Sewer Use Regulations

Appendix A.  Design of Sewers

Section 1.  General

Wastewater collection systems shall be designed separately from stormwater systems.   Wastewater collection systems shall not allow for the introduction of rain water, noncontract cooling water, and groundwater from foundation drains, sump pumps, surface drainage or any other source of inflow.  Overflows from wastewater collection systems shall also not be permitted.

New sanitary sewers and all extensions to sanitary sewers owned and operated by the Town of Harwich shall be either gravity sewers or low pressure sewers and shall be designed by a professional civil engineer, or registered sanitarian for systems generating less than 2000 gpd licensed to practice in the Commonwealth of Massachusetts, in accordance with the Guides for the Design of Wastewater Treatment Works (TR-16), and in strict accordance with appropriate Massachusetts codes and the Town of Harwich Rules and Regulations of the Sewer Department.  Plans and specifications shall be submitted to and approved by the Director before initiating any construction.  The design shall anticipate and allow for flows from all possible future extensions or development within the immediate drainage area in conformance with Town planning documents.

Section 2.  Building sewers shall be constructed of such materials and shall be a minimum four (4”) inch diameter pipe for single family residential connections and six (6”) inch diameter pipe for multi-family, commercial or industrial connections or as the Superintendent may determine.  Sewer pipe shall be made from: ductile iron with the outside coated with extra heavy bituminous coating approved for buried utilities and the inside cement lined, minimum schedule 35 P.V.C. or acceptable substitute approved by the Superintendent.  The building sewer shall be laid straight in line and grade.

Single family residential building sewers must have watertight wye cleanouts, with H-20 rated valve frame and cover box, with the word “SEWER” in raised lettering, at all locations where pipe size, slope or direction changes and at the property line. Additional cleanouts may be required for runs of 100 feet or more, or at the discretion of the Director. The cleanout shall be brought to within four (4”) inches below final grade, except for paved surfaces, (bituminous concrete, concrete, paving blocks, etc.) the cover shall be flush with the finished surface. Cleanouts in pressure sewers shall be located and constructed per the manufacturer’s recommendation.

For multi-family, commercial or industrial sewer connections manholes shall be used at all locations where pipe size, slope or directions changes. Commercial or industrial sewer connections shall include a sampling station, to be used for discharge sampling, located in the road layout at the property line. The sampling station shall consist of a precast manhole with approved frame & cover.

Pressure Sewer Laterals

If building is to be connected to a low-pressure sewer or requires a pump to lift sewage to a gravity sewer, the gravity portion of the installation shall meet the requirements of the previous paragraph.  The pressure pipe shall be minimum 1-1/4 inch diameter if a grinder pump is used and 2-inch diameter if a grinder pump is not used or other such larger size if the sewage flow and characteristics differ from a single-family residence.

Materials

Polyethylene for 1-1/4 –inch pipe through 4-inch pressure pipe with material conforming to ASTM D3350, Type PE-4710 HDPE pressure Class PC 200, SDR-11.  Fittings for use with polyethylene pipe and tubing shall be manufactured and furnished by the pipe supplier and in conformance with AWWA C901 requirements.  Joints for polyethylene pipe shall be jointed by the butt fusion method in a manner recommended by the pipe manufacturer.

Polyvinyl Chloride (PVC) Pipe- ASTM D2241 PVC pressure pipe material conforming to ASTM D1784, minimum class SDR 21 for pipe 1-1/4-inch through 4-inch, push-on joint conforming to ASTM D3139 with flexible elastomeric gaskets conforming to ASTM F477.

A ball valve with curb stop and check valve shall be installed on all low pressure and force mains, as close as feasible to a property line.   Ball valves for low pressure sewers shall be true union type constructed from PVC Type I cell classification with EPDM O-rings.  All valve components shall be replaceable.  Ball valves 2 inch and smaller shall be pressure rated to 235 psi, while valves larger than 2 inches shall be rated to 150 psi.  Ball valves shall have a Safe-T-Block seal carrier to stop flow in either direction, allowing safe removal of the downstream union nut for system service or modification.  Ball valves shall be true union ball valves as manufactured by Spears Manufacturing Company, or equal.  Check valves for low pressure sewer laterals shall be made of stainless steel or fabric-reinforced synthetic elastomer to allow for a positive seal with minimum backpressure.  Check valves shall be true union ball check valves.

Curb stop valves shall be of brass or bronze construction and two rubberized O-ring seals to provide pressure-tight seal.  Curb stop valves shall be figure H-15204 as manufactured by Mueller-Oriseal, B22 as manufactured by Ford Meter Box Company, Hayes, Nueseal, or equal.  Curb boxes shall be 2-1/2 inch shaft size two-piece screw type.  They shall be adjustable from 48-inch to 72-inch.  Curb boxes shall be constructed of cast iron and thoroughly coated with two coats of asphaltum varnish.  Curb box shall be stainless steel supplied with a hole in the “U” portion for the insertion of a stainless-steel pin.  Pins shall be supplied and shall be made of stainless steel.  Curb boxes shall be as manufactured by Ford Meter Box Company, Mueller Company, or equal.

Gravity or low-pressure pipe shall have magnetic marking tape 2 inches wide with the words “SANITARY SEWER BELOW,” installed not more than two (2’) feet below finished grade on all mainline and service laterals.

