulae and kitchen recipients-.  However, lead becomes especially damaging in the open air, so the lead fistulae, if they were correctly buried, must not have been as harmful as people thought.  Since almost all of the lead absorbed by the human body is deposited in bones, investigators have studied the bones of ancient Romans. While some studies did indicate above normal concentrations of lead, it seems unlikely that water pipes were a contributing factor. Hodge (1981) has correctly pointed out that lead pipes would not have caused contamination for two reasons: (1) because the Roman water contained high concentrations of calcium which formed deposits inside the pipes, insulating the lead and (2) because lead will never greatly affect running water. It has even been hypothesized that Romes dependence on lead water pipes lead to its decline. It has been suggested that the aristocracy died off from nothing more complicated than simple lead poisoning but these hypotheses have been falsifiedsabato 2 febbraio 13
  91. 91. Many Castella served the City of Rome Highlighted in yellow a castellum delivering water from Aqua Iulia or Tepula, near the Diocletianum Termae, Map of Ancient Rome by E.Du Perac, 1574sabato 2 febbraio 13
  92. 92. Stones and inscriptions on the pipes still show the name of the users Incription referring to the Pisoni family in Inscription referring to Marcus Aurelius a fistula aquaria found in the submerged city of Baia (Naples) T manufacture these fistulae required qualified staff, so the manufacturer engraved his name on the o fistulae together with the owner’s name –if it was a particular-, the emperor’s name or the name of a community; sometimes it was engraved the name of the project manager or the name of the monument.  In a fistula from Pompeii in the age of the emperor Hadrian (CIL 15, 7309) we can read: Imp[eratoris] Caes[aris] Trai[ani] Hadriani Aug[usti] sub cura Petroni Surae proc[uratoris] Martialis ser[vus] fecit (translation “(Property of) the emperor Caesar Trajan Hadrian Augustus, under the responsibility of Petronius Sura, the slave Martial did it”).sabato 2 febbraio 13
  93. 93. How lead pipes were built These lead fistulae were made in plates between 5 and 15 millimetres thick and 2,90 metres long; the plates were curved with hot bronze mandrels by hammering and with clay flanges; then, both sides were welded by running liquid lead over the clay flanges; finally, the tubes were connected with short muffs welded in both extremes, so the workers obtained a perfect hermeticism with scarce risks of breaking down in a normal use.  The normal calibre of the pipes was established according to the water flow.  The calibre was measured in quadrants, i. e., a quarter of a inch (0,4625 centimetres); the normal measures varied between pipes of 5 quadrants –called in Latin quinaria (2,3125 centimetres)- until pipes of 15 quadrants (6,9375 centimetres) to a smaller distribution of water, or pipes with bigger calibre to a distribution of water in a bigger scale, the vicenaria -20 quadrants (9,35 centimetres)- and the centenaria -100 quadrants (46,25 centimetres). The utilization of standard pipes (certified by a stamp) mandatory to help reduce frauds.sabato 2 febbraio 13
  94. 94. Clay Pipes were also usedsabato 2 febbraio 13
  95. 95. Cost of Building aqueducts For each metre of aqueduct: - approximately 3–4 m³ of earth had to be dug up - 1.5 m³ of concrete and bricklaying - 2.2 m² of plaster sealant. 1 - 3 Million Sesterces per KM on Average Avg capacity 0,5 M3/sec Aqua Marcia: Total cost 180,000,000 sesterces for 91 Km (£1,800,000 sterling), equivalent to approximately 2 million Sesterces per KM Aqua Claudia and Anio Novus, inaugurated toghether, had a total cost of 350,000,000 (for 68 Km Claudia + 87 km Anio) (Plinius) equivalent to 2,3 million per KMsabato 2 febbraio 13
  96. 96. Example: The Eifel Aqueduct For the Eifel aqueduct, each were 15,000 Roman feet long (4,400 m or 2.7 miles in modern units). I The complete labour expense is estimated at 475,000 man-days: with about 180 possible construction days in the year due to weather conditions, 2,500 workers would have worked 16 months to complete the project. The actual construction time appears to have been even longer, since this estimate leaves out the question of surveying and production of the building materials.sabato 2 febbraio 13
  97. 97. Inscriptions suggest control (or attempt to control) water distribution CIL 6.31566 Description of the distribution of Stone mapping the villae served by Alsietina water by allotment of aqueduct derivation time CIL 14.3676 Regulations for use of (aqueduct) water in the area of Tibur, setting sizes of channels and lenth of time for accessabato 2 febbraio 13
  98. 98. Inscriptions suggest control (or attempt to control) water distribution Part of a decree that records the arrangements for time dependant irrigationsabato 2 febbraio 13
