Appendix 20D-4 Design Requirements for Water and Wastewater System Extensions
I. General
II. Drawing Format and Content
III. Water Main Design Requirements
IV. Sewer Main Design Requirements
V. Special Appurtenances
VI. Easements
VII. Record Drawings
VIII. Review Checklist
I. General.
A. Purpose. The purpose of these design standards is to provide engineers, designers, draftsmen, inspectors and others with a reference to City of Redmond’s requirements for the design and installation of improvements to the water and sewer systems. No extension or modifications to the City’s utility system shall be made without the approval of construction drawings prepared in accordance with these standards.
The design standards included herein are intended to result in utility systems which will:
1. Provide the needed source, storage and distribution facilities system to maintain desirable levels of service during periods of maximum use.
2. Provide the needed sewer facilities to carry all anticipated sewage flows within a basin.
3. Conform to the City’s Water System Plan and General Sewer Plan.
4. Be of material strong enough to resist all expected loads, both internal and external, in order to preserve the purity and potability of the water supply and protect ground and surface waters from the escape of wastewater.
5. Be safe and economical to maintain.
Alternate materials and methods will be considered for approval on the basis of these objectives and conformance to all requirements indicated elsewhere in these standards.
B. Revisions to These Requirements. It is anticipated that revisions to these requirements will be made from time to time. The date appearing on the title page is the date of latest revision. Users should be sure that they are using the most recent revision to these requirements. This edition was approved in January, 2000. Contact the Water/Wastewater Division at (425)556-2840 to ensure this copy is the most current edition.
C. Referenced Standards. Reference herein is made to the latest edition of standards, tests, methods, and specifications of research as follows:
1. American Standards, prepared by the American Water Works Association (AWWA).
2. American National Standards, prepared by the American National Standards Institute (ANSI).
3. Standard Specifications, prepared by the American Society for Testing and Materials (ASTM).
4. Federal Specification, prepared by the Federal Government (FS).
5. Guide Book for Determination of Required Fire Flow and Grading Schedule for Municipal Fire Protection, prepared by the Insurance Services Office (ISO).
6. Standard Specifications for Road, Bridge and Municipal Construction, prepared by the Washington State Chapter, American Public Works Association (APWA) as modified by the Water/Wastewater Division.
7. Rules and Regulations of the State Board of Health Regarding Public Water Systems, prepared by the Water Supply and Waste Section, Health Services Division, State of Washington Department of Health (DOH), latest edition.
8. City of Redmond Standards, Specifications and Details, prepared by the City of Redmond.
9. Criteria for Sewage Works Design prepared by the State of Washington Department of Ecology.
II. Drawing Format and Content.
A. Material and Size. All construction drawings for developer extensions of the water and sewer system shall be 22-inch by 34-inch mylar originals. Vellum, paper, sepia reproductions, or photographic reproductions shall not be used. Plans submitted shall be designed on the computer utilizing the following formats: Microstation (*.dwg), Autocad (*.dgn), and other CAD programs (*.dgn). Hand drawn submittals shall not be accepted.
B. Drawing Content. Drawings for water and sewer shall contain all information necessary to review the design and to construct the improvements. All relevant information from other project drawings, including grading, storm drainage, road and street improvements, other utilities, landscape drawings, etc., shall be shown on the water and sewer drawings, including existing and proposed grading, other utilities and surface improvements. Combined water/sewer/storm and road drawings may be used if given prior approval.
C. Title Block/Drawing Title. The drawing title block shall include the name, address and phone number of the project developer and project engineer. In addition to the engineer’s standard title block on the bottom or right side of the drawing, the plan format shall include a drawing title generally centered on the top of the sheet which shall include the project name, section, township, and range, the number of lots or units in the project, the water system pressure zone and the Metro connection manhole.
D. Vicinity Map. The first sheet of the water/sewer drawings shall include a vicinity map showing the general location of the project.
E. Approval Block. Each sheet of the drawings shall include the standard city approval block located in the lower right hand corner of the sheet.
F. Horizontal Scale. The preferred horizontal scale for plats and short plats shall be one inch equals 20 feet and, for commercial projects, one inch equals 20 feet. Vertical scale must be one inch equals five feet.
G. Datum. Datum for design shall be City of Redmond. Not less than two site benchmarks shall be shown. Sewer inverts are not to be considered suitable benchmarks.
H. North Arrow/Bar Scale. To the extent possible, north shall be oriented to the top or to the left of each drawing. A north arrow and bar scale shall be shown in the upper left-hand corner of the drawing.
I. Drawing Layout. Drawings shall be laid out to afford the maximum understanding possible and drawings may not be approved if layout is considered confusing. It is advisable to discuss plan layout prior to preparation of a large project with the Utility Division. Provide matchlines at all appropriate locations.
