A. 
Standard manholes, special manholes and wet wells shall be constructed complete with covers in accordance with the precast concrete manhole specifications herein. Standard manholes above the foundations, unless otherwise required, shall be constructed of monolithically poured reinforced concrete sections specially cast for use in manholes.
B. 
Manhole inverts shall be carefully constructed to maintain the proper velocities through the manhole, and in no case shall the invert sections through the manhole be greater than that of the outgoing pipe. The shape of the invert shall conform exactly to the lower half of the pipe to which it connects. Side branches shall be connected with as large radius of curve as practicable. All inverts shall be troweled to a smooth clean surface.
Manholes shall be constructed of materials which shall conform to the following:
A. 
Circular precast section per ASTM C478, with a minimum wall thickness of five inches.
B. 
Mortar: one part portland cement, 1/2 part hydrated lime, three parts sand, mixed dry, with only enough water added to provide a workable consistency.
C. 
Castings:
(1) 
Cast-iron ASTM A48.
(2) 
Coating hot asphaltum applied at foundry.
A. 
General.
(1) 
Manholes shall be made of precast concrete sections of which the top section shall be eccentric or flat slab top. Bottom section shall be a precast concrete manhole base.
(2) 
Poured in place bases will not be acceptable.
(3) 
All precast manhole sections shall be manufactured in accordance with and meet the requirements of specification ASTM C-478, latest revision.
(4) 
All precast manhole sections shall be manufactured by the wet cast method.
(5) 
The minimum compressive strength of the concrete for all sections shall be 4000 psi. The maximum allowable absorption of the concrete shall not exceed 9% of the dry weight. Tests, when required, shall be in accordance with ASTM C-497, Determining Physical Properties of Concrete Pipe and Tile, latest revision. The circumferential steel reinforcement for risers, cone sections and base walls shall be a minimum of 0.12 square inches per vertical foot for forty-eight-inch diameter manholes and 0.0025 times the inside diameter in inches per vertical foot for larger diameter manholes.
B. 
Products.
(1) 
Standard manhole.
(a) 
The manholes shall be constructed of precast reinforced concrete manhole sections. The sections shall be a minimum of four feet in diameter for pipe sizes up to and including 20 inches internal diameter.
(b) 
The sections shall conform to the requirements of the Specification for Precast Reinforced Concrete Manhole Section. (ASTM C-478, latest revision). Joints shall be sealed with a preformed plastic gasket that meets or exceeds all requirements of Federal Specification SS-S-00210, Sealing Compound Preformed Plastic for Pipe Joints, Type 1, Rope Form, as manufactured by Hamilton Kent Manufacturing Co., Kent, Ohio, or BUTYL-LOK as manufactured by A-LOK Products, Tullytown, Pennsylvania; D-LOK Rubber Gasket as specified to meet the requirements of Specification ASTM C-443, as supplied by Atlantic Concrete Products Co., Tullytown, Pennsylvania, or equal.
(c) 
Manholes four feet in diameter shall have a bottom at least six inches thick and a wall at least five inches thick.
(d) 
Manholes five feet in diameter shall have a bottom at least eight inches thick and a wall at least five inches thick.
(e) 
Manholes six feet in diameter shall have a bottom at least eight inches thick and a wall seven inches thick.
(f) 
Manholes eight feet in diameter shall have a bottom at least 12 inches thick and a wall nine inches thick.
(2) 
Manhole bases.
(a) 
Manhole bases shall be precast reinforced concrete. Poured-in-place bases will not be acceptable.
(b) 
The bases shall be monolithically cast and shall consist of a manhole bottom and a wall which shall extend a minimum of six inches above the top of the highest inflowing sewer. The top of the base section shall be carefully formed to receive the tongue of the barrel section. There shall be a minimum distance of four inches between the invert of the lowest outflowing sewer and floor of the precast base to provide for the construction of a formed invert and bench wall within the manhole. No more than two lift inserts or holes shall be cast in the bases.
(c) 
All precast manhole bases shall have pipe-to-manhole flexible seals as manufactured by A-LOK Products Corporation, Tullytown, Pennsylvania, A-LOK full-compression seals, or equal.
[1] 
Pipe seals up to and including 20 inches in size shall be cast into forty-eight-inch-diameter manhole bases.
[2] 
Twenty-one-inch through thirty-inch pipe seals shall be cast into sixty-inch-diameter manhole bases.
