CLEMENTE ESPOSITO

http://www.napoliunderground.org

STRUCTURAL PROBLEMS

OF THE

SUBSOIL OF NAPLES

SOUTHERN CENTER FOR SPELEOLOGY

HISTORICAL NOTES:

The city of Naples is unique in that, in a broad sense, it was born from its own womb. The subsoil has always been the object of excavation because of the presence of material suitable for construction (tuff, pumice, pozzolana and lapilli).

photo 1 The temple of Mithra photo 2

Quarries and caves used to extract material were never abandoned but continued in use in varying capacities as cisterns or storage spaces.

photo 5 - the Grotto of Mithra a Cappella Vecchia photo 4 - Section NN

The first quarries go back to the age of the Greeks. They started at the island of Megaride (the Egg Castle) and moved onto the mainland, leaving at Mt. Echia a large tuff cave consecrated by the Greeks to the religion of the god, Mithra, and today used as a garage (photos 1, 2, 3, 4, 5, 6).

photo 3 – cross-section P photo 6–The Grotto of Mithra at Cappella Vecchia

Among other things, the Greeks built the city walls, taking tuff from underground sites. One of these, still intact (because the entrance collapsed during the time of the Greeks) was found in 1981 beneath the Pianto Cemetery (photos 7 & 8).

photos 7 & 8 - Greek graffiti in the quarry beneath the Pianto cemetery

Also, the Greeks dug the Bolla Aqueduct, providing running water from sources on the Volle plain near the slopes of Vesuvius (photo 9) and a series of hypogea of admirable beauty, with frescoes and furnishings still visible (photos 10 & 11).

photo 9 - Cistern of the Greek aqueduct beneath via SS. Apostoli

photo 10 – Greek hypogeum photo 11 – Greek hypogeum reused by the Romans

The Romans, with new excavations beneath the city, integrated the Bolla Aqueduct with the Augustean Aqueduct that brought water to Naples from the Serino at Monte Terminio (Avellino) (photos 12, 13, 14).

photo 12 – Cistern of the Roman aqueduct beneath via Duomo

The Romans also dug noteworthy quarries to build streets and tunnels to reach in a short time (given the local terrain) locations along the coast: the Seiano grotto (773

Photo 13 – Cistern of Roman aqueduct beneath via Duomo photo 14 – the “Piscina Mirabile”, terminus of the Roman aqueduct.

meters long) that leads from Posillipo to Coroglio (photo 15), and the Cucceius Grotto, also known as the Neapolitan Crypt, 774 meters in length, that connects Piedigrotta with Fuorigrotta (fotos 16 & 17).

photo 15-Seiano Grotto, Posillipo photo 16-entrance to Neapolitan crypt with the columbarium of Virgil on the left.

Photo 17 – Columbarium of Virgil seen from within the Neapolitan Crypt

The Greek and Roman aqueducts served the city for centuries, but by the early 1600s were insufficient due to the notable expansion of the city.

Photos 18 and 19 -tunnels of the Carmignano aqueduct

The Carmignano aqueduct, tapping waters of the Faenza (today Isclero) river in Benevento, was finished in 1639 and was the final stage of a new aqueduct that, with some other underground sections, integrated preexisting aqueducts (photos 18-22).

photos 20-22: cisterns of the Carmignano aqueduct

The three aqueducts were made up of a tight network of tunnels and cisterns beneath every building in the city. That network functioned until 1885, the year in which an Italian-English firm built the current pressure aqueduct. By then the city had already built

a "negative" of itself in the sunsoil--millions of cubic meters of empty spaces, all of which could be traversed. After 1885 Neapolitans lost interest in the subsoil that was born with the city and had grown with her. The people took a renewed interest in 1943 as a result of wartime events, when the quarries and grottoes were outfitted as public air-raid shelters. There were 210 of them, capable of providing for 219,000 persons (photos 23, 24, 25).

photos 23 and 24: air-raid shelters

Outside the city, many quarries not only took in persons and animals, but also served to store equipment, tools and munitions.

Photo 25 – air-raid shelter

After the war, all of these facilities were once again abandoned and, worse, were first used as dumps for rubble from wartime bombings (photo 26) and then as illegal rubbish dumps (photo 27).

That produced not only a partitioning of these ancient underground passageways but left a great many of them blocked.

Photo 26 – rubble dump photo 27 – rubbish dump

photo 28 – blocked tunnel photo 29 – blocked well

In large part, the strata in the earth beneath the city is made up of pyroclastic materials such as:-yellow chaotic (that is, loose, mixed) tuff of various sizes both near the surface and at depth (photo 30);-loose and mixed material such as lapilli (photo 31), scoriae and pozzolana of various sizes (photos 32 and 33).

photo 30 – Open-air and subterranean quarry in the Vallone San Rocco

Although the physical-mechanical properties of pyroclastic terrains under external load-bearing stress is by now fairly well understood, certain values vary due to both intrinsic and extrinsic factors, making further studies necessary at specific sites.

