弄空 meaning in Chinese

clean
deplete of
depletion

" the camps are at present not being used to their full capacity . we had emptied the septic tanks before the residents moved in . as the residents are only staying there for a short period , we will undoubtedly monitor the usage rate closely to ensure that there is no leakage of the effluent .
现时度假村仍未住满，我们已在居民搬进前把化粪池弄空，况且居民只会住上一段短时间，我们会密切监察使用情况以确保?水不会漏出。