JUDGMENT OF THE COURT (Tenth Chamber)

28 March 2019 ( )

Table of contents





I. Legal context

II. Pre-litigation procedure and proceedings before the Court

III. Request seeking the production of evidence after the close of the written part of the procedure

IV. The action

A. Preliminary observations

1. The concepts of ‘unusually heavy rainfall’ and ‘best technical knowledge not entailing excessive costs’

2. The burden of proof

B. The first complaint

1. The first part of the first complaint

(a) The agglomeration of Athlone

(b) The agglomeration of Cavan

(1) Arguments of the parties

(2) Findings of the Court

(c) The agglomeration of Cork City

(d) The agglomeration of Enniscorthy

(e) The agglomeration of Fermoy

(f) The agglomeration of Mallow

(g) The agglomeration of Midleton

(1) Arguments of the parties

(2) Findings of the Court

(h) The agglomeration of Osberstown

(i) The agglomeration of Roscommon Town

(j) The agglomeration of Roscrea

(k) The agglomeration of Thurles

2. The second part of the first complaint

(a) Arguments of the parties

(b) Findings of the Court

3. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

(a) Arguments of the parties

(b) Findings of the Court

C. The second complaint

1. The first part of the second complaint

(a) Arguments of the parties

(b) Findings of the Court

2. The second part of the second complaint

(a) Arguments of the parties

(b) Findings of the Court

3. The third part of the second complaint

(a) Arguments of the parties

(b) Findings of the Court

4. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

D. The third complaint

1. The agglomerations whose collecting systems for urban waste water do not comply with Article 3 of Directive 91/271

2. The agglomerations of Dundalk, Killybegs, Portarlington, Ringsend and Tralee

3. The agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea

(a) Arguments of the parties

(b) Findings of the Court

(1) The relevant data for examining the third complaint so far as concerns the agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea

(2) The agglomerations concerned

4. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

E. The fourth complaint

F. Conclusion

V. Costs





(Failure of a Member State to fulfil obligations — Directive 91/271/EEC — Collection and treatment of urban waste water — Exceptional circumstances — Best technical knowledge not entailing excessive costs — Principle that the costs should be proportionate — Burden of proof — Means of proof)

In Case C‑427/17,

ACTION under Article 258 TFEU for failure to fulfil obligations, brought on 14 July 2017,

European Commission, represented by K. Mifsud-Bonnici and E. Manhaeve, acting as Agents,

applicant,

v

Ireland, represented by J. Quaney, M. Browne and A. Joyce, acting as Agents, and by S. Kingston, Barrister-at-Law, C. Toland, Senior Counsel, and B. Murray, Senior Counsel,

defendant,

THE COURT (Tenth Chamber),

composed of K. Lenaerts, President of the Court, acting as President of the Tenth Chamber, F. Biltgen and E. Levits (Rapporteur), Judges,

Advocate General: N. Wahl,

Registrar: L. Hewlett, Principal Administrator,

having regard to the written procedure and further to the hearing on 19 September 2018,

having decided, after hearing the Advocate General, to proceed to judgment without an Opinion,

gives the following

Judgment

1 By its application, the European Commission requests the Court to declare that:

– by not ensuring that the waters collected in a combined urban waste water and rainwater system in the agglomerations of Athlone, Ballincollig New, Cavan, Cork City, Enniscorthy, Fermoy, Midleton, Osberstown, Mallow, Ringaskiddy (including within it the agglomeration of Carrigaline), Roscommon Town, Roscrea, Thurles and Gaoth Dobhair are retained and conducted for treatment in compliance with the requirements of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment (OJ 1991 L 135, p. 40), as amended by Regulation (EC) No 1137/2008 of the European Parliament and of the Council of 22 October 2008 (OJ 2008 L 311, p. 1) (‘Directive 91/271’), Ireland has failed to fulfil its obligations under Article 3(1) and (2) of that directive and section A and footnote 1 of Annex I thereto;

– by either not putting in place secondary or equivalent treatment or not providing sufficient evidence to demonstrate compliance in this respect with Directive 91/271 with regard to the agglomerations of Arklow, Athlone, Ballincollig New, Ballybofey/Stranorlar, Cavan, Cobh, Cork City, Enfield, Enniscorthy, Fermoy, Killybegs, Mallow, Midleton, Passage/Monkstown, Osberstown, Rathcormac, Ringaskiddy (including the flows from Carrigaline and Crosshaven), Ringsend, Roscommon Town, Roscrea, Shannon Town, Thurles, Tubbercurry, Youghal and Gaoth Dobhair, Ireland has failed to fulfil its obligations under Article 4(1) and (3) of that directive, read in conjunction with the requirements of Article 10 thereof and section B of Annex I thereto;

– by not ensuring that urban waste water entering collecting systems from the agglomerations of Athlone, Ballincollig New, Cavan, Cork City, Dundalk, Enniscorthy, Fermoy, Killarney, Killybegs, Longford, Mallow, Midleton, Navan, Nenagh, Osberstown, Portarlington, Ringsend, Roscrea, Thurles, Tralee and Waterford City be, before discharge into sensitive areas, made subject to treatment more stringent than that described in Article 4 of Directive 91/271 and in accordance with the requirements of section B of Annex I thereto, Ireland has failed to fulfil its obligations under Article 5(2) and (3) of that directive, read in conjunction with the requirements of Article 10 thereof and section B of Annex I thereto; and

– by not ensuring that the disposal of waste water from urban waste water treatment plants of the agglomerations of Arklow and Castlebridge is subject to prior regulations and/or specific authorisation, Ireland has failed to fulfil its obligations under Article 12 of Directive 91/271.

I. Legal context

2 The third recital of Directive 91/271 states:

‘... to prevent the environment from being adversely affected by the disposal of insufficiently-treated urban waste water, there is a general need for secondary treatment of urban waste water’.

3 The eighth recital of Directive 91/271 states:

‘... it is necessary to monitor treatment plants, receiving waters and the disposal of sludge to ensure that the environment is protected from the adverse effects of the discharge of waste waters’.

4 Article 2 of Directive 91/271 states:

‘For the purposes of this Directive:

...

5. “collecting system” means a system of conduits which collects and conducts urban waste water;

6. “1 p.e. (population equivalent)” means the organic biodegradable load having a five-day biochemical oxygen demand (BOD5) of 60 g of oxygen per day;

...

11. “eutrophication” means the enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned;

...’

5 Article 3 of Directive 91/271 provides:

‘1. Member States shall ensure that all agglomerations are provided with collecting systems for urban waste water:

– at the latest by 31 December 2000 for those with a population equivalent (p.e.) of more than 15 000, and

– at the latest by 31 December 2005 for those with a p.e. of between 2 000 and 15 000.

For urban waste water discharging into receiving waters which are considered “sensitive areas” as defined under Article 5, Member States shall ensure that collection systems are provided at the latest by 31 December 1998 for agglomerations of more than 10 000 p.e.

Where the establishment of a collecting system is not justified either because it would produce no environmental benefit or because it would involve excessive cost, individual systems or other appropriate systems which achieve the same level of environmental protection shall be used.

2. Collecting systems described in paragraph 1 shall satisfy the requirements of section A of Annex I. …’

6 Article 4 of Directive 91/271 provides:

‘1. Member States shall ensure that urban waste water entering collecting systems shall before discharge be subject to secondary treatment or an equivalent treatment as follows:

– at the latest by 31 December 2000 for all discharges from agglomerations of more than 15 000 p.e.,

– at the latest by 31 December 2005 for all discharges from agglomerations of between 10 000 and 15 000 p.e.,

– at the latest by 31 December 2005 for discharges to fresh-water and estuaries from agglomerations of between 2 000 and 10 000 p.e.

...

3. Discharges from urban waste water treatment plants described in paragraphs 1 and 2 shall satisfy the relevant requirements of section B of Annex I. ...

4. The load expressed in p.e. shall be calculated on the basis of the maximum average weekly load entering the treatment plant during the year, excluding unusual situations such as those due to heavy rain.’

7 Article 5 of Directive 91/271 provides:

‘1. For the purposes of paragraph 2, Member States shall by 31 December 1993 identify sensitive areas according to the criteria laid down in Annex II.

2. Member States shall ensure that urban waste water entering collecting systems shall before discharge into sensitive areas be subject to more stringent treatment than that described in Article 4, by 31 December 1998 at the latest for all discharges from agglomerations of more than 10 000 p.e.

3. Discharges from urban waste water treatment plants described in paragraph 2 shall satisfy the relevant requirements of section B of Annex I. ...

...

5. Discharges from urban waste water treatment plants which are situated in the relevant catchment areas of sensitive areas and which contribute to the pollution of these areas shall be subject to paragraphs 2, 3 and 4.

...

6. Member States shall ensure that the identification of sensitive areas is reviewed at intervals of no more than four years.

7. Member States shall ensure that areas identified as sensitive following review under paragraph 6 shall within seven years meet the above requirements.

...’

8 Article 10 of Directive 91/271 states:

‘Member States shall ensure that the urban waste water treatment plants built to comply with the requirements of Articles 4, 5, 6 and 7 are designed, constructed, operated and maintained to ensure sufficient performance under all normal local climatic conditions. When designing the plants, seasonal variations of the load shall be taken into account.’

9 Article 12 of Directive 91/271 states:

‘1. Treated waste water shall be reused whenever appropriate. Disposal routes shall minimise the adverse effects on the environment.

2. Competent authorities or appropriate bodies shall ensure that the disposal of waste water from urban waste water treatment plants is subject to prior regulations and/or specific authorisation.

3. Prior regulations and/or specific authorisation of discharges from urban waste water treatment plants made pursuant to paragraph 2 within agglomerations of 2 000 to 10 000 p.e. in the case of discharges to fresh waters and estuaries, and within agglomerations of 10 000 p.e. or more in respect of all discharges, shall contain conditions to satisfy the relevant requirements of section B of Annex I. The Commission may amend those requirements. Those measures, designed to amend non-essential elements of this Directive, shall be adopted in accordance with the regulatory procedure with scrutiny referred to in Article 18(3).

