460 billion VND needed to build 1km of expressway overpass in the Mekong Delta

The total cost of building the expressway viaduct in the Mekong Delta is only about 2% higher than the embankment option. Photo: TL

The Institute of Construction Economics has just submitted to the Ministry of Construction a research report on the investment plan for an overpass for the expressway in the Mekong Delta region.

According to the report, the construction of highways in the Mekong Delta is facing difficulties in supplying embankment materials. In the period of 2021-2025, the Mekong Delta and Southeast regions will construct 9 important national projects, requiring about 63 million m³ of sand for road embankment.

However, sand resources, mainly exploited from the Tien and Hau rivers, are increasingly scarce, making sand supply difficult. Large-scale sand mining also causes coastal subsidence and environmental pollution.

Therefore, the Institute of Construction Economics proposed a plan to combine sand-filled roadbeds with viaducts on some sections of highways in the Mekong Delta region to solve the problem of exploiting and supplying embankment materials.

Currently, the rate of viaducts on expressways is still low, with only about 70km of viaducts out of a total of more than 2,000km of expressways under construction.

The Institute of Construction Economics has compared the investment costs between building a dirt road and a viaduct, according to the investment rate announced by the Ministry of Construction, showing that building an viaduct is about 383.89 billion VND/km, 2.6 times higher than that of a dirt highway with about 188.72 billion VND/km.

However, this capital does not include costs such as compensation, resettlement, interest during construction, weak ground treatment and some other costs.

The comparison and evaluation of the effectiveness between viaducts and embankments should consider both the initial investment costs and the maintenance and repair costs throughout the design life of the project to have a more complete view.

According to the calculation of initial investment costs and maintenance costs over the project life cycle (design life of 100 years), the cost of building the embankment is 450.232 billion VND/km and the cost of building the viaduct is 459.289 billion VND/km.

The total life-cycle cost for the viaduct is 2.01% higher than that for the sand-filled highway.

The Institute of Construction Economics also pointed out that building highways on sand embankments has many disadvantages such as requiring large-scale site clearance, shortage of sand supply, difficulty in controlling sand prices, and causing subsidence and landslides during exploitation.

Regarding reinforced concrete viaducts, this option has advantages such as better control of construction progress, reduced dependence on site clearance and sand scarcity, saving land funds and land acquisition costs, while ensuring flood drainage, reducing flooding, salinity intrusion and protecting the environment.

Based on initial analysis results, the Institute of Construction Economics determined that the cost of building a reinforced concrete overpass for a highway is only slightly higher than the traditional embankment option.

However, when choosing an option, investors need to consider not only the initial investment cost but also the cost for the entire project life cycle and other factors as analyzed.