1. (1) Purpose. The purpose of this chapter is to protect public health and safety by assuring proper design and construction of all tanks used in on-site sewage systems. Proper sewage tank design and construction will help prevent:

   1. (a) Surface or groundwater leaking into tanks and adversely impacting the treatment and dispersal functions of system components; and
   2. (b) Sewage from tanks leaking into the soil and adversely impacting groundwater or surface water, or causing sewage to surface on the ground.

2. (2) Objectives. This chapter establishes requirements and provides measures to achieve effective long-term sewage treatment and limit the discharge of contaminants to waters of the state. The objectives include:

   1. (a) Establishing design and construction standards;
   2. (b) Requiring department review and approval of design and construction plans for prefabricated tanks and cast-in-place tanks; and
   3. (c) Creating a process to register prefabricated tank sizes and models built from approved design and construction plans.

[Statutory Authority: RCW 43.20.050 (2) and (3). WSR 09-23-119, § 246-272C-0001, filed 11/18/09, effective 12/19/09.]