Indore ran its sewer trunk through slums first, as gravity made it cheapest

Indian cities habitually laid sewer and drainage infrastructure to formal, revenue-generating neighborhoods first, leaving informal slum settlements without sanitation for generations — any spending on slum infrastructure was treated as a welfare cost competing for the same scarce budget as "real" city works, and it consistently lost. In Indore, a city of over a million people where roughly a quarter lived across some 183 unrecognized slum settlements, that meant most of the city's sewage went untreated into the river the whole population depended on.

The standard response to this was more subsidy, or simply waiting for formal infrastructure to eventually be extended outward to the slums. Neither solved the actual budget competition: a city administration weighing a rupee spent on a slum against a rupee spent on a licensed neighborhood's sewer line had no engineering reason to choose the slum, so slums stayed last in the queue indefinitely — not because the money was never available, but because the choice was always framed as charity against infrastructure, and infrastructure always won.

Routed the sewer trunk through slums because their low ground made it the cheapest gravity path, giving authorities reason to formalize tenure and residents to invest.

Slums occupied low-lying land that was cheapest for the city's sewer trunk.

Routing through slums avoided deep excavation and pumping, cutting costs.

The cost advantage gave the authority a non-charitable reason to formalize tenure.

Secure tenure motivated residents to invest their own money in connections.

When a disadvantaged group sits on the cheapest path to solving a system-wide problem, serving them first can be the efficient choice, not just charity.

The Indore Habitat Improvement Project ran from 1990 to 1997, jointly funded by the UK government's Overseas Development Administration, the state, the municipality, and residents themselves, eventually reaching an estimated 183 slums and roughly 400,000 residents; it won the 1993 World Habitat Award and the 1998 Aga Khan Award for Architecture.