division 7 sewer design standards 7.2 sewer main design

DIVISION 7 SEWER DESIGN STANDARDS

7.1 Introduction

Design procedures shall conform to accepted engineering practices, and shall be certified by a registered professional engineer, licensed by the State of Washington. All projects will be constructed in conformance with the current editions of the City of Lynden Development Standards, WSDOT Standard Specifications for Road, Bridge and Municipal Construction, WSDOE Criteria for Sewage Works Design.

7.2 Sewer Main Design Standards A. Pipe for gravity sewers shall be PVC pipe conforming to ASTM D3034-SDR 35.

In certain applications, the City may allow Ductile Iron pipe, which shall conform to AWWA C151 and shall be Standard Thickness Class 50.

B. Pipe for pressure sewers shall be Ductile Iron pipe which shall conform to

AWWA C151 and shall be Standard Thickness Class 50 or PVC pipe conforming to WSDOT 9-05.12(1). Fittings shall be Ductile Iron or Cast Iron. HDPE may be utilized if approved by the City.

C. Minimum pipe size for gravity sewer mains is eight (8) inches. Minimum size for

side sewers shall be six (6) inches to property line. Minimum size pipe for force main is four (4) inches unless approved by the City.

D. Minimum pipe cover shall be three (3) feet. E. Minimum grade and design criteria, unless City criteria is more stringent, shall be

in accordance with the current “Criteria for Sewage Works Design”, State of Washington Department of Ecology.

F. All sanitary services shall be installed in accordance with Section 7.3. G. All joints for gravity and pressure sewers shall be of the rubber gasket type. H. A tight line by-pass may be required to separate existing flows from the new

connection, or a grouted in-place plug shall be required at the connection of a new system to a dead end existing manhole until after final acceptance of the sewer extension.

I. Manholes shall be in accordance with Standard Details, Figures 7-2, 7-3 and 7-4.

Manholes shall be placed at each change in grade or direction. Distances between manholes shall not exceed 400 feet. Manholes shall be a minimum of five feet deep to the invert of pipe, unless approved by the City. Joints on manhole sections shall be rubber gasket type. In addition, all joints, risers and pick points shall be grouted. Manholes shall be pre-channelled. A flexible pipe-to-manhole connector shall be employed in the connection of the sanitary sewer pipe to precast manholes as required in Division 12, Section 7-05.

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J. Manhole cover shall be bolt-down type in accordance with Type 2, Figure 7-5. K. Manholes shall be installed at the end of each line of 8-inch diameter or greater

unless the 8-inch line is 150 feet or less from a manhole in which case, a cleanout may be installed at the end of the line, Figure 7-6.

L. Drop connections for sanitary sewers into manholes shall be connected outside of

the manhole in accordance with Figure 7-1. M. All gravity sewers and appurtenances shall be cleaned and tested after backfilling

by the low-pressure air test method per WSDOT 7-17.3(2)E. PVC pipe may, at the option of the City, have a mandrel of a type approved by the City, passed through it to check for any deflections in the pipe. All sewers are to be inspected by the use of a television camera before final acceptance. The costs incurred in making the inspection shall be borne by the Developer. The City shall witness all testing, and shall receive a video tape of the sewer lines.

All force mains shall be tested at a minimum pressure of at least 50 percent greater than the design operating pressure for a minimum time of 30 minutes.

N. Utilities shall be extended through the full length of the property to allow for

future extension, expansion and continuation of the city’s collection system or for conformance with the Comprehensive Sewer System Plan.

Whenever a utility mainline is to be laid in other than a public street, a permanent easement of not less than twenty feet (20) shall be provided for one utility. For more than one utility, a permanent easement shall be provided of not less than 10 feet each side of utility to edge of easement, and 10 feet separation between each utility. Manholes located on easements may require access roads for maintenance purposes.