Photo – 31- lapilli quarry photo 32 – cave-in in pozzolana strata

The many episodes of instability in the subsoil, with repercussions on the surface, that have struck--and continue to strike--Naples relatively frequently are almost always

caused by water infiltrating the ground near the surface and thus affecting the levels immediately below.

Photo 33 – Miano. Caisson lowered into a cave-in by the fire department to recover the bodies of two workers.

It is generally recognized that these inconveniences are primarily due to dysfunctional urban services, specifically those of the aqueduct and the sewerage systems; they are generally degraded, old, and have lacked sufficient maintenance and are thus unable to upgrade their capacities beyond the original specifications (photo 34).

photo 34 - 1979 cave-in on Corso Amedeo di Savoia that for a momentrevealed older structures installed even though they

undermined the road leading to Capodimonte.

Uncontrolled water leaks, due to the notable permeability of the underlying terrain as well as to the presence of the cavity, itself, find fast, hidden paths to flow along, taking

photos 35 and 36: examples of terrain sinking within the cavity

with them on-site material; this leads to erosion that manifests itself on the surface as cave-ins, sink-holes and slides. The chronicles of Naples are full of such things.

Photo 37 – landslide and collapse of tuff mass photo 38 – cave-in

photo 39 – cave-in

The presence of cavities aggravates these phenomena in that water leaks find an easy and swift outlet into underground spaces where they then wash away the loose (incoherent) earth near the surface (photos 40 and 41).

photos 40 and 41 – material being washed away within a cavity

Bear in mind that every building in the historic center is affected by the cavities of the ancient aqueducts and by the presence of cisterns and wells; there is a latent and very real potential for dangerous movements of the soil.

photo 42 – fire in a cavity photo 43 – aftermath of a fire in a cavity

What's more, because of the presence of inflammable refuse being dumped into these spaces, there has been--and continues to be--a high risk of fire. That has happened and has caused notable damage to property and even loss of human life.

In that regard, we note that there exist in parts of the city, spaces in precarious equilibrium because of inefficient water drainage, notable erosion and obvious problems of overload from above.

photo 44 – using a ground level cavity as a garage

Instability is seen from the sudden collapses when it rains heavily. Water saturates the ground and puts increased pressure on walls. We note the need for an Subsoil Office, as was noted in the First and Second Commissions from 1968 and 1970, to determine how much we know and what is yet to discover.

Photos 45 and 46: using underground spaces as garages and for storage

This same Office would be at the service of engineers and scholars and be able to furnish them with precise information.

Having such information—relly knowing what is happening in the subsoil--might help us put to better use for the people such things as underground parking (photos 44 and 45), storage spaces (photo 46), city services, museums, and all of those things that serve tourism and, with appropriate guided tours, seem to be of unique interest in the world.

As far as far as security on the surface goes, with particular attention to tuff retaining walls, it is urgent to know how many exist and how many are not properly drained (photos 47, 48 and 49).

photo 47 – Roman retaining wall

photos 48 and 49: retaining walls: - (l) vico Tronari ai Cristallini (r) vico San Gennaro dei Poveri

For the facilities seen (below) in photos 50 through 57 we note that these are being properly maintained and such is foreseen for the future.

photo 50 – Naples aqueduct photo 51 Capodimonte reservoir

As far as all services are concerned, urgent attention is due to those facilities that are already in place in the grand plan for the city of Naples.

52 – Naples aquedt., Capodimonte reservoir, distribution photo 52 - Naples aquedt., Tronti syphon discharge

All of this will serve, besides better defining and managing existing facilities, to increase the general safety in the territory under consideration, especially as we look forward to projects in the future.

We note that long-abandoned sewers (even centuries old) still exist beneath the city (Miano, beneath via Chiaia and Mt. Echia (photo 58)), which, during periods of heavy rainfall, take the overflow from regular city sewers and are subject to extreme stress. These are particularly dangerous because they are not regularly maintained since they are no longer considered operational.

Photo 54 – 800 tube to cross the Sabato river photo 55 – Naples aqueduct, channel bridge Rio Rengini

In light of what we have said so far, the proposal of Jan. 29, 1997, of the 13th commission in its 65th afternoon session should be considered an optimal point of departure for any future interventions in the subsoil.

Photo 57 – within the Scudillo reservoir

These proposals are the best that have issued from various commissions that have studied the subsoil from 1885 to the current day; there are 20 significant points

presented by Maggi and Carcarino, here presented together because they represent the same point of view.

