Residents in West Allis are picking up the pieces after weekend flooding left streets piled with damaged belongings and some homes near collapse. The flooding has raised questions about how exactly Milwaukee Metropolitan Sewerage District's (MMSD) infrastructure works.

After hearing concerns from multiple homeowners, TMJ4 went to MMSD to learn about the deep tunnel system and how, if at all, it may have impacted flooding levels in the area.

Bill Graffin from MMSD explained how their system operates on a daily basis.

Water and sewage from residential and business lateral pipes travel to municipal pipes, then MMSD sewer pipes. Once sewer water levels rise, it starts to enter the deep tunnel system.

When the deep tunnels reach certain capacity levels, MMSD officials close the gates to the

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