§ 801-41. Drainage system.

A. 

Conformance to department's specifications. The construction of the drainage system, including methods of construction and quality of materials shall conform to the applicable sections of the Department of Public Works specifications except as modified hereafter or as directed by the Board's engineer.

B. 

Storm drains. Storm drains shall be constructed of reinforced Class V concrete pipe with removable rubber gasket joints and of a strength or class adequate to withstand the H-20 live loads and dead loads which the pipe will be subjected. All joints shall be securely mortared or clamped. The pipe shall be a minimum of 12 inches in diameter and shall be laid at a minimum pitch so as to maintain a velocity of three feet per second when flowing full.

C. 

Catch basins. All catch basins shall be constructed of air-entrained cement concrete, and a standard square frame and grate, with square holes, and a granite mouth frame shall be furnished and set. All catch basins shall have an inside diameter of at least four feet, shall be constructed with a minimum depth of four feet below the invert of the outflow pipe or the bottom of the pipe trap, whichever is lower, and as otherwise shown in accordance with the latest revisions of the construction standards of the Department of Public Works.

D. 

Manholes. All manholes shall be constructed of the same materials as permitted herein for catch basins except that a standard heavy twenty-six-inch diameter cover and frame shall be furnished and set, and all other details shall be as shown in the Department of Public Works standards for manholes.

E. 

Subsurface drainage system. The subsurface drainage system as shown on the definitive plan or as ordered by the Board during construction shall be constructed of not less than six-inch diameter perforated polyvinyl chloride (Schedule 40) pipe with perforations turned up, and laid to line and grade.

F. 

Headwalls. All drainage pipe shall end in an air-entrained cement concrete or air-entrained cement masonry headwall having dimensions as specified in the Department of Public Works standards and constructed in accordance with the Department's specifications.

G. 

Compressive strength of concrete. The air-entrained cement concrete shall have a minimum compressive strength of 3,000 pounds per square inch after 28 days curing.

H. 

Tide gates. All tide gates shall be of standard manufacture, of the same size as the outfall pipe, elastomer synthetic fabric type and subject to the approval of the engineer.

I. 

Inspection required prior to backfilling. The engineer will inspect the completed drainage system or sections thereof prior to placing any backfill.

J. 

Backfill specifications. All trench backfill for the storm and subsurface drains and other backfill within the limits of the way shall conform to the base course requirements and shall be deposited to required subgrade in not more than six-inch layers and compacted to 95% of the maximum dry density as determined by modified Proctor Test, in accordance with ASTMC-1557, Method D.