Not that it makes any difference to the hurt and disruption of the community but the process began in terms of the Slums Act, not the Group Areas Act. In 1966 the sewers regularly broke and sewerage flowed in the streets. Other facts forgotten are that 90% of the land in D6 was owned by Whites, some of whom were serving City Councillors at the time of the slum declaration. The balance were Malays. A tiny number of residents were Black Africans and poor Whites.
90% of the D6 residents were tenants paying cash weekly. A 23% return was possible. Banks gave 3% at the time. Sea Point prospered mightily. The tax man did not. Maintenance was ignored. 

BTW in 1902 plague broke out in D6. The then military government used fire to stop it. Replacement buildings often were built on the rubble, which was why it was so easy to push them over in 1966.
 Slums were cleared in Britain the same way as D6 but the residents were White so it was OK. Anyway German bombs had already done most of it.