4. Regulations and/or authorisation shall be reviewed and if necessary adapted at regular intervals.’

10 Annex I to Directive 91/271, entitled ‘Requirements for urban waste water’, provides in section A, headed ‘Collecting systems’:

‘Collecting systems shall take into account waste water treatment requirements.

The design, construction and maintenance of collecting systems shall be undertaken in accordance with the best technical knowledge not entailing excessive costs, notably regarding:

– volume and characteristics of urban waste water,

– prevention of leaks,

– limitation of pollution of receiving waters due to storm water overflows.’

11 Section B — headed ‘Discharge from urban waste water treatment plants to receiving waters’ — of Annex I to Directive 91/271 states:

‘1. Waste water treatment plants shall be designed or modified so that representative samples of the incoming waste water and of treated effluent can be obtained before discharge to receiving waters.

2. Discharges from urban waste water treatment plants subject to treatment in accordance with Articles 4 and 5 shall meet the requirements shown in Table 1.

3. Discharges from urban waste water treatment plants to those sensitive areas which are subject to eutrophication as identified in Annex II.A(a) shall in addition meet the requirements shown in Table 2 of this Annex.

...’

12 Footnote 1 of Annex I, which relates to sections A and B of the annex, is worded as follows:

‘Given that it is not possible in practice to construct collecting systems and treatment plants in a way such that all waste water can be treated during situations such as unusually heavy rainfall, Member States shall decide on measures to limit pollution from storm water overflows. Such measures could be based on dilution rates or capacity in relation to dry weather flow, or could specify a certain acceptable number of overflows per year.’

13 Table 1 of Annex I to Directive 91/271 contains the requirements for discharges from urban waste water treatment plants subject to Articles 4 and 5 of the directive. It is as follows:

Parameters Concentration Minimum percentage of reduction [in relation to the load of the influent] Reference method of measurement Biochemical oxygen demand (BOD5 at 20 °C) without nitrification ... 25 mg/l O2 70-90 40 under Article 4(2) ... Chemical oxygen demand (COD) 125 mg/l O2 75 ... Total suspended solids 35 mg/l ... 35 under Article 4(2) (more than 10 000 p.e.)

60 under Article 4(2) (2 000 to 10 000 p.e.) 90 ... 90 under Article 4(2) (more than 10 000 p.e.)

70 under Article 4(2) (2 000 to 10 000 p.e.) ...





14 Table 2 of Annex I to Directive 91/271 contains the requirements for discharges from urban waste water treatment plants to sensitive areas which are subject to eutrophication. It is as follows:

Parameters Concentration Minimum percentage of reduction … Reference method of measurement Total phosphorus 2 mg/l (10 000 - 100 000 p.e.) 1 mg/l (more than 100 000 p.e.) 80 ... Total nitrogen ... 15 mg/l (10 000 - 100 000 p.e.) … 10 mg/l (more than 100 000 p.e.) ... 70-80 ...





15 Section A of Annex II to Directive 91/271 specifies the criteria for identification of sensitive areas.

II. Pre-litigation procedure and proceedings before the Court

16 By a letter of formal notice of 27 September 2013, the Commission raised with Ireland its concerns relating to compliance with Directive 91/271, taking the view that Ireland:

– had failed to ensure that waters collected in 40 agglomerations were retained and conducted for treatment in compliance with the requirements of Article 3 of Directive 91/271 and section A of Annex I thereto;

– had not put in place secondary or equivalent treatment for urban waste water discharges from 52 agglomerations, as provided for in Article 4 of Directive 91/271 and sections B and D of Annex I thereto;

– had failed to apply Article 5 of Directive 91/271 correctly in respect of 28 agglomerations; and

– had failed to apply Article 12 of Directive 91/271 in respect of 32 agglomerations.

17 By letters of 11 December 2013, 14 February 2014 and 8 April 2014, Ireland acknowledged the shortcomings regarding the system for collecting and treating urban waste water and stated that the numerous upgrading works would, in the coming years, enable that system to comply fully with Directive 91/271.

18 In the light of that information and following a meeting between the Irish authorities and Commission staff on 9 April 2014, the Commission sent Ireland an additional letter of formal notice dated 25 September 2015, replacing the previous one in full.

19 In the additional letter of formal notice, the Commission limited the first and fourth complaints to 12 and 27 agglomerations respectively, while extending the second and third complaints to 53 and 36 agglomerations respectively.

20 In its replies of 25 January and 29 July 2016, Ireland set out the advances in the programme for upgrading its system for collecting and treating urban waste water, whilst acknowledging that works were necessary in order to comply fully with Directive 91/271.

21 On the basis of the data submitted by Ireland in its replies, the Commission sent it a reasoned opinion dated 30 September 2016, calling upon it to take the measures necessary to comply with the reasoned opinion within two months of receipt thereof.

22 In the reasoned opinion, the Commission extended the first complaint to a total of 14 agglomerations, while the second, third and fourth complaints were limited to 28, 22 and 2 agglomerations respectively.

23 In its reply dated 28 November 2016, Ireland submitted new data disclosed by the Environmental Protection Agency (Ireland) on 8 November 2016. Referring to those data, Ireland stated, first, that some of the Commission’s criticisms accordingly no longer had a basis. Second, Ireland specified the dates from which the works that were in progress would enable full compliance of the system for collecting and treating urban waste water with Directive 91/271 to be achieved.

24 Since the Commission was not fully satisfied with Ireland’s responses to the reasoned opinion, it brought the present action.

III. Request seeking the production of evidence after the close of the written part of the procedure

25 After the close of the written procedure on 5 February 2018, Ireland requested leave, by a letter dated 17 September 2018, to produce new documents pursuant to Article 128(2) of the Rules of Procedure of the Court of Justice.

26 By decision of 18 September 2018, the President of the Chamber admitted those new documents as evidence in the examination of the present action for failure to fulfil obligations, while permitting the Commission to comment on them at the hearing.

IV. The action

A. Preliminary observations

27 The Commission’s action is founded on four complaints, alleging, respectively: incorrect application of Article 3(1) and (2) of Directive 91/271 and section A and footnote 1 of Annex I thereto, in respect of 14 agglomerations; incorrect application of Article 4(1) and (3) of that directive, read in conjunction with Article 10 thereof and paragraph 2 of section B of Annex I thereto, in respect of 25 agglomerations; incorrect application of Article 5 of that directive, read in conjunction with Article 10 thereof and paragraph 3 of section B of Annex I thereto, in respect of 21 agglomerations; and incorrect application of Article 12 of that directive in respect of two agglomerations.

28 Ireland denies the alleged failure to fulfil obligations in two respects. First, it puts forward for the majority of the complaints, taken individually, arguments designed to call into question the fact that the Commission has placed before the Court all the information required to enable the Court to establish that there has been a failure to fulfil obligations as alleged. Second, relying on section A and footnote 1 of Annex I to Directive 91/271, Ireland submits, in respect of the whole of the present action, that the complaints put forward by the Commission must be analysed in the light of the exceptional circumstances with which Ireland has been faced over the last two decades and having regard to the concept of ‘best technical knowledge not entailing excessive costs’.

29 That being so, it is appropriate to note at the outset the requirements that must be met in order to rely upon the concept of ‘best technical knowledge not entailing excessive costs’, as well as the specific framework in which Directive 91/271 lays down the obligations owed by the Member States, before drawing the ensuing conclusions as to the burden of proof.

1. The concepts of ‘unusually heavy rainfall’ and ‘best technical knowledge not entailing excessive costs’

30 Directive 91/271 refers, in section A of Annex I, to the concept of ‘best technical knowledge not entailing excessive costs’, which specifies, in essence, that the design, construction and maintenance of collecting systems for urban waste water are to be undertaken in accordance with such knowledge not entailing excessive costs. In addition, by footnote 1 of that annex, the EU legislature acknowledged that situations exist in which the urban waste water will not be capable of being collected or treated in its entirety. In particular, it stated that ‘it is not possible in practice to construct collecting systems and treatment plants in a way such that all waste water can be treated’ and it provided that failure to collect and treat waste water may be tolerated during ‘situations such as unusually heavy rainfall’. However, in that case, Member States are to decide on ‘measures to limit pollution from storm water overflows’ (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 56).

31 First, as regards the term ‘unusually heavy rainfall’, that term is mentioned in footnote 1 of Annex I to Directive 91/271 by way of illustration only, since it is preceded by the words ‘during situations such as’. Thus, failure to collect or treat waste water may also be allowed in other circumstances (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 57).

32 However, the objective pursued by Directive 91/271 does not permit the inference that it is normal and common for those other circumstances to arise, in particular as the word ‘unusually’ clearly indicates that failure to collect or treat waste water cannot occur in normal circumstances (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 58).

33 Furthermore, it should be pointed out that, where a Member State is faced with an exceptional situation not allowing it to collect or treat waste water, it remains obliged to adopt appropriate measures to limit pollution under footnote 1 of Annex I to Directive 91/271 (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 60).

34 Also, since the concept of ‘unusually heavy rainfall’ is not defined by Directive 91/271, it is legitimate for the Commission, in carrying out its supervision of compliance with EU law, to adopt guidelines and, as the Court does not have jurisdiction to define numerically obligations laid down by that directive, the concept of ‘unusually heavy rainfall’ must therefore be assessed in the light of all the criteria and conditions prescribed by the directive, in particular the concept of ‘best technical knowledge not entailing excessive costs’ (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 61).

35 Second, the concept of ‘best technical knowledge not entailing excessive costs’ must be examined in each specific case in the light of the objective of protecting the environment pursued by Directive 91/271, as it constitutes a concept inherent in all the provisions of that directive designed to secure such an objective whilst avoiding the imposition upon the Member States of unachievable obligations which they might not be able to fulfil, or only at disproportionate cost (see, to that effect, judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraphs 62 to 64).

36 Thus, examination of that concept requires weighing the best technology and the costs envisaged against the benefits that a more effective water collection or treatment system may provide, so that the costs incurred are not disproportionate to the benefits obtained (judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 67).

