SECTION 07000
WASTEWATER COLLECTION SYSTEMS
TABLE OF CONTENTS
07010 GRAVITY SEWERS
A. Design
B. Materials
C. Sewer Main Installation
07020 MANHOLES
A. Design
B. Materials
C. Installation
07030 SERVICE CONNECTIONS
A. Design
B. Materials
C. Installation
07040 TESTING AND INSPECTIONS
A. General
B. Sewer Main and Service Connection Testing
C. Manhole Testing
07050 REPAIRS
A. Sewer Main Repairs
B. Installation
07010 Gravity Sewer
A. DESIGN
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) All private sewer collection mains inside the Cary Utility Service area that will connect or are planning to discharge into the Cary sewer system shall comply with all Town of Cary design, siting and installation criteria outlined herein. The Owner of the private sewer collection system shall meet all State design requirements and obtain a State permit to operate the private system.
c) Gravity mains shall be installed in dedicated public right of way or in dedicated utility easements as follows:
Standard Easement Width for Sanitary Sewer Mains
|
Pipe Size (diameter) |
Pipe Depth(feet) |
Easement Width (feet) |
|
8-inch to 12-inch |
10-ft or less |
20-ft |
|
8-inch to 12-inch |
10-ft – 12.5-ft |
25-ft |
|
8-inch to 12-inch |
12.5-ft – 15-ft |
30-ft |
|
8-inch to 12-inch |
15-ft to 17.5-ft |
35-ft |
|
8-inch to 12-inch |
17.5-ft to 20-ft |
40-ft |
|
12-inch to 24-inch |
15-ft or less |
30-ft |
|
12-inch to 24-inch |
15-ft – 17.5-ft |
35-ft |
|
12-inch to 24-inch |
17.5-ft – 20-ft |
40-ft |
|
Greater than 24-inch |
Any Depth |
Specified by Town Engineer |
|
Any Size |
Deeper than 20-ft |
Specified by Town Engineer |
Dedicated easements for sewer mains and appurtenances shall be recorded as “Town of Cary Utility and Pipeline Easement” or “Town of Cary Sanitary Sewer Easement”. Town of Cary sewer easements shall not contain any other utilities.
d) No developer, contractor or property owner shall place any part of a structure, any permanent equipment, permanent retaining wall or impoundment within sanitary sewer easements or utility easements dedicated to the Town of Cary. Fences may be allowed across easements provided that appropriate access gates have been installed to allow utility maintenance. Fill or cut slopes are not allowed to extend into easements except by specific approval by the Town Engineer.
e) 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. Easements across sloped areas shall be graded uniformly across the slope to no steeper than a 5 to 1 ratio.
f) 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.
g) Mains shall not be installed under any part of water impoundments.
h) The following minimum horizontal separations must be maintained:
i. 100 feet from any private or public water supply source, including wells, 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, ductile iron sanitary sewer pipe with joints equivalent to water main standards must be used.
i) In accordance with Policy Statement Number 23, mains must be extended along natural drainage courses to the adjacent property line.
j) 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.
k) Mains over 20 feet deep require ductile iron for the entire run between manholes.
l) 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 18 inches the entire leg of sanitary sewer shall be made of water main standard ductile iron pipe and the void space between the pipe crossing shall be backfilled with 3000-psi concrete or excavatable flowable fill that meets or exceeds NCDOT specifications.
m) There shall be a minimum 5 foot horizontal separation between parallel gravity and/or force mains.
n) 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.
o) 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 and the void space between the pipe crossing shall be backfilled with excavatable flowable fill that meets or exceeds NCDOT specifications. The water main shall be centered at the point of crossing, which shall be at an approximate 90 degree angle.
2. Main Size, Slope and Design Criteria
a) Public gravity mains shall be a minimum of 8 inches in diameter.
b) Major interceptors shall be sized in accordance with the "Town of Cary Wastewater Collection System Master Plan". 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. At a minimum, all gravity sewer mains shall be designed and sized to serve the ultimate tributary buildout of the drainage basin.
|
Land Use |
Flow Factor |
|
Single Family Residential |
280 gpd per dwelling unit |
|
Multi-Family Residential |
100 gpd per 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 the North Carolina Department of Environment and Natural Resources (NCDENR).
