671 Page 472671 MANHOLES
671.1DESCRIPTION
This work consists of the construction or reconstruction of manholes.
671.2MATERIALS
Materials will conform to the following sections. A.Cast In Place Concrete: Class M6 Section 462. B.Brick: Clay or shale brick will comply with the requirements for building bricks as provided in ASTM C62. The brick will be Grade SW. C.Concrete Block: Concrete block masonry will conform to ASTM C139. The dimensions of the block may be any standard size which will produce the required dimensions in the completed structure. D.Precast Units: Precast manhole units will conform to AASHTO M 199 and Section 990.1 A.2 except that Section 990.1 A.2.h will not apply. E.Castings: Unless otherwise specified on the plans, frames and covers will consist of approved gray iron castings meeting AASHTO M 105, Class 35. F.Mortar: Mortar will consist of one part Portland cement and two parts mortar sand conforming to Sections 750 and Section 810 respectively. As an alternate, a commercially available grout conforming to Section 460.2 K may be used. G.Steel Reinforcement: Section 1010 .
671.3CONSTRUCTION REQUIREMENTS
Concrete for cast in place manholes will be hauled, placed, finished, cured, and protected in accordance with Section 460. When the foundation for a manhole is in new embankment, the embankment will be constructed at least 1 foot above the footing before the foundation is prepared. The foundation will be compacted to the same degree as specified for the adjacent embankment. Castings will be set in full mortar beds or secured as specified. Castings will be set to the correct elevation so subsequent adjustment will not be necessary. Inlet and outlet pipe connections will be the same size and kind and will meet the same requirements as the pipe they connect. Pipe sections will be flush on the inside of the structure wall and project outside for proper connection with the next pipe section. Masonry will fit neatly and tightly around the pipe. 671 Page 473Upon completion and curing of the unit, the sheeting, bracing, forms, and falsework will be removed, and the excavation backfilled. Backfill will be placed in loose layers not exceeding 6 inches thick and compacted to the same degree as specified for adjacent embankment. Installations will be finished and left in a satisfactory condition. The following specific provisions will apply to the various types of construction. A.Cast In Place Concrete: The foundation for manholes will be thoroughly moistened immediately prior to placing concrete. Moisture will be applied without forming pools of water. Steel reinforcement will be placed in accordance with Section 480. Concrete will be protected and cured in accordance with Section 460.3 M. The minimum curing time will be 72 hours. The finished surface of the concrete will present a neat and smooth appearance. Upon completion and curing of the unit, the sheeting, bracing, forms, and falsework will be removed, and the excavation backfilled. The unit will not be backfilled until the completion of the 72 hour curing period, or until the concrete reaches a minimum compressive strength of 3000 psi. Backfill will be placed in loose layers not exceeding 6 inches thick and compacted to the same degree as specified for the adjacent embankment. Installations will be completed and left in a neat appearing condition. B.Brick: Brick will be saturated with water before laying. Bricks will be laid in level courses with staggered vertical joints. Joints will be completely filled with mortar. Joints on the inside of the manhole will not be more than 1/2 inch wide. Joints on the inside of the manhole will be struck. The outside will be plastered with mortar to a smooth surface. In circular type manholes, the bricks will be laid flat and radially, with the ends exposed on the structure. When the thickness of the wall is greater than the length of a brick, the outside bricks may be laid circumferentially, using full header construction in at least each sixth course. In rectangular type manholes, the bricks will be laid in regular courses of stretchers, using full header construction in at least each sixth course. Bats or spalls will not be used except for shaping around openings or finishing out a course, in which case full bricks will be placed in the corners and the bats in the interior of the course. C.Concrete Block: The requirements for brick construction will apply when applicable. D.Precast Sectional Reinforced Concrete Units: The fabrication of precast manholes will conform to Section 560. The bottom precast section will be set in a full mortar bed and the joints between sections and around pipes will be filled with mortar. E.Adjusting Manholes: When the manhole rim and cover is to be lowered sufficiently to require reconstruction of the arch or raised more than 1 foot, or when reconstruction of 671 Page 474existing manhole is specified without change in grade, the manhole will be reconstructed to the extent necessary to provide the adjustment specified. When the rim and manhole is to be lowered to an extent which does not require reconstruction of the arch or when the rim and cover are to be raised 1 foot or less, the adjustment will be made by removing the top as necessary and setting the rim at the proper elevation on a building up of brick or concrete.
