609—TREE WELLS AND TREE WALLS

609.01 Description

This work shall consist of constructing wells and walls to protect the root system of trees, shrubs, or other woody plants at the locations shown on the Plans or as designated by the Engineer. Tree wells and Tree walls shall conform to the details shown in the Standard Drawings or as otherwise shown in the Plans.

609.02 Materials

609.03 Procedures

The Contractor shall perform excavation incidental to and necessary for constructing tree wells and tree walls in a manner that will not damage the root system of the tree. Ends and damaged sections of roots shall be cleanly cut. Roots with a diameter of more than 3 inches shall not be cut. Before any earthen fill that will exceed 12 inches in thickness is spread over the feeding root system of trees or shrubs to be protected by tree wells, an aeration layer of coarse gravel or stone, ranging from 1/2 to 5 inches in size, shall be spread over the entire area to a depth of at least 6 inches or at the rate of 3 inches for every 12 inches of earthen fill where such fills will be more than 2 feet in depth. The layer of aggregate shall be capped with sufficient fine screenings to choke the top of the porous fill. Aggregate shall not be placed inside the tree well.

609.04 Measurement and Payment

Tree wells and tree walls will be measured in cubic yards of masonry and will be paid for at the contract unit price per cubic yard for the standard specified. This price shall include excavating, and furnishing and installing stone, masonry block or block faced brick, drain pipe, geotextile fabric and backfill, including aggregate. Payment will be made under: —————————————————————————— Pay Item Pay Unit—————————————————————————— Tree well (Standard) Cubic yard Tree wall (Standard) Cubic yard—————————————————————————— 609.04 784SECTION 610—GABIONS

610.01 Description

This work shall consist of furnishing, assembling, and installing gabions in accordance with these Specifications and in conformity to the lines, dimensions, and grades shown on the Plans or as established by the Engineer.

610.02 Materials

610.03 Procedures

Gabions shall be fabricated in such a manner that the sides, ends, lid, and diaphragms can be assembled at the construction site into rectangular wire mesh baskets. Gabions shall be of single unit construction whereby the base, lid, ends, and sides are woven into a single unit or whereby one edge of these units is connected to the base section of the gabion. The strength and flexibility at the point of connection shall be at least equal to those of the wire mesh. If the length of the gabion exceeds its horizontal width, the gabion shall be equally divided into cells by diaphragms of the same mesh and gage as the body of the gabion. The length of each cell shall not exceed its width. The gabion shall be furnished with the necessary diaphragms securely tied in their proper positions on the base so that no additional tying at the junction will be necessary. Perimeter edges of the mesh forming the gabion shall be securely clip bound or selvedged in such a manner that the joints formed by tying the selvedges will have at least the same strength, durability, and integrity as the body of the mesh. The Contractor shall supply tie and connection wire in sufficient quantity to securely fasten all edges of the gabion and diaphragms. At least two cross connecting wires shall be in each cell whose height is one-third or one-half the width of the gabion. At least four cross-connecting wires shall be in each cell whose height equals the width of the gabion. The wire shall be secured through two open loops of the cage. The Contractor shall perform excavating and backfilling operations for the installation of gabions according to Section 303. Gabions shall be placed on a smooth foundation, and the final line and grade shall be approved by the Engineer.610.01