Sewer Connection

Boise City's Sewer Program local legal authority is established in Boise City Code. Industrial or commercial (e.g. restaurants) businesses that discharge or plan to discharge wastewater to the Boise City sewer system should check with the Boise Pretreatment Program.

Sewer Fees

In general, fees paid to the city prior to connection to the sanitary sewer system consist of two major components:

  1. Connection (capacity) fees
  2. Assessment fees

These fees do not pay a contractor to complete the physical connection from the building to the edge of the right of way.

Connection Fees (capacity fees)

The connection (capacity) fee is made up of three components including the trunk fee, the treatment fee and the interceptor fee. Each of these fees is paid by both new and existing development at the time of connection.

  • Trunk fee – Designed to recover the cost of over-sizing sewers to carry waste to the treatment plants and to recover a portion of the cost of the sewers in existing neighborhoods.
  • Treatment fee – Designed to recover the capital cost of constructing treatment facilities, providing room at the treatment plant for the additional waste.

Commercial connection (capacity) fees are calculated per plumbing fixture based on the estimated flow and strength of the waste. Food service and industrial type services are calculated differently. Contact Sewer Rating for an estimate.

Assessment Fees

The assessment fee is based on the average cost of an 8-inch sewer line in the street and will include a service line to the edge of the right-of-way of your property. The assessment is an average cost to construct pipe, manholes, pavement restoration, and permits as well as design, survey and inspection of the project. Residential service lines are 4-inch while some commercial and multifamily will be 6-inch or even 8-inch services. The assessment fee is an average cost of projects rather than dividing the cost of the particular project which serves your area.

Not all properties will pay an assessment fee. New subdivisions are required to pay the assessment and to construct sanitary sewers within the subdivision boundaries at the time of development. The costs for sewer are then included in the cost of your subdivision lot. If you are building on an existing lot which is being split or connecting an existing building to sanitary sewer, you should expect to pay the assessment component of the fees.


Sanitary sewers are constructed in conjunction with Ada County Highway District (ACHD) projects, on the needs of the property owner, or if there is evidence of a large number of septic system problems. City approval is based on the number of residents signing a petition agreeing to pay fees and connect, the cost and length of the sewer extension and is subject to funds being available. Contact Sewer Extensions for more information. 

View the Sewer Extension Policy

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