The reliability of the Federally Owned Water Main (FOWM) system was examined, and recommendations to improve system reliability are made. The existing FOWM system is very dependent upon three different pipe links.

The first and most important link is the Francis Scott Key Bridge river crossing. This link carries the entire FOWM supply, and if taken out of service, an alternate means of supply must be used. At present, the only alternate source of supply is through interconnections with the adjacent Arlington County, Virginia, system.

The second vital link is the 30-in. steel main which extends from the Key Bridge river crossing to the Pentagon. This line carries approximately 83 percent of the total delivery to the FOWM system. If taken out of service, all flow in the FOWM system would have to be routed through the 16-in. main along George Washington Parkway and Eisenhower Drive. During periods of high water use, flow in this 16-in. line would cause excessive friction losses. As a result, adequate system pressures cannot be maintained, and system demands cannot be fully met.

The final critical pipe link is the feed to National Airport. This link consists of a 24-in. pipe and a 16-in. pipe connected in series. At present, this is the only source of water for National Airport. If this line were taken out of service, an alternate source of supply must be found. Furthermore, the available fire flow to the airport through this line during maximum daily demands falls below Insurance Services Office requirements.

Several system improvements were evaluated to determine their contribution to the overall reliability of the FOWM system. System improvements consisted of operating existing and new interconnections, constructing new river crossings, installing a new storage tank, new line construction, and combinations of the above. System improvements were evaluated and ranked based on hydraulic performance, engineering impact, and total cost.