The Unforeseen Black Cotton Soil Variation
A 42 km rural road upgrading contract, valued at ETB 380 million with a 12% contingency, is on day 300 of a 540-day programme. At km 18+400, trial pits expose 1.2 m of black cotton soil that the geotechnical report did not identify. The resident engineer issues an oral instruction to remove and replace it with selected fill; the contractor's priced variation order is ETB 9.4 million and 21 days. The resident engineer's delegated variation approval limit is ETB 2 million. The ERA procurement manual requires tender committee approval for any variation above ETB 5 million and for cumulative variations above 10% of the contract price. The contractor's performance security expires in 30 days, and the regional office wants the road kept open for the harvest season. The contractor has already mobilized an excavator and six trucks. The supervision consultant's quantity surveyor is on leave.
1. What should the resident engineer do immediately about the oral instruction and the contractor's mobilized equipment, and what is the correct approval path for the ETB 9.4 million variation?
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Immediate action: Do not let the oral instruction stand as the contractual basis. Issue a written instruction 'subject to approval' only if the work is necessary to prevent a safety risk or further deterioration; otherwise ask the contractor to secure the site and stop. Mobilization of an excavator and six trucks does not create entitlement. Record the oral instruction, the date, the trial pit location, and any contractor notice, then confirm the position in writing within the contract's stated period.
Approval path: The ETB 9.4 million variation exceeds both the resident engineer's ETB 2 million delegation and the ETB 5 million tender committee threshold. It is 2.5% of the ETB 380 million contract price, so this item alone does not trigger the 10% cumulative test, but the cumulative total must still be checked. Prepare a variation order with joint measurement of the black cotton soil extent, rates based on the contract or properly built up, and a time-impact assessment. The file should go to the supervision consultant's team leader and then to the ERA tender committee. Work should proceed only under a written instruction and with the contractor informed that payment is subject to approval.
2. Assess the financial and contractual risks, including contingency, time extension and the expiring performance security. What conditions should be attached to any approval?
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Financial: ETB 9.4 million is about 20.6% of the ETB 45.6 million contingency. Check the remaining contingency after other variations; if the balance is low, budget reallocation or a revised contract ceiling may be needed. A 21-day extension must be tested against the programme: was the condition unforeseeable, did the contractor give notice, and is the delay on the critical path? A time extension may be justified without cost, but the contractor may claim prolongation costs, which should be evaluated separately.
Security: The performance security expires in 30 days. Before certifying any variation payment, require extension of the security to the revised completion date; otherwise the employer loses protection. If the contractor refuses, withhold the interim payment certificate and escalate.
Conditions: written instruction; approved quantities; independent survey; no payment for work outside approved limits; revised programme; extended security; and a reservation of rights on delay costs. Harvest-season pressure is a reason to plan traffic management, not to bypass approval.
3. What records and transparency measures must accompany this variation to withstand a later audit?
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The variation file should contain the original oral instruction and its written confirmation; trial pit logs and photographs with coordinates and dates; the geotechnical report and the gap identified; joint measurement sheets signed by contractor and engineer; rate build-up; the time-impact analysis; correspondence with the regional office; and tender committee minutes. Disclose the variation in the monthly progress report and project dashboard, and declare any personal relationship with the contractor. Audit will test whether the work was necessary, whether quantities were measured rather than estimated, whether rates were reasonable, and whether approval preceded payment. The file should also show that equipment mobilization was not used to create a fait accompli. Transparency protects both the engineer and the employer.