CHONGQING (CQNEWS) -- Under the vibrant cities we are living in is a huge pipeline network that serves as the blood system of the city. These underground pipelines, which transport wastewater all day to guarantee the stable operation of cities, are maintained by pipeline maintenance workers.

“The gas detection confirms that the pipe is accessible. Take care!” Domestic rubbish was salvaged up from deep underground by roaring machines in the stinky sewage lifting pumping station near the Jiuqu River sewage treatment plant of Chongqing Water Group Three Gorges Water Company. After repeatedly confirming the gas content underground, Liu Hao and his colleague Zhong Xingyu entered the underground pump room at a depth of ten meters to check the operation of equipment and facilities.

The lifting pump room is the last barrier for sewage to enter the sewage treatment plant. On weekdays, Liu Hao and his three colleagues are mainly responsible for nearly 30 kilometers of sewage pipelines and 492 external inspection wells. Dredging, maintenance, and flood control... these seemingly simple tasks are potentially fatal.

“There is hydrogen sulfide, carbon monoxide, and combustible gases in the pipeline. When the concentration of hydrogen sulfide reaches seven to eight milligrams per cubic meter, you will smell rotten eggs; if it exceeds ten milligrams per cubic meter, you will not smell the odor and you may suffocate,” said Liu Hao. The concentration of hydrogen sulfide was not high this time, otherwise, they needed to wear a breathing mask before going down for inspection.

Dense neighborhoods are also one of the key inspection targets because underground pipelines usually contain much combustible gas. When a well cover is open, the air will be heavy with the stink of foulness. A pipeline periscope is used when it’s not easy to get into a narrow well. With a weight of 20 jin, the periscope is up to seven meters in length. The photo above shows that a periscope was slowly lowered deep into the well by three pipeline inspection workers.

Through the camera on the periscope, the pipeline inspection workers can get a clear view of the underground situation on the tablet computer. "Look, the water flows gently and the water level is normal, so there is no problem." If the water flow is relatively small or the water level is very high, the pipeline is likely to be clogged, and all the nearby wells should be checked one by one, said Zhong Xingyu.

If the concentration of hydrogen sulfide and combustible gas in the well exceeds the standard level, ventilation should be carried out for more than 30 minutes with an air blower. "After ventilation is finished, we will check the nearby wells one by one to ensure that the gas content in the wells does not exceed the standard level," said Liu Hao.

As the Spring Festival approaches, Liu Hao and his colleagues have become busier. "The Chinese New Year is approaching, and it’s our greatest responsibility and obligation to ensure the safety of pipelines and the cleanliness of the city. Many people say that our work is ‘smelly’. It is tiring and dirty, but we make the city clean and safe. It’s worth doing it,” said Liu Hao.

According to statistics, there are hundreds of kilometers of sewage pipelines in downtown Chongqing, while there are only 70 pipeline inspection workers. They have to inspect about 70 to 80 wells every day to guard the invisible "lifeline" of our city. (Translated by Yuki, Fathom Language Limited)