The largest of these pipes, called ”interceptors,” are owned by Regional San. There are approximately 111 miles of gravity interceptors hidden beneath the streets of Sacramento and Yolo counties. Ranging in size from 36 to 144 inches in diameter, each interceptor conveys at least 10 million gallons of wastewater per day (mgd).
Also scattered throughout Sacramento and the eastern portion of Yolo counties are 58 miles of Regional San force mains (pipes that are under pressure) and 11 wastewater pumping facilities with the peak wet weather capacity starting at 10 mgd and increasing to 264 mgd. (Three of these pump stations are operated by the City of Sacramento.) These pumping facilities are connected to the interceptors and placed where the depth of the pipe is too great to continue to flow by gravity. At that point, the pumping facility raises the wastewater toward the earth’s surface and then allows it to continue to flow at a shallower depth by gravity, until it reaches SRWTP or another pumping facility.
Currently, the interceptor system conveys wastewater flow from the areas served by the Sacramento Area Sewer District and the cities of Folsom, Sacramento and West Sacramento.