671.4METHOD OF MEASUREMENT
A.Brick, Concrete Block, and Precast Manholes: Manholes of brick, concrete block, and precast sectional reinforced concrete units will be measured as a unit for each manhole constructed. B.Cast In Place Concrete Manholes: Manholes will be measured on a per each basis for each manhole constructed. C.Manhole Frame and Lid: Manhole rims and covers will be measured as an assembly unit with all castings in any one manhole being considered as one assembly. D.Reconstructing and Adjusting Manholes: Reconstructing and adjusting manholes will be measured as a unit for each manhole reconstructed or adjusted.
671.5BASIS OF PAYMENT
Unless otherwise specified in the plans the cost for removal of existing pipe, if necessary, to facilitate the installation of new manholes will be incidental to the associated manhole contract unit prices. A.Brick, Concrete Block, and Precast Manholes: Manholes of brick, concrete block, and precast sectional reinforced concrete units will be paid for at the contract unit price per manhole of each design furnished and accepted, inclusive of materials, labor, equipment, excavation, and incidentals necessary. B.Cast In Place Concrete Manholes: Manholes of cast in place concrete will be paid for at the contract unit price per manhole of each design furnished and accepted, inclusive of materials, labor, equipment, excavation, and incidentals necessary. C.Manhole Frame and Lid: Manhole rims and covers will be paid for at the contract unit price per assembly. D.Reconstructing and Adjusting Manholes: Reconstructing and adjusting manholes will be paid for at the contract unit price per each reconstruction or adjustment of manhole. Payment will be full compensation for furnishing materials, labor, and equipment necessary. 680 Page 475680 UNDERDRAINS
680.1DESCRIPTION
This work consists of installations of porous backfill, drainage tubing, and headwalls for subgrade drainage.
680.2MATERIALS
A.Porous Backfill: Porous backfill for underdrains will conform to Section 800, with the following modifications: The material will consist of natural sand. Crushed material is not acceptable. The percentage of material passing a #200 sieve will not exceed 2.0%. Quality testing will not be required. B.Impermeable Plastic Membrane: Impermeable plastic membrane, when required, will conform to C.Corrugated Polyethylene Drainage Tubing: Corrugated polyethylene drainage tubing will conform to Section 990. D.PVC Pipe: In lieu of corrugated polyethylene tubing a profiled wall PVC pipe may be substituted. PVC pipe and fittings will meet the physical requirement specified for polyethylene pipe and will meet the material requirements of ASTM D3034, except dimensions at time of manufacture. E.Concrete: Concrete for headwalls will conform to Class M6, Section 462.
680.3CONSTRUCTION REQUIREMENTS
The trench to receive the porous backfill will be excavated to the lines shown on the plans or as staked by the Engineer. The trench bottom will be shaped and tamped as required by the Engineer. Disposal of surplus excavation will be the responsibility of the Contractor. The porous backfill material will be placed in 1 foot layers without compaction. The backfill will be uniformly spread without segregation or contamination. Tarpaulins or other approved devices will be used as guides from the hauling vehicle to the trench to prevent pulling dirt in with the backfill. Clear and unobstructed outlets will be provided for all drains. Where possible, all outlets will have a 12 inch free fall and will be properly marked and protected with a 4 inch by 4 inch by 6 foot guide post painted with two coats of white paint. Drain installations and waste disposal areas will be shaped and left in a neat appearing condition satisfactory to the Engineer.
680.4METHOD OF MEASUREMENT
A.Porous Backfill: Porous backfill will be measured, to the nearest 0.1 ton. Material used to fill unauthorized trench widths or other dimensions will not be measured for payment.