Excavation. - The excavation for masonry walls or other special structures as ordered shall be made in open trenches of the requisite width and depth. If deemed necessary the sides of the excavation shall be supported by suitable sheeting, rangers and bracing.

If the subsoil proves insecure, the excavation may be carried to a greater depth and width than originally contemplated to allow construction of special masonry footings as ordered.

Backfilling. - The material used in backfill immediately adjacent to retaining walls or drain walls shall consist of a porous material to facilitate drainage, as shown on the plans. All backfilling material for a distance of 6 feet back from the wall shall be placed in 4-inch layers and thoroughly and satisfactorily rammed.

Measurement and Payment - The trench excavation paid for, by the cubic yard at the price bid, shall be the volume between vertical planes from the outside edges of the footings and between the natural surface and the bottom of the footings. No extra price will be paid for excavation below the bottom of the footings as shown on the plan, unless the extra depth exceeds two feet. If the extra depth exceeds two feet, the Contractor will be allowed force account and cost of materials plus fifteen (15) per cent for all such extra depth.

The price bid for trench excavation will include the necessary bracing and sheeting, all pumping to remove water, and all backfilling to the grade shown on the plan.

Any bracing or sheeting left in place by order of the Engineer will be paid for as specified for Drains, Items 3-8.