Water System Design Manual
The definition of a confined space has three features:
Large enough for a person to enter.
Restricted entry or exit.
Not designed for continuous occupancy.
Two hazards associated with confined spaces are: 1) poor air quality, and 2) the danger of
engulfment. Designs for storage tanks and underground vaults should facilitate the circulation of
fresh air into confined spaces when workers are present. The vent design should make it possible
to easily clear debris from the vents. Purveyors should identify and eliminate any design feature
that could allow inadvertent tank flooding. Confined space requirements are in chapter 296-809
Lock-out and Tag-out
Purveyors must properly identify hazards with stored energy, such as water pressure from piping
to the tank. To prevent someone from opening a valve at the wrong time, workers should use
blind-flanges or a lock-out and tag-out system.
Confined spaces are commonly designed with access hatches. These access hatches must have
adequate clearances and address other L&I safety requirements. In addition, access hatches must
have locks to prevent unauthorized entry and to help maintain the quality of the water (WAC
246-290-235(1)(a)). To facilitate air circulation and access for routine maintenance or
emergencies, DOH recommends entries at the top and bottom of storage tanks, if possible. See
Chapter 9 and WAC 246-290-235 for additional distribution-reservoir design requirements.
13.1.2 Ladder Safety and Fall Protection
Guardrails, ladders, and fall protection devices must meet the following L&I rules:
Chapter 296-24 WAC, Part J-1: Working Surfaces, Guarding Floors and Wall Openings
Chapter 296-155 WAC, Part C-1: Fall Restraint and Fall Arrest
Chapter 296-155 WAC, Part K: Floor Openings, Wall Openings, and Stairways
Chapter 296-876 WAC: Ladders, Portable and Fixed
Among other safeguards, L&I requires water system designs to:
Protect openings and holes more than 12-inches across with either a cover that will
support at least 200 pounds or a guard railing.
Protect platforms and floor openings with properly designed guardrails and toeboards.
Design fixed ladders with adequate clearances and provide side rails that extend at least
42-inches above the landing platform.