J. Profiles. Profiles shall be prepared for both water and sewer unless waived by the Water/Wastewater Division Engineer. Profiles shall be located on plan sheets and shall be oriented directly above or below the plan view when possible. Profiles may be shown on separate sheets when given prior approval.
K. Profiles Information. Finished grade above the utility shall be accurately plotted. All utility crossing shall be accurately depicted or a calculated clearance shall be shown. All physical characteristics of the utilities shall be shown true to scale. This shall include but is not limited to waterline deflection, pipe diameter, pipe slope, manhole depths, etc.
L. Plan View Information. The drawings shall indicate and identify all existing and proposed buildings, structures, utilities (water, sewer, power, phone, gas, cable TV), street improvements and paving, stream crossings, mailboxes, and other known physical features within the project area which will affect the design and construction of the water and sewer improvements. If an existing utility line is greater than 12 inches in width, the utility shall be shown on the drawings in its actual width. (See drawing content on previous page.)
M. Engineer Stamp. Drawings shall be prepared by a civil engineer with current registration in the State of Washington whose seal shall be affixed to each construction drawing and signed. (Drawings shall be stamped prior to submittal and review by the City).
N. Legend. Drawings shall include a legend of symbols used if needed to show clarity.
O. Property Data. The drawings shall include all property lines, including dimensions and bearings, ownership lines, street right-of-way lines, lot numbers, block numbers, plat names, and street names.
P. Stationing/Coordinates. The drawing shall include both centerline stationing and offsets and state plane coordinates using NAD 83-91 survey control for all mains and appurtenances.
Q. Phased Project Drawings. Phased projects shall require drawings which depict all construction necessary to complete the phase. Drawings shall be approved independently for each phase.
R. Multi-Family Projects. For projects that include multi-family units, construction drawings should include building numbers and the number of units per building.
III. Water Main Design Requirements.
A. General. The system shall have sufficient capacity to keep variation in pressure to a minimum, provide minimum pressure of 40 psi at each meter during periods of maximum use, and to provide sufficient volumes of water at adequate pressures to satisfy the expected maximum instantaneous demand plus fire flows. If 40 psi cannot be maintained at the highest meter, then close review of available flows and pressures will be made.
In general, water system extensions should be designed to incorporate the recommendations of the current Water System Plan for the City of Redmond.
B. Capacity and Sizing Requirements.
1. Design capacities and main sizing shall be determined by consideration of the following factors:
a. The proposed development and adjacent areas.
b. Current and projected populations within the areas to be served.
c. Current and projected land use within the areas to be served.
d. Commercial, multiple-family, industrial, or institutional users to be served.
e. Changes in any of the above factors which are likely to occur within a foreseeable time period.
2. In the absence of project-specific data, the following assumptions shall be used.
a. Average demand for single-family dwelling is 210 gal/day and a multi-family dwelling is 160 gal/day.
b. Required minimum instantaneous demand for a single-family dwelling is 20 gpm.
c. Average demand for typical retail commercial user shall be 2,000 gal/acre/day.
d. Demand for unique commercial and industrial installations and institutional concerns will be calculated on an individual basis.
e. Desirable fire flow shall be 1,500 gpm at 20 psi residual pressure in residential areas. Fire flow in other areas shall be as required by the Fire Department.
f. Maximum velocity in a pipe shall be 10 fps. (For example, if more than one fire hydrant is required within the water line extension, then a 12-inch diameter must be used.)
These criteria may be used to estimate the minimum, average, and maximum demands. (Submission of design calculations will not ordinarily be required, but designers should be prepared to substantiate pipe sizes, layout, population estimates, land uses, or other design assumptions when requested.)
3. Main Sizes.
a. 2'' Not to be used as part of the distribution system.
b. 3'' Not to be used as part of the distribution system.
c. 4'' Not to be used as part of the distribution system except at the end of cul-de-sac mains after the last fire hydrant.
d. 6'' Not to be used as part of the distribution system except as fire hydrant runs.
e. 8'' Minimum size for permanently dead-ended mains supplying fire hydrants, for local distribution mains in residential areas, and for minor transmission mains.
f. 10'' Not to be used as part of the distribution system.
g. 12'' or
Larger As required for transmission (feeder) mains. 12-inch diameter minimum is required in commercial and industrial zones.
C. Water Main Locations.
1. General. The preferred location for water main shall be within the rights-of-way of public streets and roads. Water mains may be installed within a public water main easement across privately owned property when necessary and only if approved. When located in easement areas, water mains shall be located within the lanes of access corridors. Water mains in non-paved areas are generally not allowed but will be determined on a case-by-case basis. Properties that are redeveloping or undergoing additional development, for which existing water mains do not meet current location standards, shall abandon the existing mains and new mains shall be constructed in accordance with current standards.
