435 Page 304435 APPROACH SLAB UNDERDRAIN SYSTEM
435.1DESCRIPTION
This work consists of excavating in place materials under the limits of a new approach and sleeper slab and installing a drainage system under the sleeper slab when no other bridge end backfill work is specified. Approach slab underdrain systems installed in conjunction with bridge end backfill work will be completed in accordance with Section 430.
435.2MATERIALS
A.Porous Backfill: The porous backfill material will conform to the requirements of 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%. B.Granular Bridge End Backfill: The granular bridge end backfill material will conform to Section 882. C.Drainage Fabric: The drainage fabric will conform to Section 831 (Drainage Fabric-Type B). D.Polyethylene Sheeting: The polyethylene sheeting will be a minimum thickness of 6 mils and will be sufficiently durable so the polyethylene sheeting will not puncture or tear when installed as intended. E.Drainage Tubing: The drainage tubing will be corrugated polyethylene drainage tubing conforming to Section 990. F.Black Steel Pipe: The black steel pipe will conform to ASTM A53.
435.3CONSTRUCTION REQUIREMENTS
A.Excavation Requirements: Excavation for placement of the new approach slab underdrain system will be done with minimal disturbance to the underlying material. Excavation for the 8 to 12 inch wide trench will be by a method that will provide a nearly vertical sided trench with the least amount of disturbance to the underlying soil. The bottom of the trench will be graded to drain away transversely from the roadway at a rate of 1/8 inch per foot. B.Installation Requirements: After the existing approach pavement has been removed and the ground surface has been shaped for placement of the granular bridge end backfill material, the Engineer will inspect the area. Those areas with predominately 3/8 inch diameter or larger in place aggregate will be covered with Type B drainage fabric prior to placement of the granular bridge end backfill material. The surfaces on which the drainage fabric is to be placed will be smooth and free of obstructions. Lapped joints in the drainage fabric will be placed transverse to the direction of 435 Page 305flow with 1 foot minimum overlap in the direction of flow. Vehicles and equipment will not be operated directly on the drainage fabric. The 4 inch diameter perforated drainage tubing will be placed in the bottom of the trench to drain toward the precast concrete headwalls. The porous backfill material will then be placed in the trench and compacted to the satisfaction of the Engineer. Granular bridge end backfill will be placed in loose lifts not exceeding 4 inches. Compaction will be accomplished with at least four complete passes using a smooth face vibratory roller or vibratory plate compactor. Each layer of granular material will be thoroughly watered prior to and during compaction.
435.4METHOD OF MEASUREMENT
A.Granular Bridge End Backfill: The quantity specified on the plans is the theoretical quantity based on plans dimensions. The plan quantity will be the quantity accepted for payment. Field measurement for granular bridge end backfill will not be made. B.Porous Backfill: The quantity specified on the plans is the theoretical quantity based on plans dimensions. The plan quantity will be the quantity accepted for payment. Field measurement for porous backfill will not be made. C.Approach Slab Underdrain Excavation: The quantity specified on the plans is the theoretical quantity based on plans dimensions. The plan quantity will be the quantity accepted for payment. Field measurement for approach slab underdrain excavation will not be made. D.Underdrain Pipe: The quantity specified on the plans is the theoretical quantity based on plans dimensions. The plan quantity will be the quantity accepted for payment. Field measurement for underdrain pipe will not be made. E.Precast Concrete Headwall for Drain: The precast concrete headwalls for drain will be measured by the number of complete precast concrete headwalls furnished and installed.
435.5BASIS OF PAYMENT
A.Granular Bridge End Backfill: The accepted quantity will be paid for at the contract unit price per cubic yard in accordance with Section 430.5 . B.Porous Backfill: The accepted quantity will be paid for at the contract unit price per ton in accordance with Section 680.5 . C.Approach Slab Underdrain Excavation: The accepted quantity will be paid for at the contract unit price per cubic yard in accordance with Section 430.5 . D.Underdrain Pipe: The accepted quantity will be paid for in accordance with Section 680.5 except payment will be full compensation for all labor, equipment, materials, and all other items incidental to furnishing and installing the drainage tubing, black steel pipe, fittings, rodent screens, and vertical drain composite. 435 Page 306E.Precast Concrete Headwall for Drain: The accepted quantity will be paid for at the contract unit price per each in accordance with Section 430.5 . 440 Page 307440 STRUCTURAL PLATE PIPE AND STRUCTURAL PLATE PIPE ARCH CULVERTS
440.1DESCRIPTION
This work consists of furnishing and installing structural plate pipe and structural plate pipe arches.
440.2MATERIALS
Structural plate pipe and pipe arches will conform to Section 990.
440.3CONSTRUCTION REQUIREMENTS
A.Fabrication: Plates will have a 2 inch lip beyond each end crest therefore the actual length of a given structure will be approximately 4 inches longer than the nominal length, except when skewed or beveled. Plates at longitudinal and circumferential seams will be connected by bolts. Joints will be staggered so no more than three plates come together at any point. B.Erection: Pipe and pipe arches will be assembled according to the manufacturer's assembly instructions. Bolts will not be torqued above 300 foot-pounds C.Installation: Trenches will be excavated to a width that allows for thorough compaction of the bedding and backfill material under and around the pipe. Where feasible, trench walls will be vertical. The trench bottom will be firmly compacted for its full length and width. The foundation for the bedding will provide a uniform stable support. Removal of unstable material or rock below the bedding grade will be performed as set forth in Section 421. The bedding will consist of an earth or gravel cradle of uniform density, shaped to fit the lower part of the pipe for at least 10% of its overall height. D.Backfill Above Bedding Grade: Material used for backfill will be embankment material encountered on the project free of organic material and rock or will be as specified in the plans. Moisture and density requirements for backfill will meet the requirements of Section 120 or as specified in the plans. The backfill material will be pre-moistened if necessary to obtain uniform moisture. Selected embankment material will be placed along the pipe in layers not exceeding 6 inches loose depth and thoroughly compacted by mechanical compactors to the specified density before the successive layers are placed. The width of the berms on each side of the pipe will be twice as wide as the external diameter of the pipe or 12 feet, whichever is less. This method of backfilling will be continued until the embankment is at least 2 feet over the top of the pipe.