Section 3.  Whenever possible, the building sewer shall be brought to the building at an elevation below the basement floor.  All buildings in which any building drain is too low to permit gravity flow to the public sewer, sanitary sewage carried by such building drain shall be lifted by an approved means and discharged to the building sewer or public sanitary sewer, as specified by the Director.

Low Pressure Grinder Pumps or Lift Pumps

Each property serviced by a low-pressure sewer shall have a dedicated pre-manufactured pump station suitable for the flow, pressure and other conditions defined by the property and the public sanitary sewer.  The station shall include an in-ground self-contained unit with submersible motor, level controls, sensors, alarms, and an emergency generator plug-in connection.  Properties whose sewage quantities and characteristics are equivalent to four or more families shall install a duplex pump.  Refer to further requirements in Appendix A, Design of Sewers, Section 23 - Grinder Pump Systems.

Section 4.  No person shall make connection of roof downspouts, exterior foundation drains, areaway drains, or other sources of surface runoff or ground water to a building sewer or building drain which is connected directly or indirectly to a public sanitary sewer. 

Section 5.  Exhaust from engines, blowoff from boilers, drainage of gasoline or any explosive liquor, liquids, or other flammable substances shall not be permitted to be discharged into any building sewer which is connected directly or indirectly to a public sanitary sewer.  At the time a connection is made to the Town’s sanitary sewer system, the interior plumbing shall be inspected to ensure that no connections to roof drains, yard drains, foundation drains, sump pumps, or other sources of drainage water is connected to the sanitary sewer.                                                        

Section 6.  The connection of the building drain into the building sewer shall conform to the requirements of the building and plumbing code or other applicable rules and regulations of the Town.

Section 7.  The Licensed Utility Installer, listed on the approved sewer connection permit, shall notify the Water and Sewer Departments, a minimum of 72 hours, before the building sewer will be ready for connection to the public sewer.  The Director will schedule the time and date to perform an inspection of the building sewer’s connection to the public sewer, connection shall be made only under the supervision of the Director or their representative.

Section 8.  All excavations for building sewer installation shall be adequately guarded with barricades and lights so as to protect the public from hazard.  Streets, sidewalks, parkways, and other public property and/or private property disturbed in the course of the work shall be restored in a manner satisfactory to the Director.

Section 9a.  Plumbers and private contractors, of established reputation and experience, who have paid the required filing fees, as stated in Section 13b, and have provided the required license and permit bonds, as stated in Section 13c, and have submitted a Certificate of Insurance with required coverage, as stated in Section 13d, may be approved by the Director as a Licensed Utility Installer (L.U.I.).

Applicants for licenses for installing sewer main and sewer services shall attend a training seminar on the installation of low-pressure pumps that is conducted by the manufacturer, and the applicant shall show evidence of course completion.

Note: The installation of grinder pumps may require other permits such as, but not limited to: electrical and plumbing.   

Section 9b.  Applicants for licenses as sewer main and sewer service installers (Licensed Utility Installer) are required to pay a filing fee.  As set by the Board (see rates and fees schedule).

Section 9c.  Applicants for licenses as sanitary sewer and building sewer installers (Licensed Utility Installer) shall obtain a License and Permit Bond in the amount of Five Thousand ($5,000.00) Dollars or an amount equal to 100% of the construction cost of any proposed sewer connection located within or on public property or an amount approved by the Director, whichever is greater.  Said license and permit bond shall remain in full force and effect for a period of one (1) year from date of acceptance by the Town of the L.U.I.’s last sewer connection.  This bond will guarantee that the Licensed Utility Installers (L.U.I.) will comply with the statutes, regulations, or ordinances of the Town of Harwich.  The license and permit bond shall be duly executed by the Principal of the L.U.I. and by a Surety Company qualified to do business under the laws of the Commonwealth of Massachusetts and satisfactory to the Director.                                   

Section 9d.  Before any Licensed Utility Installer performs any work in, on, under or around streets, sidewalks and property belonging to the Town of Harwich, it will be necessary to furnish, simultaneously with the submittal of the License and Permit Bond, a Certificate of Insurance showing that the contractor has the following coverage:

1.  General Liability -         $500,000                                Property Damage
                                          $500,000-$1,000,000             Bodily Injury

2.  Automotive Liability-     $500,000                                Property Damage
                                          $500,000-$1,000,000             Bodily Injury

3.  Workmen’s Compensation and Employer’s Liability as required under Massachusetts General Laws.

4.  Insurance shall include coverage for collapse of underground structures.

5.  Insurance shall include coverage for projects completed operations.

All above insurance coverage shall remain in full force and effect for a period of at least one (1) year from the date of acceptance by the Town of the last sewer connection installed by the L.U.I.   The L.U.I. shall take all responsibility for the work, and take all precaution for preventing injuries to persons and property in or about the work. 

Section 9e.  The L.U.I. shall pay all debts for labor and materials contracted for or by them on account of the work and shall assume the defense of and indemnify and save harmless the Town of Harwich and its Officers and Agents from all claims relating to labor and or alleged infringement of inventions, patents, or from injuries to any person or corporation caused by the acts of negligence of the L.U.I. any of its agents or employees, or any subcontractor, in doing the work or in consequence of any improper materials, implements, or labor used therein.

Section 9f.  Before the L.U.I.’s License and Permit Bond or any coverage listed in the L.U.I.’s Certificate of Insurance expires, the L.U.I.’s shall send a revised License and Permit Bond or Certificate of Insurance to the Water and Sewer Department showing that the bond or insurance coverage, is still in place.  The Licensed Utility Installer shall NOT perform any work in, on, under or around streets, sidewalks and property belonging to the Town of Harwich or any other public property if their License and Permit Bond or any coverage listed in their Certificate of Insurance has elapsed. 

