For use in the Denver Water Service Area |
The Board Of Water Commissioners
Denver Water
Engineering Standards
Chapter 10 – 24 Inch And Larger Conduits
10.01 General:
All conduits which will become part of Denver Water system shall be designed and built by Denver Water. In cases where Denver Water determines that the Conduit will not be part of its system, Denver Water may allow a Distributor to design and/or install conduits; however, Denver Water must approve the design and installation of these Conduits to insure that sound engineering and construction procedures are followed within the context of 2.08. The intent of this chapter is to state the additional design requirements for conduits and should not be construed as permission to design and install conduits.
Design of the conduit should proceed only after approval to design and/or construct the conduit is received from Denver Water. The overall plan, size, location, and any other pertinent details shall be reviewed by Denver Water prior to the submittal of plans and specifications required by l0.05.
The Distributor shall pay all costs in the design and construction of conduits including those incurred by Denver Water for inspection, testing of materials, and other Denver Water services.
10.02 Other Standards To Apply:
Chapter 10 addresses only conduits. All Standards that apply to 4 inch through 12 inch distribution mains and to 16 inch and 20 inch transmission mains shall apply to Conduits along with the additional requirements and exceptions stated herein. In case of conflict with any other section, this chapter shall govern for conduits.
10.03 Preliminary Investigation:
If the Distributor is allowed by Denver Water to conduct its own preliminary investigation, these requirements must be met:
A. Subsoil Investigation: A subsoil investigation shall be performed by a geotechnical engineer from exploratory holes dug to determine the bearing capacity and backfill suitability of the soil, presence of groundwater or bedrock, and any other condition which may affect the construction of the pipeline. Test holes shall be dug with a maximum spacing of 750 feet and at railroad, highway, and waterway crossings.
B. Alignment: A stationed alignment of the proposed conduit is required to define the route with lines, angles, and curvatures referenced to land corners and other official survey control points when available. No negative stationing is allowed. The angle points, curve points and the centerline at a minimum spacing of 100 feet shall be marked on the ground, with an accuracy of at least one part in 5,000 which shall be checked by Denver Water prior to acceptance of the survey work.
All points of intersection (PI's), points of curvature (PC's), points of tangency (PT's), angle points (AP's) and any points on the tangent (POT's) needed for intervisability shall be marked with semi-permanent steel pins in the ground such as concrete reinforcing bars, P-K nails or survey spikes.
C. Profile: A ground surface profile of the alignment in National Geodetic Survey datum tied to official survey bench marks is required. Additional semi-permanent bench marks shall be established every 1,500 feet by closed loops of Third-Order accuracy. The profile shall consist of ground surface elevations along the proposed conduit centerline at every 100-foot station and at grade breaks. All level loop and profile data shall be recorded in field books.
D. Topographical Features: Topographical features within the street or right-of-way and any topographic feature outside the right-of-way which may interfere with the operation or installation of the conduit shall be accurately shown in field books by both note and drawing. Topographic features may also be compiled by aerial photogrammetry methods.
E. Cross-Sections: In areas where the ground slope perpendicular to the centerline of the Conduit exceeds 5 percent, cross sections shall be taken at all profile points and shall extend at least 25 feet to each side of the centerline. All cross section data shall be entered into field books.
F. Utilities: All utility crossings or close utility interference shall be exposed by digging test pits. Field books shall be used to record the size, nature, and location of the interference by station offset and elevation.
G. Field Book: All survey data compiled in the determination of the route location, the extent of the interference, the centerline profile, the cross sections and level loops shall be entered into field books provided by Denver Water and submitted with the plans and specifications.
10.04 Design:
Conduits shall be designed in accordance with all other applicable sections of these Standards and the following additional requirements.
A. Line Valves: Line valves shall be placed such that service outages experienced during future repairs or construction are minimized. Generally, this will require the ability to isolate and alternately supply all mains extending from the conduit, but in no instance shall the spacing between valves exceed 2,500 feet.
Line valves shall be full line size butterfly valves with flanged end connections conforming to MS-5. Precast concrete manholes shall be placed over valve operators. The valve installation shall include a tap on each side of the valve for chlorination and/or air release. See Sheet l8 of the Standard Drawings for line valve assemblies for 24 inch and 30 inch conduits. Line valve installations for larger diameter conduits require individual approval by Denver Water.
If Denver Water requires the installation of supervisory control and data acquisition, the line valve shall be a butterfly valve with a rectangular vault housing the motor operator and telemetering equipment. Each installation will require individual approval. See 5.12.
B. Restraint Systems: All bends, fittings, line valves, and bulkheads shall be restrained by using both tied joints and kickblocks. Restraint systems must be approved by Denver Water. Kickblocks shall bear on undisturbed soil and have sufficient clearance from adjacent interference.
C. Headloss: The maximum design headloss for Conduits shall be one foot per 1,000 feet of pipeline, based on a Hazen-Williams C-value of 130 at the maximum hourly demand.
D. Blowoff Assemblies: Blowoff assemblies shall be installed at all low points in the conduit, wherever a conduit is deadended and at line valves where the conduit slopes toward the valve. See Sheet 13 of the Standard Drawings for blowoff installations for 16 inch and larger ductile iron pipe.
E. Cathodic Protection: Cathodic protection requirements for conduits will be determined by Denver Water on an individual basis. Conduits being installed in corrosive soils shall be protected using methods as determined by Denver Water. This may consist of the installation of anodes, the bonding of pipe, polyethylene encasement or other requirements determined by Denver Water in addition to the requirements in 6.41.
