A. Width of Trench.
The width of trench, if any, in which pipe are placed shall be sufficient to permit thorough tamping of bedding material under and around the pipes. At the Contractor's option, the trench may be cut wide enough to accommodate a tamping type roller on each side of the pipe.

B. Preparation of Base.
The surface upon which pipe sections are to rest shall be brought to a suitable elevation to fit the desired grade and camber, and the base shall be prepared as shown in the contract documents. When specified, the base shall be Class B bedding. When not specified, the base shall be Class C bedding.

1. Class B Bedding.
Class B bedding shall consist of a 2 inch (50 mm) cushion of sand shaped with a template to a concave saddle in compacted or natural earth to such a depth that 15% of the height of the pipe rests on the sand cushion below the adjacent ground line.

2. Class C Bedding.
Class C bedding shall consist of a concave saddle shaped with a template, or shaped by other means and checked with a template, in compacted or natural earth to such a depth that 10% of the height of the pipe rests below the adjacent ground line.

Where bedrock, shale, or very hard clay is encountered, the trench shall be excavated below the bottom of the pipe for a depth of at least 1 foot (0.3 m) and backfilled with earth and thoroughly tamped.

If the bottom of the footing is of an unstable nature, the Engineer may direct that the foundation be treated by excavating below the required elevation, then backfilled with one of the granular surfacing materials listed in Section 4120 or other suitable material approved by the Engineer. Backfilling shall be performed in accordance with Article 2402.09 or as directed by the Engineer.

Unless bedding is specifically designated in the contract documents, Class C bedding will not be required for entrance pipe 24 inches (600 mm) or less in diameter. In lieu thereof, the pipe may be bedded carefully in suitable material and the backfill compacted with a mechanical tamper to mid-height elevation of the pipe. The remaining backfill shall be according to Paragraph D of this Article.

C. Placing Pipe Sections.
Proper facilities shall be provided for lowering the sections into place without damage to the pipe. Pipe shall be carefully laid with hub, bell, or groove ends upstream. Each section shall be carefully bedded and placed in close contact with adjacent sections. The pipe section, when placed, shall be to alignment and grade established and approved by the Engineer. When lifting holes are provided or the top is indicted on the pipe, these shall be at the top, and lifting holes shall be filled with concrete or precast concrete plugs prior to backfilling.

D. Backfilling Pipe Culverts.
Culverts shall be thoroughly tamped under and around the pipe and in layers not to exceed 8 inches (200 mm) for the full length and width of the culvert.

Earth shall be filled and thoroughly tamped around and over the culvert for its full length, in accordance with Articles 2402.08 and 2402.09, so that adjacent to the pipe on each side of the culvert there shall be an embankment of thoroughly tamped or undisturbed earth.

The completed embankment shall extend on both sides of the culvert from the original ground line to at least 1 foot (0.3 m) above the top of the pipe with a slope as shown in the contract documents. The width of this fill at its top shall be not less than the outside diameter of the culvert and shall extend one-half its width on each side of the culvert center line. The height of fill shall be increased, if necessary to accommodate construction traffic, to the nominal diameter of the pipe or 3 feet (1 m), whichever is greater.

When pipe are laid wholly or partly in a trench, granular backfill material may be required for backfill as provided in Article 2402.09. The remainder of the fill, to at least 1 foot (0.3 m) above the top of the pipe, shall be compacted earth with slopes as outlined above.

If the trench has been cut wide enough to permit use of a roller, after the pipe is bedded, the backfill material under and alongside the pipe shall be thoroughly tamped with a mechanical tamper to the mid-height elevation of the pipe. The remaining backfill shall be placed and compacted as prescribed in Section 2107.

The contract documents may require placement of culvert pipe with moisture control. When not required, roadway pipe culverts placed after construction of an embankment shall be placed by methods which will produce results equivalent to those required for construction of the embankment, except that moisture determinations will be waived for backfilling completed within 48 hours after excavation.

In addition to the normal backfilling requirements, the Contractor, when ordered by the Engineer, shall build such approach fills as will provide a roadway 10 feet (3 m) in width over the culvert with grades not steeper than 10%.

E. Joints for Concrete Pipe.
When required by the contract documents, concrete pipe joints shall be wrapped with Engineering Fabric of the type specified.

Joint openings on the outside or inside of the top half of the pipe shall not exceed 5/8 inch (15 mm). Joint openings on the outside or inside of the bottom half of the pipe shall not exceed 1/4 inch (6 mm) for all sizes through 24 inches (600 mm) internal diameter, or 1/8 inch per foot (1 mm per 0.1 m) of internal diameter for all sizes larger, with a maximum of 5/8 inch (15 mm).

Larger joint openings, unless required for pipe camber, shall be fully encased with a Type C concrete collar. The concrete used shall be Class C structural concrete as specified in Section 2403. In addition to the collar, the inner surface of the joint shall be pointed full and flush with sand cement mortar for the lower 75% of the pipe perimeter.

2416.05 METHOD OF MEASUREMENT.
The quantity of pipe culvert, in feet (meters), will be the measured length of culvert installed, excluding aprons, to the nearest foot (0.1 m) with no deductions for elbows, tees, and other fittings. The quantity of pipe will be determined along the axis. Pipe laterals terminating at a tee will be from the point of inlet to a point 6 inches (150 mm) from the outside of the main, less the length of the apron, if any.

The quantity of aprons will be the quantity shown in the contract documents.

The quantity of appurtenances (elbows, tees, and other fittings) will be shown on the contract documents but will not be measured for payment.

Type C adaptors required by the contract documents or installed to correct faulty work will not be measured for payment. Type C adaptors not shown in the contract documents, but required because of changes in alignment, shall be paid for in accordance with Article 1109.03, B.

Excavation for roadway culverts will be measured for payment as provided in Section 2402.12, B. Excavation for entrance culverts will not be measured for payment.  Sand required for Class B bedding will not be measured for payment.

When granular backfill is required and furnished, Article 2402.12, D, shall apply.

When foundation treatment material has been placed at the direction of the Engineer, Article 2402.12, E, shall apply.

2416.06 BASIS OF PAYMENT.
The Contractor will be paid the contract unit price for pipe culvert of type and size specified per linear foot (meter). The cost of wrapping pipe joints, Type C adapters, and appurtenances shall be included in the contract unit price per linear foot (meter) for the pipe culvert.

The Contractor will be paid the contract unit price for aprons of the size specified per unit.

For the quantity of excavation for roadway culverts and the quantity of extra excavation for embankments, the Contractor will be paid the contract unit price per cubic yard (cubic meter). For entrance culverts, excavation shall be considered as incidental to the contract unit price for rigid pipe culvert. Sand required for Class B bedding shall be incidental to the contract unit price for pipe culvert.

When Granular Backfill is required and furnished, it will be paid for accordance with Article 2402.13, F.

Foundation treatment material furnished and placed, will be paid for in accordance with Article 2402.13, E.