SECTION 7.00
SANITARY SEWER
1. Main Location
a. All public sanitary sewer mains shall be installed in dedicated street right of way or in dedicated utility easements. Mains installed in Town right of way shall be located in the center of pavement. Mains within easements shall be centered within the easement. Mains located within NCDOT right of way shall be placed in accordance with NCDOT standards.
b. Gravity mains shall be installed in dedicated public right of way or in dedicated utility easements as follows:
Pipe Size |
Pipe Depth |
Easement Width |
12" and less |
Less than 20’ |
20’ |
12" and less |
Greater than 20’ |
30’ |
Greater than 12", up to 24" |
Less than 20’ |
30’ |
Greater than 12", up to 24" |
Greater than 20’ |
40’ |
Greater than 24" |
All depths |
Town Engineer Specified |
c. Mains paralleling a creek shall be of sufficient depth to allow lateral connections below the stream bed elevation. The top of the sewer main and laterals shall be at least one foot below the stream bed. Concrete encasement and ductile iron pipe shall be required when the cover between the top of the pipe and the stream bed is less than 3 feet.
d. Mains shall not be installed under any part of water impoundments.
e. The following minimum horizontal separations must be maintained:
i. 100 feet from any private or public water supply source, including WS-1 waters or Class I or Class II impounded reservoirs used as a source of drinking water (except as noted below)
ii. 50 feet from any waters (from normal high water) classified WS-II, WS-III, B, SA, ORW, HQW or SB (except as noted below)
iii. 10 feet from any other stream, lake, or impoundment (except as noted below)
iv. 25 feet from private wells (with no exceptions)
v. 50 feet from sources of public water supply (with no exceptions)
Where the required minimum separations cannot be obtained , ferrous sanitary sewer pipe with joints equivalent to water main standards must be used.
f. In accordance with Policy Statement Number 23, mains must be extended along natural drainage courses to the adjacent property line.
g. Mains shall be deep enough to serve the adjoining property and allow for sufficient slope in lateral lines, and shall have the following minimum covers. These requirements may be waived at the direction of the Town Engineer, in which case ductile iron pipe shall be installed.
- 4 feet from the top of pipe to finished subgrade in roadways.
- 3 feet from the top of pipe to finished grade outside roadways.
h. Mains over 20 feet deep require ductile iron or reinforced concrete pipe for the entire run between manholes.
i. Mains shall have a minimum vertical separation of 12 inches between storm pipe when the horizontal separation is 3 feet or less. Where sanitary and storm sewers cross with a vertical separation of less than 12 inches the entire leg of sanitary sewer shall be of water main standard ductile iron pipe.
j. There shall be a minimum 5 foot horizontal separation between parallel gravity and/or force mains.
k. Mains shall have a minimum horizontal separation of 10 feet from water lines, unless the top of the sewer main is at least 18 inches below the bottom of the water main and there is a horizontal separation of at least 3 feet from the closest edges of the pipes.
l. Where sewer mains cross beneath water mains with a vertical separation of 18 inches or less, or where water mains cross under sewer mains, the entire leg of sewer main shall be ductile iron pipe. The water line pipe shall be centered at the point of crossing, which shall be at an approximate 90 degree angle.
2. Main Size
a. Public gravity mains shall be a minimum of 8 inches diameter.
b. Major interceptors shall be sized in accordance with the "Master Wastewater Plan of the Town of Cary". In areas not included in the master plan, interceptors shall be designed based on the proposed land use (according to the Town's Comprehensive Growth Plan), using the following flow factors:
Land Use
Flow Factor
Residential 120 gpd/bedroom Office and Institutional 0.09 gpd/sq. ft bldg. space Commercial 0.12 gpd/sq. ft bldg. space Industrial 0.20 gpd/sq. ft bldg. space Flow factors not listed shall be as recommended by NCDEM.
c. The ratio of peak to average daily flow shall be 3.3.
d. Sanitary sewers shall be designed to carry the projected peak flow at no more than 2/3 full. The recommended minimum velocity for sanitary sewer lines is 3 fps, which may be reduced to 2.5 fps with approval from the Town Engineer.
e. The minimum grades for public sanitary sewers shall be as follows:
Main Size (in.) |
Minimum Slope |
| 8 | 0.40 |
| 10 | 0.28 |
| 12 | 0.22 |
| 14 | 0.17 |
| 15 | 0.15 |
| 16 | 0.14 |
| 18 | 0.12 |
| 21 | 0.10 |
| 24 | 0.08 |
| 27 | 0.07 |
| 30 | 0.06 |
The minimum slope for the uppermost reach of a sanitary sewer line shall be 1% regardless of sewer line size.
f. The maximum grade for sanitary sewers is l0%. The maximum velocity in sanitary sewers is 15 ft/sec. These limits may be exceeded with the approval of the Town Engineer and the incorporation of the following provisions:
i. All sewers of greater than 10% slope and the downstream run of pipe must be ductile iron pipe.
ii. High velocity manholes shall be used on all sewers with a slope greater than 10%. High velocity lines cannot tie directly to an existing line and must proceed 180o through the invert into the downstream line.
iii. Concrete anchors shall be installed on all sewers of greater than 10% slope at the following spacing:
· Not over 36' center to center on grades from 10% to 25%
· Not over 24' center to center on grades from 25% to 40%
· Not over 16' center to center on grades exceeding 40%
g. Sewer extensions should be designed for projected flows, even when the diameter of the receiving sewer is less than the diameter of the proposed extension.
h. Pipe diameter changes shall occur in manholes, with the invert of the larger pipe lowered sufficiently to maintain the same energy gradient. An approximate method of obtaining this result is to place the 0.8 depth point of both sewers at the same elevation.
3. Manhole Location
a. Manholes shall be spaced at a maximum distance of 400 feet for lines 12 inches in diameter or less, and 500 feet for lines greater than 12 inches.
b. Manholes shall be installed at each deflection of line and/or grade. The flow channel through manholes should be smooth and shall conform to the shape and slope of the entering/exiting sewer line. Either pre-cast or brick and mortar inverts may be used. Moorbase manholes shall not be used. Inside or outside drops shall be used when free drops exceed 30 inches. For inside drop manholes, the last joint of incoming sewer main shall be ductile iron. This is the only case where transition of pipe material between manholes is acceptable, and it requires a Fernco coupling encased in concrete.
c. Manholes not located in roadways and landscape areas shall have a top elevation a minimum of 12 inches above finished grade. Manholes higher than 30" above finished grade will require outside steps. Manholes shall not be obstructed from view or access.
d. Manhole tops shall be elevated above the 100 year flood plain elevation or shall be equipped with vents and watertight frames and covers.
4. Manhole Sizing
a. Manholes for pipes under 21 inches in diameter shall be a minimum of 4 feet in diameter. Manholes for sewers 21 inches in diameter or greater shall be 5 feet in diameter.
b. Inside drops require a minimum 5 foot diameter manhole. When 2 or more inside drops occur at one manhole, a minimum 6 foot diameter manhole shall be used.
Materials specified herein are acceptable for sewer service as described herein.
See Section 2.02 for instructions on requesting new product approval.1. Pipe Material
a. VITRIFIED CLAY PIPE
Vitrified clay pipe shall only be used as approved by the Town Engineer.
b. CONCRETE PIPE AND REINFORCED CONCRETE PIPE
Concrete pipe shall be in accordance with ASTM C14 and reinforced concrete pipe shall be in accordance with ASTM C76, Table III or Table IV. Pipe joints and joint materials shall be in accordance with ASTM C361.
ALL CONCRETE PIPE SHALL BE EPOXY LINED in accordance with the following:
- All interior barrel and joint surfaces which will be exposed to the sewer liquids and gases shall be prepared for lining by removing all laitance, form oil and other loose, foreign or deleterious materials which would affect the bond of the lining compound to the pipe surface. Surface preparation shall consist of sandblasting and cleaning the barrel of the pipe and the joint surface areas on which coating will be applied.
- The pipe surfaces to be lined shall be blown off with air to remove all sand, dust, and other loose materials immediately prior to application.
- The lining compound shall not be applied when the ambient temperature is below 40oF or the substrate shows over a 14% moisture reading. The compound shall not be applied under adverse atmospheric conditions that will cause detrimental blistering, pinholing, or porosity of the film.
- All application equipment shall be as recommended by the supplier of the lining compound, and shall consist of the following:
i) An airless spray system that optimizes and controls centrifuge forces in a high speed distributor unit, which with multiple pass applications along longitudinal axis of the pipe, provides a uniform lining without localized build-up, lumping, or sagging.
ii) Airless spray equipment or brush shall be utilized to coat the joint surfaces up to the gasket area. All equipment used shall be maintained in good working condition throughout the work.
