As I understand it Housing Association Tenants have to sign a covenant that they have to abide by concerning anti-social behaviour. This is classified as;
intimidation of neighbours and others through threats or actual violence
harassment, including racial harassment
verbal abuse
homophobic behaviour
systematic bullying of children in public recreation grounds, on the way to school or even on school grounds, if normal school disciplinary procedures do not stop the behaviour
abusive behaviour aimed at causing distress or fear to certain people, for example, elderly or disabled people
noise
dumping rubbish
animal nuisance, including dog fouling
vandalism, property damage and graffiti.
As you can see dumping rubbish is covered by the agreement the tenants sign up to.
As mentioned above have a word with the tenants first - if no joy there then complain to the HA.
Hope this helps!
Ross