2. Public Streets. Water mains within public street and road rights-of-way shall be preferably located on the north and east sides of the centerlines thereof, and to the greatest extent possible at 10 feet from centerline when the street is 34 feet in width or greater and seven feet from the curb face if narrower. Exceptions to this requirement may be made in order to minimize the cutting and replacing of pavement, to avoid conflicts with replacing of pavement, to avoid conflicts with other underground facilities, to permit sanitary sewers to be installed on the “low side” of streets, or for other approved reasons.
3. Private Streets. Water mains within private street and road tracts or parking areas shall be located five feet from the private street, road or parking drive centerline.
4. Variations. As nearly as practical, mains shall be installed on a particular street with the distance from the property line and/or centerline varied as little as possible.
5. Horizontal Clearance – Utilities. The minimum horizontal clearance between water mains and storm drains, gas mains, fire sprinkler mains, and other underground utility facilities, except sanitary sewer, shall be 10 feet. Horizontal clearances of less than 10 feet may be approved but in no case shall be less than five feet.
6. Horizontal Clearance – Sewer. Whenever possible, water mains shall be installed a minimum horizontal distance of 10 feet from sanitary sewer mains. Where this specified separation cannot be met, the design requirements and regulations promulgated by the Washington State Department of Ecology, regarding water main/sanitary sewer horizontal separation, shall be followed.
7. Vertical Clearance – Utilities. The minimum vertical clearance between walls of water main pipelines and pipelines/cables/conduits of other utility facilities, except sanitary sewers, shall be 12 inches. If this separation cannot be achieved, special construction techniques to protect each utility will be required. Pipelines/cables/conduits shall be installed below water mains. Exceptions to this requirement will be made on a case-by-case basis.
8. Vertical Clearance – Sewer. Water mains shall go over sanitary sewers, providing a minimum of 18 inches of vertical clearance between the walls of these pipelines. Where this specified clearance cannot be met the design requirements and regulations promulgated by the Washington State Department of Ecology, regarding water main/sanitary sewer vertical clearance shall be followed.
9. Vertical Clearance – Electrical Wires. Where overhanging electrical wires cross a water utility easement, a minimum of above-ground clearance of the longest vertical clearance of the following shall be maintained:
a. The height of the highest point of equipment that may be operating under the overhanging electrical wire plus the minimum vertical clearance specified in Table 212-2, “Minimum Vertical Clearance of Rigid Live Parts Above Ground,” of the latest edition of WAC 296-44-21230, “Vertical clearance of wires, conductors, cables, and live parts of equipment above ground, rails or water.”
b. Puget Sound Energy Vertical clearance requirements.
Notice: Wire sag shall be added to the above clearance.
10. Crossing Angles – Utilities. Water mains shall cross other pipelines/cables/conduits as close to right angles (90 degrees) as possible.
11. Depth of Cover. The standard cover over water mains shall be 36 inches for eight-inch diameter pipe and smaller, and 48 inches for 12-inch diameter pipe and larger. The maximum cover over water mains shall be 60 inches where conflicts with other utilities require the water main to be deeper.
12. Easement Widths. Where public water main easements are necessary, they shall be 20 feet in width. Easement widths of less than 20 feet may be approved if the full 20 feet is not obtainable, but in no case shall be less than 15 feet.
13. Looping. The distribution system shall be looped wherever possible.
D. Valve Requirements.
1. Valve Type. Valves two inches through 12 inches shall normally be resilient seat/wedge gate valves. Valves larger than twelve inches shall normally be butterfly valves. All valves shall meet the requirements of the City of Redmond, Water/Wastewater Division, Standard Specifications and Details.
2. Valve Size. In general, the valve sizes shall be the same as the mains in which they are installed. When approved, special valves such as plug or ball valves may be a size smaller than the main depending upon the special conditions involved.
3. Valve Locations. Distribution system valves shall be located as an assembly on branches of a tee or cross. The spacing of valves shall be such that the length of any one shut-down in commercial, industrial and multi-family areas shall not exceed 800 feet, and in other areas 1,200 feet. The spacing of valves shall be such that no more than two fire hydrants are removed from service with any separate main shutdown.
4. Air Valves. Combination air release and vacuum valves shall be installed on all high points of new water mains. The box which contains the valve and the standpipe shall be located outside the traveled portion of the roadway, preferably behind the curb and sidewalk at property line intersections but remain within the public right-of-way or water line easement. Valve assembly shall be in accordance with the City of Redmond, Water/Wastewater Division, Standard Specifications and Details.
5. Blow Offs. All dead-end mains shall terminate with a blow-off assembly or fire hydrant. All low points of a main shall have a blow-off assembly or fire hydrant. Blow-off assemblies shall be located outside the traveled portion of the roadway, behind the curb and sidewalk, but within public right-of-way or water line easement. Blow-off assemblies on pipe 12 inches and larger shall be four-inch size or a fire hydrant.
