S-10-0296 921_culvert.doc

Section C

Page

Section 921 -- Culverts

Description

921.01 Work. Work consists of furnishing and installing culverts, including excavation and backfill, selecting and hauling of rock materials, and constructing catch basins, headwalls, and outlet ditches.

Materials

921.02 Requirements. Use materials meeting the requirements of Section 961.

Construction

921.03 Excavation and Embankment. Perform excavation and embankment in accordance with Section 912.

921.04 Placement. Place culverts to provide for unobstructed inlet and outlet flow. Remove logs, debris, soil, rock, and other obstructions above and below the culvert that would impede flow into the culvert or away from the trailway. Minimize disturbance to streambeds.

Construct an inlet catch basin where NOTED ON THE TRAIL LOG or as necessary to facilitate flow into the culvert. Construct the catch basin with an 18-inch diameter flat bottom.

Construct outlet ditches where NOTED ON THE TRAIL LOG or as necessary to provide drainage. Where NOTED ON THE TRAIL LOG or where outlet ditches will not drain within 20 feet, construct an 18-inch diameter drain sump to a minimum depth of 24 inches and located at least 5 feet from culvert outlet. Fill sump with coarse rock.

921.05 Pipe Culverts. Install pipe culverts at the locations NOTED ON THE TRAIL LOG or as DESIGNATED ON THE GROUND.

(a) Placing. Skew culverts as needed to provide for free flow under the trailbed. Place culverts at stream crossings in the natural streambed on stream grade.

(b) Bedding. Excavate and remove all unsuitable material and rocks over 3 inches to a minimum depth of 6 inches below the pipe invert and to a minimum width of 1.5 pipe diameters. Bed pipe with compacted suitable material free of rocks larger than 3 inches and in a stable foundation of undisturbed or compacted soil. Shape the bed to fit the lower quadrant of the pipe exterior and provide uniform continuous support along the entire length of the pipe.

921.06 Backfilling Culverts. Backfill and compact around culverts with suitable material that is free of rocks over 3 inches. Provide for the cover height as SHOWN ON THE DRAWINGS.

921.07 Headwalls. Construct headwall at both culvert inlet and outlet. In all locations except in a turnpike section or on ditch relief culverts, the headwall shall extend from stream bank to stream bank. On turnpike and ditch relief culverts the headwall shall extend a minimum of 12 inches on both sides of the culvert.

Provide a compacted bench as a foundation for the wall.

Select rocks that have a general rectangular shape with flat top and bottom faces. Place the largest rocks on the bottom. Lay each rock stable on the course that supports it, interlocking with surrounding rocks. Do not break, jar, or displace rocks already set. Place the exposed face of each rock parallel to the face of the wall. Stagger vertical joints a minimum of 4 inches horizontally from vertical joints in adjoining courses.

Measurement

921.08 Method. Measure the quantities in accordance with Section 906.

Payment

921.09 Basis. Pay for the accepted quantities in accordance with Section 906 at the contract unit price for each PAY ITEM SHOWN IN THE SCHEDULE OF ITEMS.

The following will be considered incidental to the PAY ITEMS SHOWN IN THE SCHEDULE OF ITEMS and extra payment will not be given:

Outlet ditches, drain sumps, bedding material, catch basins, and headwalls.

Make payment under:

PAY ITEM

PAY UNIT

921(02) 12-Inch Corrugated Double Wall

PE Culvert

LF

912(03) 18- inch Corrugated Double Wall

PE Culvert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LF 921-1 (12/13/2009)