The Comprehensive Sewer Plan for the City of Shoreline has been prepared in general conformance with the requirements of the Washington Administrative Code (WAC) for sewer plans, Chapter 173-240-050. This Plan helps give the City guidelines for providing and maintaining efficient and reliable sewer services to Shoreline residents. It addresses sewer service and considers the impact on wastewater flows throughout the City. The plan also addresses capital improvement needs and estimated project costs for the near-term (10-years) and the long-term (20-years). 

To receive a copy of City of Shoreline's Comprehensive Sewer Plan 2021, please email Wastewater Customer Service at WWcustomerservice@shorelinewa.gov.

The City plans to clean 264,000 feet (or 50 miles) of our nearly 195 miles of sewer mains.  This scheduled cleaning reflects about 50 miles per year or about 4 miles of pipe per month.

A jet nozzle and hose is lowered into a manhole and launched in the upstream direction, which is against the flow. Water pressure of about 1,000 to 1,500 pounds per square inch (psi) will pull the hose up the line to the next manhole. The water pressure is then steadied to about 1,200 psi and the nozzle and hose are slowly pulled back at about 5 feet per second), scouring the inside of the sewer main as it returns to the downstream manhole.
This high pressure scouring removes debris such as grit, gravel, most grease, some tree roots, or inappropriate objects that have made it into the pipe system. Without the cleaning, sewer backups may occur.

We complete approximately 78,000 feet of closed-circuit television (CCTV) inspections every year of our sewer mains. This represents about 15 miles of pipe inspection per year or about 1.2 miles per months. The camera unit has interchangeable wheels for different types of sewer main pipe (concrete, PVC, ductile iron or HDPE). The camera itself is at the front of the unit and can swivel in all directions so our crew can see different views of the pipe.

The camera is connected to a steel cable which has copper control wires embedded internally within the cable. The cable is 1,000 feet long and is connected to a winch unit inside of the TV truck. The camera unit is launched in the downstream direction, which is going with the flow of water, and is the opposite direction of pipeline cleaning. The camera goes with the flow of water to prevent splashing on the lens.

Unlike the pipeline cleaning where we clean from manhole to manhole, we can view CCTV lines until the cable runs out. Our crews are looking for pipe deficiencies, such as leaks, low spots in the line, Fats, Oil & Grease (FOG) and/or tree roots.

As lines are viewed and recorded, we document the footage where connections are made to our customers buildings and where areas of deficiencies are located. This documentation helps us to keep the sewers flowing correctly.

Annually, we inspect about 400 different sites for Fat, Oil, and Grease (FOG). FOG is a result of fats, oil, and grease being poured down the drains of homes, apartments, businesses and/or restaurants while they are hot liquids and then slowly hardening against the inside of the sewer pipes.

Grease traps can be installed inside of a structure when flows of water are lower, or outside when water flows are higher. An outside grease trap is a large underground concrete vault where the liquid enter and goes through separate chambers to cool and solidify. The grease stays on top of the water because grease is lighter than water, and the water slowly drains away beneath the layer of grease.

Our staff can perform a sight glass test and a visual inspection of the chambers of the trap to ensure the draining water does not contain FOG. In this test, a clear plastic tube is lowered into the vault in the last, downstream chamber, where there should be no FOG, and a sample of the water is viewed to ensure the absence of FOG. If FOG is detected in this last chamber, our staff will contact the property owner and inform them of the problem and to require maintenance of the vault.

For new structures or a remodel that will include a high-likelihood of FOG, it may have a require the installation of grease traps.

Every year 3,000 of the nearly 4,800 manholes are inspected in our sanitary sewer system. That is about 250 manholes per month.

We look at the frame and cover to ensure there are no deficiencies and to check for the fit of the cover within the frame as we don’t want them to rattle when a vehicle drives across, and to ensure they are flush with the road or surface where they are located.

Below the manhole frame is the barrel of the manhole. This concrete cylinder is visually inspected for cracks, leaks, root intrusion or water that may be leaking into the structure. The manhole channel is where the sewer flows. The channel gets inspected for debris or deficiencies.

When water enters our system in any manner other than the pipes inside of our houses or businesses, it is called Inflow and Infiltration.

There are 16 lift stations in our sanitary sewer system that the City operates and performs 832 inspections per year or about 65 per month.

A lift station's purpose is to collect the gravity sewer flows in areas where there are low spots. The low spots or areas can have as few as 10 residences or as many as hundreds. A few of our lift stations have elevators that take our staff below ground about 30 feet to the wet well and dry well (the dry well contains the pumps which lift the sewer to a higher elevation).

Sewer flows are collected in a lift station's wet well. When the water level reaches a certain point inside the wet well, a pump automatically turns on and pumps (or “lifts”) the sewer to a higher elevation in our system where it can the flow via gravity to its ultimate destination – the sewer treatment plant.