Sewer Collection System

The Collection System Department’s job is to ensure that the District's network of underground sewer pipes is able to collect and transport wastewater to our treatment plant, the Soscol Water Recycling Facility. To insure that the collection system can perform this essential job, the Collection System Department provides inspection, maintenance, repair and ongoing replacement of all the District-owned sewer lines in our service area. That’s why NSD Collection System Department trucks and equipment (see below) are a common sight on local streets!

Sewer Collection System by the Numbers:

Sewer connections: 36,000 residential and business connections
Miles of sewer mainlines: 270
Pipe size: 4” to 66”
Area of service: 23 square miles
Lateral lines maintained: 27,000
Manholes: 5,651

Frequently Asked Questions (FAQs) About the Sewer System

Here's a list of frequently asked questions about the sewer system. If you have a question that is not in this list, please call the District at (707) 258-6000. 

Service Area Map

Napa Sanitation District (NSD) provides wastewater collection, treatment, and disposal services to the residents and businesses in the City of Napa, Silverado Country Club, the Napa County Airport and several adjacent unincorporated areas.  Click here to see the map.

Sewer Maintenance & Repair

NSD’s Preventative Maintenance Program involves a planned schedule for cleaning sewer lines that are highly susceptible to root intrusion, grease, and other debris. The frequency of cleaning for a sewer line is determined by the cleaning needs, with the goal of preventing sewer line blockage and overflows.

Preventing Sewer Overflows

Information on this page describes how NSD keeps sewer lines clean and free flowing, and also what YOU can do to prevent sewage back-ups.

Emergency Service for Sewer Back-ups

Napa Sanitation District has a sewer emergency on-call service available 24-hours a day, every day of the year. Our goal is to respond to all calls within 30 minutes. NSD will clear all plugged sewer laterals from the property line down to the main line and all District main lines. If the problem is in the homeowner's section of the lateral (from the house to the property line), the NSD crew will inform them of the situation. The homeowner is responsible for the upper lateral and house plumbing. For sewer emergencies, call (707) 258-6000, ext. 9.

Cleaning Sewer Lines

Crews inspect, clean and maintain sewer lines on a daily basis. It takes approximately two years to complete an entire cycle of cleaning and maintenance of the 270 miles of sewer main lines. NSD inspects and cleans the lines in a variety of ways using the following equipment:

Sewer Service Trucks & Equipment

  Vactor truck

Vactor Truck

The Vactor Truck is used for regular sewer line maintenance. It has a telescoping rotating hose reel with a nozzle at the end of the hose. The hose can deliver a high-pressure spray of up to 2000 pounds per square inch (psi) that effectively breaks up blockages in sanitary lines and flushes out debris. The Vactor also uses a high volume vacuum to remove broken up grit and debris. This is a hard-working piece of equipment: it is used to clean the entire sewer system approximately every two years.

 

  TV Truck

TV Truck

A TV Truck crew is in operation nearly every weekday, using a special camera to examine NSD's sewer system. The camera, which looks like a miniature train car, is driven down the sewer mains looking for problems in the system such as roots intruding in the line, cracks or broken lines, and off set pipes. This televised information is sent to a screen in the TV Truck and is also recorded digitally for future reference. NSD also uses a mini-cam to televise pipes as small as 3" in diameter. These smaller pipes are usually televised whenever an emergency service call is requested due to a blockage or overflow.

 
  

Plug-Up Truck

The Plug-up Truck has equipment designed for sewer line emergencies as well as regular maintenance. One of the primary pieces of equipment on the plug-up truck is the gas-powered “Eel”. The eel is a hand-driven rodding machine with sections of dual cable rods with cutting heads connected to the leader rod. A five horsepower motor rotates the rods, directed down a cleanout into a lateral to cut away roots, grease, and other obstructions.

After the eel work is complete, the crew will run a mini-camera down the line to make sure the line is clean before they leave the job site.

 
  water truck

Water Truck

The water truck is used to refill the reservoirs on the vactor trucks. This keeps the vactor truck in operation at the site. The water truck is also used for dust control, special projects (watering seeds and vegetation) wetting down rock and gravel to aid in compaction, street cleaning after sewer spills or overflows onto the streets. The water truck carries recycled water from the District wastewater treatment plant.