O. Minimum separation of potable water mains and sanitary sewer lines shall be 10

feet or in accordance with Section 2.41 of the current edition of the “Criteria For Sewage Works Design” published by the Washington State Department of Ecology.

P. Before final acceptance, the Developer shall provide the City with a certified as-

built mylar and two blueline drawings. As-built drawings shall also be provided in digital format in Version 2000 or the current release of AutoCAD. The as-built drawings shall include the exact location of all underground and above ground utilities including, but not be limited to the following information:

1. The horizontal and vertical (inverts) location of all manholes. 2. The location of all vertical and horizontal bends in the force main system. 3. The location of all side sewer saddles on the sewer main.

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4. The location of all side sewer ends with distances to the right-of-way,

distances to the nearest property corners and depth. 7.3 Standards for Wastewater Pump Stations

A. General

1. Standards and Codes

Design is to be in conformance with the current version of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, Washington State Department of Ecology publication "Criteria for Sewage Works Design" (DOE Orange Book), and the City’s Comprehensive Wastewater Plan. Sewage pump stations vary with site specific conditions, and these Standards and Codes are intended to show the general requirements of the City of Lynden. Other requirements may be imposed by the City as necessary to address specific conditions particular to the site or project. Prior to actual design, an engineering report must be submitted by an engineer licensed in the State of Washington. The report must include the Design Criteria requirements of Section G-2-1, Design Criteria, of the DOE Orange Book, as they apply to the particular project. Special attention shall be paid to hydraulic loading requirements. Under certain conditions, the report may require DOE approval. Such approval will be the requirement of the developer. The basic design of the pump station, including sizing of components shall be in accordance with Section C2 , Sewage Pump Stations, of the DOE Orange Book. Electrical work shall be executed in accordance with the current edition of the National Electrical Code and local regulations. All electrical equipment, materials, construction methods, and tests shall be in conformity with the current standards of the following in the latest adopted revision: o Underwriter's Laboratories, Inc. (UL) o National Electrical Manufacturers Association (NEMA) o Canadian Standards Association (CSA) o Electrical Testing Laboratories (ETL) o Factory Mutual (FM)

All materials and equipment shall, within the scope of UL Examination Services, be approved by the Underwriter's Laboratories for the purpose for which they are used and shall bear the UL label or pre-approved equivalent.

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2. Submittals

Two copies of material submittals shall be provided to the City unless otherwise indicated. Submittals shall include all pertinent information about the equipment manufacturer, equipment model number, nameplate data, size, layout dimensions, and capacity. Include information necessary to establish compliance of each item proposed. Control panels and control system submittals including shop drawings shall be provided with a bill of materials showing quantity, manufacturer's name, catalog number, and supplier information.

3. Project Record Drawings

A set of drawings shall be maintained by the Contractor showing any deviations from the original design. A complete set of drawings with indications of piping, structures, and electrical conduit runs shall be submitted to the City. All changes from the plans shall be clearly marked.

4. Guarantee

The Contractor shall guarantee the work and all components thereof for a period of two years from the date of acceptance. All defects shall be repaired at no cost to the City.

5. Tests

The Contractor shall notify the City a minimum of 2 days in advance of the testing and shall perform the testing with a City representative present. An electrical test report shall be provided for the following: o Nominal voltage, phase to phase o Nominal voltage, phase to neutral o Operating load voltages for each phase o Operating load current for each phase The report shall include motor manufacturer, horsepower, rpm, full load amps, and operating amperage for each leg. Pumps and control systems shall be tested for operation to demonstrate conformance with the specifications in the presence of a City representative.


