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Prominent Features of the Augustan Aqueduct in the
Naples Bay Area
W. Lorenz
1
, G. Libertini
2
, B. Miccio
3
, N. Leone
4
and G. De Feo
5
1
Wright Paleohydrological Institute and Wright Water Engineers, Inc., 2490 W. 26th Ave., Denver,
Colorado 80211 (Corresponding Author)
(E-mail: wlorenz@wrightwater.com)
2
Independent Researcher, 80023, via Cavour 13, Caivano (Na), Italy
3
Senior official of ABC Acquedotto di Napoli, 80131, via O. Morisani 28, Napoli (Na), Italy
4
Independent Researcher, 80038, via Locatelli 79, Pomigliano d’Arco (Na), Italy
5
Department of Industrial Engineering, University of Salerno, 84084, via Giovanni Paolo II 132,
Fisciano (Sa), Italy
Abstract
The great Aqua Augusta aqueduct served the Naples Bay area with fresh water during the
time of the Roman Empire. There are very prominent features of the Aqua Augusta, some
that are extraordinary when considering other great aqueducts in the Roman Empire. For
example, the deep tunnels allowed access to a spring water source from a separate
watershed, which resulted in transbasin diversion of the water supply. Each one of the
prominent features was engineered to provide water to the public for various uses. The
prominent structures included other shallower tunnels (with two major types of
construction), hydraulic chutes, arcades (one to an island), baths (located along a well-
travelled road), and storage reservoirs. Also, there is the epigraph discovered at the water
source. Important villas that may have influenced the alignment of the aqueduct are also
discussed.
Keywords:
Aqua Augusta; aqueduct; Roman; Pompeii; water supply.
INTRODUCTION
The aqueduct Aqua Augusta was one of the greatest of all of the aqueducts in the Roman
Empire. It was exceptional in size and technical complexity. The main trunk of the aqueduct
was about 103 kilometers (km) and the branches were an additional 60 km (Libertini et al.,
2014). This grand public works project provided water to a large geographical area and, in
doing so, crossed the boundaries of several natural watersheds in the Naples Bay area. The
overall route of the Aqua Augusta and the prominent features addressed are shown in Figure 1.
The aqueduct is estimated to have been built between 33 and 12 B.C. when Marcus Vipsanius
Agrippa was curator aquarum in Rome (De Feo and Napoli, 2007). The main goal of the
aqueduct was to provide water to two main harbors of the Empire, the civilian one of Puteoli
and the military one of Misenum. It also served a number of other cities attested to in an
epigraph regarding repairs that took place in the time of Constantine the Great (circa A.D. 324
to 326): Puteoli, Nola, Atella, Neapolis, Cumae, Acerrae, Baia, and Misenum (Miccio and
Potenza, 1994). Catalano (2003) and our archaeological field evidence shows that a branch of
the Aqua Augusta also served the coastal cities of Pompeii and Herculaneum.
Other important additional aims of the Aqua Augusta included the provision of water to
colonies and settlements linked to the Augustan political power and to several illustrious
residences in the area. This helps explain the considerable investment made in the aqueduct,
estimated between 150 million and 450 million sestercii (Duncan-Jones, 2010). This cost was
several times the cost of the massive baths (thermae) of Caracalla in Rome and within the
range of costs for two of the aqueducts serving Rome (as documented by Pliny the Elder).
Figure 1. The route of Aqua Augusta. The main roman roads (viae) and towns (civitates) are
indicated. Other ancient aqueducts: A) Beneventum a.; B) Abella a.; C) Bolla a. of
Neapolis; D) Gauro a. of Puteoli. Some other points of interest: E) villa Augusti; 1) springs
(where the epigraph was found); 2) Forino tunnel; 3) Mt. Paterno tunnel; 4) great arcade of
Pomigliano d'Arco; 5) crypta neapolitana; 6) baths of via Terracina; 7) piscina mirabilis.