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 minimum velocity for sanitary sewer lines shall be 3-fps. The minimum velocity may be reduced to 2.5-fps under limited circumstances only by approval of the Town Engineer.
e) Sanitary sewers shall be sized based on the Manning’s Equation with Manning’s roughness coefficient “n” = 0.013 or greater. Pipe diameter sizes used in the calculation of Manning’s Equation shall be nominal pipe sizes.
f) The minimum grades for public sanitary sewers shall be as follows:
Minimum Slopes for Gravity Sewer Mains
|
Main Size (diameter in inches) |
Minimum Slope V=3.0ft/s, depth 2/3 full (feet per 100 feet) {standard required velocity} |
|
8 |
0.61 |
|
10 |
0.46 |
|
12 |
0.36 |
|
14 |
0.29 |
|
15 |
0.27 |
|
16 |
0.25 |
|
18 |
0.21 |
|
21 |
0.17 |
|
24 |
0.14 |
|
27 |
0.13 |
|
30 |
0.11 |
|
36 |
0.09 |
Note1: All minimum slopes based on Manning’s Equation
Note2: Manning’s coefficient n = 0.013 used for all computations
g) The minimum grade for the uppermost reach of a sanitary sewer line shall be 1% regardless of sewer line size.
h) 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, which apply to all sewers either designed or installed at grades equal to or exceeding 10%:
i. All sewers with a grade of 10% or higher must have the downstream run of pipe installed with ductile iron pipe.
ii. High velocity manholes shall be used on all sewers with a grade of 10% or higher. 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 designed at grades of 10% or higher. The anchors shall be installed 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%
iv. The Town reserves the right to require all high velocity requirements outlined herein for sewer lines either designed or installed at grades of 10% or greater, regardless of the flow velocity. In cases where the design grade established on the sewer design plan is exceeded during construction and the 10% threshold is exceeded, all high velocity requirements shall apply without waiver.
i) 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.
j) 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. As an alternative, the crown of the incoming pipes may be designed for an elevation at or above the crown of the outgoing pipe.
B. MATERIALS
Materials specified herein are acceptable for sewer service as described herein.
See Standard Procedure 120 for instructions on requesting new product approval.
1. Pipe Material
a) 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 pressure class rating as follows:
Minimum Pressure Class for DIP Sewer Mains
|
Pipe Diameter |
Depth of Cover |
Pressure Class |
|
8-inch |
3-20 -feet |
350-psi |
|
10-12-inch |
3-14 -feet |
350-psi |
|
14-20-inch |
3-10 -feet |
250-psi |
|
24-64-inch |
3-8 -feet |
200-psi |
Note: For cases not specified, consult with the Engineering Department for further guidance.
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 20-ft lengths unless approved otherwise by the Engineering Department.
b) 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 and shall be supplied in minimum 12.5-ft lengths. 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. All PVC gravity sewer pipe and PVC fittings shall be manufactured in accordance with the latest version of ASTM D3034. 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 PVC pipe up to and including 15 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. The Town of Cary reserves the right to require the installation of SDR 26 or SDR 21 pipe at the discretion of the Engineering Department.
PVC pipe of any make, brand, profile or type shall not be used for installations larger than 15-inches in diameter, without first receiving written approval of the Engineering Department.
PVC pipe shall not be used for installations deeper than 20-ft.
c) 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 5.3 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.
d) 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:
· Pipe class or strength designation
· Manufacturer's name or trademark
· Nominal pipe size
e) Bedding Materials
For PVC and PVC Composite sewer mains, see section “Additional Requirements for Flexible and Semi-Rigid Pipe” and the Standard Details for bedding requirements.
