SECT-42_MANHOLES.docx

Item No. Title

42.1 GENERAL

42.3 CASTINGS

42.5 CLEANING

42.6 INSPECTION FOR ACCEPTANCE

42.1 GENERAL

Manholes shall be leak-tight and constructed of pre-cast concrete units. Cast-in-place manholes may be approved by the CITY ENGINEER or designee on a case-by-case basis for conflict resolution. Brick manholes are not acceptable.

42.2 PRE-CAST CONCRETE MANHOLES

42.2.1 GENERAL

Pre-cast manholes shall conform to specifications for Pre-cast Reinforced Concrete Manhole Sections, ASTM Designation C478, except as otherwise specified below.

42.2.2 MISCELLANEOUS REQUIREMENTS

The minimum wall thickness shall be 5 inches. Pre-cast manholes shall be constructed with a pre-cast monolithic base structure as shown on the STANDARD DRAWINGS. The minimum base thickness shall be 8 inches. No interior ladders are permitted in manholes.

Concrete for manholes shall be Type II, 4000 psi at 28 days. Barrel, top and base sections shall have tongue and groove joints. All jointing material shall be cold adhesive preformed plastic gaskets, conforming with F.D.O.T. Article 942-2.

The date of manufacture and the name or trademark of the manufacturer shall be clearly marked on each pre-cast section.

Sections shall be cured by an approved method for at least 28 days prior to painting and shall not be shipped until at least 2 days after having been painted.

Pre-cast concrete top slabs shall be used where cover over the top of the pipe is less than 3 ft. Lift rings or non-penetrating lift holes shall be provided for handling pre-cast manhole sections. Non-penetrating lift holes shall be filled with non-shrink grout after installation of the manhole sections.

Concrete surfaces shall have form oil, curing compounds, dust, dirt and other interfering materials removed by brush sand blasting and shall be fully cured prior to the application of any coatings.

Interior surfaces of manholes shall have a protective epoxy coal tar coating with a minimum dry mil thickness of 16 mils. Exterior surfaces shall have a protective epoxy coal tar coating with a minimum dry mil thickness of 9 mils. Coatings shall be applied in two (2) applications by the manhole manufacturer in strict accordance with the paint manufacturer's recommendations. Interior and exterior surface coatings shall be: Koppers Bitumastic No. 300M or approved equal. Manholes at sewer force main terminus connections must be fiberglass, fiberglass lined, with an “Agru Sure Grip©” Liner, GSE stud liner, or approved equal liner material, minimum 80 mil / 2mm thick.

42.2.3 INSPECTION

The quality of all materials, the process of manufacture, and the finished sections shall be subject to inspection and approval by the CITY ENGINEER or designee. Such inspection may be made at the place of manufacture, or at the site after delivery, or at both places, and the sections shall be subject to rejection at any time on account of failure to meet any of the specification requirements, even though sample sections may have been accepted as satisfactory at the place of manufacture. Sections rejected after delivery to the job shall be marked for identification and shall be removed from the job at once. All sections, which have been damaged after delivery will be rejected and, if already installed, removed and replaced, entirely at the CONTRACTOR'S expense.

At the time of inspection, the sections will be carefully examined for compliance with the specified ASTM designation, and with the approved manufacturer's drawings. All sections shall be inspected for general appearance, dimension, "scratch-strength", blisters, cracks, roughness, soundness, etc. The surface shall be dense and close-textured.

42.3 CASTINGS

Gray iron castings for manhole frames, covers, adjustment rings and other items shall conform to the ASTM Designation A 48, Class 30. Manhole frames and covers shall be USF 152-BV, and shall have a nominal, minimum twenty-four inch (24") opening. Castings shall be true to pattern in form and dimensions and free of pouring faults and other defects which would impair their strength, or otherwise make them unfit for the service intended. The seating surfaces between frames and covers shall be machined to fit true. No plugging or filling will be allowed. Lifting or "pick" holes shall be provided. Casting patterns shall conform to those shown or indicated on the STANDARD DRAWINGS. All manhole frames and covers shall be traffic bearing to meet AASHTO H-20 loadings. Frames shall be suitable for the future addition of a cast iron ring for upward adjustment of top elevation. In certain locations bolt down covers and gasketed covers shall be located as shown on the DRAWINGS (i.e., flood prone areas).