37 Specifically, the Court has held that facilities cannot be regarded as complying with the concept of ‘best technical knowledge not entailing excessive costs’, within the meaning of section A of Annex I to Directive 91/271, where, first, a Member State has embarked upon a large programme of works proving that there are technological solutions in order to overcome the problem of excessive spills of waste water, but that they have not been applied, and second, such a Member State has decided to finance such works, so that the related costs cannot be regarded as excessive (see, to that effect, judgment of 4 May 2017, Commission v United Kingdom, C‑502/15, not published, EU:C:2017:334, paragraph 44).

2. The burden of proof

38 It is settled case-law that, although, in proceedings brought under Article 258 TFEU for failure to fulfil obligations, it is for the Commission to prove the allegation that an obligation has not been fulfilled, by placing before the Court all the information required to enable the Court to establish that the obligation has not been fulfilled, without the Commission being entitled to rely on any presumption, account should be taken of the fact that, where it is a question of checking that the national provisions intended to ensure effective implementation of a directive are applied correctly in practice, the Commission, which does not have investigative powers of its own in this area, is largely reliant on the information provided by any complainants and by the Member State concerned (judgment of 28 January 2016, Commission v Portugal, C‑398/14, EU:C:2016:61, paragraph 47).

39 It follows, inter alia, that, where the Commission has adduced sufficient evidence to establish that the national provisions transposing a directive are not applied correctly in practice in the territory of the defendant Member State, it is incumbent on the latter to challenge in substance and in detail the information produced and the inferences drawn (judgment of 28 January 2016, Commission v Portugal, C‑398/14, EU:C:2016:61, paragraph 48).

40 In the more specific context of Directive 91/271, it is consequently incumbent on the Member State which seeks to rely on the concept of ‘best technical knowledge not entailing excessive costs’, with a view to justifying any divergence from the provisions of that directive, to submit to the Court the information enabling it to assess to what extent, in a specific case, the costs that a more effective water collection or treatment system involve would be disproportionate to the benefits obtained.

41 It should be noted that the EU legislature, conscious of the scope of the infrastructure works required for the application of Directive 91/271 and the costs of its full implementation, granted the Member States a period of several years to carry out their obligations (judgment of 4 May 2017, Commission v United Kingdom, C‑502/15, not published, EU:C:2017:334, paragraph 48).

42 Furthermore, the question whether a Member State has failed to fulfil obligations must be determined by reference to the situation prevailing in the Member State at the end of the period laid down in the reasoned opinion and the Court cannot take account of any subsequent changes (judgment of 28 November 2018, Commission v Slovenia, C‑506/17, not published, EU:C:2018:959, paragraph 50 and the case-law cited).

43 Since Ireland puts forward arguments in respect of each complaint in order to prove the compliance of the systems for collecting and treating urban waste water, and also relies, for the whole of the present action for failure to fulfil obligations, on exceptional circumstances and the concept of ‘best technical knowledge not entailing excessive costs’ to justify any divergence from the provisions of Directive 91/271, it is appropriate to examine the merits of each complaint put forward by the Commission, before assessing the matters advanced by Ireland to justify the cases in which the Court concludes that there are divergences from the directive’s provisions, whilst, under the Court’s case-law, even if the Member State concerned does not deny a failure to fulfil obligations, it is incumbent upon the Court, in any event, to determine whether or not that alleged breach of obligations exists (see, to that effect, judgment of 14 September 2017, Commission v Greece, C‑320/15, EU:C:2017:678, paragraph 21).

B. The first complaint

44 By its first complaint, the Commission contends that Ireland has failed to fulfil its obligations under Article 3(1) and (2) of Directive 91/271, read in conjunction with section A and footnote 1 of Annex I thereto, on the ground, first, that the combined systems for collecting urban waste water of 12 agglomerations do not satisfy the requirements of those provisions inasmuch as there are repeated and excessive spills from them and, second, such a system is entirely lacking in two agglomerations.

45 Ireland challenges in individual instances the data put forward by the Commission in support of its complaint and contests globally the infringement of Article 3 of Directive 91/271 by relying on exceptional circumstances and the concept of ‘best technical knowledge not entailing excessive costs’.

46 Since exceptional circumstances and that concept are relied on in order to justify the situations in which a collecting system for urban waste water does not fulfil the requirements of Article 3 of Directive 91/271, it is appropriate first of all to determine whether the evidence submitted by the Commission is capable of proving the complaint as regards each of the agglomerations that the complaint covers.

1. The first part of the first complaint

47 The Commission submits that the collecting systems for urban waste water and rainwater of the agglomerations of Athlone, Ballincollig New, Cavan, Cork City, Enniscorthy, Fermoy, Mallow, Midleton, Osberstown, Roscommon Town, Roscrea and Thurles give rise to spills of untreated waters the frequency and quantity of which do not comply with Article 3(1) of Directive 91/271 and footnote 1 of Annex I thereto.

48 Prompted by information provided by Ireland in its defence, the Commission withdrew the first part of the first complaint so far as concerns the agglomeration of Ballincollig New and the townland of Killagoley in the agglomeration of Enniscorthy.

49 Following a question from the Court at the hearing, Ireland conceded, however, that, in the case of the agglomerations of Athlone, Cork City, Fermoy and Mallow, the data put forward by the Commission showed that the collecting systems for urban waste water did not comply with the requirements of Article 3 of Directive 91/271, while maintaining that the situations of non-compliance thereby admitted had to be assessed in the light of the concept of ‘best technical knowledge not entailing excessive costs’.

50 In any event, as has been recalled in paragraph 43 above, it is incumbent upon the Court to determine whether or not the alleged failure to fulfil obligations exists, even in so far as Ireland does not deny the failure.

(a) The agglomeration of Athlone

51 In respect of the agglomeration of Athlone, it is apparent from the data forwarded to the Commission by Ireland in its reply of 11 December 2013 to the initial letter of formal notice of 27 September 2013 that more than 300 spills were recorded for 2011, equivalent to a volume of 144 294 m3 of urban waste water discharged without prior treatment.

52 In the light of those data, it must be concluded that the collecting system for urban waste water of the agglomeration of Athlone does not comply with Article 3 of Directive 91/271.

(b) The agglomeration of Cavan

(1) Arguments of the parties

53 First, the Commission refers to the document of February 2012 entitled ‘Cavan Sewerage Scheme and Treatment Works’, annexed to Ireland’s reply of 11 December 2013 to the initial letter of formal notice of 27 September 2013, which mentions one storm water overflow that did not comply with the national requirements for discharges from storm water overflows.

54 Second, the Commission refers to the report of the Environmental Protection Agency for 2016 entitled ‘Urban Waste Water Treatment in 2016’ (‘the 2016 EPA Report’) which itself refers to the information contained in the annual environmental report for the agglomeration of Cavan indicating the presence of 20 storm water overflows for the period that it covers, of which the status of 14 is unknown, the status of five is compliant with the national requirements transposing Directive 91/271 and the status of one is not compliant with those requirements.

55 Ireland submits, first, that the Commission cannot discharge the burden of proving the failure to fulfil obligations by relying on the fact that the 2016 EPA Report categorises the collecting system for urban waste water of the agglomeration of Cavan as not compliant with the national requirements transposing Directive 91/271, since the fact that that agglomeration is mentioned in the report results solely from the fact that it was included by the Commission in the procedure leading to the present action for failure to fulfil obligations. In any event, it is incumbent upon the Commission to rely on its own evidence and not on data from the Member State in question.

56 Second, Ireland puts forward the improvements in the aforesaid collecting system which have been reflected in a reduction in the number of storm water overflows present in that agglomeration.

(2) Findings of the Court

57 First of all, it is to be recalled that, although, in proceedings brought under Article 258 TFEU for failure to fulfil obligations, it is for the Commission to prove the allegation that an obligation has not been fulfilled, by placing before the Court all the information required to enable the Court to establish that the obligation has not been fulfilled, without the Commission being entitled to rely on any presumption, account should be taken of the fact that, where it is a question of checking that the national provisions intended to ensure effective implementation of a directive are applied correctly in practice, the Commission, which does not have investigative powers of its own in this area, is largely reliant on the information provided by any complainants and by the Member State concerned (judgment of 28 January 2016, Commission v Portugal, C‑398/14, EU:C:2016:61, paragraph 47).

58 Therefore, the Commission cannot be criticised, as a matter of principle, for making use of the information that is made available to it in order to carry out its task, including information from the Member State concerned itself, where it enables the alleged failure to fulfil obligations to be proved.

59 However, as is apparent from the 2016 EPA Report, upon which, inter alia, the Commission bases the first part of the first complaint, the inclusion of the data relating to the agglomeration of Cavan was due to the fact that that agglomeration was covered by the present procedure for failure to fulfil obligations, irrespective of any assessment of whether its collecting system for urban waste water complies with Article 3 of Directive 91/271.

60 Accordingly, the Commission cannot conclude from the mere mention of the agglomeration of Cavan in the 2016 EPA Report that the collecting system for urban waste water of that agglomeration does not comply with that provision.

61 In the present instance, the Commission states that it is apparent from the document entitled ‘Cavan Sewerage Scheme and Treatment Works’ of February 2012 that one storm water overflow does not comply with the relevant national requirements. In its reply, the Commission identifies that overflow as being on Thomas Ashe Street and submits that the 2016 EPA Report, which refers to the information contained in the annual environmental report for that agglomeration, supports the conclusion that there is an overflow in the agglomeration that does not comply with those requirements.

62 However, Ireland observes in its rejoinder that that overflow was removed in 2015 and that the 225 mm sewer at that location has been replaced by a new 300 mm gravity sewer following works that were completed in July 2016.

63 In the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns the agglomeration of Cavan.

(c) The agglomeration of Cork City

64 In respect of the agglomeration of Cork City, it is apparent from the data forwarded to the Commission by Ireland in its reply of 28 November 2016 to the reasoned opinion that 853 spills were counted for 2015, equivalent to a volume of 5 948 782 m3 of urban waste water discharged without prior treatment.

