3 sentences

1. 这个城市的地下管线纵横交错。

   zhè gè chéng​shì de dì​xià guǎn​xiàn zòng​héng jiāo​cuò.

   The underground pipelines of this city are a crisscrossing network.

   Source: Dong Chinese Dictionary

2. 在开挖地面之前，必须先核实地下管线的位置。

   zài kāi​wā dì​miàn zhī​qián, bì​xū xiān hé​shí dì​xià guǎn​xiàn de wèi​zhi.

   Before excavating the ground, the location of underground pipelines must be verified.

   Source: Dong Chinese Dictionary

3. 这条跨境天然气管线正式投入运营。

   zhè tiáo kuà​jìng tiān​rán​qì guǎn​xiàn zhèng​shì tóu​rù yùn​yíng.

   This cross-border natural gas pipeline has officially gone into operation.

   Source: Dong Chinese Dictionary