Expansion of an Existing System

A wastewater system expansion is required when an existing facility has a proposed change or addition that increases the water use. The increase in water use is based on Rule .1949, Sewage Flow Rates for Design Units. Examples of flow increases are addition of a bedroom(s), increase in retail sales area, or adding restaurant seats or food-stand prep area. Expansions of wastewater system must be in compliance with the current Rules.


The owner must fill out an application for an Improvement Permit and describe the existing facility and ALL proposed changes or additions. An expansion also requires locating the existing septic tank, drain field, and repair area.

Original Permit

The original permit issued by the health department, if available, will facilitate finding the system. An information request form may be submitted to the health department to find a permit.

Inspection of Site

An Environmental Health Specialist will go onsite to evaluate the proposal and to inspect the existing system to ensure that it meets state requirements. An Improvement Permit and subsequently a Construction Authorization will be issued if the existing system and the site are suitable for the proposed expansion.