F. Air Valve Assemblies: Air release and vacuum valve assemblies shall be installed at high points in the conduit, where there is an abrupt change of slope and at line valves where the conduit slopes away from the valve. See Sheet 17 of the Standard Drawings and MS-10 for air valve assemblies for use with 24 inch and 30 inch conduits. Air valve assemblies for larger diameter conduits require individual approval by Denver Water.
G. Access Manholes: Access manhole assemblies as shown on Sheet 17 of the Standard Drawings shall be installed at intervals not to exceed 1,000 feet unless otherwise approved. The access manhole may also contain an air valve assembly if the requirements for both can be satisfied. In some cases, closure assemblies may be substituted for access manholes. Access manholes are not required for 24 inch diameter ductile iron pipe except on each side of butterfly valves.
H. Special Conditions: The location and design of the outlets, tie-ins to any existing or proposed facilities and the bulkheads at the end of conduits must be approved by Denver Water.
Each conduit plan shall be examined individually to determine any special condition and/or requirements by Denver Water (e.g., pressure regulating valves, telemetry, pitots, etc.).
I. Clearance: Vertical clearance between the conduit and crossing interference shall be at least one foot. Horizontal clearance shall be at least 5 feet.
10.05 Plans And Specifications:
Detailed plans and specifications for Conduits shall be prepared in accordance with 2.07. Plan and profile scales shall be one inch equals 50 feet horizontal and one inch equals 10 feet vertical. In addition to the requirements of Chapter 2, the plans shall contain the following information and exceptions.
A. Plan View: A plan view showing:
1. The proposed alignment of the conduit and the location of outlets, valves, blowoffs, air valves, pitots, kickblocks, bends, reducers, bulkheads, and connections to all facilities
2. All existing and proposed utilities and obstructions complete with dimensions to the conduit
3. All survey bench marks and alignment data
B. Top-of-Pipe Profile: Top-of-pipe profile showing:
1. Existing ground line
2. Official street grades where the conduit is located beneath roadways
3. Proposed final ground surface where the conduit is installed within an easement and not located in a roadway
4. The elevation of grade breaks and the slopes of the conduit
5. The elevations of all outlets, valves, blowoffs, etc.
6. The location and extent of tied joints at bends, outlets, valves, etc.
7. Any proposed or existing utility crossings of the proposed conduit complete with clearance dimensions
C. Location Map: A location map, with a list of all bench marks and field book references
D. Detail Sheet: Detail sheets showing outlets, connections, valves, etc.
E. Test Holes: The location and results of the test holes.
10.06 Materials:
A. Ductile Iron Pipe: Pipe shall conform to MS-1. Ductile iron water pipe of Special Class 51 may be used for Conduits if the bedding material specified in 7.10 is used. Ductile iron pipe of Special Class 50 may be used for conduits if the well graded sand bedding material is compacted by jetting and vibrating to a minimum 70 percent relative density as determined by ASTM D 4253 and D 4254:
The bedding and pipe zone material shall be clean, free draining well graded sand or squeegee sand, and shall conform to the following limits when tested by means of laboratory sieves:
| Well Graded Sand | ||
|---|---|---|
| Sieve Size | Total Percent Passing by Weight | |
| 3/8 inch | 100 | |
| No. 4 | 70-100 | |
| No. 8 | 36- 93 | |
| No. 16 | 20- 80 | |
| No. 30 | 8- 65 | |
| No. 50 | 2- 30 | |
| No. 100 | 1- 10 | |
| No. 200 | 0- 3 | |
| Squeegee Sand | ||
| Sieve Size | Total Percent Passing by Weight | |
| 3/8 inch | 100 | |
| No. 200 | 0-3 | |
Prior to construction, the Contractor shall submit for approval by Denver Water the manufacturer's detailed shop drawings, design calculations, lists and availability of materials, and the laying schedule and marking diagram.
B. Other Pipe Materials: Conduits may be of steel or concrete if specifically approved by Denver Water. The design criteria for steel and concrete pipe shall be those currently specified by Denver Water for conduits.
10.07 Installation:
Denver Water may permit the Distributor to have their own Contractor install a Conduit. Denver Water reserves the right to install Conduits when to do so is in the best interest of Denver Water. This determination is solely at the discretion of Denver Water and the Distributor shall pay all installation costs, whether installed by their Contractor or by Denver Water.
Denver Water requires that the conduit installation be witnessed and controlled by Denver Water at the expense of the Distributor. The Distributor shall also furnish, at their own expense, such labor as may be required by Denver Water to enable thorough inspection and culling of all the materials by him and shall furnish reasonable samples of materials at the job to afford adequate testing.
10.08 Sewer Crossings:
The provisions of 8.29 shall apply to 24 inch and larger conduits.
10.09 As-Constructed Drawings:
The plan, profile and detail drawings shall be modified to reflect any changes in the design. The final as-constructed drawing shall be submitted to Denver Water.
10.10 Easement Width Requirements:
The easement width requirements in Chapter 5 and 9 do not apply to the installation conduits. The adequacy of the width and alignment of dedicated public road easement and Denver Water easement shall be determined on an individual basis by Denver Water.
Engineering Standards - Chapter 10:
Revised 07-04, Previous Revision 05-02
End