Signature Bridge Over Narayani River

Upon the announcement of a new tender call, this writer penned an article in this daily on December 22, 2022, shedding light on the shortsightedness of proposing a future bridge over the Narayani River in Narayanghat. In this piece, the writer strongly criticised the proposal for a two-lane bridge, given the expectation of a continual surge in traffic at that location. Fast forward to May of this year, and the Department of Road (DoR) awarded the construction contract to Tundi Construction in a second tender call. Unfortunately, it seems that the bridge to be built is still limited to just two lanes. Building a two-lane bridge over the Narayani River appears to lack foresight. With the ongoing expansion of the road to six lanes on both sides of the bridges, can a two-lane bridge at Narayani River effectively handle the increasing traffic flow to and from the banks, not only now but in the future? 

Putting aside considerations for future traffic demands, a two-lane bridge at this location fails even to meet the current traffic requirements. Given an estimated cost of Rs 1,700 million to build the bridge, proposing a two-lane bridge seems utterly ludicrous and non-engineering! There has been a considerable buzz surrounding the construction of this bridge, with the DoR proudly touting it as an iconic addition to the area. However, despite the excitement from the public, the proposed bridge has failed to perform even the most basic traffic demand calculations. Typically, signature bridges are not only expensive but also necessitate cutting-edge bridge engineering skills, and they are not constructed frequently. When they are, they must be designed to accommodate current and future traffic demands for decades to come.

Critical points

 For instance, the Golden Gate Bridge in San Francisco, built approximately 80 years ago, was designed with an eye towards future traffic demands for the next 100 years. Some might argue that due to budget constraints, the DoR can currently only afford a two-lane bridge and may construct another two-lane bridge in the future. However, there are a couple of critical points to consider. Firstly, the estimated cost of this bridge stands at around Rs 1,700 million, equating to Rs 4 million per metre. Drawing from the writer’s 25 years of global bridge design experience, this is a notably high estimate for a two-lane bridge, regardless of its iconic status. The writer has worked in this field in the United States, Japan, Thailand, and several other countries, and is still working in it now. 

Secondly, constructing another two-lane bridge in the future will require the DoR to allocate a similar or possibly even greater budget due to factors like inflation and evolving construction costs. The cost of building a signature bridge is not linearly proportional to the number of lanes when constructed all at once. However, the cost tends to be linearly proportional or even higher when constructed in separate installments. Frequently, the writer comes across news reports indicating that Tundi Construction is in charge of the bridge's design. However, the DoR appears uncertain regarding the specific type of signature bridge they intend to construct. It could take the form of a cable-stayed or an arch bridge. It's essential to note that there is a substantial cost disparity between building a cable-stayed and an arch bridge. 

The writer respectfully poses this question to the DoR engineers: if the bridge's type remains undecided, and the design process is currently underway, how can accurate cost estimation for the bridge be achieved? It is a fundamental principle in engineering that precise cost estimations for a bridge cannot be provided unless the design process has been thoroughly completed. Consequently, at this point in time, when both the bridge's type and design remain uncertain, the projected budget for the Narayani bridge appears to fall considerably out of line with its actual cost. These days, the DoR typically employs a "Design and Build" approach for constructing most bridges. This means that the contractor awarded the bridge construction tender is responsible for both designing and submitting the bridge design to the DoR for approval. Upon approval of the design, the contractor proceeds with the construction.

Engineering calculations

Based on the writer’s personal experience collaborating with the DoR, the writer has observed that the DoR usually initiates the process with a conceptual bridge design, often prepared by a consultant prior to issuing a tender call. This conceptual design can be likened to a rough, freehand sketch of the bridge, lacking the rigorous engineering calculations necessary to determine the bridge's type and cost. It remains a significant mystery to me how the DoR arrives at the bridge's cost before even issuing a tender call. It's genuinely puzzling that numerous images of the Narayani bridges are circulating on the internet, yet, in reality, no comprehensive engineering calculations have been conducted to ascertain the bridge's design and estimated construction cost.

The construction of the signature bridge spanning the Narayani River holds immense promise for Chitwan and the entire nation of Nepal. As we embark on the journey to bring this monumental project to life, it is of utmost importance that the DoR conducts thorough groundwork, remains receptive to expert advice, and takes proactive measures to address future potential challenges. By doing so, we can not only create an iconic symbol of progress but also establish an economically viable and innovative bridge that serves as a shining example for the entire country. The signature bridge possesses the potential to be a legacy born out of vision and collaborative efforts, one that will resonate through generations. Through deliberate and meticulous steps, coupled with an unwavering commitment to uphold the highest engineering standards and employ cutting-edge innovation and technology, we can transform this vision into a reality that not only endures but also thrives for years to come.

(Practicing structural engineer with global experience in the design of high-rise buildings, Dr. Puri holds a PhD from Tokyo University and a postdoc from the University of Illinois at Urbana-Champaign, USA.)