The aqueduct carried plenty of water of great quality from springs in the area of Serino, south
of the ancient settlement of Abellinum, to the end of the route in Misenum. The choice of the
springs of the Serino area as origin (caput aquae) of the aqueduct appears bold and extreme
for the technical possibilities of the time. Tunneling and arcades were both used along the
route. The engineering feats that were accomplished are apparent by inspection of the special
features along the path of the Aqua Augusta.
Several of the prominent features of the Aqua Augusta are presented and discussed in order of
the alignment and flow of the channel. The data for the alignment shown on the figures are
from field work by the authors and literature sources.
SPRINGS AND THE MARBLE EPIGRAPH
The aqueduct was fed by springs to the south of Abellinum. In the segment from the springs to
the Forino Tunnel, there is no evidence of noteworthy population centers in ancient times that
were served by the aqueduct. The populous Nuceria Alfaterna (present day Nocera Inferiore
and Nocera Superiore), which was near the route of the aqueduct, was served by local springs.
This segment was constructed in the area of Serino, a forested area with a wealth of rich
sources of high quality spring water. This watershed is drained by the Sabato River. The Aqua
Augusta tapped two major springs within the watershed: the Acquaro and Pelosi springs.
A marble epigraph was found near the Acquaro spring in August 1936 during construction
excavation to connect the spring to the modern aqueduct supplying the City of Naples. The
exceptional epigraph, dating from the time of Constantine the Great (circa A.D. 324 to 326),
measures 1.86 x 0.86 x 0.17 meters (m) (De Biase, 2006).
The first segment of the aqueduct was also an area of mountainous terrain, where the
aqueduct followed the contours of the hills in the present day Aiello del Sabato and Cesinali
areas. The Roman engineers used “cut and cover” methods where they could excavate into the
slopes. These shallow (2 to 3 m deep) sections were built with a concrete rubble framework to
enclose the aqueduct section with typical dimensions as shown in Figure 2a. The “cut and
cover” construction was common in aqueducts throughout the empire. The time needed for
construction of these sections was short when compared to deeper tunnel construction, shown
in Figure 2b, that was chiseled into limestone. However, the cut and cover sections were also
subject to local land slips, especially in the steeper slope segments of the aqueduct. One such
land slip occurred recently, exposing an area that the authors felt privileged to inspect, shown
in Figure 3a.
(a)
(b)
Figure 2. (a)
Cut and cover bench into hillside section; (b) Deeper tunneled section.
FORINO TUNNEL – TRANSBASIN DIVERSION
The Roman engineers designed the Aqua Augusta to take water from the Sabato River
watershed to other watersheds along the route. This transbasin diversion of water required that
the design of the alignment of the aqueduct turn to the west in the area of Cesinali to follow
the Vallone della Contrada and pass under the Monti di Forino.
The major transbasin diversion of the water from the Sabato River to the Sarno watershed was
accomplished by the construction of the Forino Tunnel at the location shown in Figure 1. This
unique tunnel had a length of approximately 6 km and is remarkable in that it is known to be
one of the longest tunnels found in any Roman aqueduct or drain project (Keenan-Jones,
2010). The Forino Tunnel was chiseled in tufa and limestone bedrock at a maximum depth of
nearly 70 m and with horizontal bends or curves in the tunnel. A typical tunnel section is
different than the cut and cover section as shown in Figure 3b.
(a)
(b)
Figure 3. (a) A cut and cover section exposed by a small landslide near the municipality of
Cesinali (in the province of Avellino); (b) Photograph of the hydraulic chute
tunneled section at Mt. Paterno Tunnel.
The Forino Tunnel included an additional 1.5-km-long steep chute at the downstream end of
the tunnel (caduta della Laura) that descended more than 150 m (a slope of 10 percent) which
was a hydraulic transition that impacted flow. In 1840, the route of the Aqua Augusta was
surveyed by Felice Abate in an evaluation commissioned by the City of Naples to investigate
the restoration of the Augusta for a water supply to the City (Abate, 1842). For the Forino
Tunnel section, Abate identified only two shafts for the entire 6-km length of tunnel. The
tunnel and access shafts were filled will sediment and were inaccessible when Abate
performed his survey. Today, the Forino Tunnel remains unexplored.