- The lining compound shall be thoroughly mixed according to the recommendations of the supplier. The lining compound shall be applied to all barrel surface areas which will be exposed to the sewer liquids and gases. The first coat (or prime coat) shall consist of four to six mils minimum dry film thickness and the finish coat shall be applied as required to yield a total minimum dry film thickness of 24 mils for the complete system. A coat of lining material shall be applied using an airless spray system to the joint surfaces which shall be exposed to the sewer liquids and gases. The coat shall consist of a minimum dry film thickness of 10 mils.
- When application is commenced, the complete operation shall be completed as soon as practical, without prolonged delays. After application, the pipe and pipe surfaces shall be protected from damage or contamination by water, excessive dust, or other contaminants until tack free. Linings shall be permitted as long a drying time as practical but at least until the final coat has dried 5 days. Minimum drying periods may be increased substantially if the drying temperature is below 65oF.
- All interior barrel surface and lined joint surface areas shall be thoroughly inspected for holidays, utilizing an electrical instrument especially designed for the purpose. The output voltage and sensitivity of the instrument shall be adjustable for the pipe moisture content and other test conditions. Each day that such test work is performed the instrument shall be tested by finding a known holiday made in the lining. All detected holidays shall be marked for easy location and patching.
- All damaged areas, holidays, thickness test areas and cored areas shall be repaired in accordance with the manufacturer's recommendations, so the repaired area is equal to the undamaged lined areas in all respects. Any damage which does occur during shipping or handling shall be repaired prior to the installation of the pipe in accordance with the manufacturer's recommendations, so the repaired area is equal to the undamaged lining in all respects.
c. A.B.S. COMPOSITE (TRUSS) PIPE
A.B.S. Composite pipe shall be in accordance with ASTM D 2680. Pipe joints shall be chemically welded or gasket joints in accordance with ASTM D 3212
d. DUCTILE IRON PIPE
Ductile Iron Pipe shall be designed and manufactured in accordance with AWWA C150 and C151 for a laying condition Type 2 and a working pressure as follows:
3" - 12" 350 psi 14" - 20" 250 psi 24" 200 psi 30" - 54" 150 psi Pipe joints shall be of the push-on type as per AWWA C111. Pipe lining shall be cement mortar with a seal coat of bituminous material, all in accordance with AWWA C104.
All buried DIP and fittings shall have bituminous coating on the exterior surface in accordance with AWWA C151.
Pipe shall be supplied in minimum 18 foot lengths unless approved otherwise by the Department of Development Services.
e. POLYVINYL CHLORIDE (PVC) PIPE
PVC Pipe shall be made of PVC plastic having a cell classification of 12454-B, 12454-C or 13364-B (with minimum tensile modulus of 500,000 psi) as defined in Specification D1784. PVC pipe shall have integral wall bell and spigot joints for the conveyance of domestic sewage. Fittings shall be made of PVC plastic having a cell classification of 12454-B, 12454-C or 13343-C as defined in ASTM D 1784. Fittings must be manufactured by pipe supplier or approved equal, and have bell and/or spigot configurations compatible with that of the pipe. Compounds with superior properties are also acceptable.
All pipe less than 18 inches in diameter shall have a maximum Standard Dimension Ratio (SDR) of 35. Where laying conditions so warrant, and in accordance with manufacturer's recommendations, lower SDR values (stronger pipe) may be required.
PVC pipe 18 inches in diameter and larger must be spiral wound as defined in ASTM F-794, Series 46. Pipe strength shall be equal to or exceed that required for pipe less than 18 inches in diameter.
f. PVC COMPOSITE (TRUSS) PIPE
PVC thermoplastic material shall be a rigid PVC plastic conforming to ASTM D-1784 for a minimum cell class of 12454-B. The Portland Cement Perlite concrete or other inert filler material shall be as described in Section 6.3 of ASTM D-2680.
Joints shall be chemically welded or gasket in accordance with ASTM D-3212. Solvent cement for joining PVC to PVC shall comply with ASTM D-2564. Pipe test specimens shall meet all the manufacturing requirements established in ASTM D-2680.
All recommendations of the manufacturer shall be followed in shipping, handling, laying, joining and backfilling of the pipe, and the pipe shall be installed in full and complete compliance with Recommended Practice D-2321.
2. Material Identification
Each length of pipe shall have plainly and permanently marked thereon the following information, as well as any additional information specifically noted in the sections below:
a. Pipe class or strength designation
b. Manufacturer's name or trademark
c. Nominal pipe size
d. Green detector tape, 3 inches in width and clearly labeled "Sanitary Sewer" shall be 18" above all PVC and ductile iron pipe force mains.
3. Manhole Materials
Manholes shall be precast concrete. All manholes shall have eccentric cone sections. Precast concrete manholes shall meet ASTM C478 as to design and manufacture. The standard joint shall be sealed with a plastic cement putty meeting Federal Specification SS-S-00210, such as Ram-Nek or a butyl rubber sealant. All lift holes must be plugged with non shrinking grout after installation.
All manholes shall have 6 inch, 3000 psi concrete bottoms resting on a minimum of 6 inches of # 57 stone. Sewer mains shall enter and exit radially through the manhole. Inverts shall be constructed with a width and height equal to 1/2 that of the effluent pipe and shall be so finished that a minimum energy loss occurs in the manhole. At each inlet and outlet of 8 inches or greater, compression connectors (flexible sleeves) shall be cast into the manhole section. Flexible connectors are to be manufactured of high quality rubber or synthetic rubber and all strap clamps or draw bolts shall be stainless steel. Boots are to meet standards of ASTM C923. Rings and clamps are to meet standards of ASTM A167 and/or ASTM C923. Manholes located outside areas of the 100-year floodplain or high groundwater shall be treated through either coating, wrapping or some other approved method to prevent weepage or attack by acidic soils.
4. Manhole Frame and Cover Materials
a. Manhole Frames and Covers shall be cast or ductile iron with "Sanitary Sewer" stamped on the cover as indicated in the details. Ring and cover shall be stamped with make and model.
For installation in roadways, use Type 1 ring and cover and place sufficient depth concrete below the pavement around the ring to insure contact with manhole. For installation in unpaved areas, use Type 2 ring and cover. Use Type 3 ring and cover for installation necessitating watertight requirements, locking covers shall be required on outfall locations
b. Castings shall be machined to give even and continuous bearing on the full length of the frame. Castings shall be free of porosity and blow holes. Manhole frames shall be bolted to the manhole. All manhole rings in roadways shall be encased in a concrete collar of 3000 psi concrete beneath the asphalt, with the cover flush with the top of pavement.
c. Watertight manhole frames and covers shall have neoprene gasket and machined bearing surfaces. Bolts shall be standard hexagonal-head, countersunk such that when fully tightened the bolt head is flush with the top of the cover. Only stainless steel tightening bolts shall be used. Castings shall be free of porosity and blow holes.
5. Step Materials
Manhole steps shall be furnished with the precast manhole sections. Steps shall be of polypropylene material reinforced with a 1/2 inch diameter reinforcing rod. Manhole steps shall be designed for a vertical load of 400 pounds and a horizontal pull out load of 1000 pounds. Steps shall be set 16 inches on center. Holes for the installation of manhole steps shall not project through the manhole wall, but shall stop a minimum of one inch from the outside wall. Steps shall be at least 12 inches clear width and shall project at least 5 inches from the wall into which they are embedded. Steps shall be located along the effluent side of the manhole. Cone or manhole top shall be oriented so that well with steps is vertical from over to shelf.
6. Bedding Materials
Sewer mains from 14 to 20 feet deep require special bedding in accordance with the Standard Details. See section "Additional Requirements for Flexible and Semi-Rigid Pipe."
1. See design criteria contained in Section 7.01A for additional installation requirements.
2. Pipe trench excavation and backfilling shall be performed in accordance with Section 5.00 of these Specifications.
3. Transitions of pipe material shall occur only at manholes.
4. Sewer line easements shall be graded smooth, free from rocks, boulders, roots, stumps, and other debris and seeded and mulched upon the completion of construction.
5. The downstream side of the last manhole(s) of a sanitary sewer line extension under construction shall be plugged with a non pneumatic plug and secured with stainless steel chain or wire rope to prevent the passage of groundwater, runoff and sediment into the sanitary sewer system. All water upstream of the plug shall be pumped out of the sanitary sewer line and all sediment and solids shall be removed and properly disposed of by the Contractor. The plug shall not be removed until the line has been inspected by the Town to insure that all possible points of inflow or infiltration have been eliminated. Failure to meet these requirements will be deemed a violation of the Sewer Use Ordinance with fines up to $1,000.00 per day.
6. Manholes located within a 100 year flood plain or in areas of high ground water shall be waterproofed by wrapping Conwrap, conseal, or approved equal.
7. Ductile Iron Pipe shall be installed in accordance with the Ductile Iron Pipe Handbook published by DIPRA and AWWA C500.
