(A) Distribution system sizing and layout.
(1) General.
(a) Distribution facilities shall be designed to provide the lowest cost over their expected life. This may not necessarily result in the lowest initial cost when long term operation and maintenance costs are considered. This policy, however, results in a water supply system that yields optimum quality at the lowest total cost to the consumer.
(b) System design shall be based on C-110, and all mains shall be sized to provide a minimum of 20 psi residual pressure at the fire hydrant under either maximum hour demand or maximum day demand plus fire flow. Maximum velocities shall not exceed ten feet per second in design.
(2) Location of water mains.
(a) General. All pipelines designed for the transmission or distribution of domestic water supply shall be located within rights-of-way dedicated for public streets or roads unless the use of an easement is specifically approved by the county.
(b) Location. In all new subdivisions, when the water mains are to be within the road right-of-way, they shall be located on the north or west side of the street. When water lines are to be constructed in existing streets, they shall be placed in the same location when practicable. However, traffic conditions, existing utilities and other physical features shall be considered. The horizontal distance between parallel water and sanitary sewer lines shall not be less than ten feet unless authorized by the Engineer.
(3) Distribution system.
(a) General. Whenever possible, the distribution system shall be in grid form so pressures throughout the system tend to equalize under varying rates and locations of demands.
(b) Layout of mains.
1. The minimum size pipe supplying fire suppression flow shall be not less than six inches inside diameter. Where over 1,000 feet of main with no side connectors would result, eight-inch or larger mains shall be used.
2. Larger mains shall be provided to serve multiple housing, school, commercial or industrial areas as determined by an engineering study.
3. The distribution system grid normally will contain an eight-inch or larger cross-connecting main at intervals of approximately 1,300 feet.
4. Dead-end mains shall be avoided if at all possible. If used, a dead-end main shall be provided with an acceptable means of flushing at the velocity required by Title 22, § 4642. In hilly areas, air release valves and vacuum breakers shall be placed at high points as required.
5. Whenever an area outside a tract can be logically served by future extension of a tract main or mains, the mains shall extend as close as practicable to the tract boundary, and be provided with a means of flushing.
6. Whenever a water main is to cross a sewage force main, the water main shall be installed a minimum of two feet above the sewer line where possible and shall be of ductile iron or AWWA C-900, Class 150 PVC pipe extending at least nine feet on each side of the force main. If the water main crosses a sewer line closer than two feet, the pipe shall be completely encased in Class B concrete for the same distance specified above.
7. If there is a situation where a sewer line must cross above a water line, the design of such a crossing must conform to state and local health laws and be approved by both the county’s Health Department and state’s Health Department.
8. All non-metallic water mains shall have a No. 10 gauge, solid, bare, soft-drawn copper wire laid along the pipe accessible in each valve box or other access opening to the system, to facilitate locating the pipe.
9. Cement coated and lined steel pipe shall not be used for mains in areas where service taps can be anticipated, or where active soil conditions exist. Welded steel, or ductile iron pipe shall not be used where active soil conditions exist.
10. Any requirements of this section that cannot be met due to terrain or other factors may be varied with the specific approval of the Engineer.
(c) Valves. The distribution system shall be equipped with a sufficient number of valves located such that no single “shut down” will result in shutting down a transmission main, necessitate the removal from service of a length of pipe greater than 660 feet in multiple-family residential, school, commercial or industrial districts, or greater than 1,320 feet in other areas, and in no case shall more that two fire hydrants be removed from service. Valves shall be located such that any section of main can be shut down without going to more than three locations to close valves. Insofar as practicable, resilient seat gate valves shall be located at street intersections opposite the curb return. If it is necessary to locate valves between intersections, they should be installed on a property line. Valves shall be of the same size as the pipeline in which they are installed.
(d) Fire hydrants.
1. Fire hydrants shall be placed at street intersections whenever possible, and shall be located to minimize the hazard of damage by traffic. Fire hydrants located at intersections normally will be installed at the curb return. All others should be located on a property line. They shall have maximum spacing as described in Chapter 23.27 of this title. Additional hydrants may be required on property frontage or on-site as indicated by the Uniform Fire Code.