E. Fire Hydrant Requirements.
1. The location of fire hydrants shall be determined on a project by project basis. In general, the following criteria shall be used, but the specific determination of the Fire Marshal shall govern:
a. Maximum hydrant spacing in single-family residential plats shall be 600 feet with the hydrants preferably located at intersections and not more than 350 feet to the center of any building lot (including flag lots). Where structures on a dead end access are over 300 feet from a hydrant, an additional hydrant may be required to be placed within 300 feet and placed in relation to the overall development and existing hydrant layout.
b. Maximum hydrant spacing in commercial, industrial and multi-family residential developments shall be 300 feet with a fire hydrant not being closer than 30 feet to any structure and with no more than 150 feet traveled distance to any portion of the exterior wall of any structure.
c. Maximum hydrant spacing in surface parking lots or along rights-of-way shall be 600 feet. This spacing will be reduced if hydrants are also for protection of structures.
2. The City of Redmond Fire Department and the Public Works Department shall jointly approve fire hydrant locations. Fire hydrants shall have the minimum setbacks from curb faces as shown on the City of Redmond Standard Details.
3. Fire hydrant line size from the main to the hydrant shall be a minimum of six inches in diameter if the length of the line is less than or equal to 50 feet. The line size from the main to the hydrant shall be a minimum of eight inches in diameter if the length of the line is greater than 50 feet.
F. Service Connections.
1. General. Water service connections including service saddle, service line, meter setter, meter box and appurtenances shall be installed as part of the construction of new water main extensions and must be installed at the locations shown on the approved project drawings. Meter boxes shall be located within a landscape area. It is not permitted to place a meter box within a hard surface area, such as asphalt or concrete. Water meters will be installed by the City upon application and payment of fees required by other city codes and resolutions.
2. Standard Sizes. The sizes of services which may be used are five-eighths inch by three-quarters inch, one inch, one and one-half inches and two inches. The use of larger sizes shall require specific approval.
3. Multiple Meter Assemblies. For adjacent residential lots/parcels, multiple service connections shall be installed in as many situations as possible. The proposed meter layouts shall be shown on the project drawings.
4. Meter Location – Residential. In general, meters shall be located in front of the lot/parcel to be served. All materials comprising the service connection shall be located within the public street right-of-way or public water line easement, whichever is applicable, with the front edge of the meter box being adjacent to the back of curb or sidewalk. Meter boxes should be located to allow ease in the periodic reading of the meter and should be placed as close to the property line as possible. Meter boxes shall not be placed within a driveway.
5. Meter Location – Commercial/Multi-Family. In commercial and multi-family developments meters shall be located behind the back of curb or sidewalk of a vehicle travel aisle and not behind parking spaces or other obstructions. Meters should be located to allow ease in the periodic reading of the meter.
G. Connections to Existing Water Mains. In general, connections of proposed water mains to existing water mains shall be made by cut-in type procedures. Connections to the existing system by tapping the existing water main while under pressure and still in service will be considered, and are subject to Public Works approval. Cut-in tees are typically required to provide for suitable valving at the assembly.
H. Miscellaneous.
1. Pipe Callouts. Pipe size shall be shown in the plan and profile view. Pipe length need not be shown, but sufficient dimensional information to locate all appurtenances shall be shown (for construction and for later maintenance).
2. Valve at Connection. A new valve shall be installed at the end of an existing main which is to be extended in order to facilitate disinfection and testing of the new main.
3. Valve Callouts. The type and size of valves shall be shown.
4. Meter Callouts. The location, service line size, size and type of meter shall be shown for all meters. This includes domestic, irrigation and fire sprinkler meters.
5. Fitting Callouts. All fittings including tees, crosses, bends, sleeves, etc., shall be shown in plan and profile and the joint connections of each fitting shall be identified in plan view with the appropriate dimensional information. Generally all valve to fitting connections shall be flanged and fitting to pipe connections shall be mechanical joint.
6. Restrained Joints. Restrained jointing systems may be required in areas of unsuitable soils or complex thrust conditions.
7. Vertical Bends. Vertical bends are not allowed in the water system unless approved.
8. Poly Wrap. Poly wrap may be required for pipes in areas where soil corrosion is considered to be a problem. Poly wrap will be required for all fittings placed in control density fill (CDF).
9. Individual PRVs. If the area has a high static pressure (over 80 psi), the plans shall indicate the need for individual pressure reducing valves.
10. Trees. Trees shall not be located within eight feet horizontally from the pipe.
11. Unstable Soils. Unstable soil conditions, such as peat, shall be removed from under pipes.
12. A.C. Pipe Crossings. Existing A.C. pipe may be required to be removed and replaced with ductile iron when crossed under or over by other utilities or where grading or other construction activities may subject the pipe to damage. The abandoned A.C. pipe shall be disposed of in accordance with the Puget Sound Air Pollution Control Agency (PSAPCA) requirement. A permit from PSAPCA to perform the abandonment is required prior to construction drawing approval.