Section 9g.  Approved Licensed Utility Installers will renew their Utility Installers Licenses by submitting a revised License and Permit Bond, Certificate of Insurance, and

License Fee by January 1st of each year.  All Utility Installers’ Licenses expire at Midnight, December 31st of each year.

Section 10.  All sanitary sewer extensions shall require inspection by a qualified inspector or the Director may determine that a building sewer installation or repair will require full time inspection by a qualified inspector.  In either case the Director will designate a private inspector as Town Inspector who shall represent the interest of the Town of Harwich during construction of any sanitary sewer extension or building sewer installation or repair, and will monitor and inspect the ongoing progress of the work, full-time observation is required.  The costs for the services performed by said Town Inspector shall be paid by the developer or owner, through the Water and Sewer Departments.  Flows will not be permitted to be discharged from any service connection until a Certificate of Compliance is submitted by the Town Inspector and the report is approved by the Director.

Section 11.  After the completion of any building sewer’s repairs or connection to the municipal sewer, the L.U.I. shall fill out a sewer connection tie card, on the forms provided at the Water and Sewer Departments’ office, for each building sewer the L.U.I. has performed work on.   The tie-card shall be completed before the inspection of the L.U.I.’s work, and before the L.U.I. backfills the building sewer and connection to the municipal sewer.

Section 12.  After completion and before the final inspection of any sanitary sewer connection or building sewer connection for residential dwellings with four (4) or more dwelling units, industrial connections, commercial connections with five (5) or more water closets, commercial connection with industrial water or waste,  connections of private sewer system or whenever the Director requires, the Licensed Utility Installer, developer or owner will furnish a reproducible digital “as-built” drawing (1” = 20’) in .PDF and .DWG format to the Director.  The as-built drawing(s) shall contain a plot plan(s) with building(s) and highway layouts, sewer layouts with profiles, force mains, force main gates, pump station(s), pump station(s) details, and descriptions of each building sewer showing the depth of all connections, pipes, and manholes, using buildings or other permanent markers as reference points.  The as-built drawing (s) shall contain any other information deemed necessary by the Director.

Section 13.  Alternative Sewer Collection Systems                                                                 

Sewer collection systems not stated in these Rules and Regulations of the Sewer Department shall only be permitted with the Director’s conditional approval.

Section 14.  Design Capacity and Design Flow

Design Factors

Design Period

Sewage collection systems shall be designed for a life span of 50 years, and interceptor sewers shall be designed to handle the maximum capacity of uses in the drainage area as determined by the Director.

Design Flow

Submit a detailed description of the procedures used for calculating sewer design flow to the Director.

The Massachusetts 310 CMR 15.000, the State Environmental Code, Title 5, shall be used for calculating the design flow for sewers.  If the Massachusetts 310 CMR 15.000, the State Environmental Code, Title 5, does not have a flow rate for the proposed use, the following methods may be used with the approval of the Director:

Flow Related to Water Consumption

When available, use existing sewage flow and/or consumption data as a basis for sewer design.  If such data are not available, using flow data from a similar community or users;                    

Per Capita Flow

Where actual flow data cannot be obtained, base residential flows from new collection systems on an average daily per capita flow of not less than 70 gallons per day (0.27 m3/day).  Add an appropriate allowance for infiltration to this flow;

In all cases, add a minimum allowance of 250-500 gpd/in. diam/mile of sewer (0.24-0.48 m3/cm of pipe diam/km/day) for infiltration to the water consumption, per capita flow or any other calculation method required by the Director.

Section 15.  Details of Gravity Sewer Pipe Design and Construction

Minimum Sewer Pipe Size

No gravity sewer shall be less than 8 inches in diameter (20 cm).

Depth

In general, sewers shall be deep enough to drain basement fixtures and to prevent freezing.   Water tight insulation shall be provided for sewers that cannot be placed deep enough to prevent freezing.  For house connections chimneys (vertical pipe) preformed block units shall be used when the sewer main is greater than or equal to 12 feet deep.

Buoyancy

Where high groundwater conditions are anticipated, the buoyancy of sewers shall be considered, and the floatation of pipe shall be prevented with appropriate design and construction of the sewer.

Slope

Minimum Slopes

All sewers shall be designed and constructed to give a velocity (when flowing full) of not less than 2.0 feet per second (0.61 m/s) based on Manning’s formula using an “n” value of 0.013.  The Director may permit the use of other “n” values if deemed justified on the basis of research or field data.  The following minimum slopes shall only be used if absolutely necessary because of grade restrictions; however, greater slopes are desirable.

Minimum Slope in Feet

Sewer Size

per 100 Feet (m/100m)

8 inches (203 mm)

0.4

10 inches (254 mm)

0.28

12 inches (305 mm)

0.22

14 inches (356 mm)

0.17

15 inches (381 mm)

0.15

16 inches (406 mm)

0.14

18 inches (457 mm)

0.12

21 inches (533 mm)

0.1

24 inches (610 mm)

0.08

27 inches (686 mm)

0.067

30 inches (762 mm)

0.058

36 inches (914 mm)

0.046

42 inches (1067 mm)

0.037

The use of oversized sewers in order to justify flatter slopes is not permitted.

