SCHEMA:
CREATE TABLE table_name_25 (year_completed INTEGER, dam_type VARCHAR, dam_constructed VARCHAR)
USER:
Which Year completed has a Dam type of earthfill embankment, and a Dam constructed of khancoban dam?

QUERY:
SELECT MAX(year_completed) FROM table_name_25 WHERE dam_type = "earthfill embankment" AND dam_constructed = "khancoban dam"