How does the 500-meter spherical radio telescope (FAST) solve the drainage problem?

The FAST radio telescope station is located in Dawodang karst depression, Kedu Town, Pingtang County, Qiannan Prefecture, Guizhou Province, with a catchment area of about 0.657km? Due to its unique address structure and perennial thunderstorm weather in Guizhou, once a once-in-a-century rainstorm occurs, a large amount of water will appear at the bottom of the site. Therefore, in order to ensure the safe operation of the telescope, the tunnel drainage project was designed and built. The total length of the drainage tunnel of FAST project is 1 12 1m, and the design scheme of pressureless tunnel is adopted. The tunnel is divided into open-cut section and open-cut section, the open-cut section is 58.588m, and the open-cut tunnel is1062.499 m. The whole drainage system consists of roadside ditch, radial ditch, ring ditch, bottom ditch, energy dissipation pool and drainage tunnel.

In addition, the mirror itself is not a closed cauldron, but is spliced by small triangles, and a drainage seam is reserved.