Idaho Admin. Code r. 58.01.08.542

Current through September 2, 2024

Section 58.01.08.542 - DISTRIBUTION SYSTEM

01.Protection from Contamination. The distribution system must be protected from contamination and be designed to prevent contamination by steam condensate or cooling water from engine jackets or other heat exchange devices.

02.Installation of Water Mains. Division 400 of "Idaho Standards for Public Works Construction," referenced in Subsection 002.02, may be used as guidance for installation of water mains. In addition, the following provisions apply:

a. Installed pipe must be pressure tested and leakage tested in accordance with the applicable AWWA Standards, incorporated by reference into these rules at Subsection 002.01.

b. New, cleaned, and repaired water mains must be disinfected in accordance with AWWA Standard C651, incorporated by reference into these rules at Subsection 002.01. The specifications must include detailed procedures for the adequate flushing, disinfection, and microbiological testing of all water mains.

c. In areas where aggressive soil conditions are suspected or known to exist, analyses must be performed to determine the actual aggressiveness of the soil. If soils are found to be aggressive, action must be taken to protect metallic joint restraints and the water main, such as encasement in polyethylene, provision of cathodic protection, or use of corrosion resistant materials.

d. The Department must approve any interconnection between potable water sources, taking into account differences in water quality between the two systems.

e. A continuous and uniform bedding must be provided in the trench for all buried pipe. Backfill material must be tamped in layers around the pipe and to a sufficient height above the pipe to adequately support and protect the pipe. Stones found in the trench must be removed for a depth of at least six (6) inches below the bottom of the pipe.

f. Water mains must be covered with sufficient earth or other insulation to prevent freezing.

g. All tees, bends, plugs and hydrants must be provided with reaction blocking, tie rods or joints designed to prevent movement.

03.Pressure Relief Valves. All pumps connected directly to the distribution system must be designed in conjunction with a water pressure relief valve of type, size, and material approved by the Department unless the Department approves another method that will prevent excessive pressure development.

04.Flow Meter Required. Unless otherwise approved by the Department, all source pumps and booster pumps connected directly to the distribution system must have an instantaneous and totalizing flow meter, equipped with nonvolatile memory, installed in accordance with manufacturer's specifications.

05.Pipe and Jointing Materials. Pipe and jointing materials comply with the standards set forth in Subsection 501.01. Pipe must be manufactured of materials resistant internally and externally to corrosion and not imparting tastes, odors, color, or any contaminant into the PWS. Where distribution systems are installed in areas of groundwater contaminated by organic compounds:

a. Pipe and joint materials which do not allow permeation of the organic compounds must be used; and

b. Non-permeable materials must be used for all portions of the PWS including pipe, joint materials, hydrant leads, and service connections.

06.Size of Water Mains. When fire hydrants are provided, they may not be connected to water mains smaller than six (6) inches in diameter, and fire hydrants may not be installed unless fire flow volumes are available. If fire flow is not provided, water mains will be no less than three (3) inches in diameter. Any departure from these minimum standards must be supported by hydraulic analysis and detailed projections of water use.

07.Separation of Potable, Non-Potable, and Raw Water Pipelines. The requirements for the protection of potable pipelines from contamination by non-potable pipelines are described in Subsections 542.07.a. through 542.07.d. For the purposes of Subsection 542.07, the term "pipeline" applies to both mains and services. The Department will use the Memorandum of Understanding with the Plumbing Bureau as guidance in determining the relative responsibilities for reviewing service lines. The conditions of Subsections 542.07.a. through 542.07.d. apply to all potable services constructed or reconstructed after April 15, 2007 and where the Department or the QLPE is the reviewing authority. Raw water pipelines must be protected from contamination from non-potable pipelines, and must not contaminate potable pipelines. They must meet equivalent separation distances shown below from either potable or non-potable pipelines.

a. Alternative separation distances may be considered for Subsections 542.07.b through 542.07.c. on a case-by-case basis when considering constructability, public health risk, environmental risk, and cost. The design engineer must submit data to the Department for review and approval showing that the proposed installation will be protective of public health and the environment.

b. Parallel installation requirements.

i. Potable mains in relation to non-potable mains.

(1) Greater than ten (10) feet separation: no additional requirements.

(2) Ten (10) feet to six (6) feet separation: separate trenches, with the bottom of the potable main above the top of the non-potable main, and non-potable main constructed with potable water class pipe.

(3) Non-potable mains are prohibited from being located in the same trench as potable mains.

ii. Potable services in relation to non-potable pipelines and non-potable services in relation to potable pipelines.

(1) Greater than six (6) feet separation: no additional requirements.

(2) Potable services are prohibited from being located in the same trench as non-potable pipelines.

c. Requirements for potable water pipelines crossing non-potable pipelines. Crossings must be perpendicular, unless otherwise approved by the Department.

i. If there is eighteen (18) inches or more vertical separation with the potable water pipeline above the non-potable pipeline, then the potable pipeline joints must be as far as possible from the non-potable water pipeline.

ii. If there is eighteen (18) inches or more vertical separation with the potable water pipeline below the non-potable pipeline, then the potable pipeline joints must be as far as possible from the non-potable pipeline, and the non-potable pipeline must be supported through the crossing to prevent settling.

iii. Less than eighteen (18) inches vertical separation:

(1) Potable pipeline joint must be as far as possible from the non-potable pipeline; and either:

(a) Non-potable pipeline must be constructed with potable water class pipe for a minimum of ten (10) feet either side of potable pipeline with a single twenty (20) foot section of potable water class pipe centered on the crossing; or

(b) The non-potable or potable pipeline must be sleeved with potable water class pipe for ten (10) feet either side of crossing. Use of hydraulic cementitious materials such as concrete, controlled density fill, and concrete slurry encasement is not allowed as a substitute for sleeving.