65 In the light of those data, it must be concluded that the collecting system for urban waste water of the agglomeration of Cork City does not comply with Article 3 of Directive 91/271.

(d) The agglomeration of Enniscorthy

66 After taking note that, in the townland of Killagoley in the agglomeration of Enniscorthy, urban waste water is collected in compliance with Directive 91/271, the Commission indicates in its reply that the 2016 EPA Report refers to information contained in the annual environmental report for that agglomeration, which states that 1% of the total volume of waste water generated was discharged via storm water overflows.

67 In that regard, it is apparent from that report that, out of the six active storm water overflows for the agglomeration, one is considered not to comply with the national requirements transposing Directive 91/271. It was, moreover, activated 30 times in 2016.

68 Therefore, it must be held that the Commission has proved that the collecting system for urban waste water of the agglomeration of Enniscorthy, apart from the townland of Killagoley, does not meet, in part, the requirements of Article 3 of Directive 91/271.

(e) The agglomeration of Fermoy

69 In respect of the agglomeration of Fermoy, it is apparent from the data forwarded to the Commission by Ireland in its reply of 25 January 2016 to the additional letter of formal notice that 108 spills were counted for 2014, equivalent to a volume of 71 500 m3 of urban waste water discharged without prior treatment, while 57 spills were recorded for 2015, equivalent to a volume of 35 337 m3 of untreated urban waste water.

70 In the light of those data, it must be concluded that the collecting system for urban waste water of the agglomeration of Fermoy does not comply with Article 3 of Directive 91/271.

(f) The agglomeration of Mallow

71 In respect of the agglomeration of Mallow, it is apparent from the data forwarded to the Commission by Ireland in its reply of 25 January 2016 to the additional letter of formal notice that, for 2014, out of the eight active storm water overflows, the estimated number of spills for a single one of those overflows was 121, corresponding to a volume of 480 000 m3 of untreated urban waste water.

72 In the light of those data, it must be concluded that the collecting system for urban waste water of the agglomeration of Mallow does not comply with Article 3 of Directive 91/271.

(g) The agglomeration of Midleton

(1) Arguments of the parties

73 As regards the agglomeration of Midleton, the Commission bases the first part of its first complaint on various reports and on a complaint sent to it in order to demonstrate that the collecting system for urban waste water of that agglomeration does not comply with Article 3 of Directive 91/271.

74 First, it relies on the data resulting from the study by White Young Green on spillages in the agglomeration of Midleton in 2011 and 2012.

75 Second, the Commission refers to the report by WYG Engineering of November 2008 and the report by Mott MacDonald of August 2011, entitled ‘Midleton Sewerage Scheme — Assessment of Pump Overflow’, in order to prove that the treatment plant of the agglomeration of Midleton suffers from under-capacity in relation to the load to be treated and that the pumped flows and storage capacity must be increased considerably. Such a finding is, moreover, said to be confirmed by data communicated to the Commission following a complaint that was sent to it.

76 Third, the Commission sets out the data of the 2016 EPA Report for that agglomeration.

77 Ireland contends, as its principal submission, that that evidence is inadmissible, on the ground that it was not sent to it before the Commission brought the present action.

78 Ireland pleads that, in any event, the data upon which the Commission relies no longer reflect the current situation. Thus, only eight spills were recorded for 2015. Furthermore, the ‘biochemical oxygen demand’ (‘BOD’) and ‘chemical oxygen demand’ (‘COD’) standards prescribed in Article 4 of Directive 91/271, read in conjunction with Table 1 of Annex I thereto, were met for 2013 to 2016.

(2) Findings of the Court

79 As regards the admissibility of the evidence adduced by the Commission, it must be stated, first of all, that in its reply of 11 December 2013 to the initial letter of formal notice of 27 September 2013, Ireland itself referred to the study by White Young Green on spillages in 2011 and 2012.

80 Next, it is apparent from the case file that the WYG Engineering report of November 2008 was commissioned by Cork County Council.

81 As regards, finally, the Mott MacDonald report of August 2011 and the complaint sent to the Commission, those documents, like those cited in the preceding paragraphs, were mentioned in the additional letter of formal notice of 25 September 2015, before being annexed to the Commission’s application.

82 Therefore, Ireland was able to obtain those documents directly or, at the very least, acting diligently, to ask the Commission to produce them at the appropriate time.

83 In any event, in order to guarantee the rights of defence of the Member State concerned, the subject matter of an action under Article 258 TFEU for failure to fulfil obligations is determined by the Commission’s reasoned opinion, so that the action must be based on the same grounds and pleas as that opinion (judgment of 8 July 2010, Commission v Portugal, C‑171/08, EU:C:2010:412, paragraph 25).

84 Here, Ireland does not dispute that the grounds and pleas of the Commission’s reasoned opinion and application in the present proceedings are identical.

85 Consequently, the evidence upon which the Commission bases the first part of its first complaint as regards the agglomeration of Midleton must be declared admissible.

86 The Commission moreover relied on the 2016 EPA Report, which refers to the information contained in the annual environmental report for the agglomeration, from which it is apparent that four storm water overflows were active in 2016 and that there were 158 spills from them, equivalent to a volume of 561 679 m³ of untreated urban waste water.

87 In that regard, first, Ireland cannot plead that these data from 2016 are old since it raises against them data from 2015 in order to challenge the matters put forward by the Commission.

88 Second, as Article 3 of Directive 91/271 lays down an obligation to collect all urban waste water, the fact that the prescribed water treatment standards in Article 4 of Directive 91/271, read in conjunction with Table 1 of Annex I thereto, were met for 2013 to 2016 has no bearing on whether the collecting system for urban waste water complies with Article 3 of the directive.

89 In the light of those factors, it must be concluded that the collecting system for urban waste water of the agglomeration of Midleton does not comply with Article 3 of Directive 91/271.

(h) The agglomeration of Osberstown

90 As regards the agglomeration of Osberstown, the Commission notes the presence of 22 storm water overflows and points out that upgrade works are in progress.

91 Whilst the existence of storm water overflows and of ongoing upgrade works is an indication that the collecting system for urban waste water is liable, in certain circumstances, to give rise to spillages and discharges of untreated urban waste water, the fact remains that, in the absence of specific and precise data concerning the compliance of those overflows and their activity, the existence of the overflows and works amounts, at most, to only a presumption of non-compliance.

92 Furthermore, and as has been noted in paragraph 60 above, the mere fact that the agglomeration of Osberstown has been mentioned in the 2016 EPA Report cannot in itself suffice to conclude that the collecting system for urban waste water of that agglomeration does not comply with Article 3 of Directive 91/271. Moreover, as the Commission has observed in its reply, there does not seem to be a reference to the data relating to that agglomeration in the 2016 EPA Report.

93 In the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns the agglomeration of Osberstown.

(i) The agglomeration of Roscommon Town

94 It is apparent from Ireland’s reply to the additional letter of formal notice that there are 10 storm water overflows in the agglomeration of Roscommon Town. Also, the 2016 EPA Report refers to the information contained in the annual environmental report for that agglomeration recording six storm water overflows, none of which complies with the national requirements transposing Directive 91/271.

95 In the light of those data, it must be concluded that the collecting system for urban waste water of the agglomeration of Roscommon Town does not comply with Article 3 of Directive 91/271.

(j) The agglomeration of Roscrea

96 As regards the agglomeration of Roscrea, the Commission notes the presence of four storm water overflows and points out that upgrade works are in progress. In that regard, the Commission refers to the 2016 EPA Report, which itself refers to the information contained in the annual environmental report for that agglomeration, but does not contain any particulars as to the compliance and activity of those overflows.

97 Whilst the existence of storm water overflows and of ongoing upgrade works is an indication that the collecting system is liable, in certain circumstances, to give rise to spillages and discharges of untreated urban waste water, the fact remains that, in the absence of specific and precise data concerning the compliance of those overflows and their activity, the existence of the overflows and works amounts, at most, to only a presumption of non-compliance.

98 Furthermore, and as has been noted in paragraph 60 above, the mere fact that the agglomeration of Roscrea has been mentioned in the 2016 EPA Report, which refers to the information contained in the annual environmental report for that agglomeration, cannot in itself suffice to conclude that the collecting system for urban waste water of that agglomeration does not comply with Article 3 of Directive 91/271.

99 In the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns the agglomeration of Roscrea.

(k) The agglomeration of Thurles

100 The Commission notes the presence of four storm water overflows in the agglomeration of Thurles and points out that upgrade works are in progress. In that regard, the Commission refers to the 2016 EPA Report, which itself refers to the information contained in the annual environmental report for that agglomeration, but does not contain any particulars as to the compliance and activity of those overflows.

101 Whilst the existence of storm water overflows and of ongoing upgrade works is an indication that the collecting system is liable, in certain circumstances, to give rise to spillages and discharges of untreated urban waste water, the fact remains that, in the absence of specific and precise data concerning the compliance of those overflows and their activity, the existence of the overflows and works amounts, at most, to only a presumption of non-compliance.

102 Furthermore, and as has been noted in paragraph 60 above, the mere fact that the agglomeration of Thurles has been mentioned in the 2016 EPA Report, which refers to the information contained in the annual environmental report for that agglomeration, cannot in itself suffice to conclude that the collecting system for urban waste water of that agglomeration does not comply with Article 3 of Directive 91/271.

103 In the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns the agglomeration of Thurles.

2. The second part of the first complaint

(a) Arguments of the parties

104 The Commission submits that Ireland has not put in place appropriate collecting systems for urban waste water in the agglomerations of Ringaskiddy and Gaoth Dobhair.

105 However, prompted by information provided by Ireland in its defence, the Commission withdrew the second part of the first complaint so far as concerns the agglomeration of Gaoth Dobhair.

106 As regards the agglomeration of Ringaskiddy, the Commission states that the urban waste water, corresponding to a load of 116 982 p.e., is not collected.

107 Ireland states that 85% of the total load generated by that agglomeration comes from industrial activities that have their own treatment plants. Accordingly, only the loads of the towns of Carrigaline and Crosshaven should be taken into consideration for the purpose of assessing compliance with Article 3 of Directive 91/271.

