EXTRA security may be installed in public housing blocks following attacks at a Tuen Mun estate by a serial rapist. Closed circuit television and iron door grilles are among measures being considered if residents are prepared to pay the cost of $40 a month. Concern among public housing tenants escalated after the most recent attack at Tuen Mun's Yau Oi Estate in which a woman was raped and murdered. The Housing Authority will survey tenants to see if they are willing to pay for the installation of security measures. Proposals are being studied by a Housing Department working group and agreed to in principle by the Housing Authority, Tuen Mun District Board members were told yesterday. Senior housing manager, Mr Chan Kwok-chuen said the working group had estimated that for a block with 612 households, each would have to pay a one-off sum of $728 for the iron grille and closed circuit system. The round-the-clock watchman service would cost another $36 a month for each household, he said. Mr Chan said residents who agreed to pay for the extra facilities would be asked to sign an amended tenancy agreement including the extra charges. At present public estate tenants pay their rates and management fees together with rents on a monthly basis which are stated on the tenancy agreement. Mr Chan said residents of Cheung Hang and Cheung On estates on Tsing Yi Island were chosen for a trial survey to be held this year. Assistant Director of Housing (Regional Management), Mr Siu Che-wing, who headed the working group, said questionnaires were being drafted for the trial survey scheduled for this summer. Mr Siu said residents would be asked if they would pay for the extra facilities, either in a lump sum or by monthly instalments over a five-year period. Mr Siu said the survey would help the authority to devise long term policy on security facilities installed at estate blocks. The facilities would then be uniformly applied at all estates. Tuen Mun Police District Commander, Chief Superintendent Ron Clibborn-Dyer, told district board members that top priority had been given to the rape and murder case at Yau Oi Estate in February. He said a serial rapist believed to be responsible for at least five assaults was still at large. Mr Clibborn-Dyer said there was a difficulty in deploying extra manpower to patrol highrise and estate buildings without taking beat patrol officers off the streets. He denied board members' accusation that police had over emphasised goldsmith shops' security and neglected residential areas.