drainage with medicated thread

例句：

1. 1. The city hasa large network of underground water drainage systems.
   这个城市拥有庞大的地下排水系统网络。
2. 2.The construction crew had to work around theclock to complete the sewerage system.
   施工队不得不昼夜不停地完成下水道系统。
3. 3.The rainwater is being divertedinto the river for drainage purposes.
   雨水被引导到河里进行排水。