2. The minimum size main serving a fire hydrant and the pipeline connecting the hydrant, shall be not less than six inches in diameter. Unless prior approval is obtained from the county and the governing fire district. Not more than one fire hydrant shall be placed on a six-inch main and not more than two on an eight-inch main, unless the mains are in a looped portion of the distribution system.
3. The type of fire hydrant installed shall be as specified by the water purveyor, fire district or local agency. The following shall be considered the minimum requirements for a fire hydrant unless otherwise approved:
a. Have a minimum of one four and one-half inch NFPA standard thread outlet, and two two and one-half inch NFPA standard thread outlets.
b. Hydrant valve should normally be located a minimum of ten feet from the hydrant and shall be connected to the main with a flanged fitting.
(e) Service lines.
1. Service lines from the water main to the property line shall be installed at the time the main is constructed wherever it is known or wherever it can be reasonably assumed that a connection is or will be required.
2. Minimum size of a service line shall be one inch inside diameter to serve single- family residences only. All service lines shall be designed to provide adequate service to the facility to be served, and shall be identified on the plans. Service lines shall be non-cemented joint type (compression fittings).
3. Service lines shall be equipped with angle ball curb stop or gate valve at the property line. A gate valve may be used only when service is two inches in diameter or larger. Installation of a valve or meter box is required.
4. Service lines shall not be allowed to tap into transmission lines, unless written approval is obtained from the county’s water purveyor.
5. The location of water service lines shall be permanently indicated by embedding the letter “W” in the curb, directly above the line. It shall be the developer’s responsibility to so mark any curb which is poured after the installation of the service lines. Where curbs do not exist and are not planned during the improvement project, a two-inch by two inch x 24 inch construction grade redwood stake shall be driven into the ground directly above the curb stop at the property line, and shall be painted bright blue and have a nail and washer with “W” stamped in the top.
6. If a lot is served by both treated and untreated water systems, the location of the service lines shall be at opposite ends of the front lot line, or as widely separated as is practical, and with the approval of the county’s Health Department. Backflow prevention devices are required in the treated (potable) water service line of all lots having both treated and untreated systems.
(f) Thrust blocks. All tees, bends, plugs, fire hydrants and other sections of piping and appurtenances that might be capable of being displaced by the action of either working pressures or test pressures within the water system shall be anchored in place by the use of thrust blocks, thrust backing or harnesses as shown on the standard drawings. The bearing areas of thrust blocking on the supporting soil shall not exceed that allowable for the soil involved. Required thrust block bearing areas shall be in accordance with standard drawings.
(g) Valve boxes and vaults. A valve box or vault or capped standpipe shall be provided for every valve installed below ground surface. The cover for all valve boxes and vaults placed in the street pavement or any location where there is vehicular traffic shall be capable of withstanding HS20 and alternative loading, and shall be metallic or of reinforced concrete.
(h) Backflow and backflow prevention devices.
1. Backflow, which is the flow of water or other liquid or foreign materials into the distribution mains of the Department’s system from another source, is strictly prohibited and shall be prevented by the installation of an appropriate, approved backflow prevention device, purchased, installed and maintained by the consumer, and certified, all at their own expense.
2. The type and complexity of the backflow prevention device shall be determined by the county and backflow prevention foundation and shall be based upon the degree of hazard caused to the public from contamination by toxic or non-toxic substances.
(i) Meters. Meters (when required by the county) shall meet the requirements of the latest revision of AWWA Standard C704 or the county, whichever is higher. All meters shall be installed in a meter box set flush with ground surface. The meter boxes shall be clearly marked as containing water meters and shall be capable of withstanding vehicular traffic if set near driveways, sidewalks or other areas subject to vehicular traffic. Meters shall not be placed in driveways.
