Is anyone minding the store at City Hall?

Not based on charges last week by two former city investigators that the city repeatedly fails to oversee contractors — sometimes with dangerous results.

In a column for City & State, former Department of Investigation Commissioner Mark Peters and First Deputy Commissioner Lesley Brovner note that during their five years at the DOI, they oversaw “multiple” cases where agencies “failed to supervise private entities” hired by the city.

Instead, city officials would “simply write a check to a private vendor, and then walk away,” leading to “multiple large-scale” failures to deliver basic care and services.

In 2015, for example, the DOI found the city Department of Homeless Services outsourced work to a private entity that charged almost twice the market rate and provided grossly inadequate housing.

A group hired by the Department of Correction to deliver health care to inmates not only failed to provide decent care, but its employees were busted for smuggling contraband into the jails. The Administration for Children’s Services also neglected “dangerously inadequate care” by contractors.

Last week, we noted how the Department of Sanitation parked garbage trucks on a residential street, wreaking havoc on the area, because it was easier than finding a more appropriate site. In all these cases, city “supervisors” and managers were failing to do their jobs.

Here’s the question: Mayor Bill de Blasio has been hiring staff like crazy. The city’s headcount is on pace to hit an all-time high this year, with 332,000 employees. No one expects city workers to provide all the massive services the city offers themselves. But if they aren’t managing and supervising, what exactly are all those people doing?