108 After taking note in the reply that a load of 17 500 p.e. had to be adopted for the agglomeration of Ringaskiddy, the Commission, relying on the data submitted by Ireland in its reply of 25 January 2016 to the additional letter of formal notice, reiterates that no collecting system exists for that agglomeration.

(b) Findings of the Court

109 Since it is not disputed that no collecting system for urban waste water exists in respect of the load of 17 500 p.e. in the agglomeration of Ringaskiddy, it must be concluded that the collecting system for urban waste water of that agglomeration does not comply with Article 3 of Directive 91/271.

110 It follows from all those considerations that the collecting systems for urban waste water of the agglomerations of Athlone, Cork City, Enniscorthy apart from the townland of Killagoley, Fermoy, Mallow, Midleton, Ringaskiddy and Roscommon Town do not comply with Article 3 of Directive 91/271.

111 Since Ireland submits, however, that the compliance of the collecting systems for urban waste water in those agglomerations must be assessed in the light of section A and footnote 1 of Annex I to Directive 91/271 and application of the concept of ‘best technical knowledge not entailing excessive costs’ would therefore justify any partial divergence from Article 3 of that directive, the matters put forward by Ireland in that regard should be examined in the light of the principles noted in paragraphs 30 to 37 above.

3. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

(a) Arguments of the parties

112 In general terms, Ireland notes the exceptional circumstances that it has faced in the past few decades in the sector of urban waste water management and treatment, stressing the initial effort necessary to render the network for collecting and treating Irish urban waste water compliant, the major reform undertaken in that sector and the effects of an economic crisis on the carrying out of that reform.

113 In particular, Ireland submits that the complaints put forward by the Commission must be analysed having regard to the investment made and works carried out by Ireland from 2000 to 2013, in the context of the fundamental reform of the system for treating urban waste water, a reform which was, however, profoundly affected by the economic crisis that Ireland suffered in 2008. Over that period, it was nevertheless possible to invest EUR 3.5 billion in order to upgrade the infrastructure for collecting and treating urban waste water.

114 In that context, Ireland states that there will be substantial investment in the short term in order to complete that upgrading. The investment amounts to EUR 2.7 billion for the period from 2014 to 2021 and will enable the system for collecting and treating urban waste water to be rendered fully compliant with Directive 91/271.

115 On a more individual level, Ireland notes, regarding certain agglomerations, the technical, legal or administrative difficulties which have been able to delay the carrying out of the necessary works.

116 Furthermore, Ireland maintains that, in view of the infrequency and limited size of the spills recorded in certain agglomerations, the individual instances of malfunction of the relevant collecting systems for urban waste water must be regarded as resulting from unusually heavy rainfall within the meaning of footnote 1 of Annex I to Directive 91/271.

117 The Commission notes that application of the concept of ‘best technical knowledge not entailing excessive costs’ is merely the expression of the principle of proportionality in connection with investment relating to infrastructure for collecting and treating waste water. In that context, Ireland fails to adduce any evidence proving that the costs necessary in order to render the systems for collecting and treating waste water compliant with Directive 91/271 are disproportionate to the environmental protection benefits.

(b) Findings of the Court

118 As has been recalled in paragraph 34 above, the concept of ‘unusually heavy rainfall’ must be assessed in the light of all the criteria and conditions prescribed by Directive 91/271, in particular the concept of ‘best technical knowledge not entailing excessive costs’.

119 Application of the latter concept must be examined in each specific case and requires weighing the best technology and the costs envisaged against the benefits that a more effective system for collecting or treating urban waste water may provide, so that the costs incurred are not disproportionate to the benefits obtained.

120 In that regard, the Court has held that facilities cannot be regarded as complying with the concept of ‘best technical knowledge not entailing excessive costs’, within the meaning of section A of Annex I to Directive 91/271, where, first, a Member State has embarked upon a large programme of works proving that there are technological solutions in order to overcome the problem of excessive spills of waste water, but that they have not been applied, and second, such a Member State has decided to finance such works, so that the related costs cannot be regarded as excessive (see, to that effect, judgment of 4 May 2017, Commission v United Kingdom, C‑502/15, not published, EU:C:2017:334, paragraph 44).

121 Since Ireland states that it has embarked upon a programme of major reform of the system for collecting and treating urban waste water, it is proven, first, that there are technological solutions in order to overcome the problem of excessive spills before urban waste water is treated. Second, the costs of the works necessary for that purpose cannot be regarded as excessive, inasmuch as Ireland has decided to carry them out.

122 In this connection, it should be borne in mind that, in accordance with settled case-law, a Member State may not plead practical or administrative difficulties in order to justify non-compliance with the obligations and time limits laid down by a directive. The same holds true for financial difficulties, which it is for the Member States to overcome by adopting appropriate measures (see, to that effect, judgment of 18 October 2012, Commission v United Kingdom, C‑301/10, EU:C:2012:633, paragraph 66 and the case-law cited).

123 Thus, mere general mention of the financial difficulties connected with the economic crisis cannot justify the fact that the collecting systems for urban waste water of the various agglomerations covered by the first complaint do not comply with Article 3 of Directive 91/271.

124 That having been said, as the Commission itself acknowledged at the hearing the existence of such an economic crisis could, for each specific case, be taken into account in the context of the balancing exercise referred to in paragraphs 36 and 119 above.

125 However, it must be stated that Ireland adduces nothing capable of proving that the costs to be incurred, in order to ensure that the collecting systems for urban waste water of the various agglomerations covered by the first complaint are compliant, are disproportionate to the resulting advantages.

126 Furthermore, mention of the works that remain to be carried out so far as concerns the collecting systems of each of the agglomerations covered by the first complaint attests the feasibility of putting in place the facilities necessary to render the systems compliant with Directive 91/271.

127 In that regard, it is to be borne in mind that the EU legislature, conscious of the scope of the infrastructure works that resulted from the transposition of Directive 91/271 and the costs of its full implementation, granted the Member States a period of several years to carry out their obligations (judgment of 4 May 2017, Commission v United Kingdom, C‑502/15, not published, EU:C:2017:334, paragraph 48).

128 As regards, in particular, the agglomeration of Midleton, Ireland states that the frequency of spills is very low, so that they cannot be classified as usual events.

129 However, as the Commission submitted in its reply, the 2016 EPA Report refers to the information contained in the annual environmental report for that agglomeration, from which it is apparent that four storm water overflows were active in 2016 and that there were 158 spills from them, equivalent to a volume of 561 679 m³ of untreated urban waste water.

130 In the absence of further details as to the spills recorded in respect of the agglomeration of Midleton, Ireland cannot assert that those spills result from unusual meteorological events the taking account of which would entail costs disproportionate to the benefits obtained.

131 It follows from all those considerations that the collecting of urban waste water in the agglomerations of Athlone, Cork City, Enniscorthy apart from the townland of Killagoley, Fermoy, Mallow, Midleton, Ringaskiddy and Roscommon Town does not comply with Article 3(1) and (2) of Directive 91/271 and section A of Annex I thereto.

C. The second complaint

132 By its second complaint, the Commission contends that Ireland has failed to fulfil its obligations under Article 4(1) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto, because, first, there is no treatment plant in six agglomerations, second, the treatment plants existing in seven agglomerations are unable to ensure compliance with the BOD and COD standards as prescribed in section B and Table 1 of Annex I to Directive 91/271 and, third, Article 3 of that directive is not complied with so far as concerns 12 agglomerations.

133 Ireland contests globally the infringement of Article 4 of Directive 91/271 by relying on application of the concept of ‘best technical knowledge not entailing excessive costs’ and challenges individually the data put forward by the Commission in support of this complaint as regards certain agglomerations.

134 Since exceptional circumstances and the concept of ‘best technical knowledge not entailing excessive costs’ are relied on in order to justify the situations in which a system for treating urban waste water does not fulfil the requirements of Article 4 of Directive 91/271, it is appropriate at the outset to determine whether the evidence submitted by the Commission is capable of justifying in law the second complaint as regards each of the agglomerations covered by it.

1. The first part of the second complaint

(a) Arguments of the parties

135 The Commission submits that the requirements of Article 4(1) and (3) of Directive 91/271 are not complied with on account of the absence of waste water treatment facilities for the agglomerations of Arklow, Cobh, Killybegs, Passage/Monkstown, Ringaskiddy and Youghal.

136 Ireland pleads, first, difficulties in planning and achieving the required facilities. It states, second, that the works enabling waste water to be treated in compliance with the requirements of Article 4(1) and (3) of Directive 91/271 are in the course of being completed or, at least, are planned.

(b) Findings of the Court

137 Article 4(1) of Directive 91/271 provides that all urban waste water entering collecting systems must before discharge be subject to secondary treatment or an equivalent treatment.

138 Under Article 4(3) of Directive 91/271, that secondary or equivalent treatment must be carried out by treatment plants the discharges of which satisfy the requirements of section B of Annex I to the directive.

139 As is apparent from Ireland’s reply of 25 January 2016 to the additional letter of formal notice and its reply of 28 November 2016 to the reasoned opinion, urban waste water of the agglomerations of Arklow, Cobh, Killybegs, Passage/Monkstown, Ringaskiddy and Youghal is not treated before discharge, on account of the absence of facilities necessary for that purpose.

140 As the question whether a Member State has failed to fulfil obligations must be determined by reference to the situation prevailing in the Member State at the end of the period laid down in the reasoned opinion, the Court cannot take account, in that regard, of any subsequent changes (judgment of 28 January 2016, Commission v Portugal, C‑398/14, EU:C:2016:61, paragraph 49).

141 Here, the reasoned opinion, dated 30 September 2016, set Ireland a period of two months from receipt thereof for complying with its obligations under Article 4 of Directive 91/271. The period granted for compliance thus expired on 30 November 2016.

