1. (1) Storage reservoirs shall be designed to:

   1. (a) Prevent entry by birds, animals, insects, excessive dust, and other potential sources of external contamination;

   2. (b) Include:

      1. (i) A weathertight roof;
      2. (ii) A lockable access hatch;
      3. (iii) A screened roof vent;
      4. (iv) An overflow pipe with atmospheric discharge or other suitable means to prevent a cross-connection;
      5. (v) A sample tap;
      6. (vi) A drain to daylight, or an alternative design approved by the department or health officer that is adequate to protect against cross-connection;
      7. (vii) Tank isolation in order to perform maintenance procedures; and
      8. (viii) Other appurtenances appropriate for the protection of stored water from contamination;

   3. (c) Be above normal ground surface level. If the bottom elevation of a storage reservoir must be below normal ground surface:

      1. (i) The storage reservoir must be placed above the groundwater table; and
      2. (ii) The top of a partially buried storage reservoir must be at least two feet above normal ground surface.
2. (2) A Group B system designed to supply fire hydrants must have a minimum distribution main size of six inches (150 mm) supplying each hydrant.

[Statutory Authority: RCW 43.20.050 and chapter 70.119A RCW. WSR 12-24-070, § 246-291-210, filed 12/4/12, effective 1/1/14. Statutory Authority: RCW 43.20.050. WSR 94-14-002, § 246-291-210, filed 6/22/94, effective 7/23/94.]