 
Rodder

Rodder (limited use)
The Rodder is used to remove roots, heavy grease, and other obstructions from inside the sewer lines by rotating a hydraulically driven continuous steel cable rod with a cutting blade or saw attached to the leading edge.

 

 

Sewer System Construction

The NSD Collection System Department does various types of construction work for the District. Crews replace or repair an average of 70 District sewer laterals each year, as well as installing or repairing 230 clean-outs. Crews also repair main lines and/or replace sections of mainlines. After construction work, the District replaces all pavement and cement, and repairs all homeowner's yards to their original or better condition.

Collection System Master Plan

In 2007, Napa Sanitation District completed a Collection System Master Plan. The plan evaluates the condition and performance of the sewer pipe collection system under both current and future (year 2030) buildout conditions. The Master Plan concluded that while the collection system has adequate dry weather capacity to handle anticipated growth, it has inadequate capacity for existing wet-weather peak flows due to excessive inflow and infiltration (I/I) entering the system. I/I occurs where there are cracks or breaks in the sewer main and lateral pipes that allow rainwater or groundwater to enter the sewer pipe system. Inflow can also come from other connections such as rain downspouts or sump pumps that are illegally connected to the sewer system.

The Master Plan concludes that the most cost-effective solution is a combination of I/I reduction projects and capacity upgrades to handle peak flows, as opposed to wholesale capacity upgrades to the system. Based on this recommendation, the District has initiated pilot projects to determine the sources of and best approaches for reducing I/I to the collection system.

Inflow/Infiltration (I/I) Projects

The Collection System Master Plan identifies several strategies for identifying and reducing inflow and infiltration (I/I) of water to the sewer system. The District is implementing the following I/I projects:
• Smoke testing sewer lines: This involves forcing non-toxic smoke through a sewer line under slight pressure to detect leaks. This can show where there are cracks that allow rainwater or groundwater into the sewer pipe, or where there are illicit connections (illegal) to the sewer system such as downspouts or sump pumps.
• Upper lateral repair: Typically, the property owner is responsible for maintenance and repair of the upper lateral. However, the District has done one project where repairs to keep out rainwater and groundwater were performed instead by the District, in order to determine if this would create a significant reduction in I/I. Pre- and post-construction flow monitoring is being done to determine the effectiveness of these upper lateral repairs.
• Lower lateral/main repair: The District repairs the lower laterals and sewer mains that belong to the District, rather than the customer. Again, pre- and post-construction flow monitoring is done to determine the effectiveness. 

Tracking Sewer Overflows

Although the Napa Sanitation District constantly cleans and maintains its sewer lines to prevent sewer overflows, sometimes they happen anyway. When there is a sewer overflow, the District responds immediately following the protocol of their overflow response plan.
NSD also began reporting sanitary sewer overflows (SSOs) electronically to the California Integrated Water Quality System (CIWQS) in May 2007. This electronic SSO data, as well as information regarding regulatory actions, is available at State Water Resources Control Board website.

Sewer System Management Plan

The Napa Sanitation District's collection system is subject to the Statewide general Waste Discharge Requirements for Sanitary Sewer Systems. This permit regulates publicly-owned sewer systems in the state of California as implementation of the state's Sanitary Sewer Overflow (SSO) Reduction Program. In compliance with this permit, NSD maintains a Sewer system Management Plan (SSMP), a comprehensive document describing operations and management practices designed to minimize the frequency and impacts of  SSOs and ensure long term effectiveness of the system.

Planning decisions are discussed at NSD Board meetings, which are open to the public. Board meeting schedules and documents can be found on the Board of Directors page. Customers are also welcome to provide feedback by contacting the District at (707) 258-6000, or info@napasan.com. Most of the current planning documents and other information referenced in the SSMP are available on the Documents page. For more information or to view the SSMP itself, please contact the District at (707) 258-6000.