142 As regards the agglomerations referred to in the first part of the second complaint, Ireland indicates in its defence that, on the date on which that pleading was lodged, works concerning the treatment plants were in progress or scheduled in order to meet the obligations under Article 4 of Directive 91/271. Accordingly, it is established that, at the end of the period laid down by the reasoned opinion, those agglomerations did not comply with the obligations stemming from Article 4, since they did not have operational waste water treatment facilities.

143 Therefore, the second complaint must be considered well founded so far as concerns the agglomerations of Arklow, Cobh, Killybegs, Passage/Monkstown, Ringaskiddy and Youghal.

2. The second part of the second complaint

(a) Arguments of the parties

144 Relying on Ireland’s reply of 25 January 2016 to the additional letter of formal notice, the Commission states that the capacity of the facilities of the agglomerations of Ballybofey/Stranorlar, Enfield, Enniscorthy, Ringsend, Shannon Town and Tubbercurry does not enable secondary or equivalent treatment of the loads of waste water to be ensured before discharge.

145 In addition, as regards the agglomeration of Rathcormac, the Commission states that the BOD/COD standards are not complied with.

146 As regards the agglomerations of Ballybofey/Stranorlar, Enniscorthy, Ringsend, Shannon Town and Tubbercurry, Ireland acknowledges the need to increase the capacity of the waste water treatment facilities. It states that works are in the course of being finalised in order to remedy those deficiencies.

147 As regards the agglomeration of Enfield, Ireland states that an assessment of the treatment plant’s capacity is underway but that a capacity upgrade is not thought to be required as the BOD/COD standards are complied with.

148 As regards the agglomeration of Rathcormac, Ireland states that the non-compliance of the waste water treatment facility resulted from operational issues that were to be resolved at the end of 2017.

(b) Findings of the Court

149 In support of the second part of the second complaint, the Commission relies on the data dated 31 December 2014 which were disclosed to it by Ireland in Ireland’s reply of 25 January 2016 to the additional letter of formal notice and in its reply of 28 November 2016 to the reasoned opinion.

150 First of all, it is apparent from those documents that:

– the load generated by the agglomeration of Ballybofey/Stranorlar is 5 532 p.e., the treatment capacity of the facilities is 4 000 p.e., and the BOD/COD standards were complied with so far as concerns 2013 to 2015;

– the load generated by the agglomeration of Enniscorthy as regards the secondary discharge was 2 107 p.e., the treatment capacity of the facilities was 1 000 p.e., and the BOD/COD standards were not complied with so far as concerns those years;

– the load generated by the agglomeration of Ringsend is 2 124 000 p.e., the treatment capacity of the facilities is 1 640 000 p.e., and the BOD/COD standards were not complied with so far as concerns those years;

– the load generated by the agglomeration of Shannon Town is 26 740 p.e., the treatment capacity of the facilities is 12 500 p.e., and the BOD/COD standards were not complied with so far as concerns those years; and

– the load generated by the agglomeration of Tubbercurry is 2 283 p.e., the treatment capacity of the facilities is 1 400 p.e., and the BOD/COD standards were not complied with so far as concerns those years.

151 Next, so far as concerns the agglomeration of Enfield, Ireland’s reply to the reasoned opinion refers to a generated load of 5 873 p.e. for 2015, whereas the treatment capacity of the facilities is 3 500 p.e. It is, however, also apparent from that reply that the BOD/COD standards had been complied with since 2013.

152 As Article 4(1) of Directive 91/271 contains an unconditional obligation requiring secondary or equivalent treatment of all urban waste water before discharge, it must be found that, in the light of the under-capacity of the facilities of the agglomerations of Ballybofey/Stranorlar and Enfield, the requirements of that provision are not complied with so far as concerns those agglomerations.

153 Even though the BOD/COD standards were complied with so far as concerns waters treated in the facilities of those agglomerations in respect of 2013 to 2015, the fact remains that a proportion of the urban waste water was not treated at all.

154 The Court has already held that, since discharges of waters that have not been treated at all do not satisfy the requirements of section B of Annex I to Directive 91/271, the treatment of urban waste water by facilities suffering from under-capacity cannot be regarded as complying with Article 4(3) of that directive (see, to that effect, judgment of 11 September 2008, Commission v Ireland, C‑316/06, not published, EU:C:2008:487, paragraphs 12 and 22).

155 Regarding, finally, the agglomeration of Rathcormac, as is apparent from the data contained in Ireland’s reply of 25 January 2016 to the additional letter of formal notice and in its reply of 28 November 2016 to the reasoned opinion, the load generated is 2 602 p.e, while the capacity of that agglomeration’s facilities is 4 000 p.e. However, the BOD/COD standards prescribed in section B and Table 1 of Annex I to Directive 91/271 were not complied with in respect of 2014 to 2016.

156 Ireland states in its defence that the exceeding of those standards is the result of operational issues but does not provide further explanation.

157 That being so, it must be held that the waste water of the agglomeration of Rathcormac is not subject to appropriate treatment before discharge. The complaint alleging non-compliance with Article 4(3) of Directive 91/271, read in conjunction with section B and Table 1 of Annex I thereto, is accordingly well founded so far as concerns that agglomeration.

158 Therefore, treatment of the waters of the agglomerations of Ballybofey/Stranorlar, Enfield, Enniscorthy, Ringsend, Shannon Town and Tubbercurry does not comply with Article 4(1) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B and Table 1 of Annex I thereto. Treatment of the waters of the agglomeration of Rathcormac does not comply with Article 4(3) of Directive 91/271, read in conjunction with Article 10 thereof and section B and Table 1 of Annex I thereto.

3. The third part of the second complaint

(a) Arguments of the parties

159 The Commission submits that Ireland has infringed Article 4(1) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto, so far as concerns the agglomerations of Athlone, Ballincollig New, Cavan, Cork City, Fermoy, Mallow, Midleton, Osberstown, Roscommon Town, Roscrea, Thurles and Gaoth Dobhair.

160 Prompted by information provided by Ireland in its defence, the Commission withdrew the third part of the second complaint so far as concerns the agglomeration of Gaoth Dobhair.

161 The Commission justifies the infringement of Article 4(1) and (3) of Directive 91/271 on the basis of the infringement of Article 3 of that directive.

162 In addition to exceptional circumstances and application of the concept of ‘best technical knowledge not entailing excessive costs’, Ireland submits that appropriate treatment of waste water is ensured so far as concerns the agglomerations of Athlone, Ballincollig New, Cavan, Fermoy, Mallow, Midleton, Osberstown, Roscommon Town and Thurles and relies, in that regard, on the data contained in its reply of 25 January 2016 to the additional letter of formal notice and in its reply of 28 November 2016 to the reasoned opinion.

(b) Findings of the Court

163 As the Commission bases the third part of the second complaint exclusively on the fact that the collecting systems for urban waste water in certain agglomerations do not comply with Article 3 of Directive 91/271, it should be noted, first, that, as is apparent from paragraphs 63, 93, 99 and 103 above, the Commission has not established that Ireland has failed to fulfil its obligations under Article 3 of Directive 91/271 so far as concerns the collecting systems for urban waste water of the agglomerations of Cavan, Osberstown, Roscrea and Thurles. In addition, the Commission withdrew the first part of the first complaint so far as concerns the agglomeration of Ballincollig New.

164 Therefore, on the basis of the Commission’s line of argument, the third part of the second complaint can only concern the agglomerations of Athlone, Cork City, Fermoy, Mallow, Midleton and Roscommon Town.

165 First, under Article 4(1) of Directive 91/271, all urban waste water entering collecting systems must before discharge be subject to secondary treatment or an equivalent treatment.

166 Consequently, in so far as agglomerations are not equipped with a system enabling all their urban waste water to be collected in accordance with Article 3 of Directive 91/271, the obligation laid down in Article 4 of the directive to subject all discharges to secondary or equivalent treatment is a fortiori not fulfilled (judgment of 19 July 2012, Commission v Italy, C‑565/10, not published, EU:C:2012:476, paragraph 34).

167 Second, pursuant to Article 4(3) of Directive 91/271, discharges from urban waste water treatment plants are to satisfy the requirements of section B of Annex I to the directive.

168 The third recital of Directive 91/271 explains that there is a general need for secondary treatment of urban waste water in order to prevent the environment from being adversely affected by its disposal.

169 Ireland states that, despite the lack of treatment plants and, consequently, of treatment of urban waste water in certain agglomerations, the BOD/COD standards are complied with.

170 It must be stated that, where the establishment of a collecting system for urban waste water has been considered to be justified in a given agglomeration, Article 4(1) of Directive 91/271 lays down an obligation of result so far as concerns treatment of the urban waste water by a treatment plant.

171 In addition, paragraph 1 of section B of Annex I to Directive 91/271 specifies that waste water treatment plants are to be designed or modified so that representative samples of the incoming waste water and of treated effluent can be obtained before discharge to receiving waters.

172 Therefore, the provisions of Directive 91/271 lay down treatment obligations designed to achieve systematic and lasting compliance with the standards that they establish so far as concerns waste water discharges. To that end, only the collection of all the waste water enables such compliance to be ensured. If there is no system enabling all urban waste water to be collected, any compliance with the BOD/COD standards that is recorded cannot be systematic in nature, since it may vary depending on factors connected with various circumstances, such as dilution of the waste water or the conduct of those emitting it.

173 In any event, paragraph 1 of section B of Annex I to Directive 91/271 lays down the obligation to take representative samples of waste water before it is discharged from treatment plants. In the absence of a reliable collecting system, the directive does not offer any other solution enabling compliance with the BOD/COD standards to be proved.

174 Consequently, it must be found that the treatment of urban waste water in the agglomerations of Athlone, Cork City, Fermoy, Mallow, Midleton and Roscommon Town does not comply with Article 4(1) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto.

4. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

175 In addition to the general context, as noted in paragraphs 112 to 114 above, in which the programme for upgrading urban waste water management was initiated, Ireland pleads, in individual instances, legal problems that have led to the treatment of urban waste water not complying with Article 4 of Directive 91/271.

176 Ireland states, furthermore, that the completion in the near future of the works concerning the urban waste water management systems of certain agglomerations covered by the second complaint should within the short term enable the facilities concerned to be rendered compliant with Directive 91/271.

