Microtunneling Sewer Project Will Bring Cleaner Water to Lahore, Pakistan
I recently traveled to Lahore, Pakistan (home of my alma mater!) as part of a project aimed at helping the city better manage wastewater, minimize urban flooding, and eliminate sewage discharges into the city’s drainage systems. I am excited to share more about this tunneling “mega project,” which is going to be a win-win for the citizens of Lahore and the environment!
Lahore, the capital of Punjab province, is the second-most populous city and a financial hub of Pakistan. With a dense population of more than 13.5 million in a metro area of just under 700 square miles, Lahore is still growing quickly due to migration from rural areas.
Lahore is undergoing rapid modernization, requiring substantial infrastructure to improve the living conditions of its residents. Water supply, sewerage, and drainage are some of the most important utilities for sustaining public life. One of the major issues Lahore is facing is that the city’s sewage effluent is being pumped into the network of stormwater channels meant for draining rainwater. This creates both health and environmental hazards and must be stopped immediately.
To combat this problem, Lahore’s Water and Sanitation Authority (WASA) has undertaken a major project in the city’s central zone (the heart of the city) to construct large underground trunk sewers using a trenchless, microtunneling boring process. Funded by the Asian Infrastructure Investment Bank (AIIB), this mega project will cost more than $165 million.
The new trunk sewers will carry the sewage effluent straight to the Ravi River, where it will be treated at a proposed sewage treatment plant. This new process will reduce contamination of the stormwater runoff in the stormwater channels, as well as eliminate the need to pump the sewage effluent, saving operation and maintenance costs of the lift/disposal stations.
Based on dry and wet weather flows, the system will convey about 630 cubic feet per second through a more than 13-mile-long pipe system. Based on the hydraulic modeling, the sewer pipe sizes will range from 60 to 126 inches (5 to 10.5 feet) in diameter. Microtunneling will be performed by jacking concrete pipes more than 30 feet below the ground level to clear all shallow utilities and foundations. A major challenge to finalizing the tunnel alignment was clearing all known utility crossings, structures, streams, and pile foundations for transportation infrastructure like the existing Orange Line train route and the proposed elevated expressway.
While in Lahore, I was continuously asked what the difference is between a microtunnel boring machine (MTBM) and the more standard tunnel boring machine (TBM). While different, both construction systems are used to develop underground pipe/tunnel systems for various needs, whether it is a trunk sewer or a subway tunnel to carry trains. In MTBM, a pipe is pushed into the ground using a jacking system, whereas in TBM, the pipe is created behind the tunnel boring machine using segmental precast concrete panels. Usually, the MTBM is limited to a 144-inch (12-foot) diameter, and a TBM system is used for larger tunnel sizes. Selecting an appropriate system depends on several factors, including soil conditions, system depth, tunnel length, access shafts, and other factors beyond the pipe diameter.
Jacking and receiving pits will be constructed every 1,000 to 1,600 feet to help lower the pipes and jacking system and to withdraw the jacking machine. Once the water is conveyed on the downstream end, a disposal pumping station will be used to discharge flows into a conveyance channel and later to the wastewater treatment plants before discharging into the Ravi River that flows west of the city of Lahore.
The countless benefits of this project to the citizens of Lahore and to their environment certainly justify the cost to build this mega project. Some of the many benefits include:
- Separating sewer flows from stormwater flows. Lahore must do something to keep its sewage from flowing into storm drain channels, ditches, streams, and rivers. This should have been done a long time back. For comparison, here in the U.S., DC Water is spending more than $2.5 billion to build an underground storage tunnel under its Clean Rivers Project.
- Eliminating flooding. Recent record flooding in Pakistan has caused unprecedented devastation across the country. Even in metropolitan areas, boats were being used for rescue operations due to extreme flooding. The trunk sewer will significantly reduce the chances of flooding in critical central business districts and residential areas.
- Maintaining drinking water quality. If sewage is not piped, it is likely to contaminate drinking water aquifers through seepage and infiltration. A primary reason to build this trunk sewer is to prevent contamination of the underground water system used for drinking.
- Being proactive instead of reactive. Investing to upgrade existing systems now will save money in the long run, since the unanticipated consequences of sewage overflows and flooding can require millions of dollars for cleanup and rehabilitation.
- Reducing impacts to traffic and citizens. Microtunneling will allow life to go on as usual aboveground while the tunnel is built underground. The disturbance or impact at the ground level is limited to the access shafts only, which is a huge benefit to businesses and residents.
- Providing pollution and odor control. Currently, most of the sewage is caried through existing open channels, streams, and major waterbodies, resulting in septic conditions, pollution, and odor in neighborhoods. Unclean water is not only unhygienic, but also causes bacterial infections, various diseases, and health issues among residents, especially for children and the elderly.
- Positively impacting the environment. Flooding has direct and indirect impacts on citizens. Floodwater impacts homes and businesses, and it also ruins public spaces like parks, schools, grocery stores, and other facilities. These negative environmental impacts must be stopped.
To accomplish these goals and be proactive, WASA will work with a joint venture of four firms, led by EBA. The proposed trunk sewers will convey the sewage to the proposed disposal station at Bund Road near the existing Gulshan-e-Ravi sewage disposal station.
Our team will provide services in two phases. During Phase 1, we will prepare design guidelines and documents to select a contractor for engineering, procurement, and construction of the project. In Phase 2, we will oversee design and construction, currently proposed for 3 years. We look forward to working with WASA’s leadership to implement their vision for such an important public service project, as well as working closely with the project management team, stakeholders, and the public to make this vital initiative a reality.
Rizwan Siddiqi, PE, is President & CEO of EBA Engineering, Inc. He can be reached at 240.547.1125, firstname.lastname@example.org, or on LinkedIn.