The project includes a lower promenade, which is expected to be submerged during heavy rains, and a 10 m high wall to contain the river. Courtesy of MWH India Private Limited
Ahmedabad, India, is undertaking a dramatic renovation of the Sabarmati riverfront, converting an 11.5 km section of the riverbanks into a model development of public spaces and valuable commercial and residential lots.
July 24, 2012—The City of Ahmedabad, India, is making progress on an ambitious riverfront development project that will convert an area that was once home to slums and illegal sewage outflows into a model development that will feature parks, malls, and theaters. Several highly prized commercial and residential parcels will be auctioned off to pay for the improvements.
The project is complex. The Sabarmati River is a nonperennial river with raging water as much as 8 m deep during the rainy season and a naturally dry bed at other times. In the dry season, the city can place low levels of water in the river from irrigation canals and hold it via dams downstream. A collection of 51 storm sewer outfalls on the banks had been illegally tapped by residents, and were flowing raw sewage into the stream much of the year. Slums and trash dumps dotted the banks.
In 1997, the Ahmedabad Municipal Corporation formed the Sabarmati Riverfront Development Corporation Ltd. to renew the area and manage the river as critical infrastructure along an 11.5 km portion of the city. Plans called for an extensive upgrade of the water, storm-water, and wastewater infrastructure, installation of promenades and retaining walls, relocation of slum residents to apartment buildings, and the creation of a wastewater effluent reuse system.
“The overall scope of the project is very wide. In a way you can say it’s like creating a city within the city,” says Nitya Shah, P.Eng., the regional manager for MWH India Private Limited, a division of MWH Global, headquartered in Broomfield, Colorado. MWH was responsible for designing the wet infrastructure on the project.
MWH designed interceptor lines—one for each bank of the river— that collect sewage from the 51 outfalls via junction chambers and direct the wastewater to Vasna and Pirana Sewage Treatment plants downstream. Creating this system with the capability to manage massive storm inflows was a design challenge, Shah says.
“Initially we thought during the dry weather we will have the gates and the junction remain closed, and during the high flood times we will open the gates and let the water flow into the river,” Shah says. “In doing so, there was an operational issue because during heavy storms, it is difficult for the operation staff to get to those gates and open them or close them.”
MWH developed an alternative that diverts a portion of the flow in the interceptor lines, which range from 900 mm to 2100 mm, to the river during storm events in the city.
“In some cases, there have been incidences in which we have received 14 inches of rain in four hours,” Shah says. “It’s very heavy rainfall. Seasonal rainfall amounts to 30 inches on average, but we have a couple of events every year when there is a torrential downpour. At that time we need the interceptor as well as the outfall to work simultaneously. That has eliminated the requirement or the need for the operation staff to go to the site and open up the gates and risk their lives.”
The retaining walls of the riverfront project are designed to repel a 200-year flood. The promenade areas are designed to be submerged during flooding.
The existing wastewater treatment plants have adequate capacity for the increased flows, but the treatment process will be enhanced by the addition of membrane bioreactors and sequential batch reactors to improve the quality of effluent. A new reuse system will pump 4 mgd of treated effluent from the plant back to the riverfront district to irrigate the 50 percent greenbelt in the nearly 200 hectare development area and for public toilet flushing and cleaning.
The project replaces slums and waste dumps. During the dry
season, water from irrigation canals can be used to fill the river.
Courtesy of MWH India Private Limited
“Once that component is executed, it will be first reuse water network in the city,” Shah says. “So there is something unique. There is a huge water demand to that public garden space. And with this being a water-scarce area, MWH proposed, ‘why not reuse [wastewater effluent]?’ It’s nothing new to the Western world, but it’s certainly a unique thing to do in India. It hasn’t been practiced anywhere else in the city before.”
The project includes another first for the city and a rarity in the nation, a 24-hour drinking water supply. Many cities in India, including Ahmedabad, have a two-hour per day water supply, and the pressure can be limited, at that. This required MWH to develop a new design that could connect to the existing system but function independently. The new system features smaller diameter lines and water meters, a new addition for domestic customers in the city.
“They are not going to change the entire city’s water supply to 24/7 immediately after this project,” Shah says. “It will take some years to get to that stage. Meanwhile, we have to make sure that although this area is part of the city, it has different operations and a different design.”
These differences will make land in the revitalized riverfront area—scheduled to be complete in late 2013—“extremely valuable,” Shah says. About 15 percent of the land will be auctioned off, with expectations that developers will place hotels, condominiums, and corporate offices there.
“It will be a model,” Shah says. “This project will certainly bring new ideas to the table and obviously it will provide new thinking to the cities trying to develop their river area. A lot of cities are thinking of adopting this type of project to improve the image of their city, attract more tourism, and to upgrade their social lives of the citizens.”