The use of lead in the Borobudur’s drain construction may cause pollution. Lead is soluble in acidic water,
especially in the presence of HNO3. Acidic rain water can seep and accumulate at lead layer. Direct contact between
lead layer and the rain water for lasting time may caused lead layers dissolution forming Pb(NO3)2. Dissolved lead
can seep into drain and can seep to the surface relief. Continued contact between dissolved lead on the surface relief
with carbonate, sulfate, and chloride ions create white deposits of PbCO3, PbSO4 and PbCl2. The lead salt deposits
can damage the rock and partly carried by flow water and enter into drain that ended at control tanks.