How do soakaway assessment bids get underbid in Borama?

A low soakaway assessment bid in Borama may not cover the same work as a complete one. The sum can cover a look at the ground and a rough pit size while soakage testing, trial excavation, test water and spoil disposal sit outside the price. Compare it with a complete bid and part of the gap is scope, not profit.

What gets left out of a cheap soakaway assessment?

The omissions follow a pattern. A complete soakaway assessment prices the trial hole or holes, a soakage test with water and timing, a record of the results, the design of the pit or trench from those results, and the disposal of excavated soil. A cheap bid may price only the first item.

Ask each bidder for a written list of what the assessment includes. Check four things in particular:

• Soakage testing. How many test holes, to what depth, and who pours and times the water?
• Water supply. Where does test water come from, and who pays to haul it?
• Recording. Who writes down the soakage rate, the groundwater level seen and the soil description?
• Spoil. Where does excavated material go, and is the haul in the rate?

If a bidder cannot answer these, the figure may stand for less work than another bidder's. General practice for soakage testing is to dig a test hole to the proposed pit base, fill it with water, and time the fall over a set period, then repeat for consistency. Confirm the depth, the number of holes and the timing against the project specification or the engineer's instruction.

How does an underbid assessment turn into ineffective effluent dispersal?

When the assessment excludes the test, the pit can be sized from assumption rather than measurement. Sand, gravel, weathered rock and clay take water at very different rates, and a pit sized for one can fail in another. The result is a soakaway that fills faster than it drains, so effluent ponds at the surface, backs up into the pipe run, or overflows after heavy Gu or Deyr rain.

The failure is expensive to correct because the fix is usually a new or enlarged pit, new pipe falls and a new connection, plus the removal of the failed structure. Ask the relevant local authority for any ground or drainage records it may hold for the plot or the street. Walk a recent soakaway on a nearby plot after rain and look for standing water, damp ground or a high water line in the pit. If the ground is tight clay or the water table is shallow, the design may need a different outlet, a raised mound, or a larger dispersal area.

Keep the test record with the as-built drawings. It shows what the design assumed, and it gives the next person a reason to trust the pit depth.

How do you detect unrealistic tender allowances before you award?

Compare the priced method with the site. A bid that allows one shallow hole for a large plot, or that has no water and no haul line, prices a smaller scope than a bid with those lines. Put the missing items in writing and ask for a revised, complete figure from every bidder.

Useful checks:

• Ask for the test method in writing, not a verbal promise.
• Ask for the rate for each item separately: excavation, testing, recording, design and spoil removal.
• Check the programme. A soakage test needs water and time, so a bid that allows a single day for the whole assessment may be cutting the test.
• Ask who supervises the test and who signs the record.

Confirm what your contract allows before you sign, and keep the assessment method, the test record and the disposal route as contract documents.

What to do next

Send each bidder a short written schedule: method, number and depth of test holes, water source, recording, design and spoil disposal, with a rate against every line. Ask them to return it with the bid. Then ask the relevant local authority for any ground or drainage records it may have for the plot or street before you award the work.