Sewage / grey water leaking onto pavement

There's been an issue with sewage leaking from the retaining wall near the bus stop for several months, certainly before this years winter freeze when it froze over and brcame a slip hazard. The amount of grey water / sewage seeping through the retaining wall has recently increased. There's a definate whif of sewage and sewage flies are feeding on the seepage. I'm not sure who is responsible for the leak but the fact is that it's leaking onto the pavement at a busy bus stop and then entering the drainage system.