13. Rockeries/Retaining Walls. Rockeries or retaining walls shall not cross or be in close proximity to water mains. Where no alternatives exist, crossings under a rockery or retaining wall shall require special construction techniques, including but not limited to, installation of steel casings.
Rockeries or retaining walls parallel (or adjacent) to water mains shall be constructed as follows:
a. The foundation of the rockeries or retaining walls shall not be located in the utility easement.
b. The foundation of the rockeries or retaining walls shall not intersect with a soil failure plane with a 1:1 slope when the plane is extended from the bottom edge of the utility or water main trench up to the ground surface.
c. The edge of the foundation of the rockeries or retaining walls shall be at least 10 feet from the soil failure plane.
d. The face of the rockeries’ or retaining walls’ stem shall be located a minimum of 10 feet from intersection of the soil failure plane with the ground surface.
e. Rockeries with stem heights up to three feet shall be located a minimum of three feet from the intersection of the soil failure plane with the ground surface.
14. In situations where multiple fittings are to be used, fittings shall not be bolted together. Fittings shall be spaced apart a minimum of five feet. If a pipe joint must be installed between fittings, the joint shall be restrained.
15. There shall not be a push-on pipe joint within five feet of a fitting.
16. In general, any water main and appurtenances that are removed during construction shall not be reused on any part of the water system.
IV. Sewer Main Design Requirements.
A. General. Design of sanitary sewers shall as a minimum comply with the “Criteria for Sewage Works Design” as published by the State of Washington Department of Ecology. Any exceptions to the design requirements shall require separate approval.
In general, sewer system extensions should be designed to incorporate the recommendations of the Sewer Comprehensive Plan for the City of Redmond.
B. Capacity and Sizing Requirements.
1. Design capacities and main sizing shall be determined for specific proposed developments and shall be determined by consideration of the following factors:
a. The proposed development and adjacent areas.
b. Current and projected population within the areas to be served.
c. Current and projected land use within the areas to be served.
d. Commercial, multiple-family, or institutional users to be served.
e. Changes in any of the above factors which are likely to occur within a foreseeable time period.
2. In the absence of project specific data, the following assumptions shall be used:
|
a. |
Single-Family Residence Unit Flow |
210 Gal/Day |
|
b. |
Multi-Family Residence Unit Flow |
160 Gal/Day |
|
c. |
Retail Commercial Areas |
2,000 Gal/Acre |
|
d. |
Industrial |
2,000 Gal/Acre |
|
e. |
I/I |
1,100 Gal/Acre |
|
f. |
Peak Factor -- in accordance with General Sewer Plan |
|
3. These assumptions may be used to design new extensions and evaluate existing systems. Submission of design calculations will not ordinarily be required except where portions of the system will need to be extended to serve additional areas or at the discretion of the Public Works Department.
4. The minimum size for an extension of a city sewer main is eight-inch diameter. Main sizes greater than eight inches shall be used only when design flows will fill an eight-inch pipe at the design slope or when a larger pipe has been used upstream.
C. Sewer Main Locations.
1. General. The location for sewer mains shall be within the rights-of-way of public streets and roads. Sewer mains may be installed within a public sewer main easement across privately owned property when necessary and as approved on a case-by-case basis. When located in easement areas, sewer mains shall be located within the lanes of access corridors. Sewers in unpaved areas are generally not allowed but will be determined on a case-by-case basis. Properties that are redeveloping or undergoing additional development, for which existing sewer mains do not meet current location standards, shall abandon the existing mains and new mains shall be constructed in accordance with current standards.
2. Streets. Sewer mains within public streets, private streets, road tracts or parking areas shall be located such that manholes are five feet south and west of centerline or on centerline. In curved street sections, additional manholes may be required.
3. Horizontal/Vertical Clearance. The minimum horizontal and vertical spacing of sewer mains between other utilities shall be as specified for water mains in Section III of these requirements.
4. Minimum Cover. The preferred cover over sewer mains shall be seven feet in order to assure gravity service and provide normal vertical separation between water and sewer mains. The minimum cover over ductile iron sewer mains shall be three feet in both paved and unpaved areas; minimum cover over other sewer mains shall be five feet in both paved and unpaved areas.
5. Easement Widths. Where public sewer main easements are necessary they shall be 20 feet in width. Easement widths of less than 20 feet may be considered if the full 20 feet are not obtainable. However, no easement shall be less than 15 feet in width.
6. Access Roads. All manholes shall be accessible to the City maintenance vehicles. If not located in a vehicle access way, then access by an improved roadway surface shall be provided. Materials of construction may include asphalt concrete, cement concrete, structurally stabilized vegetated surface, crushed surfacing, etc., as determined by the Water/Wastewater Division Engineer. Access roads shall be designed with 25-foot inside radius on curves, with slopes less than 15 percent and with paved widths as determined by the Water/Wastewater Division Engineer.
