Why do backfill compaction bids look low in Berbera?

A low backfill compaction bid in Berbera usually means a real cost has been left out, not that the work will be done cheaply. The risk sits in the omissions: a bid can price excavation and filling while leaving water supply, hauling out unsuitable material, layer control, moisture conditioning and density testing unpriced. Compare what each bid includes before comparing totals.

What costs do low backfill compaction bids leave out?

Start with the five items that are easy to price and easier to drop. Water is the first. Compaction depends on moisture content, and in a hot, dry place the moisture you add can disappear before the roller arrives, so the water has to be hauled, stored and applied in measured amounts. The second is removal of unsuitable material found below the formation level. The third is layer thickness control, because thin layers cost more machine time than one deep fill. The fourth is moisture conditioning itself, which can mean wetting dry fill or drying fill that arrives too wet. The fifth is density testing, which needs a laboratory and a schedule, not a verbal assurance.

A bid that carries none of these prices the same method with the control steps stripped out. Ask the bidder to list water source, haul distance, layer thickness, roller passes and who pays for each density test. If the answers are not in writing, the omission is in the bid.

How does the omission show up in the finished floor?

Weak or uncontrolled fill settles after the slab or floor is in place. The mechanism is simple: fill placed too dry, too wet, or in layers too thick for the roller leaves voids and loose zones. Load from the slab, stored materials, water tanks or vehicle traffic then closes those voids. The floor drops, cracks open at the slab edge or along service trenches, and doors and finishes go out of line. Settlement is often uneven, so the damage reads as a local dip rather than a general drop.

By then the backfill is buried and the cost of repair sits with the client, not the bidder. Ask the relevant municipal office or the client's engineer what records, if any, exist for the plot before you accept any fill, and walk a recent building in Berbera where the floor has seen one rainy season and one dry season. Cracks around columns and along trench lines tell you more than any bid total.

How do you close the gap before award?

Make the omitted costs visible in the tender documents. Require a method statement that names the water source and how it reaches the layer, the maximum loose layer thickness, the roller type and pass count, and how moisture will be checked. Require a testing schedule that names the laboratory, the test frequency and who pays. General practice for engineered fill is to place and compact in thin layers with each layer tested before the next is placed, but confirm the layer thickness and test frequency against the project specification and your engineer.

Ask for a bill of quantities that separates unsuitable material removal from general excavation. That single split stops the argument later about who carried the risk of bad ground.

Then check the contract. See whether it allows you to require re-testing at the contractor's cost if a layer fails, and whether variation rates for extra excavation and dewatering are already agreed. If the contract does not cover that ground, you cannot rely on it.

What to do next

Ask every bidder for the water source, the layer thickness, the roller passes, the density test schedule and the rate for removing unsuitable material, in writing, before you compare totals. Send the same questions to all bidders so the answers line up. If any bidder leaves a line blank, obtain written quotations from suppliers or laboratories for that line, then compare the bids again.