The main objective of this document is to provide guidance on triggered and assessment source water monitoring issues such as selection of fecal indicators, sample collection and shipping, source water monitoring methods, laboratory quality assurance (QA) and quality control (QC), and evaluation of fecal indicator data. This manual also provides an overview of GWR requirements and includes frequently asked questions regarding source water monitoring. Several appendices provide example forms that may assist in performing the procedures described in this guidance manual. However, it is important to note that these forms are provided as guidance and are NOT required for compliance with GWR requirements. Regarding the selection of fecal indicators, this manual provides guidance, when possible, based on aquifer type, historical data, environmental elements, and whether assessment monitoring is required by the State. The guidance provided in this manual is definitive to the extent that the available literature provided sufficient data for EPA to evaluate and make recommendations on a national level.