D. Additional Requirements for Flexible and Semi-Rigid Pipe
PVC is classified as "Flexible" pipe, and A.B.S. Composite and PVC Composite are classified as "Semi-rigid." The installation shall satisfy the requirements of the manufacturer, and/or the following, whichever is more stringent:
1. The manufacturer's specifications or other approved method shall be used in determining the stiffness class of the pipe to be installed so as to attain the required deflection control. The class of the pipe must be approved by the Town Engineer prior to installation.
2. For PVC pipe, the pipe shall be produced with bell and spigot end construction. Joining shall be accomplished by rubber gasket in accordance with manufacturer's recommendation, unless otherwise directed or approved by the Town Engineer. Flexible watertight elastomeric seals in accordance with ASTM D3212-1, may also be used. Each pipe length shall be clearly marked with information including pipe size, profile number and class number.
3. Installation of PVC pipe shall follow the recommendations of ASTM D-2321 "Underground Installation of Thermoplastic Pipe for Sewers and other Gravity-Flow Applications". For flexible pipes, bedding and embedment material shall be Class I. In any area where the pipe will be installed below existing or future ground water levels or where the trench could be subject to inundation, additional Class I material shall be used for bedding
4. Bedding and embedment material classifications shall be defined as follows:
CLASS I - Angular, (1/4 to 1-1/2 inch) graded stone, including a number of fill materials that have regional significance such as coral, slag, cinders, crushed stone, crushed gravel, and crushed shells.
CLASS II - Coarse sands and gravels with maximum particle size of 1-1/2 inch, including variously graded sands and gravels containing small percentages of fines, generally granular and non-cohesive, either wet or dry. Soil types GW, GP, SW and SP are included in this class.
CLASS III - Fine sand and clayey gravels, including fine sands, sand-clay mixtures, and gravel-clay mixtures, Soil Types GM, GC, SM, and SC are included in this class.
CLASS IV - Silt, silty clays, and clays, including inorganic clays and silts of medium to high plasticity and liquid limits. Soil Types MH, ML, CH and CL are included in this class. These materials are not recommended for embedment.
5. The minimum trench width shall be one pipe diameter plus 9 inches on each side of the pipe.
6. The bedding (6" minimum) and embedment materials shall be in accordance with ASTM D-2321. The embedment materials shall be installed from trench wall to trench wall and from the invert to a minimum of 6" above the crown of the pipe.
7. The bedding and embedment material shall be compacted to a minimum of 90% Standard Proctor density for Class I materials.
8. The maximum allowable deflection after installation shall BE LESS THAN 5% for flexible pipe and 3% for semi-rigid. A mandrel test on truss pipe shall only be required if the Inspector finds a problem during the visual inspection.
9. If hydraulic jack shoring is utilized for trench walls, it shall be restricted to the area just above the top of the pipe. This will ensure the embedment materials and pipe will not be disturbed when the shoring is removed.
1. Main Location
a. Force mains shall be installed with a minimum cover of 4 feet measured from the top of the pipe to the finished subgrade.
Force mains shall be installed in dedicated public right of way or in dedicated utility easements as follows:
Pipe Size |
Pipe Depth |
Easement Width |
12" and less |
Less than 20’ |
20’ |
12" and less |
Greater than 20’ |
30’ |
Greater than 12", up to 24" |
Less than 20’ |
30’ |
Greater than 12", up to 24" |
Greater than 20’ |
40’ |
Greater than 24" |
All depths |
Town Engineer Specified |
c. Force mains shall discharge at the invert of the receiving manhole and shall be as close as possible to 180 degrees from the outlet pipe.
d. Sewage Combination Air Valves shall be installed at all the high points or runs exceeding 3000’ of all force mains in accordance with the Standard Details. The valve size shall be determined by the designer and approved by the Town Engineer.
e. Force main valves shall be resilient-seated wedge gate type spaced as determined by the Town Engineer. Resilient-seated wedge gate valves shall be manufactured in accordance with AWWA C509.
See Section 2.02 for instructions on requesting new product approval.
1. Pipe Materials
Force mains smaller than 4 inches in diameter shall be PVC, while larger pipes shall be DIP. Pipe and fittings within pump stations shall be ductile iron.
Ductile Iron Pipe shall be designed and manufactured in accordance with AWWA C150 and C151 for a laying condition Type 2. Pipe joints shall be of the push-on type per AWWA C111. Pipe lining shall be cement mortar with a seal coat of bituminous material, all in accordance with AWWA C104. Working pressure shall be as follows:
4" - 12" 350 psi 14" - 20" 250 psi 24" 200 psi 30" - 54" 150 psi PVC Pipe Force mains smaller than 4 inches in diameter shall be SDR 21 or schedule 40 PVC premiere pipe with push joints. Pipe and joints shall meet all applicable requirements of ASTM D-2241 and D-1785. PVC pipe requires the installation of 3 inch wide detector tape a maximum of 2 feet below the finished grade.
2. Pipe Fitting Materials
Pipe fittings shall be cast or ductile iron designed and manufactured per AWWA C110. Fittings up to and including 12 inches shall be designed for an internal pressure of 250 psi. Fittings larger than 12 inches shall be designed for an internal pressure of 150 psi. Joints for fittings shall be mechanical joint and shall be cement mortar lined with a seal coat of bituminous material, in accordance with AWWA C104.
All buried DIP and fittings shall have bituminous coating on the exterior surface in accordance with AWWA C151.
Pipe shall be supplied in minimum 18-foot lengths unless approved otherwise by Department of Development Services.
3. Material Identification
a. Force mains shall be appropriately identified upon installation so they will not be confused with potable water lines. Green detector tape 3 inches in width and clearly labeled sanitary sewer shall be laid a maximum of 2 feet below the finished grade.
b. Force main valves shall have valve box covers marked "Sewer".
4. Manhole Materials
See section 7.01 B-3 for manhole material requirements.
1. See design criteria contained in Section 7.02 A for additional installation requirements.
2. Reaction blocking for all fittings or components subject to hydrostatic thrust shall be securely anchored of 3000 psi concrete thrust blocks poured in place. The reaction areas are shown in the Standard Details. No concrete shall interfere with the removal of fittings.
3. The receiving manhole for a force main shall receive an interior coating of Koppers "Super Service Black" or a PVC or resin lining with a total dry film thickness of 10 mils. All nicks and scratches shall be touched up prior to acceptance of the manhole.
4. Manholes containing valves shall receive a PVC or resin lining or a bituminous or coal tar epoxy coating on the interior.
1. All residential subdivision lots shall be served by gravity unless otherwise approved by the Town Engineer. If a pump is approved, it shall be privately maintained, must pump into a service connection placed on the lot, and must have a note on the recorded plat indicating that a private pump is required to serve the lot.
2. Service connections to the main lines shall be perpendicular to the main line and to the edge of the right of way or easement line.
3. Cleanouts are required on all services with a maximum spacing of 75 feet on 4 inch services and 100 feet on 6 inch services, and at the right of way line or edge of easement. All cleanouts shall extend a minimum of 6 inches above finished grade or meet the optional cleanout method requirements in accordance with the Standard Details.
4. Sewer cleanouts located in paved areas, which bear vehicle loading, must have ductile iron risers, ductile iron fittings and brass caps or meet optional cleanout method requirements in accordance with Standard Details.
5. All 6 inch service connections shall be into a manhole unless otherwise approved by the Town Engineer.
6. All service lines which are connected into manholes shall not be through the cone section or manhole joints. Service lines shall be installed 6" above, but no more than 30 inches above the invert or shall be installed with a standard drop. Multiple service connections shall not be maintained by the Town. The use of wyes in the line is preferred over the use of service saddles.
1. Pipe Materials
Cast Iron Soil Pipe shall be heavy weight hub and spigot meeting Federal Specifications WW-401. The joints shall be rubber type elastomeric as per ASTM C425.
PVC Pipe shall be schedule 40 or greater supplied in 18 feet lengths. The pipe may be joined by elastomeric gaskets.
Ductile Iron Pipe shall be used for sanitary sewer with services with less than 3 feet of cover or in excess of 20 feet of cover.
2. Service Saddle Materials
PVC or ABS service saddles shall be of the same material as the main, and shall be solvent welded and fastened with double stainless steel bands.
Ductile Iron Pipe service saddles may be "ROMAC C" type consisting of a virgin SBR gasket compounded for sewer service, a ductile iron saddle casting, a 304 stainless steel adjustable strap for fastening the gasket and the saddle casting to the sewer main and a 304 stainless steel adjustable circle clamp for securing the service line into the SBR gasket.
