Apart by about $8 million in salaries — and a new random drug testing policy — Vancouver and its police union are set to start contract mediation Monday.The city and the Vancouver Police Guild, which represents about 180 rank-and-file officers, have been unable to agree on a new contract. The old one expired at the end of 2011. The sides agreed to a third-party mediator to attempt to unite the two proposed contracts.But that may be tricky: While the two sides are stuck on the size of salary increases and other financial issues, if the battle between Portland and its police union is any indication, the random drug testing policy may be the biggest battle.Portland and its police union sparred over the policy, which the city implemented against union wishes in January. Union members filed agrievance asking the city to “cease and desist,” objecting to the cost, and also to the inclusion of steroids in the testing.Vancouver’s random drug test policy seems couched from Portland’s policy, with both cities using the terminology that police and administration have a “joint desire to achieve a workforce that is 100 percent drug free.”At least half of all officers would be randomly chosen for testing each year. The test would screen officers for use of marijuana, opiates, cocaine, amphetamines and phencyclidine or PCP. Anabolic steroids could also be included.