(j) Corporation valves, curb valves and bronze fittings. Miscellaneous bronze fittings (i.e., elbows, insulation couplings) shall be used where appropriate throughout the system, subject to the approval of the county. Corporation and curb valves and miscellaneous bronze fittings shall conform to the materials specifications.
(k) Pressure regulating stations. Pressure regulating stations shall be required within the distribution system to control pressures between different pressure zones. Whenever pressure reducing stations are installed within the system they shall be located in a concrete vault and installed as per standard drawings, and installed with enough shutoff valves and bypass piping to facilitate quick removal and repair.
(l) Blow-offs (flushouts). AU blow-offs (flushouts) shall be a minimum outlet size of and shall be designed for a minimum operating pressure of 150 psi. A blow-off or fire hydrant shall be installed at the terminus of all dead-end water mains or non-circulating flow water mains. The blow-off shall be sized to provide a minimum of two feet per second velocity in the attached main.
(m) Air and vacuum release valves. Air and vacuum release valves shall be installed in the water system at all points where it is indicated that air pockets may form. The design shall be such as to insure the release of air automatically from the water main. These valves may also insure the entrance of air into the water main when the pressure inside the line is below atmospheric pressure. All valves shall be designed for a minimum of 250 psi operating pressure. The inlet to each valve shall be provided with a gate valve or corporation stop to provide a positive closure between the main pipeline and the air and vacuum release valve, and the air and vacuum release vent outlet shall be installed above ground in such manner as to preclude back-flow.
(n) Check valves. All check valves shall seat readily and completely to assure water tightness. The face of the closure element and valve seat shall be bronze, composition or other non-corrodible material that will seat lightly under all prevailing conditions of field use. All check valves, four-inch and larger in size, for use on distribution mains, shall be designed for a minimum of 125 psi cold water working pressure.
(4) Sizing and selection of pipe.
(a) General. All mains will be sized by the applicant in accordance with these standards or the supplying water agency standard, whichever is higher. The county reserves the right to deny use of certain types of materials in specific circumstances.
(b) Pipe fittings.
1. Joints.
a. Joints and fittings shall conform to applicable AWWA specifications. Mechanical joints for straight lengths of pipe will be allowed only when specifically approved by the Engineer.
b. Flange joints are required when installing four-inch and larger line valves in steel pipe, four-inch and larger tapping sleeves, and other fittings. No other type of joint shall be used without the specific approval of the Engineer.
2. Closure fittings.
a. Mechanical couplings shall be of a gasketed, sleeve-type, with diameter to properly fit the pipe; tolerance on pipe and coupling, together with proper bolt and gasket arrangements, shall be sufficient to ensure permanent watertight joints under all conditions.
b. Where pipes of different outside diameter are connected together, or where pipe is connected to fittings of different materials, great care shall be taken to ensure that the proper ring or adapter is selected.
3. Repair fittings. Repair clamps, repair sleeves, joint clamps and similar devices shall not be used to repair or join new water mains. Pipe damaged during installation shall be removed and replaced.
4. Miscellaneous pipe fittings. Adapters, plugs, end caps, bulkheads, slip sleeves, anchor boxes, lock-joint gaskets, yokes and rods, and other appurtenances shall be used where appropriate throughout the system, subject to the approval of the Engineer. The county does not intend to unreasonably limit the installation of any type of fittings, joint or proprietary device; however, the installation of any such fitting, not specifically approved by these standards, is subject to the approval of the Engineer. Written request for approval of deviating items shall be made in advance through the Engineer.
5. Tapping sleeves. Tapping sleeves or clamps shall be used to tap existing water mains that are in service and under pressure without interrupting service. No tap shall be made on any existing water main without written consent of the County Engineer and water purveyor. Notification shall be made a minimum of 48 hours in advance. Care shall be exercised to select sleeves and gaskets that are properly sized to fit the type and class of pipe to be tapped. Where four-inch or larger tapping sleeves or clamps are used, a thrust block shall be formed and poured behind the sleeve to prevent possible damage to the main from pressure shocks, which develop as valves are first opened.
