This package contains low poly models that are very optimized assets. I already created a sample scene with proper light map.

this package contains including:
Customized 5 wall sets
2 different type of room
single and double doors
pipes, wires, lights, power boxes and 2 type of drums and creates .

Every assets had a prefab setup for you with proper collider. you can create your own sewer levels using this assets package.