1. See design criteria contained in Section 7.03 A for additional installation requirements
2. Each separately owned structure requires a separate tap to a public sewer.
3. All service connections to existing sanitary sewer mains shall be made by the Town. Service connections on new mains may be by the Contractor, but must include the use of wye connections. Taps on new lines may only be approved by the Development Review Director.
4. Service taps into mains shall be made on the top quarter of the main with the wye saddle angled towards the direction of flow in the main.
5. Service lines between 3 and 14 feet in depth do not require special bedding. PVC service lines between 14 and 20 feet in depth shall require Class I bedding from 4 inches below the service line to 4 inches above the service line.
6. Four inch lines shall have a minimum slope of 1.0 ft./100 feet and 6 inch lines shall have a minimum slope of 0.60 ft/100 feet.
7. Service connections made using a "ROMAC CB" sewer saddle shall be made only when the service line is iron pipe and only when the sewer main is 8", 10", or 12" diameter concrete, ductile iron, or PVC sewer pipe. This service connection shall not be used when the sewer main material is truss sewer pipe. The opening in the sewer main for the "ROMAC CB" sewer saddle shall be cut with a hydraulically or pneumatically driven circular tapping saw of the same nominal diameter as the sewer service line.
Pumps shall be submersible centrifugal type. Vacuum priming, suction lift, submersible grinders, or above grade pumping units are not allowed. All pump stations that will be privately operated and maintained must meet the North Carolina Building Code in addition to the Town of Cary Standard Specifications.
All stations shall have a minimum of 2 pumps of equal capacity. The pumps shall be solids handling, centrifugal pumps capable of handling flows in excess of the expected peak flow. Where 3 or more pumps are required, they should be of such capacity that with any one unit out of service, the remaining units will have capacity to handle peak flows. Pumps and force mains shall be sized to provide a minimum velocity in the force main of 2.5 fps and a maximum velocity of 10 fps.
The submersible pump station structure shall consist of the wet well, duplex pumps and rails, pump controls and related appurtenances , discharge piping, valves and valve vault, cover slabs and access hatches.
The wet well shall have a minimum diameter of 6 feet, and shall be large enough to easily accommodate the removal of each pumps and the basket strainer. The wet well shall be designed to have a diameter sufficient to provide storage for a pump operating cycle of at least 3 minutes without being excessively deep.
All stations which are maintained by the Town shall incorporate a chemical feed and storage facility for odor control purposes unless the Town Engineer grants approval otherwise. The Town requires sewage grinders, on-site backup power, chemical feed facilities, and odor control facilities at all pump stations. Sizing of these items will be based on expected flow volumes and characteristics.
Wastewater pump stations, all related structures and controls, shall be protected from physical damage by the 100 year flood. Stations shall be designed to remain fully operational and accessible during the 25 year flood. The 100 year flood elevation shall be shown on all site plans. All sewage pump stations shall be equipped with an alternate power source. Alternate power sources include on-site stand by power, or dual power feeds from separate electric substations.
Small package type pump stations or grinder pumps shall only be allowed for private pump stations which only serve one site. These pump stations will be allowed only if the flow rate is less than 100 gpm and the force main is less than 4 inches in diameter.
The site shall be graded generally to drain away from the pump station, and to remove storm water runoff from the site in a non-erosive manner.
The site shall be stabilized by crushed stone, low maintenance vegetative ground cover or other suitable materials. Visual screening and landscaping shall be provided in accordance with the approved site plan.
The site shall be secured by a 6 foot high chain link fence topped with 3 strands of barbed wire. Fence products shall be only new materials using hot dipped galvanized iron or steel components and aluminum coated fabric. Line posts, top and bottom rails, gate and fabric shall be as specified on the approved site plan. Gates shall permit 180 degree opening, be located so as to provide vehicle accessibility for lifting the pumping units, and be a minimum width of 12 feet.
The site shall feature adequate turn around areas for a WB-40 service vehicle and provide a minimum 12 foot wide access road to the site with grades not to exceed 10%.
A high pressure sodium vapor light of minimum 600 watt capacity is required. The light shall be mounted on a Class V utility pole at a height of 30 feet and be controlled by a photo cell.
Suction and discharge piping shall be Class 50 ductile iron flanged pipe in accordance with AWWA C 141. Discharge Piping and Valves shall produce a minimum head loss while maintaining a minimum velocity of 2.5 feet per second. All exposed piping shall have adequately sized and located thrust rods.
The discharge connection elbow shall be a straight through fitting with no flap valve and shall be permanently installed in the wet well along with the discharge piping. The pumps shall be automatically connected to the discharge connection elbow when lowered into place. The entire weight of the pump shall bear upon the guides and base support with no part of the pump bearing directly on the floor of the sump. A stainless steel wire rope fabricated into 8 foot sections connected together with stainless steel 0-rings shall be provided for lifting each pump from the wet well. All hardware used shall be 316 stainless steel. A check valve and a gate valve shall be provided for the discharge pipe of each pump. A 1/4 turn plug valve shall be provided on the discharge pipe from the valve vault.
Check valves shall be iron bodied, fully bronze mounted with bronze clapper disc and bronze seat ring, and shall have a spring loaded lever arm capable of being mounted on either side of the valve and rated for 175 psi working pressure.
Gate valves and check valves on the discharge side of each pump shall be located in a valve vault separate from and adjacent to the wet well. A Victaulic coupling shall be installed on each discharge main between the wet well and the valve vault. The valve vault shall consist of a precast concrete manhole base section at least 6 feet in diameter, or a cast in place concrete, custom built section, or a precast concrete rectangular structure at least 6 feet square, all complete with a drain that goes to the wet well and that has a back water valve on the drain line, access ladder attached or manhole steps per the Details attached to the vault wall, and access cover cast in the top slab.
A +/- 2% accuracy pressure gauge with a 3 inch or larger dial, stainless steel case, and graduated to 30 psi shall be provided on each discharge pipe. The gauge shall be installed between the check and gate valves. Isolation seals shall be provided between the gauge and force main. The gauge shall be oriented so that it is easily legible from the valve vault.
The access cover for the valve vault shall be a square hatch of 1/4 inch aluminum diamond pattern plate with steel hinges on an aluminum frame cast in place in the cover slab.
The wet well shall be precast concrete manhole sections conforming to ASTM C-78. Extended bases or another foundation shall be used to provide adequate bearing surface if needed. All concrete shall have a minimum 28 day compressive strength of 3000 psi.
Manhole section joints shall be of a durable mastic sealing material. The joints shall be further waterproofed on the outside of the wet well by the application of asphalt, overlapped by a 12 inch wide band of inorganic asbestos felt, and a finish mopping of asphalt. The interior side of the joints shall be plastered smooth with portland cement grout. The interior of the wet well shall then receive two successive coats of Koppers "Super Service Black", PVC or resin lining, with a total dry film thickness of 10 mils. All nicks and scratches shall be touched up in the field before backfilling.
The wet well shall have a vent made from ductile iron, flanged joint pipe fittings. An insect screen shall be included at the exposed end of the vent pipe. The screen shall be bronze or aluminum insect screening.
Electrical service to all pump stations shall be three phase, 240 VAC or 480 VAC. The electrical power entrance shall be through a meter base, followed by a NEMA 3R heavy duty, single throw, fusible safety switch with a solid neutral. This shall be followed by a NEMA 3R heavy duty, double throw, three pole safety switch which feeds the control panel from one side and heavy duty, circuit breaking 4 wire, 4 pole receptacle assembly as manufactured by Crouse-Hinds or other approved equal from the other side. All of these electrical components shall be suitably sized to be capable of service with all pumps running.
All electrical components, including panels, shall be sealed off in accordance with the N.C. Electrical Code requirements for electrical service to gas pumps.
The pump station shall be provided with an alarm dialer in a lockable NEMA 4 enclosure. The dialer shall have a 100 word vocabulary and shall be capable of creating customized messages. The operating environment shall be -10oF to 130oF, with a 90% relative humidity, non-condensing. The alarm dialer shall operate on 120 VAC, and shall have a rectangular backup battery capable of providing 4 hours of standby power with surge protectors on the power lines and telephone lines. The alarm dialer shall monitor high water condition through normally open/normally closed contacts, shall have the capability of dialing four phone numbers, and shall work on a standard telephone service. The Contractor shall be responsible for obtaining the installation of the telephone service. The dialer shall be the Butler National Corporation Model ADAS II, Microtel Model MCS 200 or MCS 205, the Capital Controls Company Model 1520, or approved equal. The alarm dialer enclosure shall be equipped with a thermostatically controlled space heater when it is exposed to the weather.
Seal failure and high temperature signals from all pumps shall be ganged into a common "pump trouble" alarm to be transmitted from the dialer.
