; and (C) threats to the community water system’s source water and distribution system from intentional acts, including intentional contamination, sabotage, and theft of any chemical of interest (as designated under Appendix A to part 27 of title 6, Code of Federal Regulations, or any successor thereto). (3) Assessment of alternatives Assessments submitted pursuant to paragraph (1) shall include a comparison of the disinfection methods used by the community water system and reasonably available alternative disinfection methods, including a determination of whether reasonably available alternative disinfection methods could reduce the community water system’s vulnerability to the threats identified pursuant to paragraph (2). (4) Periodic review and resubmission Each community water system submitting a vulnerability assessment pursuant to paragraph (1) shall review, revise as necessary, and resubmit such assessment not less often than every 5 years. (5) Guidance Not later than one year after the date of enactment of the Safe Drinking Water Act Amendments of 2017 , the Administrator shall provide guidance to community water systems for the preparation of vulnerability assessments under this subsection. (b) Source water and distribution system protection plans (1) In general Not later than 4 years after the date of enactment of the Safe Drinking Water Act Amendments of 2017 , each community water system shall submit to the Administrator source water and distribution system protection plans. (2) Mitigation of identified threats Plans submitted pursuant to paragraph (1) shall identify strategies and resources to mitigate the threats identified in assessments prepared pursuant to subsection (a). (3) Emergency response planning Plans submitted pursuant to paragraph (1) shall include specific emergency response plans for the threats identified in assessments prepared pursuant to subsection (a). (4) Periodic review and resubmission Each community water system submitting a plan pursuant to paragraph (1) shall review, revise