Consider the following statements in respect of dams: 
1) In a gravity dam, a grout curtain is provided near the toe to reduce the exit gradient. 
2) A drainage gallery with its drainage pipe system provided in a gravity dam reduces the uplift pressure at all levels below the upstream water level. 
3) An earthquake acceleration of 0.1g acting vertically downward causes a decrease of 10% in the unit weight of concrete and of water in a gravity dam. 
4. The Tehri dam is a gravity dam. 
Which of the above statements are correct?