1. General
Pump station control equipment shall be located within the structure housing above finished grade within 6 feet of the wet well. An aluminum weatherhood with a clear height of 7 feet, an overhang of at least 4 feet and a thickness of 3/16 inch shall be provided for control equipment exposed to the weather. The back panel and side panel shall also be 3/16 inch thick aluminum. The support structure for the weatherhood shall be made from structural steel members assembled to provide individual, direct support to the control equipment panel, transfer switch, safety switches, meter base and the weatherhood. The steel frame shall be painted with a two component, high build epoxy polyamide paint system designed for severe service.
2. Pump Wiring
A junction box shall be provided for power and control wiring to each pump. The junction box shall be located on top of the wet well top slab. Submersible pump power and control cable shall be run in conduit through the slab, into the junction box, and shall terminate in the box with power and control wiring to the pump station electrical panel.
3. Enclosure
NEMA 3R Enclosure - Enclosure shall be NEMA type 3R of suitable size to house all components. A locking hasp shall be provided in addition to screw clamp type latches. Enclosures shall be fabricated from 14 gauge steel. The top of the enclosure shall serve as a drip shield and the seam free sides shall prevent rain and sleet from entering. Inner panels shall be made of 12 gauge steel and shall be painted white. The enclosure and interior panel shall be painted with heat fused modified polyester powder, electrostatically applied over a phosphatized base. Enclosures shall be ANSI/ASA 61 gray.
Hinged Inner Door - An inner door shall be furnished. Overload reset push buttons, circuit breakers, switches and pilot lights shall be the only components accessible with door closed. Door shall be hinged and may be opened when service is required.
Line Terminal Block - A terminal block shall be furnished with properly sized line lugs to accept the main power source entering the control panel. Load lugs shall be adequate to accept all required load side wiring requirements. All live parts shall be fully shielded.
Motor Circuit Breakers (200-240 VAC) - A properly sized, molded case, thermal magnetic circuit breaker shall be provided for each pump motor. Line and load sides shall be equipped with lugs properly sized for the horsepower and current rating of the motor(s). They shall be attached to mounting brackets which are specifically manufactured for use with the particular circuit breaker. The interrupting rating shall be 10,000 RMS symmetrical amps.
Motor Circuit Breakers (440-480 VAC) - A properly sized, molded case, hydraulic-magnetic circuit breaker shall be provided for each pump motor. Line and load sides shall be provided with lugs properly sized for the horsepower and current rating of the motor(s). The interrupting rating shall be 5,000 RMS symmetrical amps.
Transformer Primary Circuit Breaker (When Transformer Is Required) - A properly sized, two pole, molded case circuit breaker shall be furnished ahead of the control power 120 VAC power transformer for short circuit protection and disconnecting power to the transformer. The circuit breaker shall conform to the specifications for the motor circuit breaker(s).
Control Power Transformer (When neutral Is not Available At Jobsite - Std. On 460 VAC) - An industrial quality control transformer shall be furnished to provide control voltage. The transformer shall be sized with an adequate KVA rating to provide 120 VAC power for all items required in the control and alarm circuits. Transformer shall be protected in its secondary by properly sizd fuses and/or circuit breaker(s).
Magnetic Contactors and Overload Relays - A magnetic contactor shall be furnished for each motor. A separate, panel mounted, 3 leg (three phase) or 1 leg (single phase) overload relay shall be supplied for each motor. Each leg of the overload relay shall be equipped with a properly sized overload heater. Contractor and overload relay shall be properly sized for the required horsepower, voltage and phase.
Elapsed Time Meters - Six digit, non-resettable elapsed time meters shall be mounted in the control panel enclosure to record the running time of each pump.
Condensation Strip Heater With Thermostat - A strip heater shall be furnished to prevent condensation within the control panel enclosure. The heater shall be controlled by a panel mounted, adjustable thermostat.
Phase & Voltage Monitor - A phase failure, reversal and under voltage monitor shall be supplied to prevent the motors from running under low voltage, phase loss, or phase reversal conditions. The monitor will lock out the control circuit until the problem is corrected and automatically reset.
Lightning Arrestor - Suitable lightning arrestors shall be provided to protect motors and control equipment from lightning induced line surges.
Thru-Door Overload Reset Push Buttons - Overload reset push buttons shall be provided for each overload relay. Push buttons shall be mounted so that with the inner door closed, overload relays may be reset without entering the high voltage compartment.
Switches - Heavy duty industrial grade oil tight switches shall be provided for each pump for "Hands-Off-Automatic" operation selection. All switch components shall be made of corrosion resistant metals and polyesters. Contact blocks shall be made of see-through polycarbonate for simplified inspection of contacts. Cams and strokes shall be Teflon impregnated for abrasion free service without lubrication. The switches required shall be as follows:
Switch Function: Voltage
(Name Plate)Manual-off-Automatic: 120 VAC
Pilot Lights - Full voltage heavy duty industrial grade oil tight pilot lights shall be provided. All pilot light components shall be made of corrosion resistant metals and polyesters. An insulated socket shall be furnished to eliminate the possibility of shock during bulb change. Lens shall be made of lexan. The pilot lights required shall be as follows:
Pilot Light Function
(Name Plate)Voltage Lens Color PUMP 1 120 VAC GREEN PUMP 2 120 VAC GREEN Seal Failure Circuit Test Push Button (illuminated) - Heavy duty industrial grade oil tight push buttons shall be provided for each submersible pump motor. All push button components shall be made of corrosion resistant metals and polyesters. Contact blocks shall be made of see-through polycarbonate for simplified inspection of contacts. An insulated socket shall be furnished to eliminate the possibility of shock during bulb change. Lens shall be made of lexan. The push buttons required shall be as follows:
Push Button Function
(Name Plate)Voltage Lens Color P1 SEAL FAIL 120 VAC AMBER P1 SEAL FAIL 120 VAC AMBER Seal failure shall be directly wired to the alarm dialer.
Pump Alternator Circuit (For Duplex Pump Operation) - The electro-mechanical alternator relay shall be of industrial design specifically for use in pump applications. It shall have single pole double throw heavy duty 10 amp silver cadmium oxide contacts enclosed in a transparent cover. The snap action contacts shall transfer when the unit is de-energized. The circuit shall never be closed or opened while current is being conducted. The alternator circuit shall be manually operable with the capability of selecting an independent pump by use of a toggle switch.
Control Relay (s) - Plug-in control relays with 120 VAC coils shall be provided as required. Contact rating shall be 5 amps minimum. Sockets shall be of the same manufacture as the relays and hold-down clips shall be furnished to prevent the relay from sliding out of the socket.
High Wet Well Level Alarm - The control panel shall be provided with a suitable alarm circuit, activated by a separate level control. This alarm shall signal a high water condition in the sump. Terminals shall be furnished in the control panel for connection of an externally mounted alarm device. A red flashing light shall be provided as a visual alarm of the high water condition in the wet well.
Liquid Level Controls - Ultrasonic level indicators are preferred over mercury level control switches. In both cases, levels shall indicate pumps on, lead pump on, lag pump on, and high level alarm functions. The mercury switch shall be encapsulated in polyurethane foam for corrosion and shock resistance. Level switches shall be weighted to hold desired position in the sump. The cord connection for the control shall be numbered 16-2, rated for 13 amps, and shall be type SJTO. To ensure optimum longevity, contacts shall be rated for 20 amps at 115 VAC and shall be sealed in a heavy duty glass enclosure. No junction boxes or cable splices of any kind will be allowed in the wet well.
High Temperature Shutdown Circuit(s) - The high pump motor temperature circuit shall provide terminals for connection of the leads from the temperature sensor provided in the pump motor windings. Upon a high temperature condition in the pump windings, the control power to the pump motor contactor shall be disconnected, thus stopping the pump motor. The pump shall automatically restart when the pump motor temperature returns to an acceptable level. High temperature sensor shall be directly wired to alarm dialer.
Ground Lug(s) - Equipment ground lugs shall be provided for grounding the enclosure. The ground lugs shall be suitable for the service provided to the enclosure and shall be sized per table 250-95 of the N.E.C. In all cases the enclosure must be adequately grounded per article 250 of the N.E.C.
Terminals - Terminals shall be provided for connecting mercury float switch leads, temperature sensor and seal failsensor leads. Terminal blocks shall be rated for 600 volt use and accept a wire range of #22-8. All live parts shall be fully shielded. Block shall be constructed of nylon and have insulating walls on all sides of the lug. Blocks must be U.L. recognized.
Construction Standards - Subpanel shall be drilled and tapped to accept machine thread bolts (self tapping screws are not acceptable). All control wiring shall be 16 AWG machine tool wire, Carol type 76512 or equal. All control wire shall be color coded or numbered in accordance with JIC standards. Power (motor) wiring shall be in accordance with the National Electrical Code. Major groups of wires shall be contained in a plastic wiring trough such as Panduit type E or other approved equal.