(2) If potable pipeline is below non-potable pipeline, the non-potable pipeline must also be supported through the crossing to prevent settling.

d. Non-potable pressure pipelines must not be:

i. Closer horizontally than ten (10) feet from potable mains.

ii. Closer vertically than eighteen (18) inches from potable pipelines.

08.Separation from Subsurface Wastewater Systems and Other Sources of Contamination. A minimum horizontal distance of twenty-five (25) feet must be maintained between any potable water pipe and a septic tank or subsurface wastewater disposal system. Guidance on separation from other potential sources of contamination, such as stormwater facilities, may be found on the Department website http://www.deq.idaho.gov.

09.Dead End Mains. All dead end water mains must be equipped with a means of flushing at a water velocity of two and one-half (2.5) feet per second.

a. Dead ends must be minimized by looping whenever practical in order to provide increased reliability of service and reduce head loss.

b. Flushing must be designed in such a way as to minimize any erosion of unprotected areas and, if applicable, be coordinated with the owner of the receiving system. No water main flushing device may be directly connected to any sewer.

c. Stub outs for future main connections must meet all requirements for dead end mains listed in Subsection 542.09 as determined by the Department. Flushing devices may be temporary in nature.

10.Repair of Leaks. Leaking water mains must be repaired or replaced upon discovery and disinfected in accordance with American Water Works Association (AWWA) Standards, incorporated by reference into these rules at Subsection 002.01.

11.Separation from Structures. Water mains must be separated by at least five (5) feet from buildings, industrial facilities, and other permanent structures.

12.Shut-Off Valve Required. All new PWSs, and portions of existing systems undergoing material modification of distribution or transmission lines, must include an accessible and lockable shut-off valve at each service connection in the section of distribution or transmission line that is being constructed or modified within the project. Shut-off valves may be installed in a meter vault.

13.Minimum Pressure at Building Sites. Any PWS constructed or undergoing material modification where topographical relief may affect water pressure at the customers' premises must provide the Department with an analysis which demonstrates that the pressure at each designated building site will be at least forty (40) psi, based on dynamic pressure in the main, as set forth in Subsections 552.01.b.i. and 552.01.b.v., plus a static compensation from the elevation of the main to the elevation of each building site.

a. If forty (40) psi cannot be provided at each designated building site, the Department may require that reasonable effort be made to provide notification to existing and potential customers of the expected pressure.

b. The Department will not authorize a service connection at any designated building site where analysis indicates that pressure will be less than twenty (20) psi dynamic pressure (or twenty-six point five (26.5) psi for two (2) story buildings).

14.Isolation Valves. A sufficient number of valves must be provided on water mains to minimize inconvenience and sanitary hazards during repairs.

15.Air Valves. At high points in water mains where air can accumulate, provisions must be made to remove the air by means of air release and vacuum relief valves or combination air release/vacuum relief valves. Air release valves, vacuum relief valves, or combination air release/vacuum relief valves may not be required if vacuum relief and air release functions in the pipeline can be adequately handled by approved appurtenances such as fire hydrants.

a. The open end of an air valve must be extended to at least one (1) foot above grade and provided with a twenty-four (24) mesh or similar non-corrodible screened, downward-facing elbow. When the air vent on an air relief valve cannot be practically installed above ground, the vent may be below grade provided the air vent is extended to the top of the valve vault and provided with a twenty-four (24) mesh or similar non-corrodible screened, downward-facing elbow. In addition, for below ground vents, the valve vault must be rated for appropriate traffic loading in traffic areas and the vault drained to daylight or provided with adequate drainage to prevent flooding of the vault.

b. Discharge piping from air valves or combination air release/vacuum relief valves may not connect directly to any storm drain, storm sewer, or sanitary sewer.

16.Backflow Protection. Automatic air relief valves must be equipped with a means of backflow protection.

17.Surface Water Crossings. For the purposes of Subsection 542.17, surface water is defined as all surface accumulations of water, natural or artificial, public or private, or parts thereof which are wholly or partially within, which flow through or border upon the state. This includes, but is not limited to, rivers, streams, canals, ditches, lakes, and ponds. Surface water crossings, whether over or under water, must be constructed as follows:

a. Pipe used in above water crossings must be adequately supported and anchored, protected from damage and freezing, and be accessible for repair or replacement.

b. Pipe used in under water crossings must have a minimum cover of two (2) feet. When crossing a water course that is greater than fifteen (15) feet in width, the following must be provided:

i. The pipe will be of special construction, having flexible, restrained, or welded water-tight joints; and

ii. Valves are to be provided at both ends of water crossings so that the section can be isolated for testing or repair; the valves will be easily accessible and not subject to flooding; and

iii. Permanent taps or other provisions to allow insertion of a small meter to determine leakage and obtain water samples will be made on each side of the valve closest to the supply source.

Idaho Admin. Code r. 58.01.08.542

Effective July 1, 2024