C. SEWER MAIN INSTALLATION
1. General Requirements
a) See design criteria contained herein for additional installation requirements.
b) Pipe trench excavation and backfilling shall be performed in accordance with Section 05000 of these Specifications.
c) Transitions of pipe material, pipe separations, grade changes and all angular deflection changes shall occur only at manholes.
d) Ductile Iron Pipe shall be installed in accordance with the Ductile Iron Pipe Handbook published by DIPRA and AWWA C500.
e) All sewer mains installed with less than 3-ft of cover and deeper than 20-ft shall be ductile iron pipe.
f) Class I bedding shall be required for all sewer installations, regardless of pipe material, when the trench bottom is unstable due to water, rock, infiltration or soil type.
g) All bedding, embedment and backfill materials shall be compacted to a minimum of 95% Standard Proctor density regardless of material. In instances where compliance with compaction requirements is questionable as determined by the Inspector, testing shall be provided by the Contractor and a reputable licensed Geotechnical Engineer to verify compliance.
h) The minimum trench width shall be one pipe diameter plus 9 inches on each side of the pipe.
2. Additional Requirements for Flexible and Semi-Rigid Pipe
a) PVC is classified as “Flexible” pipe, and PVC Composite is classified as “Semi-rigid.” The installation shall satisfy the requirements of the manufacturer, and/or the following, whichever is more stringent:
b) The manufacturer's specifications or other approved method shall be used in determining the stiffness class of the pipe to be installed to attain the required deflection control. The class of the pipe must be approved by the Town Engineer prior to installation.
c) 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.
d) 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.
e) Installation of PVC Composite (Truss) pipe shall comply with ASTM 2321. For semi-rigid sewer installations, bedding and embedment material shall be Class I.
f) 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, whether flexible or semi-rigid.
g) 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.
h) The bedding (6-inch minimum below the pipe) 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-inches above the crown of the pipe.
i) 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.
j) 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.
07020 MANHOLES
A. DESIGN
1. Manhole Location, Siting and Design
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 in diameter.
b) Manholes shall be installed at each deflection of line and/or grade. The flow channel through manholes shall have a uniform and smooth finish free of irregularities or obstructions. The invert channel shall conform to the shape and slope of the entering/exiting sewer line. Either pre-cast or brick and mortar inverts may be used.
c) The maximum flow deflection angle in a manhole shall be dependent upon pipe size as shown in the following table.
Maximum Allowable Flow Deflection
|
Pipe Size (largest pipe controls) |
Maximum Deflection Angle per Manhole |
|
8-10 inch diameter |
90 degrees |
|
12-20 inch diameter |
75 degrees |
|
>20-inch diameter |
60 degrees |
d) Free falls of wastewater flow into the manhole invert from incoming sewer mains shall not be allowed, except under limited circumstances.
e) In certain isolated circumstances standard free drops may be allowed, not exceeding 20-inches, when pipe diameter changes occur at a manhole. In these cases, the smaller diameter pipe crown shall be positioned no higher than the larger diameter pipe crown to limit the drop. When free drops are necessary due to pipe size changes, the Contractor shall take preventive measures to prevent free drops into the manhole invert, such as building a flume or trough up to the incoming invert, or piping the flow to the primary invert flow channel.
f) Drop manholes are not allowed without the written approval of the Engineering Department. While certain physical constraints may dictate the need for drop manholes, they may not be used merely to decrease trenching depth. Upstream slope changes shall be used to avoid the need for drop manholes.
g) In the event that drop manholes are required, they shall be constructed with an outside drop connection. The entire incoming sewer main leading to the drop shall be made of ductile iron pipe. Drops shall be concrete encased and constructed in accordance with the Standard Details.
h) Inside drop manholes shall only be allowed in unique circumstances on a limited basis and can only be approved by the Town Engineer.
i) Manholes shall not be obstructed from view or access. It is illegal to bury or obstruct access to manholes.
j) Manhole covers shall be elevated as follows:
· Roadways: Manholes installed in roadways and road shoulders shall be installed with the cover flush with the top of pavement.
· Outside of Roadways: Manholes installed outside of roadways shall be elevated at least 1-ft above the surface grade unless otherwise noted.
· Wooded Outfalls: All manholes installed in wooded, forested or brushy areas shall be elevated at least 2-ft above the surface elevation.
