Question

1. many cities have combined sewers. in good weather, these systems funnel sewage to treatment plants. during rainstorms street runoff is combined with sewage. combined sewers in cities can be problematic because ______.

○ sewers are often blocked by trash that people have thrown into them
○ street runoff often causes the sewers to deteriorate
○ the sewers cannot handle the volume of waste from street runoff and sewage
○ street runoff cannot flow into the sewers and be safely taken to treatment plants

Explanation:

Combined sewers carry both sewage and stormwater. During rainstorms, the large volume of street runoff mixes with sewage, overwhelming the system's capacity, which is the core problem with this infrastructure. The other options do not address the defining issue of combined sewer overflow from excess volume during wet weather.

Answer:

the sewers cannot handle the volume of waste from street runoff and sewage