765 SECTION 720 – MANHOLES, INLETS, AND CATCH BASINS
720.01 Description
This work shall consist of the construction, reconstruction, or adjustment to grade of manholes, inlets, and catch ba sins in accordance with 105.03. MATERIALS
720.02 Materials
Materials shall be in acco rdance with the following: 10 Castings ....................................................................... 910.05 Clay or Shale Brick ..................................................... 905.01 Clay Pipe ..................................................................... 907.08 Concrete Brick ............................................................. 905.02 Concrete Masonry Blocks ........................................... 905.03 Concrete ...................................................................... 702 Hydrated Lime ............................................................. 913.04 Joint Filler.................................................................... 906.01 Joint Mortar ................................................................. 901.08, 907.12 20 Non-Reinforced Concrete Pipe .................................... 907.01 Precast Concrete Manholes, Inlets, and Catch Basins ........................................ 907.04 Reinforced Concrete Pipe ............................................ 907.02 Reinforcing Bars .......................................................... 910.01 Water ........................................................................... 913.01 CONSTRUCTION REQUIREMENTS
720.03 General Requirements 30
The construction of the items listed in this specification shall be in accordance with 203.14. Excavation shall be to the established bottom of the foundations. The finished surface shall be firm and smooth. If soft or yielding spots are encountered at this elevation, they shall be removed, backfilled with suitable material, and tamped into place. If rock is encountered at the bottom elevation, the excavation shall be carried down 6 in. further and backfilled with approved material tamped to the required elevation. 40 Concrete construction shall be in accordance with the requirements for structural concrete. Masonry shall be in accordance with the requirements for the respective type. Exposed corners of concrete shall be rounded to a 1/4 in. radius. Air-entrained concrete will not be required in the precast portions of concrete manholes or catch basins. Frames for castings and bearing plates for manholes shall be set in full mortar 720.03 766 beds and secured as shown on the plans or as otherwise approved. The mortar shall be composed of 1 part cement to 2 parts No. 23 fine aggregate, by volume. Castings shall be set to the finished pavement elevation so that subsequent adjustments are not necessary. 50 Iron hood traps in catch basins shall be installed in walls as shown on the plans and so placed that a 6 in. seal is formed. Joints between hoods and walls shall be made gas tight. Mortar for laying brick and masonry units shall be composed of 1 part masonry cement and 2 parts mortar sand. Mortar for plastering may be the same or it may be composed of 1 part of a combination of portland cement and hydrated lime and 2 parts mortar sand. The lime shall not exceed 10% of the cement. In any case, proportioning shall be by volume. Ingredients, except water, shall be dry mixed, after which water 60 shall be added to bring the mortar to a stiff paste and mixing continued until a uniform mixture results. Required plaster coats on the inside and outside shall be at least 1/2 in. thick and shall be smooth, clean, and watertight. Inlet and outlet pipes shall extend through walls a sufficient distance to allow for connections on the outside and the concrete or mortar carefully placed around them to prevent leakage around their outlet surfaces. Unless otherwise shown, the inside ends shall be flush with the inside walls. The pipe shall be of the same size and kind as that 70 with which it connects on the outside. Where castings are adjacent to or are surr ounded by cement concrete construction, each casting shall be entirely separated from the concrete by a preformed joint filler not less than 3/8 in. thick. The cost of each joint, including the material, shall be included in the price for the structure. Grates shall be placed with the maximum dimension of the rectangular opening parallel to the direction of flow. The surface of the grate shall be flush w ith the top edge of the frame, wingwall, and headwall. The frame shall be galvanized and anchored into concrete. The frame 80 shall be factory assembled. All joints shall be fully welded. Adjusting slots for curb boxes shall be of the dimensions shown on the plans. One slot shall be located at each end of the curb box, and one slot shall be located at the approximate centerline on the back