Thimphu thromde spends about Nu 20 million (M) every year to maintain roads, mainly potholes.
According to the thromde’s chief engineer, Yeshi Wangdi, potholes in the city were mainly caused by poor drainage system, which leads to surface runoff water.
A thromde official said thromde repairs potholes on a daily basis. “We carry out the work departmentally.”
Yeshi Wangdi said potholes get bigger every time it was repaired because of wear and tear. “Potholes are like cancer. It spreads.”
He said that to reduce maintenance cost of roads, thromde is now awarding contractors road construction works along with drainage improvement works. “This would address the issue of surface runoff water that deteriorates the quality of road.”
He said they are replacing the RCC drains with bigger size of hume pipes. “We decided the hume pipe size after calculating surface runoff water.”
Another thromde engineer said a catch pit was constructed in every 10 to 15m, which would serve as a reservoir for surface runoff water. “Excess water on the ground will go in catch pit and flow through hume pipes.”
The chief engineer also said thromde is also improving sewer lines, using improved quality of blacktopping material and installing cables in certain interval along the road to join any cables by private residents to reduce the maintenance cost of roads.
He said bitumen used for blacktopping roads give in when exposed to water for long time, forming potholes. “Currently, we use only asphalt concrete. To improve the resistance on bitumen, we would now use a second layer dense bituminous macadam.”
It is not only surface runoff water that is an issue in Thimphu thromde.
Surface runoff sewer and water along Norzin Lam and Bhutan Youth Development Fund area during monsoon is also a serious issue.
In the last fiscal year, thromde awarded a Nu 40M worth project to six contractors to connect sewer lines in whole thromde area, which was disconnected from city sewer and those that did not have sewer lines.
Construction Development Corporation Limited (CDCL) was supposed to blacktop the road after the sewer lines was laid.
Yeshi Wangdi said the sewer project did not go as planned, as sewer pipe suppliers could not supply it on time, although they initially agreed they could. “Laying sewer lines is underway.”
He said the project to lay sewer line got extended in the current fiscal year. “We also had to engage CDCL for road resurfacing works, as they are included in the sewer package.”
CDCL resurfaced about 4.7km of road within the thromde.
A contractor said executing road works in Thimphu thromde was difficult because of various underground cables installed without proper plan.
Yeshi Wangdi agreed and said that was because most residential building owners wanted to convert their buildings to commercial buildings and when they lay cables for higher voltage of electricity, they dig the ground. “This practice damages the road causing wear and tear.”
He said thromde has now mandated all constructions in Thimphu to keep provisions at certain intervals, which could be used to lay any cables in the future. “That way, people need not dig the ground randomly.”
Meanwhile, Yeshi Wangdi said they are planning to change sewer lines and drainage in Norzin Lam.
Edited by Tashi Dema