[3] 
Thirty-three-inch through forty-eight-inch pipe seals shall be cast into seventy-two-inch diameter manhole bases.
[4] 
Flexible pipe to manhole seals shall meet Rubber Gasket Specifications ASTM C-443 and Test Performance Requirements A.S.T.M. C-425 for Compression Joints.
[5] 
Installation of pipe-to-manhole flexible seal shall be made in accordance with the manufacturer's suggested specifications.
(3) 
Risers and top section.
(a) 
The top of base walls, the ends of reinforced concrete risers and the bottom ends of precast tops shall be so formed that, when risers and tops are assembled with the base, they will make a continuous manhole. Joints shall be of such design as will permit effective joining and placement without irregularities in the interior wall surface of the manhole.
(b) 
Manhole barrels shall consist of riser and top section with a minimum wall thickness of five inches. The top section shall be eccentric conical section with thickened upper walls with the smallest inside diameter equal to 30 inches, to receive the manhole frame and cover. No more than two lift inserts or holes shall be cast in each barrel or top section.
(4) 
Manhole steps.
(a) 
Manhole steps shall be of extruded 6061-T6 aluminum and shall be the equal of ALCOA Stock No. 12653A or Polypropylene step PS4B as manufactured by M.A. Industries, Peachtree City, Georgia, or equal.
(b) 
Manhole steps shall be cast into the walls of base, risers and conical top sections and shall be aligned vertically and spaced so as to be on equal centers in the assembled manhole at a maximum distance apart of 12 inches. Steps shall be located a minimum of six inches from the ends of base, riser and top sections and shall be securely embedded in manhole sections by mortar or cast-in-place polypropylene inserts.
(c) 
Manhole step dimensions shall meet the requirements of OSHA Standard 1910.27 for fixed ladders.
(5) 
Manhole frames and covers.
(a) 
Casting shall be tough gray iron, free from cracks, holes, swells and cold shuts. All manhole casting shall be made accurately to the pattern and to the dimensions shown on plans, and shall be planned where marked, or where otherwise necessary to secure perfectly flat and true surfaces. All lids which rock and do not lie solid after construction is finished will be condemned and must be replaced by perfect lids.
(b) 
Anchor bolts.
[1] 
Anchor bolts for bolting manhole frame to precast or brick manholes shall be three-fourth-inch-diameter galvanized all-thread steel rods with five-inch hook for embedment in the manhole top and a minimum two-inch projection through the bars of the frame.
[2] 
Two bolt slots or inserts shall be cast into the manhole top, positioned at 180° at the time of manufacture.
(c) 
All standard manhole frames and covers shall have a nominal weight of 400 pounds and shall be Campbell Foundry Pattern No. 1203B, or equal. All frames shall have brick rings. All covers shall be solid with no vents.
(d) 
All watertight manholes shall have waterproof manhole frames with bolted lids and shall be Campbell Foundry Pattern No. 6544 or equal 440 pounds with anchor bolts and bolt holes.
A. 
Precast concrete bases.
(1) 
All precast concrete bases shall be installed on a layer of crushed stone, which shall have a minimum depth of eight inches. The crushed stone shall conform to the quality and grading requirements specified in § 201-141.
(2) 
All pipe openings shall have pipe-to-manhole flexible seals as specified herein.
(3) 
In constructing drop manholes, the contractor shall use one of the following methods:
(a) 
Encase and support the riser and incoming pipe with concrete down to undisturbed earth as shown on the detail sheet. Encasing the riser with brick will not be acceptable. Care shall be taken to have all pipes laid to correct lines and grades before concreting is undertaken.
(b) 
Purchase precast base with a ninety-degree bend precasted into the base section and protect the vertical pipe with precast drop collars.
(c) 
Purchase a minimum five-foot-diameter manhole and run the drop internally inside the manhole. Internal piping to be secured by expansion bolts and stainless steel bands.
B. 
Masonry work.
(1) 
The top of all precast manholes may be brought to proper grade for receiving manhole frames by using not more than three courses of brick or precast concrete grade rings. Masonry construction shall be performed by experienced and qualified workmen only. All work shall be laid plumb, straight, level, square and true. Brick shall be laid in full beds of mortar and shoved into place. All joints shall be full and not more than 1/2 inch in thickness. The contractor shall set in place and bond in the masonry all necessary steps and miscellaneous items specified elsewhere. The masonry wall shall be parted on the inside and outside with a one-half-inch coat of Portland Cement mortar.