D. Manhole Requirements
1. Manhole Spacing. Manholes shall be installed at a maximum of 350-foot spacing. Manholes shall be installed at the end of all dead end mains and junctions.
2. Profile Call Outs. Manhole callouts in the profile shall include manhole number, stationing, type, size, and compass locations of penetrations, and shall be shown complete for each manhole shown on the plans. Inlet pipe crowns shall be one-tenth higher than outlet pipe crowns.
Example: MH #2, Type I-48
Station 13 + 42 – 5' LT
I.E. 348.75 – 8'' N in
I.E. 348.95 – 6'' S in
I.E. 359.75 – 8'' E in Drop Connection
I.E. 348.75 – 8'' E in
I.E. 348.65 – 8'' W out
3. Plan Callouts. Manhole callouts in the plan view shall include manhole number, stationing, type, and size.
4. Manhole Numbering. Upon first submittal of the construction drawings for review, the City of Redmond Water/Wastewater Division staff will assign numbering convention for wastewater manholes. The Developer’s Engineer is required to incorporate these numbers onto the construction drawings. These numbers must be legible and not interfere with wastewater appurtenances.
5. Knockouts. Knockouts and channeling shall be provided in manholes where future extensions are anticipated. These shall be shown on the plans.
6. Drop Manholes. Drop manholes shall only be allowed where approved on a case-by-case basis. Generally, drop manholes will not be approved if the drop is less than five feet in connecting to existing manhole structures and will not be approved in new construction unless used in conjunction with a deep trunk extension. Drops shall be constructed of ductile iron and ductile iron shall be used to the next upstream manhole. Drop manholes shall be outside drops. Inside drops will not be allowed.
7. Maximum Depth. The maximum depth of a manhole without special detailed design shall be 25 feet.
8. Ladder. The ladder and eccentric cone shall be located directly over the outlet pipe.
E. Side Sewer Requirements.
1. Size and Slope. Side sewer stubs shall be six inches in diameter and shall be extended to the property or easement line. Side sewer slope shall be a minimum of two percent. If slope is greater than two percent, the invert elevation at the property line shall be shown.
2. Finish Floor Elevations. Minimum finish floor elevations shall be shown on all lots where gravity service is in question. The minimum finished floor must be 5.0 feet above the side sewer invert at the property line and may be greater depending on the distance to the structure.
3. Tee Locations. Side sewer tees shall extend from public mainlines. Connection at a manhole is not preferred and will not be accepted without prior approval.
4. Branch Configurations. Six-inch side sewers shall connect to eight inches or larger mainlines with a tee. Wye connections shall only be used on six-inch to six-inch connections or four-inch to six-inch connections.
5. Double Services. Double services for single family residences shall be wyed within the lots being served. The maximum allowable differential between the floor elevations of the residences shall be two feet. A joint use side sewer agreement must be provided.
6. Service to Properties. Side sewer stubs shall be provided for all platted lots. Stubs to unplatted land shall be provided as required by the Water/Wastewater Division Engineer. Multiple side sewers shall not be used in lieu of extending a sewer main. Side sewers shall generally be perpendicular to the street centerline.
7. Side Sewer Location. Side sewers shall be located on the platted lot to be serviced and run directly from the building to the sewer main. Side sewers on adjacent lots shall not be installed in a common trench.
8. Side Sewer Length. Side sewers shall be a maximum of 150 feet in length unless otherwise approved.
9. Cleanouts. Cleanouts shall be provided at every bend and at every 100-foot increment.
10. Backwater Valves. Backwater valves shall be installed on all side sewers where the finish floor elevation of the building is lower than the invert elevation of the upstream manhole.
F. Connections to Existing Sewers. Connections to existing sewers for main extensions shall be made by connecting to an existing manhole or constructing a new manhole over an existing pipeline. Drawings showing connections to existing manholes shall call for core-drilling and rechanneling. Drawings, which show a new manhole installed over an existing sewer, shall show a detail of construction for building over the pipe.
G. Miscellaneous.
1. Pipe Callouts. Pipe size and manhole to manhole length shall be shown in the plan view. Pipe size, manhole to manhole length, pipe material, slope in percentage, and pipe class or strength (if not standard) shall be shown in the profile. Pipe material shall not change between manholes. Pipe slopes shall be designed to tenths of a percentage. Establish slopes then calculate inverts. Do not set inverts then calculate slopes.
2. Slope on Dead End Run. Minimum slopes on the last manhole to manhole section of dead-end run shall be one percent in order to promote flushing velocities. Exceptions to these requirements may be approved by the Water/Wastewater Division Engineer.
