PULP MILLS (JUDGMENT) 20 Obligations of Uruguay following the end of the negotiation period — Scope of Article 12 of the 1975 Statute — Absence of a “no construction obligation” following the end of the negotiation period and during the judicial settlement phase. * Alleged breaches of substantive obligations. Burden of proof — Precautionary approach without reversal of the burden of proof — Expert evidence — Reports commissioned by the Parties — Independence of experts — Consideration of the facts by the Court — Experts appearing as counsel at the hearings — Question of witnesses, experts and expert witnesses. Optimum and rational utilization of the River Uruguay — Article 1 of the 1975 Statute sets out the purpose of the instrument and does not lay down specific rights and obligations — Obligation to comply with the obligations prescribed by the Statute for the protection of the environment and the joint management of the river — Regulatory function of CARU — Interconnectedness between equitable and reasonable utilization of the river as a shared resource and the balance between economic development and environmental protection that is the essence of sustainable development (Article 27 of the 1975 Statute). Obligation to ensure that the management of the soil and woodland does not impair the régime of the river or the quality of its waters (Article 35 of the 1975 Statute) — Contentions of Argentina not established. Obligation to co-ordinate measures to avoid changes to the ecological balance (Article 36 of the 1975 Statute) — Requirement of individual action by each party and co-ordination through CARU — Obligation of due diligence — Argentina has not convincingly demonstrated that Uruguay has refused to engage in the co-ordination envisaged by Article 36 of the 1975 Statute. Obligation to prevent pollution and preserve the aquatic environment — Normative content of Article 41 of the 1975 Statute — Obligation for each party to adopt rules and measures to protect and preserve the aquatic environment and, in particular, to prevent pollution — The rules and measures prescribed by each party must be in accordance with applicable international agreements and in keeping, where relevant, with the guidelines and recommendations of international technical bodies — Due diligence obligation to prescribe rules and measures and to apply them — Definition of pollution given in Article 40 of the 1975 Statute — Regulatory action of CARU (Article 56 of the 1975 Statute), complementing that of each party — CARU Digest — Rules by which the existence of any harmful effects is to be determined : 1975 Statute, CARU Digest, domestic law of each party within the limits prescribed by the 1975 Statute. Environmental impact assessment (EIA) — Obligation to conduct an EIA — Scope and content of the EIA — Referral to domestic law — Question of the choice of mill site as part of the EIA — The Court is not convinced by Argentina’s argument that an assessment of possible sites was not carried out — Receiving capacity of the river at Fray Bentos and reverse flows — The CARU water quality standards take account of the geomorphological and hydrological characteristics of the river and the receiving capacity of its waters — Question 10