The Aqua Augusta continued from the exit of the Forino Tunnel in a much shallower section
(although there are no archaeological remnants in this section) through the area of present-day
Mercato San Serverino. Then the aqueduct turned west towards Castel San Giorgio with the
“cut and cover” shallower tunnel sections following the contours along the side of the hills in
the area. It then reached the area of Mount Paterno (before and after this mountain, there are
various archaeological remnants as directly observed by the authors).
MOUNT PATERNO TUNNEL AND HYDRAULIC CHUTE
The Mount Paterno was a barrier to a direct route of the aqueduct to the Sarno plain.
Therefore, the Romans constructed a tunnel of about 1.5 km, descending an elevation
difference of about 13 m, from 83 to 70 m above sea level (asl) (Vv. Aa., 1883).
There is much more known about the mount Paterno Tunnel than the Forino Tunnel. Abate in
his survey discovered various deep shafts where he was able to identify the alignment of the
tunnel. One of the unique aspects of this section is that there was a hydraulic chute at the end
of the tunnel where the slope of the channel was at least 15 percent, which created a hydraulic
jump in the water flow. This resulted in a “full flow” section where the flow constantly filled
the channel section. In March 2015, the authors observed a section of the chute, see Figure 3b.
Thick calcium carbonate deposits up to the top vault of the channel section are shown,
indicating the full flow conditions that persisted. This hydraulic condition certainly controlled
the flow capacity of the aqueduct in this segment.
BRANCH TO POMPEII AND HERCULANEUM
There were many branches of the Aqua Augusta; however, one of the most significant is the
branch to Pompeii, because Pompeii has such a special place in archaeological history. The
branch headed south, turning gently around the Vesuvio (Vesuvius mons), in the direction of
Pompeii, where the supply by an aqueduct sufficient for the needs of the town is well
documented (Catalano, 2003). It is probable that the aqueduct did not point directly towards
Pompeii, but that it remained on a higher altitude and continued towards Oplontis, where the
present-day Torre Annunziata, and Herculaneum (now Ercolano), are located, and the channel
served several villas set along the path on the south side of Vesuvius. The remains of an
aqueduct near Herculaneum and of a castellum aquae in the town were found (Catalano,
2003).
Some researchers have judged that the alignment of the main channel of the Aqua Augusta
should have followed this southern route on its way to Neapolis rather than being located on
the northern slopes of Vesuvius mons. However, this hypothesis cannot be proven. In fact, a
path south of Vesuvius would have been a technically very demanding undertaking with
prohibitive costs. To reach Neapolis at an altitude of about 41 m asl (i.e., that of Ponti Rossi
and of the arches near via Vergini, the main remains of the ancient aqueduct in modern
Naples) it would be necessary to overcome the valley of the Sarnus River with a series of
arches over 14 km long and the valley of the Sebethus River with another arcade with a length
of almost 10 km. Moreover, the two long arcades would have had a considerable height, up to
40 m in the central parts of the valleys. In addition, a path south of Vesuvius did not allow the
aqueduct to serve the towns of Nola, Acerrae, and Atella.
In contrast, the path chosen by the Romans first ran just below the surface on the divide
between the valleys of Sarnus and Clanius Rivers and, after going on the north side of the
slopes of Vesuvius, then ran on the divide between the river valleys of Sebethus and Clanius
Rivers with an arcade of approximately 3.6 km and of limited height. Moreover, this route
allowed for opportune branches to provide water to the aforementioned towns (Figure 4).
THE VILLA OF THE EMPEROR AUGUSTUS
The Emperor Octavianus Augustus was often in Campania and had several properties in the
Naples Bay area. It is noteworthy that several of these properties were in Pausillypon, Baiae,
and Nola. Since the Aqua Augusta was planned and constructed during the reign of Augustus,
some researchers have inferred that the path of the Aqua Augusta was influenced by these
property locations.
