New York’s Sewer Mapping System

A number of years ago we came across an excellent article on – of all things  the New York City sewer system.

What caught our attention was that how the data relating to the sewer system was being modernised and made more accessible.

The challenge that organisations find today isnt so much the development of system data but how to capture in a format that can be interrogated current and historical information.


New York City’s sewer system, an engineering marvel and a murky source of an urban legend about sewer residing alligators contains 6,600 miles of mains and pipes.

Placed end to end, the city’s sewers would stretch from Times Square to Alaska and back.

About 70 percent of that vast sewer system consists of combined sewers, which carry runoff from storms as well as waste from sinks, tubs and toilets.

Some of the pipes still in use were laid 150 years ago when the modern sewer system began.

For decades, city workers and contractors who want to make any change to New York’s vast water and sewer networks have had to retrieve browning maps, drawn by draftsmen and stored away in each borough hall and the department offices in Queens.

To help them find the sewer and water main maps — some dating back to the Civil War — city clerks have had to consult indexes, created by each borough before the city was unified in 1898.

The maps were cataloged on 3-by-5-inch cards.

In the coming months, though, visiting the department or borough halls to get maps, or calling to get the information on them, will become unnecessary.

For nearly a decade, the department has been scanning, reformatting and piecing together the tens of thousands of linen, Mylar and vellum maps of the city’s water mains and sewers.

More than just digital replicas, these maps are linked to millions of bits of information, or attributes — the size of the pipes, the dates they were built and repaired, what they were made of — that can be called up and sorted with the click of a mouse.

The maps can be updated instantly when water mains and sewers are installed, removed or repaired.

Thanks to global satellite positioning technology, the maps are accurate to within 18 inches.

And because they are on a central database, a growing number of department workers will have access to them not just on office computers, but outdoors on laptops using the city’s new wireless data network, NYCWiN.

It is expected that the maps to make department workers more efficient by cutting down the time spent retrieving them.

By feeding customer complaints, repair records and other information into the map database, the city hopes that planners and engineers can spot trends and anticipate problems.

“They are going to make people a lot more productive because they are not going to have to climb down in the sewer and not have to drive back to the office,” said Emily Lloyd, the commissioner of the Department of Environmental Protection.

“Having to move people around to collect information is very time-consuming.”

A consolidated database may also break down walls between city agencies by making it easier for, say, the Department of Transportation engineers to figure out where sewer mains are before they start building roads.

The foundation for the online water and sewer maps was laid in the 1990s.

Planners recognized that they needed a map of the city above ground that could serve as a precise geographic anchor for the underground maps.

This led to the creation of NYCityMap, an interactive database linked to a quilt of aerial photographs of the entire city.

The map, which was made available to the public in 2001, divides the city into 1,873 2,500-square-foot “tiles.”

It includes the exact locations of every manhole cover, sewer and fire hydrant the department maintains.

Those points of reference became the framework for the water and sewer maps. The maps of the city’s water mains had been scanned in the 1990s, but only in the last few years have they been reformatted and linked to a database of attributes.

In 2002, a process began to scan all the sewer maps, which took nearly a year, and to digitally stitch them together so the more than 6,000 miles of sewers would form a seamless map.

Fusing the maps was challenging because each borough uses its own measurement systems.

Unlike NYCityMap, which New Yorkers can use, some of the information on the sewer and water maps will be kept from the public because of security concerns.

(This post is based on the article “Old Sewer Mapping System Undergoes a Welcome Update” by Ken Belson, New York Times, August 19 2008)

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