721AUTOMATIC DRAINAGE GATES

721.01Description

This work shall consist of furnishing and placing cast-iron, automatic, hinged, flap-gate valves to the outlet ends of pipe or headwalls in accordance with 105.03.

721.02Materials

The cast-iron flap and seat shall be mach ined accurately to ensure watertightness. They shall be in accordance with the applicable requirements of 910.05(b).

721.03Construction Requirements

The gate shall be constructed to offer minimum resistance to water flowing through it. When the water elevation in the outlet stream is 1/2 in. or more above or below the bottom of the valve, the valve shall open or close, as the case may be. The valve shall be able to resist a head of at least 10 ft.

The end of the pipe, or headwall, to which the flange is attached shall be vertical. The flange shall be attached using either rivets, bolts, or other approved means.

721.04Method of Measurement 20

Automatic drainage gates will be measured by the number of units installed.

721.05Basis of Payment

The accepted quantities of this work will be paid for at the contract unit price per each for automatic drainage gate, of the size specified, complete in place.

Payment will be made under:

Pay Item Pay Unit Symbol

Automatic Drainage Gate, _____ in. x _____ in. ...................... EACH width height Automatic Drainage Gate, _____ in. ......................................... EACH diameter

If the gate is fastened to the end of a pipe, no additional payment will be allowed for that portion of pipe extending beyond the outside face of the headwall.

721.05