  99. 99. Payments and Frauds The flow of water was continuous, so users paid a fixed amount according to the size of the pipe serving their house and not for the water actually used. T avoid frauds in the last part of the distribution system, Frontinus mandated the insertion of a brass pipe o (a 25 cm segment) at the beginning of each derivation pipe (fistula). Unlike lead, brass cannot be stretched, to enlarge the section, which is the main factor in determining the amount of water to reach the user. Correctly inserted, the calix was set half-way up the wall of the castellum, perpendicular and horizontal to it. But, if it were placed lower in the tank or angled downward (whether deliberately or accidentally), there would be more pressure and more water, just as there would be if the calix were directed into the flow (XXXVI.2, CXIII.1-2). A larger calix could be placed in the tank or a larger pipe fixed to it. Or pipes could be placed at different levels below the surface of the water. Some were not even fitted to calices or, if a new pipe was installed, the old one was left in place to draw water, which then was sold. The result was that, of the 14,018 quinariae officially delivered by the nine aqueducts of Rome then in use, another 10,000 quinariae were diverted illegally (LXIV.2, LXXIV.4).sabato 2 febbraio 13
  100. 100. Frontinus identified and tackled the problem of illegal connections Frontinus for the first time made “serious”checks of the aqueducts to identify illegal taps and frauds, which he blamed on “foreigners”, not roman citizens (cives romani). He did this by calculating the amount of water entering the aqueduct with that coming out at the distribution basin. . . . a large number of landed proprietors, past whose fields the aqueducts run, tap the conduits; whence it comes that the public water courses are actually brought to a standstill by private citizens, just to water their gardens. Water was supposedly only piped into the abodes of those lucky enough to have official authorization, but having running water was so desirable that Romans were constantly bribing water officials to tap an aqueduct. Frontinus described a problem called "puncturing": . . . There are extensive areas in various places where secret pipes run under the pavement all over the city. I discovered that these pipes were furnishing water by special branches to all those engaged in business in those localities through which the pipes ran, being bored for the purpose here and there by the so-called "punctures". How large an amount of water has been stolen in his manner, I estimate by means of the fact that a considerable quantity of lead has been brought in by the removal of that kind of branch pipe.sabato 2 febbraio 13
  101. 101. Maintenance of Aqueducts After construction, the building trenches were filled in, the surface flattened, and a maintenance path built. The maintenance path also served to delimit areas where farming was not permissible. The aqueduct to Lyon, France was marked with the following inscription[cite this quote]: “By command of Emperor Trajanus Hadrianus Augustus, no one is permitted to plough, sow, or plant within the space determined for protection of the aqueduct.” Besides repairing leaks maintenance implied cleaning the conducts from deposits. The calcium deposits brought up ad dumped on the ground near the inspection shafts allowed archaeologists in modern times to find the long forgotten path of the aqueducts in the (then little built) roman countryside A very high percentage of maintenance workers, public slaves, managed to become free citizen by buying their freedom. Contrary to other “less fortunate” slaves, they had the chance to receive bribes from the landowners whose properties were crossed by the aqueducts, not to report (and sometimes even to build) illegal taps.sabato 2 febbraio 13
  102. 102. Maintenance of the aqueducts Such a complex system needed continuous maintenance. In the time of Nerva and Trajan, a body of 460 slaves were constantly employed under the orders of the curatores aquarum in attending to the aqueducts. This is close to the current ratio in terms of man per volum of water served (Ritrovare o calcolare ratio) They were divided into two families, the familia publica, established by Agrippa, and the familia Caesaris, added by Claudius; and they were subdivided into the following classes: The villici: attended to the pipes and calices. The castellarii: supervised all the castella, both within and without the city. The circuitores: had to go from post to post, to examine into the state of the works, and to keep watch over the laborers.. The silicarii: had to remove and relay the pavement when the pipes beneath it required attention. The tectores: had charge of the masonry of the aqueducts. With the fall of the roman Empire aqueducts began degrading not much for the arrival of the so called “barbarians”, but for lack of maintenance and, in the absence of state control, the proliferation of private taps along their course.sabato 2 febbraio 13
  103. 103. Example of Problems: Leakages This is a close up of mineral deposits from Mineral deposits indicate leakage. View of the the Neronian arches on the Caelian hill. interior of the arches of Aquae Felice show signs of leakage of water from the modern day aqueduct.sabato 2 febbraio 13
  104. 104. At times arches needed to be reinforced The two arches on the left are both remains of repair made to Aqua Claudia. The original stone structure is all but gone. These are both excellent examples of the amount of materials used for each arch. These two arches are only partial repairs, compared to others that were made.sabato 2 febbraio 13