Rod9966

Hi Guys, I have a problem and I need your assistance. I have 59000 litres of stormwater trapped in a concrete sediment pond. It currently has a ph of 11 and I need to reduce this to no greater than 9 prior to discharge into bio basin. I have Hydrochloric Acid available at a concentrate of 33%. My question is how much of this Acid will i require to treat the 59000 litres to reduce the ph level from 11 to 9. I can assure you this is not an exam question from my sons grade 6 chemistry class it is a real world problem a poor old layman like myself would like to solve but im too old and tired. Sorry. Any assistance would be appreciated. I have had those at work come up with figures like .0076ml, 67 litres , 445 litres and one over 1000ltrs of acid required. Can I leave it to you guys to solve this one for me. Many thanks Rod