As part of an ongoing investigation into union corruption in Philadelphia, the FBI has acknowledged yearlong wiretaps of Philadelphia Building and Construction Trades Council leader John Dougherty and City Council Majority Leader Bobby Henon.

Along with the rest of us, city officials were well aware of the federal investigation after FBI and Internal Revenue Service agents conducted very public raids of Henon's City Hall office, Dougherty's home, and the offices of IBEW Local 98, the electricians union headed by Dougherty. That was last August. Since then, federal investigators have intercepted calls to and from numerous union and city officials, including Mayor Kenney.

All of which begs the question: Why would the mayor's office place the Philadelphia Building and Trades Council at the center of labor negotiations on the $500 million, taxpayer funded construction project known as Rebuild, when the council's leader is under federal investigation?

The mayor's spokewoman, Lauren Hitt, says the negotiations aren't about one person who is under federal investigation, but about 21 different organizations that signed onto the city's memorandum of understanding around the Rebuild project.

I guess that's fair. But when federal search warrants say officials are seeking evidence concerning allegations such as embezzlement of union funds, extortion by an unnamed public official, mail and wire fraud, tax evasion and the use of "economic fear" to manipulate and pressure contractors, it gives me pause.

To be clear, neither Dougherty nor Henon has been charged with wrongdoing at this point. But the longstanding pattern of exclusion that Philadelphia's building trade unions have engaged in is more than troubling.

To be blunt, if racism and sexism were crimes, the numbers would paint a compelling case against many of Philadelphia's skilled trade unions. And the City of Philadelphia would stand accused as a willing accomplice.

In Fiscal Year 2016, an astounding 63 percent of small, city-funded construction projects had no people of color or women on the workforce, 42 percent of midrange city-funded construction projects had no people of color or women on the workforce. And 9 percent of the largest city-funded construction projects — those with the most scrutiny and oversight — had no minority workforce at all. The same thing happened in Fiscal Year 2015, when 44 percent of city-funded projects had no women or people of color on the workforce.

How does that happen in a city where the majority of people are black and brown? It's a public-private partnership of sorts.

First, the building trades unions build a political organization composed of millions in campaign contributions. Then a parade of mayors signs executive orders mandating that labor deals on major city-funded construction go through the unions. Then the city pretends that it will punish those who exclude women and people of color from taxpayer-funded projects.

The punishment rarely, if ever, comes.

That's because the unions largely determine the labor pool on city-funded construction projects. That reality leaves the door open for the kind of brazen racial exclusion that we've seen in much of the city-funded construction in Philadelphia.

A 2008 document called the Philadelphia Building and Construction Trades Council AFL-CIO Diversity Commitment and Plan gives a bird's-eye view into the numbers that make such discrimination possible.

The document, signed by representatives of 12 unions — the electricians and carpenters refused to sign — promised that the Philadelphia Building and Trades Council would ensure that "minorities and women are fully utilized in the pending expansion of the [Pennsylvania Convention] Center."

Those who signed submitted their membership numbers by residency and race, and the results were fascinating.

On average, just 19 percent of the union's members were women or people of color, and only 28 percent of each union's members lived in Philadelphia. Just 12 percent were black, nearly 4 percent were Hispanic, 1 percent were women, and less than 1 percent were Asian or Native American.

Were it not for the Laborer's Union, which is majority black and Philadelphian, the numbers would be even worse.

So while we are told that the problem of getting people of color into the building trades unions is a "long-vexing issue," the reality is that it is an issue of political will.

The building trades are overwhelmingly white, male and suburban. The city has known this for years. It's documented. Yet we continue to go the unions and ask them to find ways to get blacks and others into their organizations, all while funding all white construction projects with brown folks' tax dollars.

I don't pretend to know what will happen with the federal investigations of Dougherty and Henon. But I do know we must stop pretending the problem with union diversity is some impossibly complex puzzle.

The unions are exercising their right to exclude people from their private organizations.

If that doesn't change, we must exclude them from our tax dollars.