Paved with good intentions but potholed with reality

For at least two decades, Hijri Road has been a nuisance for the people who live in Gulshan Town’s Metroville Colony.

So when UC 6 chairman Nasir Ashfaq managed to get the Karachi Development Authority to fix the inner neighbourhood service lane, they insisted on paver blocks this time. Three years later, sewerage still overflows from time to time, but at least by the time they clean it up there is still a road underneath the muck.

“When we installed pavers, we’ve seen that the lifespan of the road increases,” said the UC chairman. “The problem hasn’t resurfaced.”

Neighbourhood after neighbourhood is switching to the newer technology. End of last year, Mayor Murtaza Wahab even announced a Rs281 million push to redo roads in District Central alone.

“Paver work … is now a preferred option for local union council level leadership because of its sustainability,” Wahab told Dawn.

The success of an experiment at a nasty spot on the well-worn 26th Street persuaded the city government it was making the right choice. And if you take the FTC flyover from Gora Qabristan and exit on to Sharea Faisal, you’ll notice the difference there too.

These two spots would keep ponding no matter how many times the city patched them up. But since these strips were done over in blocks in 2022, there has been a marked difference.

A bigger experiment for an entire underpass at Gulistan-i-Jauhar was undertaken a year later. The decision raised eyebrows at the time, but the mayor defended it as a solution to persistent water damage. But when should pavers ideally be used in Karachi, and is this construction material actually a solution to one of this city’s worst problems: potholes?

Why pavers in the first place?

Pavers became popular when clay bricks fell short as Europe patched itself back together again after WWII.

The Netherlands introduced them in 1951, Brazil has relied on them for entire favelas, and use has doubled in the United States every five years. And according to Farhad Jatoi, the managing director at Magnacrete, pavers have long been tested in far more demanding environments such as ports and steel mills.

Karachi began using them under very different pressures. When a road is not designed or levelled properly, rainwater or sewerage tends to sit on it. This eats away at the top coat of asphalt. Potholes appear in days, even on new roads.

The engineers needed to keep the city’s roads in working condition and could not keep repairing them every time a gutter overflowed. They couldn’t wait for Karachi’s entire drainage to be fixed either.

And so when the Umar Sharif underpass was repeatedly breaking down, they decided to fix it once and for all by patching it with pavers. The same approach was taken for Jehangir Road, which would keep flooding with sewage because it is about 2 feet lower than its surrounding areas.

“We only install them in places where there’s subsoil water, leaking sewerage lines, or underground cross-connections causing repeated damage,” said one of the city government’s senior engineers, Ishrat Rehan. Pavers are the response to chronic drainage failures, even if they are a “majburi” for a city with few workable choices.

As per the Karachi Metropolitan Corporation’s latest progress report of the district Annual Development Programme, at least Rs4.2 billion were sanctioned for paver-related work in the city, with District Central seeing the largest share of around Rs1.13bn. The data, however, did not include figures from Districts Malir and Keamari.

The science of soil failure

Judge a road’s strength not by what you can see, but what lies beneath.

The roads you see in Karachi are built a little like Caked Alaskas. You scoop out the ground and refill the length of the strip with layers of soil or aggregate (crushed stone, gravel, sand, or recycled material).

This layer is pressed down by rollers. In the end, a thin layer of smooth, durable black asphalt is spread evenly over the top. The stronger the compression or compacting, the better the........

© Dawn Prism