School Het Oogappeltje Wommelgem: annulment – abnormal price detection method unverifiable and price investigation of selected items insufficient
The Council of State annuls for the second time the award decision of the municipality of Wommelgem for the extension and renovation of primary school Het Oogappeltje, because the submitted documents do not show that the detection of apparently abnormal unit prices was carried out in accordance with the contracting authority's own methodology — using a 1% rule and 30%/50% thresholds — and because the investigation of the selected items did not meet the requirements of a normally diligent contracting authority, as abnormal unit prices were accepted based on vague and general findings without requesting price justification.
What happened?
The municipality of Wommelgem tendered works for the extension and renovation of primary school Het Oogappeltje via an open procedure with price as the sole award criterion. Nine tenderers submitted offers. Brebuild was the lowest (€2,547,534.66) and VMG-De Cock second lowest (€2,563,662.95) — a difference of only approximately €16,000. A first award decision (6 June 2017) had already been annulled by the Council of State (judgment 244.492 of 16 May 2019). A new award decision of 29 July 2019 again awarded to Brebuild. The bill of quantities contained approximately 2,800 unit prices. The authority described a detection methodology consisting of: (1) selecting items representing at least 1% of the total offer amount; (2) calculating the average unit price per selected item; (3) identifying unit prices more than 30% below or 50% above this average. This methodology identified only four items for further investigation. The Council found the second plea well-founded on two grounds. First, the authority had applied the 1% rule at chapter level rather than individual item level, which was insufficient. The confidential annex 5bis — the working document underlying the price investigation — merely listed unit prices side by side without calculating averages or percentage deviations, and contained no clear indication of items flagged for further investigation. The Council concluded it could not be established that the detection was carried out in accordance with the authority's own methodology. Second, for the vast majority of selected items no price justification was requested. The acceptance of abnormal prices was based on vague generalities such as 'very large differences between prices' or 'chapter total price in line with other tenderers'. Specifically: for items 02.00 (site facilities) and 03.12.20.B (demolition), unit prices of two tenderers including the chosen one were more than 50% above average — the mere observation of large price differences did not constitute diligent investigation, especially given earlier indications of front-loading. For item 15.21 (ground floor slabs), prices 30% below average were accepted based solely on a chapter-level comparison. The second condition — only requesting justification when a single tenderer had a low price — was unsound: two of nine tenderers with apparently low prices does not exempt from investigation. Annulment ordered. Costs: court fee €200, contribution €20, legal costs €770.
Why does this matter?
This ruling provides a detailed analysis of price investigation requirements for unit prices. The authority has discretion to set detection criteria, but must apply them consistently and verifiably. A comparison table listing unit prices side by side, without calculating averages and deviations, is insufficient proof that the methodology was followed. Items selected for investigation must actually be investigated — vague generalities do not suffice to accept prices previously detected as potentially abnormal.
The lesson
As a contracting authority: (1) fully document your detection methodology — not just the outcome but intermediate calculations; (2) apply the 1% rule at individual item level, not chapter level; (3) actually investigate all items flagged by your own criteria; (4) do not limit investigation to cases where only one tenderer has an abnormal price; (5) be alert to front-loading signals. As a tenderer: a deficient price investigation is a strong ground for annulment.
Ask yourself
As a contracting authority: do my working documents prove I applied my stated methodology? Did I apply the 1% rule at the right level? Did I investigate all flagged items with specific reasoning? As a tenderer: does the stated methodology match the underlying documents?
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 →