Eight new perimeters in the Tyrrhenian: how to check whether your route crosses them

A submarine cable route freezes months before the ship sails: corridor chosen, survey done, specification written. If yours runs through the Tyrrhenian, the Ligurian Sea or the waters around Sardinia, as of yesterday there are eight more perimeters it may cross. Finding out is not a matter of opening a file: the polygons must be rebuilt by hand, from two columns of numbers.

And the yardstick that project will be judged against inside them does not exist yet: it arrives with a later decree, on no fixed date.

What appeared, and where

The environment ministry decree of 1 September 2026, in Official Gazette No. 227 of 30 September, establishes six SCIs and two SPAs under Article 1, «i seguenti siti insistenti nella Zona di protezione ecologica (ZPE) del Mediterraneo nord-occidentale, del Mar Ligure e del Mar Tirreno» — sites lying inside the Ecological Protection Zone of the north-western Mediterranean, the Ligurian and the Tyrrhenian.

The SCIs: IT0000003 Banco di Santa Lucia, 5,894 ha; IT0000004 Ulisse-Doria-Janua seamount complex, 112,656; IT0000005 northern part of the Baronie seamount, 62,286; IT0000006 Sisifo-Tiro-Enarete seamount complex, 72,436; IT0000007 Paola submarine ridge, 105,100; IT0000008 central Tyrrhenian for the protection of Caretta caretta, 3,620,268. The SPAs: IT0000009 Mare Sinis Iglesiente, 177,425; IT0000010 Mare Nurra, 713,896. Total 4,869,961 hectares, close to 48,700 square kilometres. With the Vercelli and Palinuro seamounts, from 2023, sites beyond territorial waters now number ten.

The perimeter is a list of vertices

Every site uses the same wording: it is bounded «dalla congiungente i seguenti punti, con coordinate UTM, riportati nella rielaborazione grafica allegata al presente decreto, del quale costituisce parte integrante» — by the line joining the following points, in UTM coordinates, shown in the graphic annex, an integral part of the decree. Four to ten points per site, two columns, mE and mN.

First trap: the zone is not the same throughout. Seven sites are in UTM WGS84 zone 32N (EPSG: 32632); the Paola submarine ridge is in zone 33N (EPSG: 32633). Set the reference system once and that polygon lands hundreds of kilometres away.

Second trap: two sites carry eastings outside the band. Sisifo-Tiro-Enarete reaches 941,789 mE in zone 32N, the central Tyrrhenian 908,090. Our own arithmetic: a value like that puts the point more than 440 kilometres east of the central meridian of zone 32, past the eastern edge of the nominal band, which closes at 12 degrees east. The transformation stays well defined and a GIS performs it; but a converter that infers the zone from the value, or validates it against the band limits, returns a point in another sea without flagging anything.

Joining the dots is not enough: we checked

We recomputed every polygon’s area from the published vertices. For seven sites out of eight it matches the declared surface to within a few hundredths of a per cent. For the SPA Mare Nurra it does not: joining the six points in the gazette gives roughly 731,000 hectares against the 713,896 declared — more than 17,000 hectares, 2.5 per cent too much.

The answer is in the cartography the ministry published for the consultation: the Mare Nurra map carries eight vertices, not six, and the eastern side is not a chord between two points — it follows the twelve-mile limit of territorial waters, which is a curve. Our reading: where a site abuts the outer limit of the territorial sea, the vertex list does not rebuild the perimeter. You need the graphic annex the decree calls an integral part of it.

Where the annex is

The closing notice says the decree «sarà consultabile, unitamente ai relativi allegati, sul sito internet del Ministero» — will be available, with its annexes, on the ministry website — and Article 1(10) adds that the standard data forms and the shapefile cartography «sono pubblicati sul sito internet del Ministero», are published there.

As we write, that section still holds only the two sites from 2023, last updated 24 December 2024. The only downloadable maps remain those of the public consultation closed on 31 January 2025: scales of 1:1,500,000 and 1:3,000,000, surfaces different from the decreed ones (Baronie 63,112 against 62,286; central Tyrrhenian 3,640,633 against 3,620,268) and, for IT0000009, a different name — Mare Bosa Iglesiente, which became Mare Sinis Iglesiente in the decree. Anyone checking a route today is comparing it against a version that is not the one in force.

The yardstick comes later. The obligation does not

Article 2 defers: conservation objectives and measures will be identified «Con successivo decreto del Ministro dell’ambiente e della sicurezza energetica, sentiti il Ministero dell’agricoltura […] e il Ministero della difesa, da adottare entro i termini previsti dagli articoli 3 e 6» of Presidential Decree No. 357 of 8 September 1997 — by a later ministerial decree, after consulting agriculture and defence, within the limits those two articles set.

We read them. Article 3(2) of DPR 357/1997 sets designation as an SAC «entro il termine massimo di sei anni, dalla definizione, da parte della Commissione europea dell’elenco dei siti» — six years at most from the Commission defining the list. Article 6 contains no time limit at all: it says only that «Gli obblighi derivanti dagli articoli 4 e 5 si applicano anche alle zone di protezione speciale», extending Articles 4 and 5 to SPAs. So the cross-reference gives no date: it gives a clock that starts in Brussels — Article 4 of the decree provides precisely for sending maps and data forms to the Commission — and runs six years at most. The six-month term for measures sits in Article 4, which the decree does not cite.

Meanwhile Article 5, appropriate assessment, applies from today. Paragraph 3: proponents of works not directly connected to the site’s conservation «ma che possono avere incidenze significative sul sito stesso, singolarmente o congiuntamente ad altri interventi, presentano, ai fini della valutazione di incidenza, uno studio» — but capable of significant effects on it, alone or cumulatively, must submit an assessment study to Annex G. Paragraph 4: for projects already subject to environmental impact assessment the appropriate assessment «è ricompresa nell’ambito della predetta procedura», folded into it. Paragraph 6: the authority rules «entro sessanta giorni dal ricevimento dello studio», within sixty days of receiving it, and may ask for additions «una sola volta», once only; the clock then restarts from the day they arrive.

Two things we do not know. Article 5 leaves it to the regions, «per quanto di propria competenza», to name the authorities that scrutinise the study: in the ZPE, beyond the territorial sea, there is no region. The decree assigns management to the ministry’s biodiversity and marine protection directorate, with technical and scientific support from ISPRA, and wants surveillance «svolta dalle autorità competenti», by whoever is competent, without naming the appropriate-assessment authority. And whether a given submarine work in the ZPE is subject to environmental impact assessment at all is a separate question the decree does not settle. These are questions to put before detailed design, not after. Anyone laying or repairing submarine cables adds them to the fifteen-day notice already owed for work at forty metres or deeper.

Two threads, applied

First thread. Comparing the route against the official perimeters becomes a clause in the specification and an acceptance checkpoint: which source, which version, downloaded when, with which reference system per site and how the stretches following the territorial-waters limit are handled. The record goes out with the design, it does not get reconstructed afterwards.

Second thread. Route, survey, as-built, depths and binding perimeters stop being loose files between ship and archive and become a single map of the network, on which an AI runs the diagnosis and a crew closes the fault: when a perimeter changes or an annex appears, the question which sections does it touch has an answer in minutes, not a verification campaign. Where an AI over network data is needed it runs within the client’s perimeter — on-premise or dedicated cloud with a data centre in Italy — alongside CSIDIA, the group’s other company. Our own crews, no subcontracting.

Do you have a route in the Tyrrhenian, the Ligurian Sea or around Sardinia, and a specification that does not name these eight codes? Talk to an engineer: the comparison between route and perimeters belongs before detailed design, and in the specification.