Guarantee - The manufacturer of the control panel shall furnish a warranty for one year from the date of shipment stipulating that all equipment shall be free from defects in design, materials and workmanship. The control panel manufacturer shall furnish replacement parts for any component proven defective, whether of his or other manufacturer during the guarantee period, except those items which are normally consumed in service, such as light bulbs.
Sewage Pumps and Motors - Pumps shall be submersible, non-clog centrifugal sewage pumps capable of passing a 3 inch sphere as manufactured by Flgyt, Hydromatic, Fairbanks-Morse, Myers, and ABS. Submersible pumps shall be provided each capable of handling raw, unscreened sewage at peak design flow. Major pump components shall be of gray cast iron devoid of burrs, pits or other irregularities. The pump motors shall be sealed submersible type, and shall be three phase, 60 Hertz, 240v/480v motors with a maximum speed of 1750 RPM. The motors shall meet the U.S. requirements of Class I, Division I, Group D for hazardous locations, and shall be sized to non-overloading throughout the entire operating range of the pump.
Stator winding shall be of the open type with insulation good for 180oC maximum temperature.
Motor shall have two heavy duty ball bearings to support the pump shaft and take radial and thrust loads, and a sleeve guide bushing directly above the lower seal to take radial load and act as flame path for seal chamber. Ball bearings shall be designed for 30,000 hours B-10 life. Stator shall be heat shrunk into motor housing.
A heating sensor thermostat shall be attached to and embedded in the winding and be connected in series with the motor starter contactor coil to stop motor if temperature of winding is more than 220oF. The thermostat shall reset automatically when the motor cools to a safe operating temperature. The common pump shaft shall be of 416 stainless steel.
The pump motor shall be protected by two mechanical seals mounted in tandem with a seal chamber between the seals. Seal chamber shall be oil filled to lubricate seal face and to transmit heat from shaft to outer shell. Seal face shall be carbon and ceramic and lapped to a flatness of one light band. Lower seal faces shall be tungsten carbide.
A double electrode shall be mounted in the seal chamber to detect any water entering the chamber through the lower seal. Water in the chamber shall cause a red light to turn on at the control panel. This signal shall not stop the motor but shall act as a warning only.
Power cables to pumps shall be AWG (min) hypalon jacketed type SPC cable of 30 feet in length as a minimum.
Lift Out Rail System - The lift out systems shall consist of a straight elbow that bolts to the bottom of the basin, a combination disconnect assembly with a seal flange that mounts to pump, rail support guides that fasten to wall of basin and guide and support brackets that mount to pump.
Guide rails shall be Schedule 40 galvanized steel pipe.
The discharge quick disconnect shall be tapered and have a holding groove machined into the face to hold a sealing O-ring. The tapered seat shall allow the pump to be nearly sealed to the discharge elbow before the sealing faces make contact. A guide plate and adjustable guide bar shall be fastened to top of the pump to insure good alignment and for support of the pump.
The rail support and mounting bushing shall be securely mounted to the basin wall and shall not be attached to the basin cover or cover frame.
The guide rail support shall be adjustable so that a perfect vertical alignment of the rails can be obtained.
1. Description
a. The grinder system shall include all necessary parts including a rotating screen, hydraulic power pack with electric motor, grinder with hydraulic torque motor, controls, wiring, conduit and accessories as described herein and as necessary for a complete and operating installation.
b. The equipment shall be installed as recommended by the manufacturer, and in compliance with all OSHA, local, state and federal codes and regulations.
c. The grinder installation shall be provided fully operational for the intended purpose of grinding solids in the influent flow.
2. Quality Assurance
a. All equipment shall meet the requirements of the following standards:
1. ASTM A536 - Standard Specifications for Ductile Iron Castings
2. ASTM A36 - Standard Specifications for Carbon Steel Plate
3. AISI 4140 - Heat Treated Hexagon Steel
4. AISI 4130 - Heat Treated Alloy Steel
5. AISI 1018 - Carbon Steel
6. 45-50 Rockwell C
7. National Electrical Manufacturers Association (NEMA)
b. Qualified manufacturers shall have a minimum of 5 years experience in the manufacturing of grinding and controlling equipment and a minimum of 20 installations at equivalent applications. A listing of names and dates of installations for verification by the Town Engineer.
3. Submittals
a. Submittals shall include system hydraulic schematics, electrical wiring diagrams complete for field wiring, terminal identifications, and control panel schematics. Electrical and control information shall be provided to allow coordination of field wiring to place the system in the desired operation.
b. Submittals shall include complete mounting and installation instructions, including size, length and spacing of all supports and anchor bolts.
c. Submittals shall include painting instructions.
d. Submittals shall include: Operation and maintenance manuals shall be submitted prior to startup of the grinder system. These manuals shall include all necessary technical information for the proper operation and maintenance of the grinder system. Manuals shall include installation details and wiring diagrams and control panel schematics specific to this installation. The O&M manuals shall include comprehensive equipment descriptions, operating instructions, troubleshooting techniques, recommended maintenance schedules, assembly and disassembly instructions, and recommended lubricants. Lubricants by several manufacturers, including UNOCAL, shall be included in the listing. Final O&M manuals shall also be submitted in electronic form on CD or diskette.
4. Requirements for "Pre-Approved Equal" and "Or-Equal" Products
a. Equipment of equal quality and efficiency may be available from manufacturers and suppliers other than those specified. No attempt is made to preclude the furnishing of similar quality items by other manufacturers. The use of alternate equipment and products will be considered if it can be demonstrated that these items have equal or superior construction performance, operating and maintenance costs, offer a present worth cost equal to or less than the specified items and do not adversely affect other system components.
b. Pre-approved equal products: In-channel sewage grinder systems other than those specified must receive pre-bid approval from the Town Engineer as described herein.
c. Submittals for substitution of items for those specified must be made and must receive pre-bid approval.
d. Manufacturers and suppliers desiring equipment or products to be included as "pre-approved equal" shall submit data directly to the Town Engineer:
5. Acceptable Manufacturers
Screens, grinders, hydraulic drives and controllers shall be supplied as an integrated system by a single supplier. The screening and grinding system shall be the "Channel Monster" Model CMD-1800 as manufactured by JWC Environmental/Disposable Waste Systems, Inc., or equal.
6. Identification
Each unit of equipment shall be provided with a corrosion resistant substantial metal nameplate, securely affixed in a conspicuous place. Nameplate information shall include equipment model number, serial number, manufacturer’s name an location and important performance data.
7. Screen
a. General
i. A horizontally rotating screen shall be located in the channel and shall direct all solids in the flow stream into a dual counter-rotating shaft grinder. The screen shall be self-cleaning and driven by the grinder drive mechanism.
ii. Each screen shall include a continuous screen belt, sprockets and shafts.
b. Components
i. Screen belt shall a close mesh design, made of high impact nylon for high abrasion resistance. The close mesh screen shall permit high flows and divert captured solids directly into the grinder.
ii. The openings on the revolving drum screen shall be no larger than 5/8" x 3/4".
iii. Screen shafts shall be made of AISI 1018 carbon steel with a tensile strength of not less than 85,000 psi. The shaft diameter shall be a minimum of 1-inch.
iv. Radial and axial loads of the screen shafts shall be borne by two sealed oversized Conrad-type ball bearings. Bearings shall be protected by Buna-N double lip seals. Lip seals shall be rated at 10 psi continuous duty.
8. Grinder
a. General
i. Grinder shall be a two-shaft design, capable of continuous operation, processing wet or dry. Bar screens or single shaft devices utilizing a single rotating cutter bar with stationary cutters shall not be acceptable.
ii. Two-shaft design shall consist of two parallel shafts alternately stacked with inter-meshing cutters and spacers positioned on the shaft to form a helical pattern. The two shafts shall counter-rotate with the driven shaft operating at approximately two-thirds (2/3) the speed of the drive shaft.
iii. Each grinder shall include a guide plate, frame, end housings, covers, shafts, side rails, hydraulic power pack with motor, cutters, spacers, bearings and seals.
b. The combination of the grinder and the screen shall not cause more than 5 to 8-inches of headloss, depending on downstream conditions, when passing a flow of 1,000 gpm.
c. 95% of the particles exiting the grinder shall be no larger than 1/2".
d. Components
i. Grinder end housings shall be A536 cast ductile iron and shall be designed to protect the bushings while guiding solids directly into the cutting chamber. The cutting chamber shall have a nominal height of 18-inches.
ii. Top covers shall be ductile iron and bottom covers shall be hot rolled plates.
iii. The grinder drive and driven shafts shall be made of AISI 4140 heat treated hexagon steel with a tensile strength rating of not less than 149,000 psi. Each shaft hex shall be a minimum of 2-inches.
iv. The inside profile of the side rail shall be concave to follow the radial arc of the cutters. The side rail shall be affixed to the grinder and maintain a clearance not to exceed 5/16-inch between the major diameter of the cutter and the concave arc of the side rail. This clearance shall act to direct larger particles toward the cutters to assure fineness of grind. High flow side rails shall have evenly spaced slots which increase flow and decrease head loss. Side rails shall be of ASTM A536 cast ductile iron.