· 100-Year Flood Zone: All manholes located within the 100-year flood elevation shall be elevated at least 18-inches above the 100-year flood elevation or specify watertight covers and vents that extend at least 18-inches above the 100-year flood elevation.
k) Manholes higher than 30 inches above finished grade will require outside steps.
l) When connecting a new sewer main to an existing main, the connection shall be established with a “Doghouse” type of manhole inserted over the existing main. In designing a manhole connection with a doghouse manhole, the angular separation between any incoming or outgoing mains shall be greater than 35 degrees and in accordance with manufacturer recommendations.
2. Manhole Sizing
a) Manholes shall be sized as shown in the following table. The next larger size shall be required if the pipe size, depth, drop connection or number of main line connections warrants a larger size. In consideration of main line connections, all will be considered regardless of type, whether inside drop, outside drop, force main or standard connection.
Manhole Sizing Guide
|
Manhole Size
(diameter, feet) |
Main Pipe Size
(diameter, inches) |
Depth
(invert to surface) |
Inside Drop Connection (number) |
Standard Main Line Connections (number) |
|
4-ft |
8-16 inches |
3-12-ft |
none |
2 |
|
5-ft |
16-30 inches |
12-20-ft |
1 |
3 |
|
6-ft |
36-54 inches |
20-30-ft |
2 |
4 |
B. MATERIALS
1. Concrete Manholes
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.
2. Manhole Frame and Cover Materials
a) Manhole Frames and Covers shall be Class 35 gray iron with "Sanitary Sewer" and the Town symbol forged into the cover as indicated in the details. Ring and cover shall be stamped with make and model. All manhole frames and covers shall be domestically made and manufactured in the USA from domestic iron.
b) For installation in roadways, use Type 1 ring and cover and place sufficient depth concrete below the pavement around the ring to ensure 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 in all outfall locations
c) 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, except in paved streets.
d) 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.
e) 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.
3. Manhole Step Materials
a) 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. The eccentric cone shall be oriented so that the steps are vertical over the downstream invert of the primary flow path to allow ease of access for maintenance, camera or cleaning operations.
C. INSTALLATION
1. General Requirements
a) The upstream side of the last manhole(s) of a sanitary sewer line extension under construction shall be plugged by constructing a brick/block wall to prevent the passage of groundwater, runoff and sediment into the sanitary sewer system. All water upstream of the wall 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 wall shall not be removed until the line has been inspected by the Town to ensure 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.
b) Manholes shall not be buried or hidden, which is a violation of the sewer use ordinance and subject to penalty by fines.
c) All manhole connections, whether incoming sewer main or service lateral, shall be cored with a concrete coring machine. All pipe connections must be made with flexible watertight couplings or boots.
d) All external manhole joints shall be wrapped with an approved joint seal material.
2. Manholes Subject to Inundation
a) Manholes subject to flooding shall be watertight and vented 18-inches above the 100-YR flood elevation. In flood prone areas, the manholes shall be vented at least every 1000-ft or every other manhole, whichever is greater.
b) The exterior of all manholes within the 100-year flood elevation shall receive an exterior coating of the manhole with Koppers bitumastic coal tar epoxy or an approved epoxy coating at 40-mils to prevent weepage or attack by acidic soils.
c) All manholes subject to inundation extended above the ground surface shall receive an external frame chimney seal from an approved manufacturer.
3. Manholes Located on Large Collection Mains
a) The Town reserves the right to require all manholes located on interceptor or outfall mains 24-inches in diameter and larger to have the manhole interior, and bench coated with an approved epoxy coating at 80-mils thickness. The preferred method of application is field application after the manholes are installed for a monolithic holiday free coating. Factory application will be allowed contingent upon the joints receiving a field application.
4. Manholes Located on Sanitary Sewer Force Mains
a) All manholes, vaults or wells located on pressurized sanitary sewer force mains, including manholes with air-release valves, shall receive an internal epoxy coating. The epoxy product must be approved by the Town and installed at a minimum 80-mils thickness.
b) All manholes located on gravity mains that that serve as discharge points for sanitary sewer force mains shall receive an interior epoxy coating at 80-mils thickness. In addition to the receiver manhole, the Town reserves the right to require epoxy coating of the next 2 consecutive manholes downstream of the receiver manhole or all