Attach 3.CS 412-Amend2-Bentonite Sealant P1.pdf

AG-3D47-S-10-0001

Amendment No. 2 Attachment No. 3

NRCS November 2009 WV Deckers Creek Acid Mine Drainage Treatment Project Goat Site 1 & Beulah Chapel Site 1 412-1

Construction Specification 412

Bentonite Sealant

1. Scope

This work consists of furnishing all material, equipment, and labor necessary for the installation of sodium bentonite sealant in the channel subgrade areas at locations shown on the plans for Beulah Chapel Site 1.

2. Materials

The sodium bentonite sealant shall consist of high-swelling chemically unaltered bentonite with no additives.

Bentonite may be in the form of powder, granules, or a combination of each. Bentonite shall contain at least 85% montmorillonite.

3. Installation

Excavate the channel to its design subgrade profile as shown on the plans. All existing water flow shall be diverted from the channel. The area to be treated shall be drained of ponded water and dried. Remove all trash, vegetation, roots, and rocks greater than 2-inches from the subgrade surface.

For channel subgrades excavated into rock, the subgrade shall be over-excavated 6-inches minimum. Soil material from sources approved by the Contracting Officer’s Representative shall be installed in the rock subgrade and treated as specified herein. For channel subgrades which expose jointed limestone, the limestone shall be over-excavated 2 feet. The limestone subgrade shall be backfilled with 2 feet of soil from sources approved by the

Contracting Officer’s Representative. Compaction of backfill over limestone shall be in accordance with

Subsidiary Item Earth Backfill, Class C; Construction Specification 23.

The soil subgrade or soil backfill subgrade shall be mechanically tilled to a depth of 6-inches. Areas inaccessible for mechanical equipment shall be tilled with manual tools and achieve the same quality of preparation. Remove all trash, vegetation, roots, and rocks greater than 2-inches from the tilled soil layer. If the soil layer is dry, apply water while tilling to achieve the moisture conditions specified in Construction Specification 23, Section 10, Part

A(1). Continue tilling until the 6-inch soil layer achieves consistency throughout its depth. Drag or roll the soil surface smooth for bentonite application.