Figure 4. A hypothetical path south of the Vesuvius mons would have required the
construction of two long and very expensive arcades (A and B). In contrast, the path
built by the Romans passed on the divides (C and D) between the valleys of the
small river Clanius on the north and of the small rivers Sarnus and Sebethus on the
southern side. These valleys have slopes so subtle as to be visually imperceptible.
However, the heights of the divides were another story, with the Campania plain
reaching Neapolis with an elevation of 41 m asl. The elevations of some areas are
indicated in meters asl.
In the segment of the aqueduct in the vicinity of the north slopes of Vesuvius mons near Nola,
the sumptuous front part of a villa was found under several meters of volcanic deposit.
Ongoing archaeological excavations have led to the interpretation that it was the famous villa
owned by Augustus (by inheritance from his natural father, Gaius Octavius). It was in this
villa (not yet fully excavated) that Augustus chose to die in A.D. 14 (D’Arms, 1970). Some
have believed that the alignment of the Aqua Augusta was planned on the north side of
Vesuvius mons (rather than to the south) because of the Emperor’s villa. However, the villa
was located about 80 m above the level of the aqueduct in that area. The predilection of the
great emperor for the place, so much so that he chose it for his last days of life, may not have
been motivated by the fact that it was a family property, however. The villa was surrounded
by civitates and places where Augustus had assigned lands to loyal veteran soldiers and where
he could be surrounded by people who deeply liked and respected him.
Figure 5. The villa of Augustus (villa di Augusto) surrounded by the centuriationes ordered
by him and where many of his veterans were allocated: 1 = Abellinum; 2 = Ager
Campanus I; 3 = Ager Campanus II; 4 = Acerrae-Atella I; 5 = Neapolis; 6 = Atella
II; 7 = Nola I-Abella; 8 = Nola II; 9 = Nola III; 10 = Nola IV-Sarnum; 11 = Nuceria
I; 12 = Nuceria II. Data for the centuriationes are from Chouquer et al., 1987 and,
only for Suessula centuriatio, from Libertini, 2013. The image was proposed in a
recent meeting (Libertini et al., 2016).
POMIGLIANO d’ARCO ARCADE
There were three major stretches of arched construction in the Aqua Augusta: (i) Mura
d’Arce, (ii) the arcade near Pomigliano d’Arco, and (iii) the Ponti Rossi. Together, these three
account for 3.6% of the total length of the main channel of the aqueduct.
The Pomigliano d’Arco arcade seems to have been one of the longer continuous stretches of
opus arcuatum in an ancient Roman aqueduct (Keenan-Jones, 2010). There are very few
material remnants of this arcade; however, it has been shown to have a length of about 3.6 km
and a maximum height of over 12 m. In a small final stretch, the canal bridge, oriented
towards the north-west, had to change direction, towards the south-west. Although it does not
exist today, this arcade bridge long survived the deactivation of the aqueduct. This is known
because in the early Middle Ages, many towns were known for their locations beyond the
arches of the aqueduct (in the perspective from Neapolis), such as foris arcora (beyond the
arcade; e.g. Pumilianum foris arcora, present day Pomigliano d'Arco, Licinianum foris
arcora, Licignano, part of present day Casalnuovo di Napoli, Mascarella foris arcora, extinct
medieval center) or also a foris arcora (likely, present day Afragola) (Libertini, 2011).
TUNNEL AT THE CRYPTA NEAPOLITANA
In the first century B.C., the gulfs of Neapolis and Puteoli were divided by the Pausilypon
(Posillipo) hill. Therefore, the road that connected these locations was long and traversed
steep hills and it was a long journey. At the end of the first century B.C., a major road tunnel
was constructed, the crypta neapolitana, at 5 m high, 4.5 m wide and 705 m long. It was built
by Lucius Cocceius Auctus, an engineer who came from this area and probably worked for
Agrippa. The route of the Aqua Augusta also required that a tunnel be constructed through the
Pausilypon hill.
The aqueduct tunnel at the crypta neapolitana is the third major tunnel in the route of the
aqueduct. The aqueduct tunnel does not lie in the road tunnel, but actually runs separate and
parallel to it at a height of 50 cm from the base of the tunnel on its north side.