3. Minimum Slopes. Minimum slopes on main lines are:
8'' = 0.0050 ft/ft
10'' = 0.0032 ft/ft
12'' = 0.0025 ft/ft
4. Steep Slopes. Pipe designs on steep slopes, 20 percent or greater, shall include the required use of ductile iron pipe and pipe anchors which will need to be detailed and located by the designer.
5. Deep Sewers. For deep sewers, pipe strength design data or calculations shall be submitted when requested. Ductile iron pipe shall be used where there is more than 15 feet to the invert of the pipe.
6. Unstable Soils. Unstable soil conditions, such as peat and other organic material, shall be removed from under pipes.
7. Trees. Trees shall not be located within eight feet horizontally from the pipe.
8. Building Footings. Public sewers shall not be located closer than 10 feet to a structure. Building footings shall be designed, or sewers located, such that the footing shall not bear on the pipe. In general, footing shall not be higher than a one-to-one slope beginning at a point two feet horizontal from the pipe invert.
9. Rockeries/Retaining Walls. Rockeries or retaining walls shall not cross or be in close proximity to water mains. Where no alternatives exist, crossings under a rockery or retaining wall shall require special construction techniques, including but not limited to, installation of steel casings.
Rockeries or retaining walls parallel (or adjacent) to sewer mains shall be constructed as follows:
a. The foundation of the rockeries or retaining walls shall not be located in the utility easement.
b. The foundation of the rockeries or retaining walls shall not intersect with a soil failure plane with 1:1 slope when the plane is extended from the bottom edge of the utility or sewer main trench up to ground surface.
c. The edge of the foundation of the rockeries or retaining walls shall be at least 10 feet from the soil failure plane; and
d. The face of the rockeries’ or retaining walls’ stem shall be located a minimum of 10 feet from the intersection of the soil failure plane with the ground surface.
e. Rockeries with stem heights up to three feet shall be located a minimum of three feet from the intersection of the soil failure plane with the ground surface.
10. In general, any sewer main, manhole, and appurtenances that are removed during construction shall not be reused on any part of the sewer system.
V. Special Appurtenances.
A. General. From time to time, special appurtenances will be required for various development projects including, but not limited to, sump pumps, pressure reducing stations, backflow preventors, booster pump stations, sewage pump stations, grinder pumps, oil water separators, and grease interceptors. Calculations and designs for these appurtenances shall be reviewed and approved on a case-by-case basis.
Sump pumps are not allowed within the City system unless approved due to unusual conditions. If approved, special easements and agreements shall apply and shall be in place prior to construction drawing approval.
Location and size of pressure reducing stations shall be determined by the Water/Wastewater Division. A pressure reducing station design shall include detailed plans and sections drawn at a horizontal and vertical scale of one inch equals 10 feet, delineating the vault layout, piping configuration, gravity drain and appurtenances. Notes referencing standard details without a detailed drawing are not acceptable. Refer to the City of Redmond Standard Details and Specifications for pertinent design information.
Location and size of backflow preventors shall be shown on the construction drawings. Backflow preventors shall be installed in accordance with the latest editions of the AWWA Cross Connection Control Manual and the Uniform Plumbing Code (UPC). If the backflow preventor is to be installed within a vault located on the exterior of the building, a detailed design shall be included with the construction drawings delineating the vault layout, piping configuration, gravity drain and appurtenances. Refer to the City of Redmond Standard Details and Specifications for pertinent design information.
Booster pump station and sewage pump station applications shall be determined by the Water/Wastewater Division. Design criteria shall be dictated by the particular application and will require coordination with the Water/Wastewater Division.
Grinder pump applications are restricted to single-family residences and single commercial buildings which are physically unable to connect to the sanitary sewer system by gravity. For single-family residential applications, each grinder pump shall have its own individual force main. The pressure discharge line shall be connected to a gravity side sewer from the sewer main. A maximum of four pressure lines shall be collected and manifold into one gravity side sewer connection.
Oil water separators shall be required for underground parking structures, gas stations, and for all facilities where there is potential for the discharge of oily contaminated waters. The design shall follow criteria established by King County Metro.
Grease interceptors shall be required for all commercial buildings with kitchen and/or cafeteria facilities. In addition, no grease, oil, sand, liquid waste containing grease or flammable material or other harmful ingredients in excessive amounts shall be discharged into any public sewer without the installation of a grease interceptor. The sizing of the interceptor shall be in accordance with Appendix “H” of the latest edition of the UPC recognized by the City. Approval of the interceptor sizing by the Water/Wastewater Division is required prior to installation. Inspection of the grease interceptor shall be the responsibility of the Building Division.
VI. Easements.
A. General.
1. All easements needed for water and sewer main extensions shall be provided by the Developer in the name of the City. The required easements shall be shown on the construction drawing and the easement legal description or plat markup shall be submitted for review at the same time construction drawings are submitted for review.
