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Sanitary Sewer Monitoring

There are two sewer systems in our community. The sanitary sewer system is designed to carry dirty water from homes and businesses directly to WLSSD, where sewage and other waste is safely treated. The second system, known as the storm sewer system, is built to handle runoff from the land and roads and drains water directly to area streams, rivers and lakes. These systems are meant to be separate, but sometimes clean storm water enters the sanitary sewer.

WLSSD regularly monitors the sanitary sewers lines each year to determine maintenance and repair needs. Sewer lines can be damaged through natural soil movement, tree root growth, and corrosion, among other causes. This leads to excess water entering the system which can overwhelm the sanitary sewer system and the waste water treatment plant.

Inflow and Infiltration

WLSSD receives an average of 38 million gallons of wastewater each day through an extensive network of sanitary sewer lines. These lines start at homes and businesses and often feed into city or town owned lines before entering the sewer mains owned and maintained by WLSSD. Inflow and infiltration (I&I) is when stormwater or groundwater flows into sewer pipes from cracks or leaks. Water can also enter the sanitary sewer system from homes that have sump pumps installed to discharge into the sanitary sewer system which is illegal in the WLSSD service area. This excess water usually occurs during rainfall or snow melt events and can lead to sewage backups or overflows. For example, during the 2023 spring snow melt, WLSSD received 2-3X the average water flow for nearly 5 days.

Closed Circuit Television Video

To prevent I&I, it is important to inspect sewer lines to monitor for maintenance and repair needs. Routinely, our staff inspects WLSSD owned lines through a process called Closed Circuit Television Video (CCTV). A camera crawler is lowered through manholes to access the sanitary sewer. Staff control the crawler from a van and are able watch and record the inside of the pipe. They assess whether the sewer line is in good condition or if it needs cleaning, repairs, or replacement.

Daytime monitoring in your neighborhood

WLSSD staff perform this critical process throughout the summer and fall. Most of the time, monitoring occurs during the day and they access the WLSSD owned sewer lines from manholes. The crawler will not be assessing private sewer lines nor those owned by cities or towns. Some of the sewer lines are located alongside roadways, others directly under the roadway, and occasionally run through easements in people’s backyards. If you notice the orange signs, cones, or workers wearing reflective vests, please drive carefully. Whether it is WLSSD staff, or other utility workers along roadsides, they are likely helping maintain a service that we all benefit from daily.

WLSSD records CCTV on approximately 20 miles of pipe each year and our equipment allows us to assess a maximum of 1500 feet of sewer line at a time. Each section usually takes a few hours when the robot can continuously travel through the line. During this time, the staff will park the white van near the manhole and place orange signs and cones to signal their presence. They will load the robot into the manhole, send it out to record, and then reel it in. There may be noise from a generator to power the process, but staff will work as quickly as possible to be out of the area. Sometimes there are roots, rocks, or other objects causing a blockage that can slow down and sometimes stop the robot.

At times, the sewer line is less easy to access as it travels through wooded areas or occasionally through yards. Instead of the van, staff may need to use a UTV with the similar equipment to access manholes.

Nighttime monitoring

Certain sections of pipe inspection occur during nighttime hours when sewer flows are at their lowest so the inside of pipes can be viewed efficiently and effectively. If this is the case, hours of work will likely be from 9 PM to 7 AM.

WLSSD and our contractors will do everything we can to minimize our impact during a project like this and will not be noticeable to most residents.

• Our trucks and equipment will make very little noise.
• Our team will use lights at each of the manholes to ensure safety and effectiveness during the project. Manholes along the pipeline are located both in the street and in wooded areas.
• Odors are unlikely; however, opening manholes could release some odors.

Web Map

The above map shows WLSSD sanitary sewer mains. WLSSD routinely monitors the gravity sewer mains (green, red, yellow).