9. Guide Plate and Frame
a. A guide plate and frame insert shall be provided by the manufacturer for inserting the grinder/screen assembly into the manhole. The insert shall allow for easy removal and replacement of the grinder/screen assembly, without fasteners.
b. The insert shall be a one piece welded fabrication specifically designed for the grinder/screen assembly and shall be made of 316 stainless steel. The insert shall be anchored to the manhole with stainless steel anchor bolts. The frame and guide plate insert shall be grouted into the manhole base, with the channel invert formed smoothly throughout.
c. The screen/grinder assembly shall be provided with suitable lifting eyes (at least two) sized to support the assembly during insertion/removal in the frame.
d. The frame shall be designed for installation in a 48-inch diameter manhole and shall house the screen and grinder assemblies.
10. Overflow Bar Screen
a. An overflow bar screen shall be provided, fully coordinated with the guide plate and frame assembly. The overflow bar screen shall be constructed entirely of 316 stainless steel. Bars shall be 1/2-inch diameter with 2-inch clear spacing between the bars. An angle or rectangular bar frame shall be provided around the screen perimeter, for mounting of the screen to the manhole. The bar screen shall extend the full width of the manhole and three feet above the top of the rotating screen/grinder assembly. The bar screen shall not interfere with the removal and replacement of the rotating screen/grinder assembly from the manhole. No pathway for solids larger than the bar spacing to pass the assembly shall be permitted with the screen/grinder unit and bar screen in place.
11. Required Torque
The required running torque per horsepower shall be minimum 1,500 in-lb. continuously and 2,350 in-lb. at momentary load peaks.
12. Cutters and Spacers
a. The inside configuration of cutters and spacers shall be hexagonal so as to fit the shafts with a total clearance not to exceed 0.015-inches across the flats to assure positive drive and increase the compressive strength of the spacers.
b. Cutters and spacers shall be AISI 4130 heat treated alloy steel, surface ground for uniformity and through-hardened to a minimum 45-50 Rockwell C.
c. Cutter configuration shall consist of one shaft with 5-tooth double edged cutters and one shaft with 11-tooth cam cutters. To maintain particle size, the height of the tooth shall not exceed ½-inch above the root diameter. Cutter root diameter overlap shall not be less than 1/16-inch or greater than 1/4-inch to maintain the best possible cutting efficiency while incurring the least amount of frictional losses.
d. The cutter shall exert a minimum force of 650 lb. per HP continuously and 960 lb. per HP at momentary peaks loads at the tooth tip.
13. Cutter Shaft Bearings and Seals
The radial and axial loads of the shafts shall be borne by four sealed oversized deep grooved ball bearings. The bearings shall be protected by a combination of a replaceable and independent tortuous path device and end face mechanical seals. Face materials shall be a minimum of tungsten carbide to tungsten carbide not requiring an external flush or any lubrication. The mechanical seal shall be rated at 90 psi continuous duty. The bearings and seals shall be housed in a replaceable cartridge that supports and aligns the bearings and seals as well as protects the shafts and end housings. O-rings shall be made of Buna-N elastomers. Products requiring continuous or occasional lubrication or flushing shall not be acceptable.
14. Hydraulic Power Unit
a. The hydraulic power pack shall include the following:
i. 16½-inch x 16½-inch x 12½-inch, epoxy coated, 10 gallon (US) capacity reservoir
ii. positive displacement pump driven by a 5 HP TEFC, C-face, electric motor
iii. combination oil level and oil temperature gauge
iv. 10-micron return line oil filter
v. oil temperature limit switch set at 160 °F
vi. oil level switch
vii. filler breather
viii. pressure switch preset at 2,850 psi
ix. 120-volt 4-way solenoid valve
x. relief valve preset at 3,000 psi
xi. 2½-inch, 0-3,000 psi oil filled gauge
xii. suction strainer
xiii. flexible hose rated for a minimum 3,500 psi working pressure
b. The hydraulic power unit shall be rain resistant, suitable for outdoor installation, located as shown on the drawings. The unit shall be installed in accordance with the manufacturer’s recommendations.
c. The entire hydraulic system shall be designed for 3,000 psi maximum pressure. At idle load conditions, the system operating pressure should be in the 200 to 400 psi range. Continuous operating pressure above 2,000 psi is not acceptable. As solids are encountered, pressure shall be automatically increased on a demand basis to provide the required torque necessary to continue rotation of the cutters. Should the grinder demand pressure in excess of 2,850 psi, a pressure switch shall instantly activate and a 4-way valve be shifted. The rotation of the cutters shall instantly reverse for about one-half (½) to one (1) revolution or about ½-second. At the end of this time, the valve shall again be shifted and the cutters return to the forward direction.
d. If the obstruction has been cleared, the unit shall continue to operate in the forward direction. If the obstruction has not cleared, the reversing sequence shall repeat until the torque requirement is reduced or until it has had to repeat the reversing cycle nine (9) times within a 45-second time span. If nine (9) reversals have occurred within 45 seconds, the controller shall shut down the hydraulic unit and activate an overload relay and illuminate an indicating light.
e. Hydraulic connections between the torque motor and the power pack shall consist of two ½-inch flexible hoses rated for 3,500 psi each. The manufacturer shall supply sufficient length of hydraulic hose to accommodate location of the power pack and hydraulic drive motor as shown on the drawings.
f. Upon completion of installation, the hydraulic power unit shall be filled with a high quality fluid with a viscosity of approximately 100 to 250 SSU at 100 °F , with good chemical stability and anti-foaming properties. The grades of hydraulic fluid shall be in accordance with the manufacturer’s recommendations.
g. A fiberglass enclosure shall be provided to completely cover the hydraulic power pack and motor. The enclosure cover shall be of one-piece FRP construction, mounting on a one-piece FRP flanged base. The enclosure cover shall be hinged on one side with a spring-loaded hook on the opposite side. The entire hydraulic power pack shall be exposed when the cover is opened. Hinges and hook assemblies shall be stainless steel. The enclosure base shall be secured to the concrete slab with stainless steel anchor bolts. An adjustable polypropylene weather proof vent shall be provided on the top side of the enclosure to prevent heat buildup and trapped vapors. A thermostatically controlled exhaust fan with FRP weather hood shall be provided. The exhaust fan shall be powered from the control panel. The contractor shall provide all terminations, power and control wire and conduit to place the fan in operation. The enclosure shall be insulated with 2 pound density polyurethane foam. Finished exterior surface shall be white polyester gelcoat with UV inhibitor.
15. Electric Motors
a. Electric motors shall be NEMA Design ‘B’, TEFC, 460 volt, 60Hz, 3-phase type, suitable for the intended service.
b. Motor shall be 5 HP with 6.6 FLA maximum.
c. Motor shall be Baldor, Reliance, U.S. Motor, or equal.
16. System Controls
a. The grinder system shall be provided with a single control panel, suitable for wall mounting as shown on the Drawings. The control panel shall include all power and control circuits to provide the functional requirements specified herein and as shown on the Drawings.
b. A programmable controller shall be included in the panel. Upon the grinder encountering a jam or overload condition, the controller shall stop the grinder and screen and reverse their direction of rotation to clear the obstruction. If the jam is cleared, the controller shall return to normal operation. If the jam condition persists, the controller shall repeat the reversing cycle up to eight additional times within 45-seconds (total of nine cycles) before signaling a grinder overload condition. Upon a grinder overload condition, the controller shall shut down the grinder and screen and activate an overload contact.
c. If a power failure occurs while the grinder is running, the grinder shall resume running when power is restored. A 0-60 second adjustable time delay device shall be included in the control panel to select time delay until restart after power restoration. If the grinder is stopped due to an overload condition and a power failure occurs, the overload indicator shall reactivate when power is restored.
d. The control panel shall provide overcurrent protection. The overload relay shall be adjustable so that the range selected includes the FLA rating and service factor.
e. The control panel shall be equipped with a Hand-Off/Reset-Auto (HOA) selector switch. In the Off/Reset position, the motor shall not run. In the Hand position, the motor shall run continuously. In the Auto position, the grinder shall stop and start by remote control signal. The control panel shall include dry contacts for future addition by others of a remote maintained contact start/stop control signal when in Auto mode. The control panel shall not allow remote resetting of overload condition. Overload reset shall be accomplished by switching the HOA switch to the Off/Remote position.
f. The oil temperature limit switch, oil level switch, pressure switch and 4-way solenoid valve shall all be pre-wired on the hydraulic power pack to a single junction box on the power pack. Terminals shall be provided in the control panel and in the power pack-mounted junction box for field wiring between these devices and the control panel. Terminals shall also be provided in the control panel and in the junction box for field wiring between the control panel and the hydraulic power pack motor. Junction box shall be NEMA 4X.