2. Easement widths shall be a minimum of 20 feet, 10 feet on all sides of pipelines or appurtenances.
3. Easements shall be prepared on the City of Redmond standard forms.
4. An alternative to separately recording a standard easement form is to record an easement on the face of a plat or short plat. If this is the method used, a standard City of Redmond dedication statement shall be included in the documents.
5. Buildings, structures, garages, carports, dumpster enclosures, decks, trees, rockeries, retaining walls, etc., shall not be located in easement areas.
6. New easements, in accordance with current standards, shall be granted for properties which are redeveloping or undergoing tenant improvements.
7. Before a project is accepted by the City, signed easements with the legal description of the as-built locations of the water and sewer extensions shall be provided and shall be reviewed and approved by the City.
VII. Record Drawings.
A. General. Prior to submittal to the City, the “originals” of the drawings shall be revised to incorporate information pertaining to the water and sewer system improvement as it was constructed. The record drawings shall meet the following minimum requirements.
1. The record drawings shall provide the size, length and material of the as-constructed pipelines between fittings and manholes.
2. The record drawings shall provide the size and joint type of each fitting and appurtenance actually installed.
3. The record drawings shall provide the actual horizontal and vertical constructed water and sewer mains, fittings and appurtenances, correcting the location data provided in the drawings.
4. If applicable, the record drawings shall indicate the size, location and type (whether single or double) of all water and sewer service connection stubs installed by the developer/contractor.
5. The record drawings shall indicate areas of excessive cover and any other unique feature of the project.
6. The record drawings shall be clearly denoted as such, with as-constructed information shown as a revision to the original design.
7. The record drawing location of easements shall match the final legal descriptions of the easements granted to the City.
In addition to the requirements listed above, the City has a Record Drawing review process. Refer to the latest edition of this process for more details.
VIII. Review Checklist.
Project
Project #
Reviewed by
Date
City of Redmond
Utility Division
Plan Review Checklist
1. Please include a vicinity map (Section II(D)).
2. Please include a City approval block (Section II(E)).
3. Please include a benchmark (Section II(G)).
4. Please include a north arrow and a bar scale (Section II(H)).
5. Please include a drawing title (Section II(C)).
Water Zone
Metro Manhole
6. Please include existing and proposed grading (Section II(B)).
7. Please include property lines and all associated data (Section II(O)).
8. Please include all existing and proposed buildings, structures, paving, etc. (Section II(B)).
9. Please include all existing and proposed utilities (water, sewer, storm, power, phone, gas, cable) (Section II(L)).
10. Please include name, address, and phone of project developer and project engineer (Section II(C)).
11. Please include the City standard notes which are attached.
12. Please revise the locations for water mains as follows:
13. Please revise the locations for sewer mains as follows:
14. Please show profiles for the following:
15. Please revise the profiles as follows:
16. Please add air release/vacuum valves at all high points including dead end cul-de-sacs.
17. Please adjust meter locations as follows:
18. Please show irrigation meters and backflow preventors.
19. Please show additional valving as follows:
20. Please call for individual pressure reducing valves.
21. Please show 20-foot water and sewer easements on the plans as follows:
22. Please show manhole access roads and easements as follows:
23. Please revise manhole and pipe callouts in accordance with design requirements (Sections IV(D) and IV(G)).
24. Please include existing City manhole numbers. All new manholes must be numbered utilizing the City’s numbering convention prior to construction drawing approval (Section IV(D)).
25. Please adjust side sewer locations as follows:
26. Please show all fire sprinkler piping and the required backflow preventor. Please make revisions as follows:
27. Please provide a copy of the landscape plan for the site.
28.
29.
30.
31.
Note: Referenced sections are from “City of Redmond Design Requirements Water and Wastewater Sewer System Extensions.”
Standard Water/Wastewater Notes
A. General.
1. Any deviations regarding the water and sewer improvements shall be submitted to the City of Redmond, Water/Wastewater Division Engineer for approval prior to implementation in the field.
2. All work and materials shall conform to the Standard Specifications and Details of the City of Redmond. Water and Sewer Specifications and Details shall be the specifications and details in effect on the date of approval of these construction drawings.
3. The contractor shall be responsible for locating all existing underground utilities. Call underground locate service, 1-800-424-5555, for utility marking.
4. No work shall commence prior to a pre-construction conference at the City of Redmond.
5. Coordinate with landscaping improvements. No trees shall be planted within eight feet of water or sewer improvements.
B. Water.
1. All fire hydrants shall be covered with a burlap sack until the water system has been placed into service.
2. Fire hydrants shall be equipped with Storz connectors.
C. Sewer.
1. Side sewers shall have a minimum slope of two percent.
2. New sanitary sewer mains shall be plugged and not put into service until lines have been cleaned, flushed and tested.