177 In the light of the considerations noted in paragraphs 118 to 121 above and the fact that Ireland has produced nothing capable of demonstrating that the costs of rendering compliant the facilities for treating urban waste water in the agglomerations covered by the second complaint are disproportionate, it must be concluded that the treatment of urban waste water in the agglomerations of Arklow, Athlone, Ballybofey/Stranorlar, Cobh, Cork City, Enfield, Enniscorthy, Fermoy, Killybegs, Mallow, Midleton, Passage/Monkstown, Rathcormac, Ringaskiddy, Ringsend, Roscommon Town, Shannon Town, Tubbercurry and Youghal does not comply with Article 4(1) and/or (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto.

D. The third complaint

178 By its third complaint, the Commission submits that the more stringent treatment of urban waste water entering sensitive areas and the corresponding catchment areas, under Article 5(2) and (3) of Directive 91/271, is not carried out in the agglomerations of Athlone, Ballincollig New, Cavan, Cork City, Dundalk, Enniscorthy, Fermoy, Killarney, Killybegs, Longford, Mallow, Midleton, Navan, Nenagh, Osberstown, Portarlington, Ringsend, Roscrea, Thurles, Tralee and Waterford City. Prompted by information provided by Ireland in its defence, the Commission withdrew this complaint as regards the agglomeration of Waterford City.

179 First, the Commission pleads the non-compliance of the collecting systems for waste water of the agglomerations covered by the first complaint in the present action for failure to fulfil obligations in order to substantiate non-compliance of the treatment systems with Article 5 of Directive 91/271.

180 Second, the Commission relies in respect of the other agglomerations covered by the third complaint on the data that were submitted to it by Ireland in its replies to the additional letter of formal notice and the reasoned opinion.

1. The agglomerations whose collecting systems for urban waste water do not comply with Article 3 of Directive 91/271

181 Under Article 5(1) of Directive 91/271, Member States must identify sensitive areas on the basis of the criteria laid down in Annex II to the directive.

182 Article 5(2) and (3) of Directive 91/271 lays down an obligation to treat urban waste water before discharge into sensitive areas, in such a way that the standards prescribed in section B of Annex I to the directive are complied with. That urban waste water must be subjected to more stringent treatment than the treatment provided for in Article 4 of the directive.

183 Such an obligation also applies as regards discharges from treatment plants situated in the relevant catchment areas of sensitive areas, pursuant to Article 5(5) of Directive 91/271.

184 By analogy with what has been stated in paragraph 166 above, if the collecting system for urban waste water of an agglomeration does not comply with Article 3 of Directive 91/271, the view must a fortiori be taken that the treatment of the urban waste water of that agglomeration that is discharged into a sensitive area cannot be ensured.

185 It is common ground that urban waste water of the agglomerations of Athlone, Cork City, Enniscorthy apart from the townland of Killagoley, Fermoy, Mallow and Midleton is discharged into areas that have been identified as sensitive in accordance with the criteria defined in Annex II to Directive 91/271 and that those agglomerations have a p.e. of more than 10 000.

186 Also, it is clear from paragraph 131 above that the collecting systems for urban waste water of those agglomerations do not comply with Article 3 of Directive 91/271.

187 Therefore, the treatment of urban waste water in those agglomerations cannot comply with Article 5 of Directive 91/271, read in conjunction with section B of Annex I thereto.

188 On the other hand, as is apparent from paragraphs 63, 93, 99 and 103 above, the Commission has not proved to the required legal standard that that the collecting systems for urban waste water of the agglomerations of Cavan, Osberstown, Roscrea and Thurles do not comply with Article 3 of Directive 91/271. It is also apparent from paragraph 48 above that the Commission withdrew the first part of the first complaint so far as concerns the agglomeration of Ballincollig New.

189 In the case of the agglomerations of Osberstown and Thurles, the Commission has not provided other material in support of the third complaint, which must be rejected in their regard. However, in the case of the treatment of urban waste water of the agglomerations of Ballincollig New, Cavan and Roscrea, the material provided by the Commission in support of this complaint will be examined in paragraphs 193 to 221 below.

2. The agglomerations of Dundalk, Killybegs, Portarlington, Ringsend and Tralee

190 The Commission relies on Ireland’s replies to the additional letter of formal notice and reasoned opinion indicating that treatment of the waste water of the agglomerations of Dundalk, Killybegs, Portarlington, Ringsend and Tralee, which do not have any treatment plant or whose treatment is insufficient, would be compliant upon completion of the works in progress.

191 Ireland does not dispute that information, but states that the works in progress should enable compliance with the requirements of Article 5 of Directive 91/271 to be ensured:

– in respect of the agglomeration of Dundalk, in the third quarter of 2017;

– in respect of the agglomeration of Killybegs, on 1 January 2018;

– in respect of the agglomeration of Portarlington, in the second quarter of 2017;

– in respect of the agglomeration of Ringsend, in the second quarter of 2022; and

– in respect of the agglomeration of Tralee, in the fourth quarter of 2017.

192 Since it is undisputed that the question whether a Member State has failed to fulfil obligations must be determined by reference to the situation prevailing in the Member State at the end of the period laid down in the reasoned opinion and that, according to the information disclosed by Ireland, the works in progress will come to an end after 30 November 2016, the third complaint is well founded so far as concerns the agglomerations of Dundalk, Killybegs, Portarlington, Ringsend and Tralee.

3. The agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea

(a) Arguments of the parties

193 The Commission, relying on the data as resulting from Ireland’s replies to the additional letter of formal notice and reasoned opinion, submits that urban waste water discharged into sensitive areas is not treated in accordance with the requirements of Article 5 of Directive 91/271, read in conjunction with Article 10 thereof and section B and Table 2 of Annex I thereto, so far as concerns the agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea. More specifically, the Commission submits that, even assuming that the treatment complies with those provisions in the case of phosphorus as regards the agglomerations of Cavan, Killarney, Longford, Navan, Nenagh and Roscrea, nitrogen reduction is not carried out although nitrogen is declared as a limiting nutrient for the sensitive areas into which the treatment plants of those agglomerations discharge waste water. In addition, the Commission observes in respect of the agglomeration of Ballincollig New that, following further assessments carried out by the Environmental Protection Agency, Ireland stated that nutrient removal is not required.

194 Ireland submits that the data put forward by the Commission have been updated, as is shown by the letter of 8 November 2016 from the Environmental Protection Agency to the Irish Minister for Housing, Planning, Community and Local Government, which it annexed to the reply to the reasoned opinion. Ireland states that it is clear from that document that it was concluded in respect of the agglomerations of Cavan, Killarney, Longford, Navan, Nenagh and Roscrea that a reduction of nitrogen as a limiting nutrient was no longer necessary so far as concerns discharges from those agglomerations’ treatment plants into the sensitive areas concerned. As regards the agglomeration of Ballincollig New, Ireland states that that document concludes that the area into which the waters treated by that agglomeration’s system is discharged is not sensitive.

195 The Commission observes that the documents submitted at the time of the Environmental Protection Agency’s letter of 8 November 2016 amount to preliminary matters that call for additional decisions in order to alter the designation of the sensitive area concerned and the discharge licences and permits that relate thereto. It refers in that regard to the judgment of 4 May 2017, Commission v United Kingdom (C‑502/15, not published, EU:C:2017:334).

196 Ireland submits that the conclusions which the findings of the Environmental Protection Agency reach are definitive and directly applicable, as the amendments to the register of sensitive areas and to the discharge licences amount only to technical implementing arrangements. It refers for this purpose to the judgment of 6 October 2009, Commission v Sweden (C‑438/07, EU:C:2009:613).

197 In case it should be of use, Ireland annexed to its defence the decisions amending the licences for the treatment plants of certain agglomerations, including that of Killarney, which were adopted between 29 June and 7 July 2017.

(b) Findings of the Court

(1) The relevant data for examining the third complaint so far as concerns the agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea

198 It is not disputed that the agglomerations of Ballincollig New, Cavan, Killarney, Longford, Navan, Nenagh and Roscrea have a p.e. of more than 10 000.

199 Also, it is common ground that the urban waste water of those agglomerations is discharged into areas that have been identified as sensitive pursuant to the criteria defined in Annex II to Directive 91/271.

200 Whilst initially the sensitive waters into which discharges are made from the treatment plants of the agglomerations of Cavan, Killarney, Longford, Navan, Nenagh and Roscrea were identified as such on account of their sensitivity both to nitrogen and to phosphorus, Ireland informed the Commission in its reply to the reasoned opinion that, in the light of new data, treatment for nitrogen reduction was no longer necessary.

201 As regards the area of discharge of waters treated by the system of the agglomeration of Ballincollig New, Ireland states that, under the conclusions of the letter of 8 November 2016, no evidence of eutrophication had been found and that all biological and nutrient conditions were below threshold levels between 2010 and 2015. That said, Ireland does not dispute the fact that that area is still designated as sensitive.

202 At the outset, it should be recalled that the question whether a Member State has failed to fulfil obligations must be determined by reference to the situation prevailing in the Member State at the end of the period laid down in the reasoned opinion and the Court cannot take account of any subsequent changes (judgment of 28 November 2018, Commission v Slovenia, C‑506/17, not published, EU:C:2018:959, paragraph 50 and the case-law cited).

203 The data to which the parties refer come, first, from Ireland’s reply to the additional letter of formal notice and, second, from its reply to the reasoned opinion. The letter of 8 November 2016 from the Environmental Protection Agency to the Irish Minister for Housing, Planning, Community and Local Government was annexed to Ireland’s reply to the reasoned opinion. That letter in return refers to the review of sensitive areas which was carried out by the Environmental Protection Agency in 2016 on the basis of data collected between 2010 and 2015 (‘the 2016 EPA Review’). That review forms Appendix 1 to the letter.

204 It is apparent from those data that in the case of the agglomerations of Killarney, Longford, Navan, Nenagh and Roscrea, Ireland did not carry out nitrogen reduction complying with Directive 91/271, although nitrogen is declared as a limiting nutrient for the sensitive areas into which the treatment plants of those agglomerations discharge the treated waters.