6. Operation and Maintenance Manuals

The Contractor shall prepare 3 copies of Operation and Maintenance manuals. The manuals shall include, as a minimum, the following: o Catalog data and a complete parts list for all equipment and devices o Cut sheets for equipment and components o Pump performance curve and operating point o Preventative maintenance procedures o Trouble shooting and calibration information o Control program printout with all inputs and outputs identified o System schematics, shop drawings, and record drawings o As-built wiring diagrams

7. Training

Training by manufacturer’s representative shall be provided to the City for operation of the lift station control system. Training shall include, as a minimum, o Preventative maintenance procedures o Control system operation o Trouble shooting o Calibration and Testing procedures o Equipment operation

B. Site Layout

1 General

Lift stations shall be located within City right of way or within a dedicated easement. Lift stations shall be accessible to service equipment and shall be adjacent to City streets unless a pre-approved access route is provided. Specific pump station locations, as determined by the City, may require a chain link fence and gate.

2. Control Panel Location

Pump control panels shall be placed in a building, or if a building is not utilized the panels shall be located so that access is on a concrete pad that is a minimum of 0.20 feet above the wet well lid elevation. The panel shall be accessible from a location opposite the wet well access hatch, but not more than 10 ft. away. The operator is not to be endangered by exposure to the open wet well.

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C. Equipment

1. Pumps

Pumps shall be manufactured by Flygt, and shall be rated explosion-proof. Motors shall have two mechanical seals with a water detector probe in the seal oil chamber. Motors shall have an embedded thermostat for thermal alarm. An automatic wet well flush valve shall be included with the pump installation. Pumps shall be rail-mounted with the , Flygt Rail System . Rails and fittings shall be stainless steel.

2. Valves and Valve Vault

Valves are to be located in a vault separate from but adjacent to the pump wet well. Each pump discharge line is to be fitted with a resilient seat gate valve or a plug valve, DeZurik PEC Eccentric, or approved equal. Each pump discharge line is to be fitted with a swing check valve, American Flow Control 50-SC, or approved equal. The valve shall have an external lever with weight or spring.

3. Motor Controls

Consultation with the City is required to determine effects of pump discharge on downstream conveyance systems. Pumps shall be controlled in accordance with the sewage system capacity as approved by the City. Pump motors less than 3 horsepower may be operated without soft starts or variable frequency drives unless site conditions dictate otherwise. Pump motors 3 horsepower and larger are subject to flow conditions that may require control with variable frequency drives. VFD’s shall be programmed according to operating parameters for each site (automatic restart after utility or phase failure, etc.) VFD’s shall be Allen-Bradley. Each 3 phase motor to have phase failure relays wired for shutdown of 3 phase motors (phase loss, unbalance, low voltage).

4. Control Panels

Control panels shall contain a programmable logic controller (PLC) for logic operation. The PLC shall be manufactured by Allen Bradley. Control panels shall have heaters, fans and a 110 volt 20 amp electrical outlet for maintenance purposes. Supply Uninterruptible Power Supply (UPS) sized appropriately for each station. To be a continuous on-line


type and maintain control power (120 VAC) load on battery backup for up to 4 hours. UPS to have built in transient voltage surge suppresser for clean power to the PLC, and other power sensitive equipment. Be wired so there is the ability to go to line power in the event of a malfunction with the UPS. For panels with VFD's provide manual or automatic control mode. Run in hand mode - manual speed; Run in auto mode analog speed set-point. Have blown fuse indicators, re-settable hour and occurrence meters. A nameplate including motor and pump data shall be mounted inside the cabinet door.

5. Auxiliary Power

Lift stations with pump motors 3 horsepower or greater shall be equipped with an automatic starting generator set and automatic transfer switch. The generator shall be sized to operate all pump motors in the lift station simultaneously. The generator may be sized to start one motor at a time in conjunction with motor control programming. Generator shall have a secure enclosure. Stations without generators shall have a manual transfer switch located outside for use of a portable generator. Generator sets shall be propane or diesel powered with a 24 hour fuel capacity, or natural gas. The manufacturer shall be Cummins/Onan or approved equal.