Photo 53 – Bourbon sewer no longer in use

1 - Create an authority for the Province of Naples that oversees and coordinates all operations in the subsoil; it shall be a central data collection service for urban services that have to do with geology that affects surface terrain;

2 - create a system that constantly monitors water supply, one that shall be able to identify and pin-point leaks in the system in a timely fashion;

Photos 54-56 – flood, 21 Sept. 1911 – ground level dwellings buried - debris wash reaches the first floor

3 - create for Naples a system for the collection and dispersal of surface waters laden with refuse (photos 54-56);

4 - pass laws (regional or national) that shall facilitate the granting of concessions for use of the subsoil of Naples;

5 - pass national laws to reorder the Italian urban areas on the basis of knowledge of the geological and man-made environment and create an urban (and non-urban) 'vulnerabilty index' with proposals for environmental restoration;

photo 57 – cloudburst in the Gulf of Naples; residual lava flows

6 - compel both private and public institutions to report the presence of cavities in the subsoil beneath their property or within their jurisdiction;

7 - develop and introduce anti-seismic norms applicable to urban services (aqueduct lines, sewers, the methane gas network, etc.);

8 - require those in charge of work at the surface or in the subsoil to present an authorized cost estimate for the work to be done;

9 - require geological studies and subsequent reports for any work done on structures at sites where there has been a cave-in or where work has been done;

10 -reconstruct a profile of the sea bottom where there are man-made structures that have been submerged as a result of post-Roman bradyseisms;

11 - reconstruct the stratigraphic profile of sediments within historic times and reconstruct how urbanization has altered the territory;

12 - generate with modern methods a geological-structural map of the subsoil;

13 - generate with modern methods a map of the cavities in the subsoil that impinge on buildings, streets and urban services, including the geotechnical characteristics of the terrains (foto 58 and 59);

photo 58

14 - determine the state of conservation of rock in vaults, columns, walls, etc. in the cavities that served as quarries and evaluate stability locally and over an extended area to include how existing or future structures and infrastructures might be affected.

15 - pinpoint vertical wells, locate cavities and the urban service conduits (sewer lines, water pipes, gas lines, etc.), including the possible presence of aqueducts and sewers in loose and permeable terrain uphill from cavities.

16 - determine possible cause and effect between movement of conduits and movement of earth, or vice versa;

17 - generate informative teaching materials for all school levels to make the young more conscious of problems connected with the subsoil;

18 - institute an adequate national geological service;

19 - entrust only qualified civil engineers with planning and directing work that effects the soil and subsoil.

20 - rebuild the national technical-organizational structure.

Photo 59

It is thus clear that further commissions will not produce anything new; the time for studying things is past! We have to start to work by providing region, province and town with the human and financial resource that they require in order to solve the hydrologic problems in Campania and of the Neapolitan subsoil in particular, problems that for decades have been almost disowned.

The creation of a special office for the subsoil has been a positive, if very tardy, first step. It only reaffirms that for anything to get done in our city, terrifying events have to occur. These are human and financial provisions that were requested in vain in years past. From

a point of view of both conscience and prevention, it is extremely important to know that the first thing this special office did was to provide for digitally archiving all existing data--locations, dimensions, characteristics and images of cavities, tunnels and sewers. This included everything we knew about the aqueducts and even retaining walls and their potential dangers. We do well to remember that the first Subsoil Commission mentioned this back in the distant 1970s. The first positive result of digitalization - that is, rapidly accessible systematic knowledge - is the campaign to rebuild and shore up retaining walls. Important also is the fact that municipal authority, in the name of public safety, intervened even in cases of walls on private property, recovering cost from the owners, themselves.

photo 60 – mass of toilet paper in a well that served as a toilet photo 61 – a cavity flooded by liquid waste

Without waiting for further tragedies, we would be well advised to undertake a campaign to make the public aware of these things so that they see the need to report the presence of wells and cavities (including entrances). Such reports at the moment continue to be sorely lacking. Residents, merchants and entire condominiums resist, their concern being more with the expenses they might incur and less with preventing very serious problems. And a lot of them have dirty consciences, pretending to know nothing of sewage discharge in spaces that are right below their own homes and establishments (photos 60 and 61).

Any investigation in the zone of Cappella dei Cangiari, or on the Corso Vittorio Emanuele, or in the zone of Corso Amedeo di Savoia or the Sanità (to cite just a few examples among many that have come to our attention) would lead to some notable surprises.

As far as encouraging people to report willingly the existence of cavities, it would help if there were norms to regulate the use of these spaces in an eco-friendly fashion. Here, the Public Administration could set a good example. In the San Rocco Vallone, for example, any talk about cleaning it up and turning it into a public park cannot help but make mention of the presence of such spaces, some of enormous dimensions.

Translator: Jeff Matthews