2. Wastewater in the PI system flows by gravity for the entire length of the interceptor until reaching the Potomac Pumping Station in Washington, DC.

3. The PI system conveys an average wastewater flow of 65 million gallons per day (MGD).

4. Wastewater flows from the PI system are treated at the Blue Plains Advanced Wastewater Treatment Plant, located on the southern tip of Washington, DC, prior to discharge into the Potomac River.

5. The PI system serves multiple jurisdictions including the District of Columbia, Montgomery County, Fairfax County, Loudoun County, Town of Vienna, Town of Herndon, Dulles Airport, Naval Research Center, and the National Park Service.

6. The 86th U.S. Congress authorized the design and construction of the PI on June 12, 1960. The intent was to safeguard the Potomac River against wastewater discharges from designated sewersheds not already connected to adequate sewage disposal facilities.

7. The PI was constructed using reinforced concrete pipes, except in some of the tunnel segments where the pipe was cast-in-place.

8. Segments of the PI are sometimes completely above-grade, while some segments of the PI are well over 100 feet below grade.

9. The PI crosses the Potomac River at two locations. Both river crossings were constructed as tunnel segments and are not visible from the river.

10. The PI's venting structures promote the transfer of air into and out of the PI, and the vents also help to reduce corrosion of the concrete pipes, manholes, and access shafts.