of the curb box. Galvanized or stainless steel 3/8 in. UNC x 3 1/2 in. round head, square shoulder bolts with one flat washer, one lock washer, and one nut each shall be used in each slot to anchor the curb box to the frame such that the top of the curb box is flush with the top of the curb. Bolts shall be torqued to a minimum of 120 ft lb. Steel grating Type 12 shall be a galvanized grating which shall be of sufficient strength to support a 12,000 lb wheel load with a maximum fiber stress of 20,000 lb/sq 720.03 767 in. The grating shall seat firmly in, but shall not be secured to, the frame. The length and width of the grating shall leave no more than 3/8 in. clearance on each side when placed in the frame. The grating shall be cut so all riveted or welded connections are left intact. If a manhole is constructed within the pavement area or within an area that may be paved at some future date, the height of the casting used shall be based on the depth of pavement constructed or proposed and a bearing plate for such casting will also be 100 required. Adjusting rings or steps of alternate types to those shown on the plans may be used subject to approval. If a manhole is constructed outside the proposed pavement area and outside an area that may be paved at some future date, the height of the casting used shall be at least 7 in. and a bearing plate for such casing will not be required. The manhole bottom shall be constructed of a precast bottom section, or of class A concrete formed in place. A precast cover shall be placed on a manhole in which headroom is limited. 110 Only competent masons shall be employed in laying units. Brick or other masonry units shall be laid in courses with full and close joints of mortar and finished properly as the work progresses. No joint shall exceed 3/8 in. in width. All units shall be wetted thoroughly immediately prior to being laid. Broken or chipped units will not be allowed in the face of the stru cture. No spalls or bats sh all be used except for shaping around irregular openings or where necessary to finish out a course. As nearly as practicable, adjoining courses shall break joints at a 1/2 unit. Courses shall be level except where otherwise necessary . If brick is used, at least one course in each seven shall be composed of headers. 120 The pipe used in pipe catch basins shall be of the bell-and-spigot type. Reinforced concrete spring boxes shall be constructed of class A concrete to the dimensions and at locations shown on the plans or as otherwise specified. If the completed structure is partially or completely under or at its nearest point is within 5 ft of pavement, sidewalks, curbs, gutters, or similar miscellaneous existing or proposed structures, the excavated space not occupied by the newly completed structure shall be filled to the required subgrade elevation with material in accordance 130 with 211.02. Placement of this material sha ll be in accordance with 211.04. If the completed structure is not located as set out above, the backfill shall be with approved material which, when compacted, shall meet the required subgrade density. Material excavated for the structure shall, if suitable, be utilized as backfill. If the excavated material is in excess for use in the work, the excess shall be used in embankment where locations are available or otherwise disposed of as directed. If the excavated material is unsuitable, it shall be disposed of in accordance with 201.03. 720.03 768 When finally accepted, all structures shall be free from any accumulation of silt, debris, or other foreign matter. 140 The Contractor may precast inlets, catch basins, or manholes, subject to approval. If precast concrete inlets, catch basins, or manholes are used, a layer of structure backfill of minimum thickness of 4 in. shall be used under each unit for ease in positioning. If holes are formed or field cut in precast inlets or catch basins to receive the pipe structures, the pipes shall be conn ected directly to the precast unit, by means of a class A concrete collar of a minimum longitudinal and radial thickness of 6 in. Holes formed or cut in the wrong place shall be plugged satisfactorily with a class A concrete mixture. 150 Horizontal joints may be used in the construction of precast catch basins. A sketch of the type, location, and sealing material planned for each joint shall be submitted for approval. No joints shall be closer than 3 in. above standing water for those catch basins requiring hoods. Grade and location adjustments to precast inlets and catch basins caused by unforeseen conditions shall be handled as if the units were being cast-in-place. All additional adjustments required due to precasti ng will not be paid for directly, but the cost thereof shall be included in the cost of the inlet or catch basin.