Slope Between Manholes

Sewers shall be laid out with uniform slope between manholes.

High Velocity Protection

Velocities greater than 12 feet per second (3.7 m/s) shall not be permitted under any flow conditions, unless the Director approves special provisions that will protect against pipe erosion and impact.

Steep Slope Protection

Securely anchor sewers on 15 percent slopes, or greater, to prevent displacement.

Impervious Dams

Impervious dams shall be installed every 300 feet to control the flow of groundwater within the pipe bedding material, when:

Alignment

Sewers shall be laid out in a straight line and alignment, and shall be checked with a laser beam.

Sewer Pipe Material

Sewer pipe material shall be as specified in Appendix B, Construction Technical Specifications, Section 12.

Sewer Pipe Inspection and Testing

The specifications shall include deflection and leakage testing of sewer pipes, as stated in Appendix B, Construction Technical Specifications, Sections 17 and 18.

Section 16.  Details of Sewer Manhole and Cleanout Design and Construction

Manholes and cleanouts shall be as specified in Appendix B, Construction Technical Specifications, Section 13.

Manhole Inspection and Testing

The specifications shall include a requirement for the inspection and testing of manholes for leaks or damage as specified in Appendix B, Construction Technical Specifications, Section 21.

Section 17.  Inverted Siphons (Depressed Sewers)

Inverted siphons shall only be allowed if there is no other option and it is approved by the Director.  Depressed sewers shall have no less than two barrels with a minimum pipe size of 6 inches (15 cm) and shall be provided with necessary appurtenances for convenient flushing and maintenance.  Manholes shall have adequate clearances for cleaning equipment and for inspection and flushing.  The design shall provide for sufficient heads and pipe sizes to secure velocities of at least 3.0 feet per second (0.92 m/s) for average flows under initial conditions.  The inlet and outlet details shall be arranged so that the normal flow is diverted to one barrel and so that either barrel may be taken out of service for maintenance.  A hose connection shall be provided to the siphon for flushing purposes.

Section 18.  Aerial Crossings

Aerial crossings shall only be allowed if there is no other option, and it is approved by the Director.  All aerial crossings shall provide appropriate support for all joints and pipes used for aerial crossing.  The supports shall withstand frost heaves as well as overturning, settlement, flooding, thermal expansion, vibrations, and other loads that may act against the piping.  Precautions against freezing shall be provided (e.g., insulation and increased slope).  Expansion joints between above-ground and below-ground sewers shall be provided.  Where buried sewers change to aerial sewers, special construction techniques to minimize damage from frost heaves shall be used.  Ductile iron pipe with restrained mechanical joints are required.  The bottom of the pipe shall be no lower than one (1’) foot above the 100-year flood elevation level.

Section 19.  Location of Sewers in Streams

Sewers shall be designed to minimize the number of stream crossings.

Cover Depth

The top of all sewers entering or crossing a stream shall be sufficiently below the natural bottom of the stream bed to protect the sewer line.  The following cover requirements shall be met:

Horizontal Location

Sewers located along streams shall be located sufficiently outside of the stream bed to allow for stream widening in the future and for the prevention of siltation during construction.

Structures

Locate sewer manholes or other structures outside of streams whenever possible.  Where structures must be located in a stream, they shall not interfere with the free discharge of flood flows or navigation in the stream.  The manholes’ covers shall be no lower than one (1’) above the 100-year flood elevation level.

Alignment

Sewers shall cross streams perpendicular to the flow without a change in grade.

Materials

Sewers entering or crossing streams shall be watertight and free from changes in alignment or grade.  Joints shall be restrained in order to prevent movement from stream forces.  Ball-and-socket or restrained joints designed for hard service applications shall be provided.

Backfill materials shall be stone, coarse aggregate, washed gravel, or other materials that will not readily erode, cause siltation, damage pipe during backfill, or corrode the pipe and shall be approved by the Director.  In large stream crossings, where required by the Director, place riprap over the sewer pipe for stability and to prevent erosion.

Siltation and Erosion

The design engineer or L.U.I. shall include construction methods that will minimize siltation and erosion in the project specifications the construction methods for sewers in or near streams.  Such methods shall control siltation and erosion by limiting unnecessary excavation, including disturbing or uprooting of trees and vegetation, dumping of soil or debris, or pumping silt-laden water into the stream.  Specifications shall require cleanup, grading, planting, and restoration of all work areas to begin immediately.

Section 20.  Protection of Water Supplies

Cross Connections

No physical connection shall exist between a public or private potable water supply system and a sewer or any appurtenance that would permit the passage of wastewater or polluted water into the potable supply.  No sewer shall come into contact with a water pipe and no water pipe shall pass through any part of a sewer manhole or any part of the sewer system.

Relation to Water Works Structures

Sewers shall be located as far as possible from public water supply wells or other potable water supply sources and structures.                                                       

Engineering plans shall show all existing waterworks units, such as treatment facilities, basins, pipes, wells, or other waterworks units that are within 50 feet of the proposed sewer or to within the minimum distances required by the Director.

Water Mains’ Relation

Horizontal Separation

Whenever possible, lay out sewers at least 10 feet (3.0 m) from any existing or proposed water main.  If local conditions prevent a lateral Separation of 10 feet, the Director may make an exception on a case-by-case basis when supported by data from the design engineer.  Such an exception may allow the sewer to be installed closer than 10 feet to a water main, provided that it is laid out in a separate trench with the top (crown) of the sewer at least 18 inches (46 cm) below the bottom (invert) of the water main or is encased in a water tight sleeve.

