The Sagar Island Drinking Water Grid and the Salinity Front
A coastal mandal in Krishna district draws drinking water from a 12-km pipeline fed by a infiltration gallery on the riverbank. For three years the gallery's chloride reading in May has risen: 340 mg/L, then 410, then 520 mg/L, against the 250 mg/L permissible limit. The executive engineer has three options costed: (a) shift the gallery 4 km upstream and lay new pipeline at Rs 9.2 crore, protecting supply for 15 years; (b) install a 2 MLD desalination plant at Rs 4.1 crore plus Rs 60 lakh annual running cost and 1.4 MW of power; (c) do nothing this year and issue tanker supply in May–June at Rs 35 lakh per season. The mandal has 28,000 residents, 60% dependent on this scheme; groundwater in the habitation is already at 1,800 mg/L chloride. The state's coastal salinity ingression is projected to advance 2 km inland per decade under current extraction.
1. Which option should the engineer recommend, and on what decision criteria?
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The recommendation must be built on life-cycle cost per protected person-year, not on lowest first cost.
- (a) Upstream shift: Rs 9.2 crore / (28,000 × 15) ≈ Rs 219 per person-year, and it addresses the cause (moving ahead of the salinity front) rather than the symptom.
- (b) Desalination: Rs 4.1 crore + 15 × Rs 0.6 crore = Rs 13.1 crore / (28,000 × 15) ≈ Rs 312 per person-year, plus 1.4 MW of continuous load and brine disposal on an already saline coast.
- (c) Tankers: Rs 35 lakh × 15 = Rs 5.25 crore, but delivers no reliable year-round supply and leaves 40% of residents on 1,800 mg/L groundwater - this is the highest health cost, lowest capital cost trap.
Criteria to state explicitly: (i) does the option buy time ahead of a front moving 2 km/decade - only (a) does; (ii) recurring fiscal exposure - (b) locks the state into power and O&M forever; (iii) equity - the 40% not on the scheme remain exposed under all options unless the grid is extended.
So recommend (a) plus extension of the grid to the remaining 40%, financed partly by avoiding the desalination O&M. The judgement being tested is refusing the politically attractive 'plant' and the cheap 'tankers' in favour of the option that is cheapest per person-year and attacks the cause.
2. The MLA pressures for the desalination plant because it is visible and can be inaugurated. How should the engineer respond without being insubordinate?
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The engineer should not frame this as a confrontation of 'technical truth vs politics'. The professional move is to convert the dispute into a shared decision with written trade-offs:
- Put the three options on one page with life-cycle cost, per-person-year cost, time to commissioning, power requirement, and risk of failure. Numbers, not adjectives.
- Offer the MLA a visible win inside the technically sound option - e.g., the upstream gallery, new pipeline and the 40% grid extension can be inaugurated too, and the MLA can claim the larger coverage.
- State the risk of (b) plainly: recurring O&M of Rs 60 lakh/year is the first line cut in a budget squeeze, and a plant that stops is worse than no plant.
- Escalate only if overruled in writing - record the advice in the file so accountability is not silently transferred.
The ethics being tested is integrity plus prudence: the officer owes the political executive honest advice, owes the public the cheapest safe water, and owes the institution a documented record. Refusing to speak is a dereliction; leaking to the press is disloyalty; silently complying is corruption of the technical function.