720.04 Grade Adjustment of Existing Structures
When grade adjustment of existing structures is specified, the frames, covers, and gratings shall be removed and the walls rec onstructed as required. The cleaned frames shall be reset at the required elevation. If so specified or if it is determined that the existing casting and supporting walls are in good condition, an approved device may be used to adjust the manhole casting cover to the correct grade without reconstructing the walls or resetting the frame. Upon completion, each structure shall be cleaned of any accumulations of silt, debris, or foreign matter of any kind and shall be kept clear of such accumulation until 170 final acceptance of the work. Excavation and backfill shall be done in accordance with 720.03. If an existing casting is unfit for further use, a new casting shall be furnished with payment at the contract unit price per each for castings of the type specified, furnished, and adjusted to grade. This payment sh all include and be full compensation for furnishing the new casting, placing and adju sting it to grade, including any necessary removal, construction, or reconstruction of not to exceed 12 in. average height of the upper portion of the masonry. 180 When manholes, catch basins and inlets are adjusted to grade and are to abut existing concrete construction, the castings shall be entirely separated from the adjacent concrete by a preformed expansion jo int no less than 3/8 in. in thickness. The 720.04 769 cost of furnishing and placing the preformed expansion joint material will not be paid for directly, but shall be included in the payment for reconstructed catch basin, or reconstructed inlet, or castings furnished and adjusted to grade. The preformed expansion joint material shall be in accordance with 906.01. On resurface contracts the castings shall, unless otherwise directed, be adjusted to 190 grade after the last binder course has been laid and before placing the surface course.
720.05 Capping Existing Structures
All structures directed to be capped shall be as shown on the plans or by filling the structure with class A concrete after the existing drainage has been maintained. The flow of water through pipes or underdrains in structures shall be perpetuated. Alternate methods for capping shall be submitted for approval before they may be used.
720.06 Method of Measurement 200
Manholes, inlets, spring boxes, and catch basins, both new and reconstructed as applicable, will be measured per each unit, complete in place. Castings adjusted to grade and castings furnished and adjusted to grade will be measured per each unit complete in place, if the average adjustment height does not exceed 12 in. If corrections to the stru cture involve portions exceeding an average adjustment height of 12 in., the additional work will be measured by the linear foot for the type of structure involved. The capping of existing structures will be measured by the number of structures 210 capped. 720.07 Basis of Payment The accepted quantities of manholes, inlets , spring boxes, catch basins, castings adjusted to grade not exceeding 12 in., and castings furnished and adjusted to grade not exceeding 12 in. will be paid for at the contract unit price per each, complete in place. That portion of a reconstructed structur e which exceeds 12 in. in average height will be paid for at the contract unit price per linear foot, for structure, of the type 220 specified, reconstruct, complete in place. The capping of inlets and other structures will be paid for at the contract unit price per each for cap inlet. Payment will be made under: Pay Item Pay Unit Symbol Casting, ____, Adjust to Grade ................................................. EACH 230 type 720.07 770 Casting, ____, Furnish and Adjust to Grade .............................. EACH type Catch Basin, ____ ...................................................................... EACH type Inlet, ____ .................................................................................. EACH type Inlet, Cap ................................................................................... EACH Inlet, type H, with Slotted Drains .............................................. EACH Inlet, type HA, with Slotted Drains ........................................... EACH 240 Manhole, ____ ........................................................................... EACH type Pipe Catch Basin, ____ in. ........................................................ EACH size Spring Box ................................................................................. EACH Structure, ____, Reconstructed .................................................. LFT type The cost of both inlets, the 12 in. pipe connecting the two inlets, the Type 5 castings, the concrete filler between the barrier wall and the inlet, and other 250 miscellaneous materials shall be included in the cost of the inlet, Type H. The cost of the inlet, the Type 5 casting, the concrete filler between the barrier wall and the inlet, and other miscellaneous materials shall be included in the cost of the inlet, Type HA. The cost of both inlets, the 12 in. pipe connecting the two inlets, the Type 5 castings, the concrete filler between the barrier wall and the inlets, the slotted drain pipe, the concrete collar around the slo tted drain pipe, and other miscellaneous materials shall be included in the cost of the inlet, Type H, with slotted drains. The cost of the inlet, the Type 5 casting, the concrete filler between the barrier wall and the inlet, the slotted drain pipe, the concrete collar around the slotted drain pipe, and other 260 miscellaneous materials shall be included in the cost of the inlet, Type HA, with slotted drains. The cost of excavation, backfill, reinforcing bars, structure backfill, concrete collar required for pipe connection to structures, removal, disposal and replacement of pavement, or surface material, casting removal, installation of concrete cap, HMA wedge, damage repair to pavement and shoul ders, and necessary incidentals shall be included in the cost of the pay items. 270 720.07