Vertical Separation

Whenever sewers must cross water mains, lay out the sewer so that the top of the sewer is at least 18 inches (46 cm) below the bottom of the water main.  The sewer joints should be equidistant and located as far away as possible from the water main joints.  When the sewer cannot meet the above requirements, relocate the water main to provide for this separation or reconstruct it with mechanical-joint pipe for a distance of 10 feet (3.0 m) on each side of the sewer.  One full-length (twenty feet) water main pipe shall be centered over the sewer so that both joints will be as far from the sewer as possible.

Where a water main crosses under a sewer, adequate structural support shall be provided for the sewer to maintain line and grade. 

When it is impossible to achieve horizontal and/or vertical separation as stipulated above, both the water main and sewer shall be constructed of mechanical-joint cement-lined ductile iron pipe or another equivalent that is watertight and structurally sound.  Both pipes shall be pressure tested to 150 psi to ensure that they are watertight, and one of the pipes shall be installed in a water tight sleeve for a horizontal perpendicular distance of 10 feet (3.0) on each side of the other pipe.  Any joints in the watertight sleeve shall be as far as possible from the water main’s intersection with the sewer.                                        

Section 21.  Details of Low-Pressure Sewer Design and Construction

Layout:  The branched configuration of a pressure sewer is required.  Looped piping shall not be permitted.  Pipe routing shall include long radius sweeps no less than those recommended by the pipe manufacturer. 

Pressure pipes shall be designed and installed so that a minimum of five (5) feet of cover material exists over the crown of the pipe at all times. Appurtenances such as isolation valves, air release valves, and clean-outs shall be provided as required by the Director.

Pipe Size:  The diameter of the pressure sewer shall be calculated so that it provides a cleansing velocity based on the average daily flow of the system.  Force Mains shall have a minimum velocity of three feet per second, 3ft/sec.

Minimum low-pressure sewer pipe sizes shall be as follows (unless there is a significant change in grade):

Number of Homes

Minimum

or Equivalent

Pipe Size

1-3

1.5

4-9

2

10-18

2.5

19-30

3 (Model recommended)

>30

Must be modeled

 

Isolation Valves

Isolation valves shall be required to allow isolation of individual girder units, system expansion, and at key locations such as at the property line.

Ball valves for low pressure sewer manholes shall be true union type constructed from PVC Type I cell CLASSIFICATION WITH EPDM O-RINGS.  All valve components shall be replaceable.  Ball valves 2 inches and smaller shall be pressure rated to 235 psi, while valves larger than 2 inches shall be rated to 150 psi.  Ball valves shall have a Safe-T-Block seal carrier to stop flow in either direction, allowing safe removal of the downstream union nut for system service or modification.  Ball valve ends shall be as needed to connect to Schedule 430 PVC pipe in low pressure sewer manholes.  Ball valves shall be true union ball valves as manufactured by Spears Manufacturing.

Curb Stop Valve

Curb stop valves shall be located at the property line of the street or easement of the sewer main.  Curb stop valves shall be of brass or bronze construction and two rubberized O-ring seals to provide pressure-tight seal.  Curb stop valves shall be figure H-15204 as manufactured by Mueller-Oriseal, B22 as manufactured by Ford Meter Box Company, Hayes, Nuseal, or equal.  Curb boxes shall be 2-1/2-inch shaft size two-piece screw type.  They shall be adjustable from 48-inch to 72-inch.  Curb boxes shall be constructed of cast iron and thoroughly coated with two coats of asphaltum varnish.  Curb box rods shall be stainless steel supplied with a hole in the “U” portion for the insertion of a stainless-steel pin.  Pins shall be supplied and shall be made of stainless steel.  Curb boxes shall be as manufactured by Ford Meter Box Company, Mueller Company, or equal.

Air Release Valves

Air and vacuum valves shall be installed on low pressure mains.  The air and vacuum valves shall be designed to release air from the main when the main is being filled and/or air becomes entrapped in the main, and to admit air into the sewer main when pumps are stopped and the main is being drained by gravity.  The body and cover of air and vacuum valve shall be cast iron, floats of stainless steel, protective hood of steel, seats of Buna-N, and miscellaneous internal parts of stainless steel, Manufacturer-Crispin, or equal.  Air and vacuum valves shall be located in a manhole or structure with a diameter of 60 inches to allow access for repairs and maintenance.

Cleanout Connections

Cleanouts shall be installed on the pressure mains at sags and other locations where debris can accumulate and clog the lines, and proper valving to conduct required maintenance shall be provided.

Miscellaneous

Magnetic marking tape two (2) inches wide with the words “SANITARY SEWER BELOW,” shall be installed not more than 2 feet below finished grade on all mainline and service laterals.

Section 22.  Force Mains

Minimum Size

Force mains shall have a minimum velocity of three feet per second, 3ft/sec.

Force Main Pipe Material

Force main pipe material shall be as specified in Appendix B, Construction Technical Specification, Section 14.

Velocity

At design average flow, velocity in excess of 3 feet per second (0.91m/s) shall be maintained.

When the daily average design detention time, in the force main, exceeds 20 minutes, the manhole and sewer line receiving the force main discharge or the sewage shall be treated so that corrosion of the manhole and the exiting line are prevented.  The corrosion is caused by sulfuric acid biochemically produced from hydrogen sulfide anaerobically produced in the force main.            

