The best tree structure is the tree with 10 leaves which gives minimum error and the minimum samples in one leaf is 15. Area beneath 4.5 m is considered as unsafe whereas above 5.5 m is safe except in Deltaic Fluvial plain. Beach, alluvial fan deposits, Madhupur clay and tertiary and early quaternary bedrock is safe with 4.5 to 5.5 m. Research shows that pH does affect to the adsorption ability of Arsenate. In acidic and near-neutral pH, iron-oxide adsorbs Arsenate resulting in the deceasing Arsenic access in groundwater. Hence, groundwater is safe at low pH. The main mechanism that release Arsenic into the aquifer is the reductive dissolution of iron(hydro)oxide (FeOOH) in Detaic tidal, fluvial and alluvial deposits. Marsh clay and peat areas are also safe.