Section 3 - Design Requirements

3.18 Fire Hydrant Spacing Requirements

All fire hydrant spacing shall, at a minimum, meet the requirements of the International Fire Code Section 507, or as required by the Skamania County Fire Marshal.

3.17 WSDOT/Railroad Crossings

The developer shall obtain and make full payment for any permits required from Washington State Department of Transportation (WSDOT) / railroad prior to constructing a water main under any highway or railroad tracks. The permit should be on behalf of the PUD. All requirements of the permit shall be met prior to acceptance of any construction. Requirements usually include boring with a steel casing for installation of the water main.

3.16 Water Demand vs. Meter Size

The water meter size shall be determined by the water customer or their designee. Water services shall be sized as required by water demand and on-site fire protection service flow. Service piping 2 inches in diameter and smaller shall be either Municipex (PEX-A) with tracing wire or Type “K” copper. Service piping for water meters 3 inches or larger shall be a minimum of 4 inches and be Class 52 zinc coated ductile iron pipe with V-bio polyethylene encasement or PVC AWWA C900 with tracing wire. No 2 to ½ or 3-inch water service piping shall be allowed.

For water services that require more flow than available through a standard ⅝ inch by ¾ inch residential meter, the water meter size requested should be sized to serve the expected peak and continuous demands. Guidance for the safe maximum operating capacity and the recommended rate for continuous operation can be found in the American Water Works Association Standards, C-700 through C-710. General guidance can be found in the American Water Works Association Manual of Water Supply Practices M22, Sizing Water Service Lines and Meters.

The minimum diameter for a new service pipe is 1 inch. The service pipe shall be reduced at the meter as necessary.

3.15 Cross-Connection Control

The prevention of non-potable water or any deleterious substance from entering the distribution system is extremely important to public safety. The PUD recognizes the Washington State Department of Health regulations (WAC Chapter 246-290-490) regarding the protection of the public via minimum requirements for design, construction, operation, and maintenance of public water supplies. All developers or applicants constructing public water mains or facilities should be familiar with, and comply with, these requirements. These referenced regulations and standards are a minimum, and the PUD specifically reserves the right to require additional safety features and items as may be deemed appropriate by the PUD. Premise isolation by a reduced pressure backflow assembly (RPBA) approved by the PUD is required for all customers with access to auxiliary water supplies connected to a piping system, whether or not an interconnection exists between the auxiliary supply and the PUD water system.

3.14 Deflection at Pipe Joints

Water main pipe joints may be deflected to achieve a non-linear alignment, provided the deflection at each joint does not exceed the maximum deflection recommended by the pipe manufacturer. The deflection angle or bend radius shall be stated on the civil plans. No bending of PVC pipe itself is allowed.

3.13 Thrust Blocks & Restrained Joints

All joints, valves, and fittings shall be mechanically restrained. Thrust blocks are only allowed at “live taps” and where connections are made to the end of an existing main. Restrained joints must be Megalug or approved equal. Tie rods may not be used for buried water mains.

Underground flanged joints are only allowed for restraining valves installed for “Live Taps”. 2 adjacent MJ joints may be joined with a Foster adapter, or similar PUD approved product.

3.12 Isolation Valves

Isolation valves must be installed to facilitate new connections to the system, and to provide for the isolation of pipe segments during maintenance. Generally, 2 isolation valves per tee, and three isolation valves per cross are required. At least one isolation valve per 1,000 feet of main run must be installed. Live taps may be allowed at the PUD’s discretion.

Where tees or crosses are installed to provide for both new and future connections, isolation valves should be located to minimize loss of service when the future connection is made.

3.11 Air & Blowoff Valves

Air release valves or combination air release valves may be required at high points within the proposed water system as deemed necessary by the PUD. Standard blowoff assemblies shall be installed at the end of dead-end mains. See PUD standard details for further guidance.

3.10 Coordination with Other Utilities; Water Main Profiles

The water main shall be located more than 5 feet from other non-sanitary sewer utilities, measured center-to-center. An edge-to-edge separation of 3 feet may be allowed where no reasonable alternative exists, if approved by the PUD staff. Water mains must be deflected vertically, or vertical bends must be used, as necessary, to provide 6-inch minimum crossing clearance with other utilities.

Distance between water main and sanitary sewer utilities shall be in accordance with Washington State regulations.

To facilitate coordination with other utilities and PUD staff review of proposed water facilities, water main profile drawings must be included for all mains 12 inches or larger in diameter. Profile drawings should show all crossings with other utilities.

3.9 Depth of Cover

The minimum pipe cover is 3 feet for water mains smaller than 12 inches and 4 feet for water mains 12 inches and larger. Deviations may be allowed on a case-by-case basis subject to PUD approval. The cover shall not exceed 6 feet unless greater depth is required to avoid other utilities or obstructions, or where special circumstances arise and greater cover is approved by the PUD.