Variable Terrain

As far as possible, the alignment and depth of a force main should provide a constant upgrade profile.  All force mains shall be designed and installed so that a minimum of five (5’) feet of cover material is over the crown (top) of the pipe at all times.

Air Relief Valve

An automatic air relief valve shall be placed at all relative high points in the force main and at 400 feet intervals on level force main runs.   All air relief valves shall be protected from freezing.

Drain Valves

Drain valves at all relative low points in the force main shall be provided.  These valves shall be connected to gravity sewers or provided with connections for vacuum pumper trucks.   All drain valves shall be protected from freezing.

Termination

Force mains shall enter the gravity sewer at a point not more than 2 feet (0.61 m) above the flow line of the receiving manhole.

Testing

Leakage Testing shall be as specified in Appendix B, Construction Technical Specifications, Sections 17 and 18.

Section 23.  Grinder Pump Systems

Pumping equipment shall include an integral grinder capable of handling a reasonable quantity of foreign objects that may find their way into a building’s sewerage system.  The grinder pump shall be capable of processing foreign objects without jamming, stalling, or overloading, and without making undue noise.  The grinder shall provide a positive flow of solids into the grinding zone.  Grinder pump stations shall be of the wetwell type.

A list of suitable manufacturers will be available from the Director.  Properties whose sewage quantities and characteristics are equivalent to four or more dwelling units shall install a duplex pump.

Design of Pump Station

Access:  Outside installation shall be designed with the service manhole constructed of the same material, and at least as thick as the tank.  The manhole shall have an opening at the surface with a minimum inside diameter of 30 inches (76 cm); its cover shall be securely lockable.  The size of the manhole shall allow for the performance of maintenance and repair functions.

Tank

Construct each tank of concrete or custom-molded, fiberglass reinforced polyester resin using a filament wound process, layup and spray technique, or other approved process that will ensure a smooth and resin rich interior surface that is designed for two times the maximum loading.

The basin shall be concrete, fiberglass-reinforced polyester resin, or other material meeting the minimum strength specifications herein. The basin shall be furnished with one PVC closet flange or one flexible inlet flange suitable for connection to the household gravity line.  At a minimum, the basin wall and bottom shall withstand two times the anticipated maximum pressure exerted on the basin, either from soil loadings or buoyancy forces.  All station components must function normally when exposed to these loadings.  All seals and joints shall pass factory tests to ensure that they are water tight.

Electrical Equipment

Wiring and electrical connections shall be NEMA rated for the environment in which they are to be placed.  System shall include an emergency generator plug-in connection.

Pumps

Pump Removal

The grinder pump shall be readily removable without the need for manual disconnection of piping.

Grinder

The grinder shall be positioned immediately below the pumping elements, securely fastened to the pump motor shaft, and driven directly by the same motor.  The grinder shall be a rotating type with a stationary hardened and ground stainless steel shredding ring that carries stainless steel cutter bars.  This assembly shall be dynamically balanced and run without objectionable noises or vibrations over the entire range of recommended operating pressures.

Pump Opening

The grinder shall be capable of reducing all components in normal domestic sewage or the sewage to be discharged from the building drain, including a reasonable amount of foreign objects (e.g., paper, wood, plastic, glass, and rubber).  Objects shall be reduced to finely divided particles that will pass through the passages of the pump and a minimum 1.25-inch (3.2 cm) diameter discharging pipe.

Intake

The grinder shall be positioned so that solids are fed into it from the bottom in an upward flow, reducing the possibility of overloading or jamming.  In addition, sufficient turbulence shall be created to keep the tank bottom free of permanent deposits or sludge banks.

Check Valve

The grinder pump shall be equipped with a check valve that is installed in a horizontal position on the discharge pipe.  This valve shall provide a full- ported passageway when open.

Ventilation

Adequate ventilation shall be provided in accordance with local and national codes.

Controls

Sensing devices to detect wastewater levels for initiating pump operation and to detect high water levels shall be installed.  Level sensing devices shall only be used and shall not be located near flows entering the well.                       

Section 24.  Pumping Station

Design Capacity

A sewage pumping station shall handle the projected peak sewage flows of its tributary sewer collection system.  As recommended by TR-16, Guides for the Design of Wastewater Treatment Works (Technical Report #16) and the Hydraulic Institute’s Recommended Standards for Pumping Stations. This information may be included in the Comprehensive Management Plan or other engineering report and any applicable updates or amendments.  Pumping stations shall accommodate future expansion, when in the opinion of the Director it is appropriate.

Site Layout

Stations shall be readily accessible to personnel and service vehicles during all weather conditions.

Flood Protection

Wastewater pumping stations shall be protected from physical damage by the 100-year flood elevation and shall remain fully operational and accessible during the 100-year flood.  All entrances and/or unsealable openings of the station shall be a minimum of one (1’) foot above the 100-year flood elevation.  These flood elevations shall be determined from the Federal Emergency Management Agency, and U.S. Army Corps of Engineers, and from the local regulations and ordinances.

Environmental Considerations

Wastewater pumping stations shall be sensitive to the environmental conditions of the site.  Visual impacts, architectural style, security, noise levels, odor control, and landscaping shall be considered carefully in station design and shall be reviewed and approved by the Director.