6. Level Controls

Float switches and sensors for wet well level control shall have the following minimum configuration:

o Low Level Alarm and all pumps off (with redundant float) o Lead Pump On o Lag Pump On o All Pumps Off o High Level Alarm and all pumps on (with redundant float) o Alarms shall have exterior flashing lights Lift stations with less than 5 horsepower motors may use float switches. Lift stations with motors 5 horsepower and greater shall use an analog level control device such as an Omega pressure transducer or approved equal. Float operation shall be provided for low and high wet well alarms in addition to a transducer. Submerged transducers shall be installed within a stilling well, configured so that sludge and grease will not foul the probe. Probes and floats must be positioned for easy access from above for maintenance and replacement.

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Supply 1 spare transducer with each site. Have low level alarm bypass for when you want to pump station down below low float.

7. Alarms and Telemetry

A visual alarm shall be provided for all lift stations, consisting of a flashing red or yellow light. Telemetry shall conform to the existing City SCADA system (including equipment and software) with functions to consist of a minimum of 8 discrete input and output channels and 1 analog channel. Minimum alarm conditions to be reported are: o High Wet Well o Low Wet Well o Pump 1 Fail (Overtemp, Seal, Drive Fail) o Pump 2 Fail (Overtemp, Seal, Drive Fail) o Power Fail o Intrusion Telemetry shall also report on demand wet well level, which pumps are running, amps on motors running and pump hours . Provide power supply as recommended by the manufacturer. Provide all necessary analog and digital I/O for project plus one additional card of each type. Supply a copy of the program for each PLC.

D. Structures

1. Wet Well The wet well shall be a precast concrete structure in accordance with WSDOT standard plans for catch basin and manhole structures. Minimum wet well diameter shall be 60 inches. The wet well shall be designed for ease of access to pumps and equipment, while conforming to Dept. of Ecology sizing criteria. The wet well shall be accessible from the finish ground surface with an aluminum double door hatch sized to allow pumps on rail system to be easily removed without disassembly, and positioned to provide direct access to floats and other equipment. Hatch shall be rated for H-20 loading. Ground shall slope 2% away from the wet well structure. No wet well and dry well combination structures will be allowed. Pump retrieval chains shall be stainless steel. Chains shall be attached to the wet well lid for access during flooded wet well conditions. Cable hangers within the wet well shall be made of nylon or approved non-metallic material. Hooks shall be stainless steel.


Wet well shall be vented with a minimum 6-inch diameter galvanized steel 180 degree welded return bend. Screening (1/4-inch opening, 14 gauge) shall be welded on the outside opening. Discharge piping within the wet well shall be full diameter from the pump discharge. Piping shall be ductile iron within the wet well.

2. Valve Vault The valve vault shall be separate from the wet well and shall be a precast rectangular vault. Access shall be provided with an H-20 rated galvanized steel or aluminum hatch at finish grade. Piping shall be ductile iron within the valve vault, extending to a minimum of 10 feet outside the valve vault. A drain shall be installed in the vault to discharge into the wet well. A pinch type check valve shall be fitted on the drain line to prevent sewage in the wet well from entering the valve vault.

3. Generator Building. Generators shall be housed in insulated buildings. Buildings shall be constructed of City approved materials which are compatible with the surroundings. Split face concrete block with metal roofs are the general standard. Buildings shall have double steel doors, sized for equipment removal. Hardware shall be stainless, and keyed to the City standard key system. Buildings shall be ventilated with automatic louvers that open when equipment is running. A thermostatically controlled heater shall be provided. The building interior shall be completely finished and painted. Switched lights and 110V power shall also be provided. An exterior light shall be installed above the door. A minimum 5’ x 6’ concrete pad shall be constructed outside the door. Electrical control panels for the pump station and generator shall be located inside the building. Plans for the building shall be submitted to the City for review, which shall include suitability of building materials, finishes, landscaping, fencing, security, colors, grading, lighting and other relevant factors. Buildings may be subject to building permit requirements, depending on size.