42.4 CONSTRUCTION DETAILS

42.4.1 BEDDING

Base sections shall be placed on bedding rock conforming to the requirements in Section 32.8.2. The bedding rock shall be firmly tamped and made smooth and level to assure uniform contact and support of the pre-cast element. Refer to Section 32.9.2 for density requirements. Refer to the STANDARD DRAWINGS for additional bedding details.

42.4.2 CAST-IN-PLACE BASES

Cast in place bases shall be utilized only when specifically approved by the CITY ENGINEER or designee. Unless otherwise specified, cast-in-place bases shall be at least eight (8) inches in thickness and shall extend at least six (6) inches radially outside of the outside dimension of the manholes section. Reinforcement and connection to the riser sections shall be designed by the ENGINEER OF RECORD and submitted to the CITY ENGINEER or designee for approval.

42.4.3 PRE-CAST MANHOLES

A pre-cast base section shall be carefully placed on the prepared bedding so as to be fully and uniformly supported in true alignment and making sure that all entering pipes can be inserted on proper grade.

The first pre-cast section shall be placed and carefully adjusted to true grade and alignment. All inlet pipes shall be properly installed so as to form an integral watertight unit. The sections shall be uniformly supported by the base structure, and shall not bear directly on any of the pipes. (All PVC or DIP connections to manholes shall be flexible “Kor-N-Seal” Watertight rubber pipe boot with stainless steel connection or tensioning band.)

Pre-cast sections shall be placed and plumbed to provide vertical alignment with a ½-inch maximum tolerance per 5 feet of depth. The completed manhole shall be rigid, true to dimensions, and watertight. Pre-formed flexible plastic joint sealer conforming to Federal Specifications SS-S0210 (GSA-FSS) “RAM-NEK” shall be used. Exterior joints (wall surface) shall be wrapped with “EZ-Wrap” adhesive flexible joint sealant or approved equal.

42.4.4 EXCAVATION AND BACKFILLING

Requirements of Section 32 shall apply.

42.4.5 PLACING CASTINGS

Casting shall be fully bedded in mortar with adjustment brick courses placed between the frame and manhole. Bricks shall be a minimum two (2) and maximum four (4) courses. Mortar shall conform to ASTM C-270, Type M, and the bricks shall be clay and conform to ASTM C-216, grade SW, size 3 ½" (W) x 8" (L) x 2 1/4" (H). The CITY ENGINEER or designee may, on a case-by-case basis, approve the use of concrete collars or "doughnuts" to bring manhole rings and covers to finish grade provided that at least one (1) course of brick is utilized between the concrete collars or "doughnuts" and the rings and covers.

Top of manhole castings located in pavement, shouldered areas, and sidewalks shall be set flush with grade. Top of manhole castings located outside these areas shall be placed 2" above grade.

42.4.6 CHANNELS

Manhole flow channels shall be as shown in the STANDARD DRAWINGS, with smooth and carefully shaped bottoms, built up sides and benching constructed using cement and brick with no voids. Channels shall conform to the dimension of the adjacent pipe and provide changes in size, grade and alignment evenly. Cement shall be Portland Cement Type II only.

42.4.7 PIPE CONNECTIONS

Special care shall be taken to see that the openings through which pipes enter the structure are provided with watertight connections. For ductile iron and PVC pipe, connections shall conform to ASTM C 923, "Standard Specifications for Resilient Connectors between Reinforced Concrete Manhole Structures and Pipes." For concrete pipe connection shall be made with non-shrink nonmetallic grout. Flexible rubber “Kor-N-Seal” watertight pipe boots are required for all PVC and DIP connections.

42.4.8 DROP MANHOLE CONNECTIONS

Drop manhole connections shall conform in all respects to details shown on the STANDARD DRAWINGS (external drop connections – ONLY!).

42.5 CLEANING

All newly constructed manholes shall be cleaned of any accumulation of silt, debris, or foreign matter of any kind, and shall be free from such accumulations at the time of final inspection.

42.6 INSPECTION FOR ACCEPTANCE

No visible leakage in the manhole or at pipe connections will be permitted. All manholes shall be inspected by the CITY ENGINEER or designee prior to acceptance. All manholes failing to meet the specification set forth in Section 42 above shall be reconstructed or replaced by the CONTRACTOR to comply with these specifications. Pressure grouting of manholes for repair shall be approved in writing by the City Engineer, or designee, on a case-by-case basis. Interior wall grout, concrete mortar plastering shall not be accepted for manhole leak repairs.

SECTION 42 - MANHOLES