Types of Stations

Wastewater pumping stations fall into three categories: wetwell/drywell, submersible, or suction lift.  The preferred type of station is the Suction Lift type.  The Director may approve other types under certain circumstances.

Structural Design        

Earthquake Loads and Uplift Forces

Stations shall withstand earthquake loads and uplift forces from high groundwater conditions.

Separation

Wet and drywells, including their superstructure, shall be completely separated.  Common walls shall be sealed against gas leaks.

Equipment Removal

Provisions shall be made for removing all equipment (i.e., pumps, motors, mechanical screens, motor control centers, etc.) from the station.  Access openings, hatches, and/or skylights shall be sized accordingly.  Permanent hoisting devices shall be provided as necessary.

Substructure

Station substructures shall be constructed of reinforced concrete, either cast-in-place or precast.  Small, prefabricated stations may be constructed of steel plate or fiberglass with the approval of the Director.                                    

Access

The designer shall minimize the confined spaces and shall indicate which spaces meet the definition of confined space on the drawings.  Suitable, safe, and separate means of access shall be provided for dry and wetwells.  Stairways and/or steps are required for drywells and wetwells containing either bar screens or mechanical equipment that requires inspection or maintenance.  A landing with railings shall be provided for stairways or ladders for every 10 vertical feet.  Local, state and federal safety codes shall govern in all cases.

Pumps

Number of Pumps

As a minimum, two pumps shall be provided, with each pump being capable of handling peak design flows.  Where three or more pumps are provided, the overall station capacity shall be capable of handling peak design flow when any one pump is out of service.

Design

Pumps shall be designed specifically for wastewater use and shall be non-clogging and as allowed by the Director. 

Incoming Wastewater and Rate Discharge

Pumping stations shall balance the rate of incoming wastewater with the rate discharged.

Each pump shall have an individual intake valve.

Pump suction and discharge openings shall be a minimum of 4 inches in diameter.

Centrifugal Pumps

Centrifugal pumps shall be used in the drywell/wetwell pumping stations.  The pump casing and suction elbow shall be provided with a clean-out access port.  Impellers shall be enclosed or semi-open.  To ensure primed pump conditions, the wetwell level shall not drop below the centerline of the pump impeller under normal operating conditions.

Submersible Pumps

Submersible pumping stations may be used when, in the opinion of the Director, circumstances warrant.  It shall be possible to remove and replace the submersible pumps without dewatering the wetwell or disconnecting the piping.  Pumps shall be of the pull-up design, using a lifting cable and guides for pump removal.  The pump shall be connected to the fixed discharge piping with a self-locking coupling.  Shaft seal failure or potential seal failure detection alarms shall be provided.  Submersible pumps may also be used in a wetwell/drywell configuration, with the Director’s approval.

Suction Lift Pumps

Suction pumps shall be self- or vacuum-priming.

Location:  The pump equipment compartment shall be above grade or offset, and shall be isolated from the wetwell to prevent humid and corrosive sewer atmospheres form entering the equipment compartment.  Access to the wetwell shall not be located in the equipment compartment.  Valves shall not be located in the wetwell.

Self-priming Pumps

Self –priming pumps shall be capable of rapid priming at the lead pump-on elevation.  Such self-priming and repriming shall be accomplished automatically under design operating conditions.  Suction piping shall not exceed the size of the pump suction and shall not exceed 25 feet (7.6 meters) in total length.  Priming lift at the lead pump on elevation shall include a safety factor of at least 4 feet (1.2 meters) from the maximum allowable priming lift for the specific equipment at design operating conditions.  The combined total of dynamic suction lift at the pump-off elevation and required net positive suction head at design operating conditions shall not exceed 22 feet (6.7meters).

Vacuum-priming Pumps

Vacuum-priming pump stations shall be equipped with dual vacuum pumps capable of automatically removing all air from the suction lift pump.  The vacuum pumps shall be adequately protected from sewage damage.  The combined total of dynamic suction lift at

the pump-off elevation and required net positive suction head at design operating conditions shall not exceed 22 feet (6.7 meters).

Wetwells

Divided Wells

The wetwell shall be divided into two sections that are properly interconnected and gated to facilitate repair and cleaning.

Storage Capacity

The effective storage capacity of the wetwell shall be based upon the recommended number of pump starts per hour and the design filling time.  The effective volume of the wetwell shall be based on a filling time of 30 minutes under design average-daily-flow rates.  To determine the frequency of starts used for design, refer to the pump manufacturer’s warranty.

Where tributary wastewater flows are anticipated to be significantly less than the design average flow, provisions should be made so that the filling time under initial conditions does not exceed 30 minutes (i.e., providing a divided wetwell or shortening the wetwell operation range) and the duration of storage in the pump station and force main does not result in septic conditions in the system or the release of objectionable odors to the environment.                              

Pump Protection

Pumps shall be protected from large solids by readily accessible mechanically cleaned bar racks (screen) or combination device located at the wetwell influent.  Bar racks should have clear opening not exceeding 1.25 inches (3.1 cm) unless pneumatic ejectors are used or special devices are installed to protect the pumps from clogging or damage.

Floor Slope

The wetwell floor shall have a minimum slope of 1-to-1 to the hopper bottom.  The horizontal area of the hopper bottom shall be no greater than is needed for proper installation and function of the wetwell inlet.

Vortexes

The wetwell and suction inlets of dry-pit pumps shall eliminate the possibility of vortexes.  The required submergence of the intake valves shall be determined for the day-pit pump’s location.  Intake valves should be flared, with the inlet opening facing down.  Every effort shall be made to minimize flow rotation in the wetwell.

