Zandvliet waiting dock: rejection of annulment appeal – negative unit prices for soil disposal in Rotterdam insufficiently justified, contracting authority's assessment margin not exceeded
The Council of State rejects the annulment appeal by the temporary association HYE–Boskalis against the award by De Vlaamse Waterweg for the construction of a waiting dock at Zandvliet, because the negative unit prices for soil disposal in Rotterdam (-€4/m³ and -€5/m³ for items 2 and 3 of conditional part 1) were insufficiently justified — the adjustment of a reference price for Maas sand of €6.50/m³ down to €4 and €5/m³ due to 'lesser quality' lacked further specification or argumentation, and the contracting authority did not exceed its assessment margin.
What happened?
De Vlaamse Waterweg tendered construction of a waiting dock for inland shipping on the Scheldt-Rhine connection at Zandvliet via open procedure, with price as the sole award criterion. Five tenderers submitted bids, including HYE–Boskalis (€17,984,618.94) and Herbosch-Kiere–Hens (€18,938,294.56). The dispute concerned items 2 and 3 of conditional part 1 (excavation and disposal of sand), which were crucial: item 3 alone represented on average 23% of the total tender price but only 5% in HYE–Boskalis's bid. HYE–Boskalis offered negative unit prices of -€4/m³ and -€5/m³ for soil disposal in Rotterdam, justified by Boskalis's position as the largest sand supplier on the Dutch market (3-5 million m³/year) and a supply contract for Maas sand at €6.50/m³, adjusted downward for 'lesser quality' (loamy sand). The authority found this adjustment lacked further specification. Six pleas were all rejected. The Council confirmed the authority's broad assessment margin for price justifications, found the adversarial procedure compliant with Article 69(3) of Directive 2014/24/EU (two rounds of questioning sufficed), held that the specification clause requiring pricing based on 'own findings and borings' was an execution clause not a regularity requirement, and found no violation of equal treatment since tenderers with abnormally low prices and those with normal prices were not in comparable situations regarding the requirement for own soil investigations.
Why does this matter?
This ruling is a key reference for price investigations involving negative unit prices in earthworks. It confirms the contracting authority's broad assessment margin, the tenderer's burden of proof (vague quality assessments without detailed justification are insufficient), the nature of specification clauses about own borings as execution provisions rather than regularity requirements, and the limits of the adversarial procedure under Article 69 of Directive 2014/24/EU.
The lesson
As a tenderer with negative unit prices: provide a concrete, detailed and substantiated justification — adjusting a reference price based on a vague quality assessment is insufficient. Bring all relevant elements in the price justification itself, not in later proceedings. As a contracting authority: clearly identify the 'crucial element' requiring further justification. Two questioning rounds suffice as an adversarial debate.
Ask yourself
As a tenderer: is my justification for negative prices concrete and detailed? Have I objectively substantiated the adjustment of a reference price? As a contracting authority: have I clearly communicated which element is crucial? Is my assessment motivated and within my margin?
About this database
The Council of State (Raad van State / Conseil d'État) is Belgium's supreme administrative court. In disputes over public procurement — from contract awards to tenderer exclusions — the Council of State is the final arbiter. The rulings in this database are summarised by TenderWolf in plain language, with practical lessons for tenderers and contracting authorities. View all rulings →