4. Accessory Equipment

A ¾” water service with meter, frostproof hose bibb, and approved backflow device shall be installed within 10 feet of the wet well. The hose bibb shall be provided with a locking device. An outside light shall be provided for night maintenance operations.

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7.4 Sanitary Service Installation Specifications A. For new development, the Developer is responsible for installing the sanitary

service from the sanitary main to the property line in accordance with Figures 7-7 and 7-8. The Property Owner is responsible for installing sanitary service from the property line to the house.

For an existing main, the Property Owner is responsible for installing the sanitary service from the main to the house.

B. Service shall be six-(6) inch minimum from the main to the property line.

C. From the property line to the house, the following size service shall be installed: 1. Four-(4) inch minimum for single family. 2. Six-(6) inch minimum for multiple family. Larger pipe may be required

by plumbing code.

D. Service pipe from main to property line shall be PVC and shall conform to the requirements of ASTM D3034 SDR 35. Sewer pipe shall have flexible gasketed joints.

E. The minimum grade for the six-(6) inch side sewers to the property line shall be

two (2%) percent. Where this is impractical due to the depth of an existing street sewer or to the arrangement of any building, grade may be reduced to 1 % when approved by the City. Service shall have a maximum slope of 1 foot horizontal to 2 foot vertical. Structures with basements or below grade areas require backwater valves in the service lines.

F. Cleanouts on service lines shall be in accordance with the current plumbing code

and Figure 7-6. A cleanout shall be provided for each total change of 90 degrees of grade or alignment and in no case shall the spacing of cleanouts exceed 100 feet. A cleanout shall be located within 2 feet of the house. Cleanouts shall consist of a wye branch in the side sewer. All cleanouts shall be extended to grade. When required by the City, the Owner shall install an approved casting to provide ready access to the cleanout stopper. No cleanout is required at the property line. A testing tee shall be installed when required.

G. Side sewers shall not be constructed on private property prior to completion and

acceptance of the main line and side sewer on public right of way or easement unless approved in writing by the City.

H. Side sewers shall be constructed with a maximum deflection not to exceed

manufacturers recommendations. Larger changes in direction shall be made by use of standard 11-1/4 bends or cleanouts.

I. Grease traps or interceptors shall be installed for all restaurants and other such

facilities requiring grease traps per the Uniform Plumbing Code. All grease traps


shall be privately owned, designed and constructed in conformance with said code and inspected by the City.

J. Sewer saddle shall be Romac, style “GB.” Side sewers shall not be backfilled

prior to inspection by the City. Should any such work be covered up without such approval it must be uncovered for examination at the Property Owners expense. All side sewers shall be tested and/or videotaped after backfilling.

K. Staking of lots and/or property lines to assure correct sanitary service locations is

the responsibility of the Property owner. Locations are to be as shown on the approved drawings. Errors due to failure to provide a property survey or due to changing lot locations during final plat approval shall be corrected by the Property Owner at the time of such change or when the error is detected.

L. Where services are ended at the property line, and will be extended in the future,

a cap shall be glued on the end of the service line. The end of the sewer shall be marked with a pressure treated 2x4 painted green, with depth to the sewer painted on it. 2x4 shall be wrapped with #12 copper wire.

M. Before final acceptance, the Developer shall provide the City of Lynden with a certified as-built mylar and two blueline copies. In addition all final as-built

drawings shall be furnished in digital format in Version 2000 or the current release of Autocad. The as-built drawings shall include the exact location of

all underground and above ground utilities and shall include, but not be limited to, the following information:

1. Stationing and depth of all sewer wyes into the main. 2. The location of all side sewer tees into the sewer main including the

following:

a. The ends must be tied out to the corresponding corners and right-of-way and sewer main stationing and offset..

b. The depth of the end at the end of stub must be noted.

c. Location of all cleanouts.

Division 7 of 11

Rev November 06

division 7 sewer design standards 7.2 sewer main design

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