Sewage Channels

Sewage channels located in wetwells shall be covered with nonskid, corrosion-resistant grating.  They shall be installed flush with a floor, and capable of supporting anticipated loads.  All channels shall be drained when not in use.  Where the side meets the floor of the channel, fillets shall be provided.

Inlet Sewers

Sewer piping entering the wetwell shall not have air in the pump suction line.

Drywells

Automatic heating and dehumidification equipment shall be provided in all drywells.  The electrical requirements shall meet those outlined in subsequent paragraphs of this section.                                                        

A sump pump shall be provided in the drywell to remove extraneous water.  The discharge pipe of the sump pump shall be equipped with dual check valves and shall be pumped from the drywell into the wetwell above the high-water level.  Water ejectors connected to a potable water supply shall not be permitted.  All floor and walkway surfaces shall slope to a point of drainage.  Pump seal leakage shall be piped or channeled directly to the sump.

Valves

Suitable shutoff valves shall be placed on the suction lines and on the discharge lines of each pump (except on submersible and vacuum-primed pumps).  A suitable check valve shall be placed on a horizontal section of each discharge line between the shutoff valve and the pump.

Unless adequate space is available in a dry pit pump room, valves on the discharge piping (including flow meters, if required) shall be in a separate underground precast concrete vault.;

Every pump station shall include appropriate valves and quick disconnects to allow the Town to bypass the existing pumping equipment and valves.  The piping shall allow the Town to install temporary piping into the wet well, and discharge to a location downstream of the check and shutoff valves.

Valves shall not be located in wetwells.

Section 24. Controls

All pump stations, grinder pump stations, vacuum sewer stations, and other sewer handling facilities required by the Director shall be connected to the Water and Sewer Departments’ Supervisory Control and Data Acquisition (SCADA) System.

All sensing, alarm, and SCADA system devices shall be of the same type, configuration, and function as that used by the Water and Sewer Departments.  Each pumping station shall have its own screen display, processor logic controller (PLC), and communications equipment for the SCADA system and shall also display the required monitoring controls and alarm on the all SCADA system screens of the water and/or sewer systems.

Level Sensing Devices

Level sensing devices shall not be affected by flows entering the wetwell or by the suction of the pumps.  All wall penetrations between the wet and drywells shall withstand gas leaks and be located as high as possible to prevent overflow from the wetwell to the drywell.  The pumps shall be automatically alternated.  Running-time meters shall be installed at all pumping stations for each pump.                                                          

Alarm Systems

Alarm systems shall be provided for all pumping stations.  At a minimum, the alarm system shall be activated in any one of the following cases:                                              

Section 26.  Pump Station Ventilation

General

Adequate ventilation shall be provided for all pumping stations.  Where the pump pit is below the ground surface, mechanical ventilation is required, especially when screens or mechanical equipment requiring maintenance or inspection are located in the wetwell.  The wet and dry well ventilation systems shall not be connected.  In pits more than 15 feet (4.6 m) deep, multiple inlets and outlets shall be installed.  Switches for the operation of ventilation equipment shall be marked and located conveniently.  If odors are a problem, an odor control system shall be installed.

Wetwells

Ventilation may be either continuous or intermittent.  For continuous ventilation, at least 12 air changes per hour shall be provided.  For intermittent ventilation, at least 30 air changed per hour shall be provided.  Heating shall be installed where needed.

Drywells

Ventilation shall be continuous. Heating and dehumidification are required.  At least 6 complete air changes per hour shall be provided.

Section 27.  Flow Measurement

Suitable devices, as approved by the director, for measuring wastewater flow and power consumption shall be installed in all pump stations.

Section 28.  Pump Station Water Supply

Water under pressure shall be provided for cleanup at the pumping station.   If a public water supply is used, a Reduced Pressure Zone (RPZ) backflow preventer or other approved device shall be installed on the water service entering the station.  No other potable water supply and other piping systems or fixtures shall be connected to the systems supplied by the public water supply.

Section 29.  Electrical

Electric Equipment

Electrical systems shall be designed and installed in strict conformance with the latest edition of the National Electrical Code.  Electrical equipment in enclosed places where gas may accumulate shall be noncorrosive and in compliance with the National Electrical Code requirements for Class I Group D, Division I locations.         

Submersible Pump Motors

Electrical supply and control circuits shall allow disconnection at a junction box located at or accessible from outside the wetwell.  Terminals and connectors shall have watertight seals located outside of the wetwell and shall be protected by separate strain relief.

The motor control center shall be located outside of the wetwell and protected by a conduit seal or other appropriate sealing method meeting the requirements of the National Electrical Code for Class 1. Division 2 locations.

The pump motor shall meet the requirements or the National Electrical Code for Class 1. Division 2 locations.

Submersible pump motors that are totally submerged during the pumping cycle are not required to protect against explosions.

Power cords for pump motor shall be flexible and serviceable under conditions of extra hard use.  Ground fault interruption protection shall deenergize the circuit in the event of any failure in the electrical integrity of the cable.

Power cord terminal fittings shall be provided with strain relief appurtenances, and shall facilitate field connecting.

Section 30.  Emergency Operations

When the Director deems it is necessary, an independent natural gas or propane engine-generator type source of electric power shall be provided for electrically driven pumps.  This source shall be automatically activated when or if any pha