g. The controller shall indicate each of the following statuses with an indicator light on the panel face:
i. Power On
ii. Grinder Overload
iii. Motor Overload
iv. Run
v. Oil Over Temperature
vi. Low Oil Levelh. Engraved phenolic laminate plastic identification nameplates, with white letters on black background, shall be provided for each switch, indicator light, gauge, etc. on the control panel and in the system.
i. The controller shall be rated at 208/230/460 VAC, three phase, 60 Hertz.
j. A single enclosure shall house all power and control devices, relays, terminal blocks and motor starter. Control and indicating devices shall be mounted in the front of the enclosure. Indicating lights shall be integral transformer type with low voltage long life 6-volt lamps. Lamps and selector switches shall be heavy duty type. The control panel and all control devices shall be NEMA 4X. Enclosure shall be equipped with full hinged door, suitable for wall mounting as shown on the drawings.
k. A lockable disconnect switch shall be provided on the outside of the control panel to disconnect power to the entire grinder system.
l. One set of normally open (NO) contacts shall be provided in the control panel for remote indication of each of grinder "fail" and grinder "run" status. Grinder overload, motor overload, oil overtemperature, low oil level and oil pressure alarms shall be ganged together to a common grinder "fail" alarm. The control panel shall provide 120 VAC power to these alarm circuits for remote indication at an existing alarm dialer system.
m. Contacts shall be provided for a future remote maintained contact emergency stop pushbutton, to be provided by others. These contacts shall be jumpered.
n. Motor starter shall be full voltage type with 120-volt operating coil and captive terminal screws. Overload relay shall be mounted directly to the contactor. The relay shall be sized to the motor full load amperage (FLA).
o. The entire grinder system, including screen, hydraulic power pack, control panel, and instrumentation shall be powered from a single 460 VAC, 3 phase, 60 Hz power connection as shown on the Drawings.
17. Spare Parts
a. The following spare parts shall be provided as a minimum:
i. Three (3) of each type of fuse found in the system
ii. Three (3) of each type of lamp bulb found in the system
iii. One (1) complete set of gaskets
iv. Three (3) cutters
v. Three (3) Spacersb. The motor controller shall have sufficient space within its enclosure for the storage of motor controller spare parts. Grinder spare parts shall be packaged in suitable containers for long term storage and shall bear labels clearly designating the contents of each package and the equipment for which they are intended.
18. Factory Test
Each grinder, screen and motor controller shall be factory tested to ensure satisfactory operation.
19. Installation
The grinder/screen and motor controller shall be installed in accordance with the manufacturer’s installation instructions and in compliance with all OSHA, local, state and federal codes and regulations.
20. Field Quality Control
The Contractor shall provide the services of a factory trained manufacturer’s representative to check the installation and to start-up the grinder system. The factory representative shall have complete knowledge of the proper installation, operation and maintenance of the equipment supplied. The representative shall inspect the final installation and supervise a start-up test of the equipment. The Contractor shall submit the manufacturer’s factory representative’s report of satisfactory installation and startup to the Town Engineer.
J. Odor Control and Chemical Facilities
All stations shall incorporate a chemical feed and storage facility for odor control purposes unless the Town Engineer grants approval otherwise. The Town may require comminution rather than strainer baskets, on-site backup power and chemical feed facilities. This determination will be based on expected flow volumes and characteristics.
Chemical feed facilities should consist of the following as a minimum:
- Liquid chemical storage tanks with a capacity of 2,500 gallons
- 2 Wallace & Tierman Encore chemical feed pumps
- Modular building to house tanks and pumps with lights, heater and sump pump
- Containment system in case of tank or piping failure
Consideration shall also be given to gas phase odor control measures to eliminate odors emanating from the pump station site. Measures shall be submitted for approval to the Town Engineer.
Modular building to house chemical feed facilities shall be adequate to provide sufficient storage, clearance, and containment of chemicals. All supplementary or miscellaneous items, appurtenances, and devices incidental to or necessary for a sound, secure, and complete installation shall be designed and sealed by a NCPE.
L. Warranties and Documentation
Warranties - The pump manufacturer shall warrant to the Developer and subsequently the Town, that the pumps, motors, and controls supplied shall be free of defects in workmanship and material for a period of one year. The warranty shall be in printed form and made applicable to the Town (as Warrantee) at the time of acceptance for maintenance by the Town.
Documentation - Documentation to be supplied to the Town Engineer shall be three complete Operation and Maintenance manuals, including one in digital form, which include the following:
1. Cover Sheet Listing: Pump manufacturer; source of repair parts, complete with address and phone number; operating conditions - rated capacity and TDH of each pump; model number, serial number, impeller diameter of each pump; all data plate information from each pump motor; data on other equipment included as components in the pump station.
2. Pump Performance Curve with operating conditions indicated on it.
3. Detailed dimensional drawings of the pump and pump base elbow.
4. Detailed dimensional drawings of the pump motor.
5. A control panel wiring diagram.
6. Pump and motor Installation and Service Manual.
7. Detailed information related to other components of the pump station.
Before the operational test is conducted, the required copies of the Operation and Maintenance Manuals, including one in digital form, shall be delivered to the Town, and the wet well shall be thoroughly cleared of dirt, mud, gravel and other foreign debris. The operational test shall check the proper functioning of the pumps and pump controls. The pump, components, and motor serial numbers shall be verified. All components of the pump station shall be checked to ensure that they are capable of performing the service intended. The operational test shall be performed by the Town. The Contractor or Developer shall ensure that a representative from the pump station equipment manufacturer is present at the operational test to review proper operation of the equipment.
7.05 INSPECTION, TESTING AND REPAIR
The Contractor shall furnish all materials, labor, and equipment to perform all testing. Water for testing purposes will be provided by the Town and arranged for by the Contractor.
All materials used must be approved by the Inspector prior to installation. Rejected materials shall be immediately removed from the job.
Gravity sanitary sewer lines shall be clean and free from obstructions, and shall be visually inspected from every manhole. Lines which do not exhibit a true line and grade or which have structural defects shall be corrected. Sanitary sewer service connections shall be visually inspected prior to backfilling.
Low-pressure air testing shall be performed before all laterals or stubs are installed on the line, and after the trench has been backfilled to finished grade. Plugs shall be installed at each manhole to seal off the test section. The line will be pressurized with a single hose and monitored by a separate hose connection from the plug. Air then shall be slowly introduced into the sealed line until the internal air pressure reaches 4.0 psig. The air pressure shall then be allowed to stabilize for a minimum of 2 minutes at no less than 3.5 psig (plus groundwater pressure, if any). When the pressure reaches 3.5, the time required for the pressure to drop 1.0 psi will be observed and recorded. The line shall be "acceptable" if the pressure does not drop more than 1.0 psi in the time prescribed for the test in the Sanitary Sewer Air Test table found in the Details.
If the section fails to meet these requirements, the source of leakage shall be repaired and the pipe section re-inspected
The Inspector may require that an infiltration test be performed that shall not exceed 100 GPD/inch/mile.
See Section 7.01D for additional testing requirements for flexible and semi-rigid pipe.
The mandrel (go/no-go) deflection test must be performed on each line prior to acceptance, and no less than 30 days after installation. The Contractor shall supply the mandrel used for this performance test. The mandrel device shall be cylindrical in shape having 9 possible contact points with the pipe. The mandrel's length and diameter (ID of proving ring) shall be in accordance with the following tables, and shall be subject to the Inspector's approval.
For flexible pipes other than Polyethylene the following shall apply:
Nominal |
Proving Ring |
Diameter |
6 |
6 |
5.65 |
8 |
8 |
7.40 |
10 |
10 |
9.31 |
12 |
10 |
11.22 |
15 |
12 |
14.09 |
For semi-rigid pipes the following shall apply:
Nominal |
Minimum |
Diameter |
8 |
8 |
7.52 |
10 |
10 |
9.46 |
12 |
10 |
11.40 |
15 |
12 |
14.31 |
The force main shall be completely filled with water, all air shall be expelled from the pipe, and the discharge end of the pipeline shall be plugged and adequately blocked before the hydrostatic test begins.
The force main shall be tested to a pressure of 150 psi or three times the rated Total Dynamic Head of the pumps in psi, whichever is larger, as measured at the lowest elevation of the pipeline, for a duration of 2 hours. The pressure gauge used in the hydrostatic test shall be calibrated in increments of 10 psi or less. At the end of the test period, the leakage shall be measured with an accurate water meter. All visible leaks are to be repaired regardless of the amount of leakage.
Pipe Size Allowable Leakage |
|
Pipe Size |
Gallons |