205 On the other hand, it is not apparent from those data that that is so in the case of the agglomeration of Cavan. Therefore, in the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns that agglomeration.

206 As regards the agglomeration of Ballincollig New, it is apparent from the 2016 EPA Review that no evidence of eutrophication had been found and that all biological and nutrient conditions were below threshold levels between 2010 and 2015. In Ireland’s submission, it follows that there is no obligation to remove the nutrients and, therefore, no infringement of Article 5 of Directive 91/271.

207 However, irrespective of whether or not there is such an obligation, it is to be noted that, according to Ireland’s reply to the additional letter of formal notice, in respect of 2013 to 2015 nutrients were removed pursuant to Article 5 of Directive 91/271, in terms of both phosphorus and nitrogen reduction. In the absence of additional data, it must be held that the Commission has not provided information allowing a determination that the complaint has been made out so far as concerns the agglomeration of Ballincollig New.

208 As regards the data which are derived from the assessments forwarded by the Environmental Protection Agency in its letter of 8 November 2016 annexed to Ireland’s reply to the reasoned opinion, data upon which Ireland relies in order to assert that inadequate treatment of nitrogen, or of phosphorus and nitrogen, is no longer relevant for the purpose of establishing the treatment’s compliance with Article 5 of Directive 91/271, it is to be noted that it is indicated on page 2 of the 2016 EPA Review that any change in the designation of a sensitive area will necessitate further analyses.

209 Ireland maintains, however, that such a necessity concerns only the areas that the 2016 EPA Review recommends be designated for the first time as sensitive.

210 In that regard, it must be stated, first, that the 2016 EPA Review specifies that the results collected so far as concerns, inter alia, the agglomeration of Longford require confirmation by further analyses, even though the discharge areas for that agglomeration’s treatment plants were designated as sensitive before 8 November 2016.

211 Second, as the Environmental Protection Agency itself acknowledges in its letter of 8 November 2016, the findings and conclusions mentioned in the 2016 EPA Review are liable to have consequences for the designation of a sensitive area and for the discharge licences of the treatment plants concerned. Thus, in that letter, the Environmental Protection Agency states that the 2016 EPA Review will be followed by the adoption of recommendations and the amendment of statutory instruments. It is thus those amendments that enable compliance with the requirements of Table 2 of Annex I to Directive 91/271 to be prescribed.

212 In this respect, it should be noted that Article 12(2) of Directive 91/271 imposes on the Member States the obligation to ensure that the disposal of waste water from urban waste water treatment plants is subject to prior regulations and/or specific authorisation. Under Article 12(3), such instruments are to contain conditions to satisfy the requirements of section B of Annex I to the directive.

213 Whilst it is true that the findings and conclusions mentioned in the 2016 EPA Review concern not only amendments in the identification of the nutrients to be treated, but also the need to designate new sensitive areas, the fact remains that the identification of a nutrient responsible for the eutrophication of the waters of a discharge area is what determines its designation as a sensitive area.

214 Thus, the waters of an area may be sensitive to phosphorus or nitrogen, or to both those nutrients.

215 Therefore, Ireland cannot assert that, inasmuch as the 2016 EPA Review advocates only limiting the sensitivity to phosphorus of the areas into which the treatment plants of the agglomerations of Killarney, Longford, Navan, Nenagh and Roscrea discharge the treated waters, the amendments which stem therefrom consist only of technical arrangements.

216 In fact, it is to be noted that Ireland annexed to its defence the decisions amending the licences for the treatment plants of certain agglomerations covered by the third complaint, which were adopted between 29 June and 7 July 2017.

217 However, as the period set by the reasoned opinion expired on 30 November 2016, the Court cannot take account of such documents for the purpose of determining whether the failure to fulfil obligations that is alleged by the Commission has taken place.

218 It is therefore on the basis of the data put forward by the Commission that the Court should examine whether the discharges from the treatment plants of the agglomerations concerned are compliant.

(2) The agglomerations concerned

219 As is apparent from Ireland’s reply to the additional letter of formal notice, the discharges from the treatment plants of the agglomerations of Killarney, Longford, Navan, Nenagh and Roscrea do not comply with the requirements of Table 2 of Annex I to Directive 91/271 so far as concerns the reduction of nitrogen.

220 For the reasons given in paragraphs 209 to 217 above, the data resulting from the letter of the Environmental Protection Agency of 8 November 2016 and from the 2016 EPA Review annexed thereto cannot be regarded as evidence capable of calling into question the data put forward by the Commission.

221 Therefore, it must be held that the treatment of urban waste water of the agglomerations of Killarney, Longford, Navan, Nenagh and Roscrea does not comply with Article 5 of Directive 91/271.

4. Application of exceptional circumstances and of the concept of ‘best technical knowledge not entailing excessive costs’

222 In addition to the general context, as noted in paragraphs 112 to 114 above, in which the programme for upgrading urban waste water management was initiated, Ireland pleads, in individual instances, legal problems that have led to the treatment of urban waste water not complying with Article 5 of Directive 91/271.

223 Ireland states, furthermore, that the completion in the near future of the works concerning the systems for treating urban waste water of certain agglomerations covered by the third complaint should within the short term enable the facilities to be rendered compliant with Directive 91/271.

224 In the light of the considerations noted in paragraphs 118 to 121 above and the fact that Ireland has produced nothing capable of demonstrating that the costs of rendering compliant the facilities for treating urban waste water in the agglomerations covered by the third complaint are disproportionate, it must be concluded that the treatment of urban waste water in the agglomerations of Athlone, Cork City, Dundalk, Enniscorthy apart from the townland of Killagoley, Fermoy, Killarney, Killybegs, Longford, Mallow, Midleton, Navan, Nenagh, Portarlington, Ringsend, Roscrea and Tralee does not comply with Article 5(2) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto.

E. The fourth complaint

225 By its fourth complaint, the Commission submits that no prior regulations and/or specific authorisations are provided for relating to the discharges from waste water treatment plants, in accordance with Article 12(2) and (3) of Directive 91/271, as regards the agglomerations of Arklow and Castlebridge.

226 In the case of the agglomeration of Arklow, Ireland highlights the legal difficulties connected with establishing a treatment plant which have not allowed the necessary authorisation procedure to be initiated.

227 In the case of the agglomeration of Castlebridge, the waste water is stated to be conveyed to a larger agglomeration for which examination of a revised licence is underway.

228 In any event, Ireland submits that the exceptional circumstances that it has faced warrant dismissal of the fourth complaint.

229 Since Ireland does not dispute that, on the date on which the period set by the reasoned opinion expired, that is to say, 30 November 2016, the treatment plants of the agglomerations of Arklow and Castlebridge did not have valid discharge licences, it must be held that the treatment plants of those agglomerations do not comply with Article 12 of Directive 91/271.

230 Moreover, as Ireland failed to produce anything capable of demonstrating that the costs of rendering compliant the facilities for treating urban waste water in the agglomerations covered by the fourth complaint are disproportionate, it must be concluded that the systems for treating urban waste water of the agglomerations of Arklow and Castlebridge do not comply with Article 12 of Directive 91/271.

F. Conclusion

231 In the light of all the foregoing considerations, it must be held that Ireland has failed to fulfil its obligations:

– under Article 3(1) and (2) of Directive 91/271 and section A and footnote 1 of Annex I thereto by not ensuring that the waters collected in a combined urban waste water and rainwater system are retained and conducted for treatment in compliance with the requirements of that directive so far as concerns the agglomerations of Athlone, Cork City, Enniscorthy apart from the townland of Killagoley, Fermoy, Mallow, Midleton, Ringaskiddy and Roscommon Town;

– under Article 4(1) and/or (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto, by not putting in place secondary or equivalent treatment so far as concerns the agglomerations of Arklow, Athlone, Ballybofey/Stranorlar, Cobh, Cork City, Enfield, Enniscorthy, Fermoy, Killybegs, Mallow, Midleton, Passage/Monkstown, Rathcormac, Ringaskiddy, Ringsend, Roscommon Town, Shannon Town, Tubbercurry and Youghal;

– under Article 5(2) and (3) of Directive 91/271, read in conjunction with Article 10 thereof and section B of Annex I thereto, by not ensuring that urban waste water entering collecting systems from the agglomerations of Athlone, Cork City, Dundalk, Enniscorthy apart from the townland of Killagoley, Fermoy, Killarney, Killybegs, Longford, Mallow, Midleton, Navan, Nenagh, Portarlington, Ringsend, Roscrea and Tralee be, before discharge into sensitive areas, made subject to treatment more stringent than that described in Article 4 of that directive and in accordance with the requirements of section B of Annex I thereto; and

– under Article 12 of Directive 91/271, by not ensuring that the disposal of waste water from urban waste water treatment plants of the agglomerations of Arklow and Castlebridge is subject to prior regulations and/or specific authorisation.

232 The action is dismissed as to the remainder.

V. Costs

233 Under Article 138(1) of the Rules of Procedure, the unsuccessful party is to be ordered to pay the costs if they have been applied for in the successful party’s pleadings. Since the Commission has applied for costs and Ireland’s failure to fulfil obligations has essentially been established, Ireland must be ordered to pay the costs.

On those grounds, the Court (Tenth Chamber) hereby:

1. Declares that Ireland has failed to fulfil its obligations:

– under Article 3(1) and (2) of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment, as amended by Regulation (EC) No 1137/2008 of the European Parliament and of the Council of 22 October 2008, and section A and footnote 1 of Annex I thereto by not ensuring that the waters collected in a combined urban waste water and rainwater system are retained and conducted for treatment in compliance with the requirements of that directive, as amended, so far as concerns the agglomerations of Athlone, Cork City, Enniscorthy apart from the townland of Killagoley, Fermoy, Mallow, Midleton, Ringaskiddy and Roscommon Town;

– under Article 4(1) and/or (3) of Directive 91/271 as amended by Regulation No 1137/2008, read in conjunction with Article 10 thereof and section B of Annex I thereto, by not putting in place secondary