I think you converted the wrong way.
28,000 gallons x (3.785 L/gallon) = 1E5 ESTIMATED. You need a better answer than that.
How many mols do you need? That's M x L = approx 1E5 mol HCl.
M HCl = mols HCl/L HCl. You know M and mols, solve for L. That really looks like a simple problem to me. Think in mols. That's the secret to most chemistry problems.