Desilting a pond: the 60:40 test and a contractor's convenient rate
Ward 5 of Rampura Gram Panchayat seeks approval to desilt a community pond before the monsoon. The tank is rectangular, 40 m long and 25 m wide, and silt must be removed to a uniform depth of 0.6 m. The assistant engineer's approved estimate fixes productivity at 2.50 cubic metres of silt per person-day of unskilled labour, and the district wage rate is ₹250 per person-day. Excavated silt bulks up by 20% when disturbed. A local contractor quotes ₹350 per tractor-trolley, each trolley carrying 6 cubic metres, to move the silt to a farmer's field 2 km away, and states that the job needs 120 trips. The shelf of projects shows ₹55,000 available under the material head. Muster rolls will be checked by the social audit team, and the VDO knows that attendance cannot be adjusted to make the ratio look right.
1. Verify the contractor's trip count, compute the labour and material cost, and decide whether the work satisfies the 60:40 wage-material requirement.
Read the worked answer
Volume of silt: 40 × 25 × 0.6 = 600 m³.
Trips: bulked volume = 600 × 1.20 = 720 m³. At 6 m³ per trolley, 720 ÷ 6 = 120 trips. The contractor's figure is arithmetically correct.
Labour: 600 ÷ 2.50 = 240 person-days; 240 × ₹250 = ₹60,000.
Material: 120 × ₹350 = ₹42,000.
Total: ₹1,02,000. Wage share = 60,000 ÷ 1,02,000 = 58.82%.
The 60:40 test requires the wage share to be at least 60%; here material is 41.18%. So although the trip count is right, the work as quoted is not compliant and cannot be passed as it stands. Note that the material head has ₹55,000 available, so money is not the constraint - the ratio is.
2. The contractor offers to reduce his rate so that "the ratio works out". What is the maximum permissible material cost and rate per trip, and what else must the VDO check?
Read the worked answer
With labour fixed at ₹60,000, the wage share is at least 60% only if material M satisfies 60,000 ÷ (60,000 + M) ≥ 0.60, i.e. M ≤ (2/3) × 60,000 = ₹40,000.
Per trip: 40,000 ÷ 120 = ₹333.33, so the rate must be ₹333 per trip or less. At ₹333: material = ₹39,960; total = ₹99,960; wage share = 60.02%, which passes.
But a falling quote is a warning, not a solution. The VDO must check:
- ₹333 against the district schedule of rates; a rate below SoR often means the silt will be dumped in the nearest drain rather than carried 2 km to the field.
- Whether the trolley actually carries 6 m³; overloaded/underloaded trips change the count.
- A cleaner alternative: add a genuine labour component - spreading the silt in the fields is a permissible activity. Twelve extra person-days (₹3,000) give labour ₹63,000 against material ₹42,000; total ₹1,05,000; share = exactly 60.00%. This is legitimate; reducing the productivity norm or padding muster rolls is not.
3. Thirty workers are available on average. How many working days are needed? What if attendance averages 26, and what if the sarpanch insists on finishing in 6 days with only 37 workers available?
Read the worked answer
Total requirement is 240 person-days.
- 30 workers: 240 ÷ 30 = 8 working days.
- 26 workers: 240 ÷ 26 = 9.23. A partial person-day cannot be counted as a full day, so round up: 10 working days.
- 6 days with 37 workers: 240 ÷ 6 = 40 person-days needed per day, but only 37 workers exist. Maximum achievable in 6 days = 37 × 6 = 222 person-days < 240. Minimum feasible period = 240 ÷ 37 = 6.49, rounded up to 7 days.
The VDO should tell the sarpanch that the work cannot be compressed to 6 days with 37 workers, and record 7 days in the estimate. Writing 40 attendances a day when 37 worked is exactly the falsification the social audit will catch, and it converts an arithmetic shortfall into a disciplinary charge.