(2) 
Mortar to be used in brickwork, setting manhole frames and parging shall be prepared by thoroughly mixing one volume of Type II portland cement with three volumes of sand and sufficient clean water to produce a rich mass of approved consistency. Mixing mortar on the ground or any paved surface shall not be permitted. Sand to be used in making mortar shall be clean, well-graded and shall pass a standard No. 4 sieve.
(3) 
All mortar to be used in joining manhole section, filling lift holes in risers shall be an approved mixture of sand, cement and Embeco aggregate.
(4) 
Masonry shall not be constructed during cold weather (air temperature below 40° F.) unless necessary precautions are observed.
C. 
Flow channels and bench walls.
(1) 
In precast bases, the flow channels and bench walls in each manhole shall be carefully formed of mortar and brick, or concrete, to 3/4 pipe section.
(2) 
The minimum depth of flow channel shall be equal to 3/4 the diameter of the pipe to which it connects. The channel shall be graded to give a smooth, uninterrupted flow through the manhole.
(3) 
Bench walls shall be pitched a minimum of one inch per foot from the inside periphery of the manhole to the edge of the flow channel.
(4) 
The contractor has the option to pour the flow channels or to have them precast by the manhole manufacturer.
D. 
Manhole frames and covers. Manhole frames and covers shall be brought to proper grade as previously noted, set in one-fourth-inch bed of mastic, and anchored in place with the top two three-fourths-inch-diameter anchor bolts, which shall be securely embedded in the top of the manhole.
E. 
Waterproofing.
(1) 
The entire outer surface of all precast concrete manholes shall be coated with two coats of an approved bitumastic coating. Coating shall be Carboline/Kop-Coat 300-M Epoxy or Pennsbury 32-B-4 Epoxy.
(2) 
A rubber boot shall be cast integrally into each manhole cone or flat slab top section to prevent surface infiltration. The boot shall be Water-LOK Manhole Entry Sleeve as manufactured by A-LOK Products, Tullytown, Pennsylvania, or equal.
A. 
Water test method.
(1) 
All manholes will be tested for exfiltration by plugging any pipes entering the manhole and then filling the manhole with water to a point two feet above the top of the upper riser. The test water shall remain in the manhole a sufficient time for absorption before starting the test. The loss of test water shall not exceed one inch per hour for two hours.
(2) 
When the sewer line is tested by the water test method, the manhole may be tested in conjunction with the line test. The Township may require the contractor to retest individual manholes separately on a twenty-percent random basis as a part of the contract. The Township may request additional testing and, if so ordered, the work must be retested by the contractor. If such work is found to be in accordance with the contract documents, the Township will pay the cost of retesting. If such work is found not in accordance with the contract documents, the contractor shall pay such cost.
B. 
Negative air pressure (vacuum) method.
(1) 
The contractor may test concrete manholes by the Vacuum Method in accordance with ASTM C 1244-93. The contractor shall provide all testing equipment and appurtenances and conduct such tests or retests in the presence of the Township Inspector, or his representative, and to his satisfaction. The contractor shall provide three copies of the manhole test results to the Engineer.
(2) 
All lift holes, any pipes or other penetrations entering the manhole are to be plugged, taking care to securely brace the pipes and plugs to prevent them from being drawn into the manhole. The test head shall be placed at the top of the manhole in accordance with the manufacturer's recommendations. A vacuum of 10 inches of mercury shall be drawn on the manhole, with the valve on the vacuum line of the test head closed, and the vacuum pump shut off. The time shall be measured for the vacuum to drop to nine inches of mercury. The manhole shall pass if the time for the vacuum reading to drop from 10 inches to nine inches of mercury meets or exceeds the values indicated below.
Minimum Test Times for Various Manholes/ Depths
Depth
Diameter
(feet)
48 inches
(time in seconds)
60 inches
(time in seconds)
72 inches
(time in seconds)
8
20
26
29
10
25
33
36
12
30
39
43
14
35
46
51
16
40
52
58
18
45
59
65
20
50
65
72
22
55
72
79
24
59
76
87
C. 
If the manhole fails the initial test, the contractor shall make necessary repairs, and the manhole shall then be retested until a satisfactory test is obtained. Use or failure of vacuum testing shall not preclude acceptance by appropriate water infiltration or exfiltration testing.