This document outlines requirements for contractors performing inspection, testing, and maintenance of main line valves and backflow prevention devices, primarily focusing on protecting drinking water quality and supply. Key tasks include inspecting valve accessibility and functionality, operating valves to ensure full closure, and compiling data into an Excel spreadsheet. For backflow prevention devices, the contractor must provide all necessary resources for inspection, testing, and annual certification, coordinating water shutdowns with the Contracting Officer's Representative (COR). Emergency repairs for failing devices are required to be completed on the same day as the scheduled testing or complaint. Installers must be Maryland State Board of Plumbing-approved Master Plumbers, capable of installation, certification, and providing manufacturer warranties. The document also provides an extensive list of backflow prevention devices with their locations, sizes, and types (RPZ or DC). Additionally, the contractor is responsible for developing a Standard Operating Procedure for flushing activities, including contingencies for critical areas and performing work outside regular hours if needed. They must also assist in developing customer and media notifications for the unidirectional water main flushing program. Pressure gauges used for flushing must be calibrated. The contractor is not liable for system damage during flushing unless due to unsatisfactory or negligent operations. The file emphasizes adherence to AWWA M-44 manual for valve inspections and operations.