Before the tunnel, the aqueduct branched and reached the large imperial villa near la Gaiola at
the end of Pausilypon hill, also known as villa Pollii after its first owner (Vedius Pollio),
where there is a long tunnel (about 770 m), the Grotta di Seiano, which lies on the other side
of the hill.
AQUEDUCT ARCADE TO AN ISLAND
Immediately after the tunnel, another secondary branch ran along the side of the hill to a
unique section of the Aqua Augusta system. This section crossed over the sea and provided
water to the small island of Nisida (Nisida) (Lettiero, 1560), where there were sumptuous
residences, in particular that of Lucullus (D’Arms, 1970) but also that of Marcus Iunius
Brutus, in which Brutus and Gaius Cassius Longinus plotted to assassinate Julius Caesar in 44
B.C. (Lancaster, 2007).
There is little in the way of archaeological evidence of this constructed section (thought to be
opus arcuatum), other than piers that were identified as Roman construction (Cardone, 1992).
This section is unusual in that it appears to be one of only two examples of a Roman aqueduct
crossing saltwater, with the other at Cadiz, the ancient port city in southwest Spain (Keenan-
Jones, 2010).
BATHS OF VIA TERRACINA
The building of the Roman aqueducts provided water in quantities that promoted the
proliferation of bath complexes. The baths were central to the Roman social life, and their
importance grew from the late first century B.C. into the first century A.D. There were several
baths in the Neapolis region before the construction of the Aqua Augusta. However, there
were many other baths built likely because of the construction of the Aqua Augusta.
There were frequent travelers on the Roman road system in the Naples Bay region because the
area was known for the resorts and villas of the Roman elite. At the end of the crypta
neapolitana, the new road bent to the north and reconnected with the old road. Here, there
was a resting place for travelers (Marcianum) with a thermal spa complex. The remnants of
the Aqua Augusta have been excavated near the baths of via Terracina and the aqueduct
provided the water used in the bath complex.
The baths of via Terracina are extraordinary since the complex appears to have been located
specifically for traveling clientele, rather than located in a community for residents. It was a
major complex with three principal baths: the apodyterium, the frigidarium, and the
caldarium. The complex included a semi-circular latrine that was flushed with the water from
the aqueduct. The complex is a major archaeological site today.
STORAGE RESERVOIRS – PISCINA MIRABILIS
As shown in Figure 1, after turning around the south side of lake Avernus (lago d’Averno),
the aqueduct headed towards Baia and Bavli, and finally reached Misenum and its military
port. The port was the main and fundamental goal for the construction of the aqueduct, ending
inter alia, in the imposing Piscina Mirabilis (De Feo et al., 2010) and in other cisterns
(piscinae) in the area, much like the so-called Dragonara near Miseno cape, and Cento
Camerelle, Lusciano, and Cardito in Puteoli. The area needed imported water. In particular,
the military port needed large quantities of water and for this critical necessity the aqueduct
was essential. Later, with the fall of the Roman military power and the decay of the fleet, the
military port lost its function and consequently the Aqua Augusta lost the fundamental reason
for its existence.
Figure 6. Photograph of the interior of the Piscina Mirabilis.
CONCLUSIONS
There are many prominent features of the Aqua Augusta. The technical characteristics of the
work, author observations, and the documentation of classical texts and archaeological
evidence tell the story of a magnificent water conveyance achievement by the Romans
(Lettiero, 1560; Abbate, 1842 and 1862; Vv. Aa., 1883; Miccio and Potenza, 1994).
The prominent features and extraordinary aspects of the Aqua Augusta include the epigraph
discovered at the Acquaro Pelosi springs, Forino Tunnel, Mt. Paterno tunnel, the branch to
Pompeii and Herculaneum, Octavianus Augustus’ villa, the Pomigliano d’Arco arcade, the
Crypta Neapolitana tunnel, the baths of via Terracina, and the Piscina Mirabilis. These
features of the Aqua Augusta demonstrate how unique this aqueduct was in the Roman
Empire, and in world history.
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