There probably already is

250,000 gallons (if it was 10 cars and all 10 converted perfectly to HCl, and all of it went into the water supply) into a water table of, lets be conservative with 10 billion gallons, is 0.00002% concentration or .02ppm

Compare this to your stomach, which has an hydrochloric acid concentration of 5000ppm.

So yes, I would have no issue with it. All the water you drink mixes with a much higher concentration of HCl every time you drink it.

Like I said, their is a hysteria building around this and a total lack of nuance and understanding.

That amount of hydrochloric acid doesn't just magically dilute evenly into the water table in one instant.

It's actually more mixed than you would think since it forms HCl in the atmosphere and falls down with rain.

For reference 1 inch of rain over 1 sq. mile is approximately 18 million gallons.

So even if we concentrated the full 250k gallons (remember that HCl is just one byproduct too, so we are being very generous with 250k gallons, most of the byproducts are carbon monoxide/dioxide), but 250k gallons into 1 sq mile of rain fall....138ppm

In reality this will fall over thousands of square miles too.

HCl itself isn't going to be a direct issue in the water supply. HCl interaction with all those other things in the environment that were otherwise inert is the big problem here. If you dump your HCl in a limestone environment, we'll you'll dissolve a bunch of rocks. It gets more problematic when there heavy metal compounds get dissolved into solution and suddenly people can't use their wells or municipal water has to shut down or work extra hard at filtration.

Problem is the only way you know if this is occurring is constant sampling and testing over the affected region by a competent and trustworthy set of testing groups.