Define the hydrogeological domain from public records, i.e., well logs, environmental studies, regulatory investigations..
1. are you upgradient or downgradient from the waterworks?
2. what elevation within the "sand" aquifer is the waterworks taking its water from?
3. are you going to establish your own pumping wells? where are you going to put them and how much water are you going to use?
if you can't answer the above, retain a hydrogeologist to establish your site's baseline conditions and judge operational impacts from your own groundwater use..