Can I sue my landlord for not fixing the septic field?

We've requested numerous times to have the septic field fixed, each time we talk to him he promises to fix it but has done nothing and he always ured us that there was NO danger. However, ground water tests have now confirmed e-coli contamination. Since he has known about this problem, done nothing to fix it, knowingly exposed us to the danger, can we sue him for negligence?