6. Line valves. Line valves shall be gate valves conforming to the county specifications. Line valves shall be the same size as the main and shall open to the left (counterclockwise) with resilient seat. Line valves in ductile iron or P.V.C. pipelines shall have push-on ends. Line valves in welded steel pipelines and in ductile iron, and cast iron, pipelines in connection with tapping sleeves or clamps, or tee’s shall have flange ends.
(c) Corrosion mitigation. For all steel, cast iron or ductile iron replacements/installations, the applicant shall provide the county with a soil resistivity survey of the work area conducted by a corrosion specialist certified by the National Association of Corrosion Engineers or a corrosion engineer registered by the State of California. The submitted survey shall form the basis for proposed mitigation measures to be submitted with the plans and specifications for county review.
(5) Storage facilities.
(a) Design. All steel tanks, standpipes, reservoirs and elevated tanks for water storage serving more than four services shall comply with “AWWA D100" or A.P.I. Standard 12B Bolted or Welded Equivalent and also meet all foundation and seismic requirements of the Building Code, and all environmental conditions required by the project’s conditions of approval.
(b) Venting. Venting shall equal one and one-half times the discharge area. A minimum four-inch discharge is required.
(c) Repairing and painting. All inspection, repairing, painting and repainting of steel tanks, standpipes, reservoirs and elevated tanks for water storage shall comply with “AWWA D102".
(6) Booster stations.
(a) General.
1. Pumping facilities may be needed to provide adequate water pressure in the distribution system. The type, size and location of all pumping stations within the distribution system shall be specifically authorized by the Engineer. The county will prohibit the installation of pumping facilities where, in its opinion, the installations would be injurious to the operation, or future operation, of the distribution system.
2. All plans and specifications submitted to county for review and approval of pumping stations shall be signed by and prepared by, or under the direct supervision of, the Design Engineer.
(b) Environmental documentation. Environmental documentation for pumping stations should be dealt with at an early date so that the cumulative impacts of development can be considered. Normally, this means that special water supply facilities, such as pumping stations, should be discussed in the project’s environmental document. Performing environmental documentation on a pumping station as a separate project may result in significant delays to the applicant and can be against CEQA policies.
(c) Engineering and geology. It is extremely critical that no grading occur on a potential pumping station site prior to obtaining engineering and geologic approval of the grading plan.
(7) Telemetry and control systems.
(a) Telemetry and/or data acquisition and control systems installed for use by the county to collect data, monitor, remotely control and coordinate the operations of its water system, or the operations between a distributor’s water system and the Department’s system, shall be designed and installed by the applicant following county approval. Maintenance shall be the responsibility of the water supplying agency.
(b) Connections to the existing distribution system or supply mains will be made by the county’s water purveyor unless the county’s water purveyor specifically grants written permission to the applicant or a contractor to make the connection. The county’s water purveyor may install all fabricated pipe, tapping sleeves, valves and the like supplied by the applicant/contractor that are necessary to construct the connection and charge the applicant for any required work.
(8) Materials.
(a) All materials furnished shall be new, undamaged and clearly marked to allow identification during installation. Everything necessary to complete all installations in accordance with the engineering standards of the county shall be furnished and installed whether shown on approved drawings or not, and all installations shall be completed as fully operable functioning parts of the water system.
(b) Where mains are extended (or replaced) by the applicant, it shall be the applicant’s responsibility to provide all materials necessary for the installation.
(c) Acceptance of materials, or the waiving of inspection thereof, shall in no way relieve the applicant of the responsibility for furnishing materials meeting the requirements of the Materials Specifications.
(d) New water industry products or materials will be evaluated by the county if the Engineer feels the product or material has some merit. The county will establish the criteria for testing and evaluating the product. Adequate lead time shall be allowed for testing of previously unapproved materials so as to not delay the project. The Department reserves the right to accept or reject any product or material regardless of the test results. The cost of testing and evaluating shall be incurred by the applicant.
