Special_207_Earthwork_Geosynthetics.pdf

SPECIAL CONTRACT REQUIREMENTS

TO

STANDARD SPECIFICATIONS

FOR CONSTRUCTION OF ROADS

AND BRIDGES ON FEDERAL HIGHWAY

PROJECTS FP-03

DIVISION 200

EARTHWORK

SECTION 207

EARTHWORK GEOTEXTILES

Replace Section 207 in the FP-03, in its entirety, with the following:

Section 207. — EARTHWORK GEOSYNTHETICS

Description

207.01 This work consists of furnishing and installing geotextile in separation, stabilization, and filter applications, geogrid in stabilization applications, and geomembrane in moisture barrier applications.

Geosynthethics are designated according to the tables in Section 714.

Material

207.02 Conform to the following Subsections:

Geomembrane 714.05 Geotextile 714.01 Stabilization geogrid 714.03

Construction Requirements

207.03 General. Identify, store, and handle geosynthetics according to ASTM D4873 and the manufacturer’s recommendations. Elevate and protect geosynthetic rolls with a waterproof cover if stored outdoors. Limit geosynthetics exposure to less than 10 days of ultraviolet radiation.

For seams sewn on-site, conform to the manufacturer’s recommendations. Obtain approval of the seam before installation. Use thread consisting of high strength polypropylene or polyester. Do not use nylon thread. Use thread that is resistant to ultraviolet radiation and a contrasting color to the geotextile.

Submit a seam assembly description and a sample of the sewn material at least 14 days before installation when geosynthetic joints are sewn as follows:

(a) Assembly description. Include the seam type, seam allowance, stitch type, sewing thread tex ticket numbers and types, stitch density, and stitch gauge.

(b) Sewn seam samples. Sew seam samples using the same equipment and procedures used to sew production seams. Submit samples that have at least 6 feet (1.8 meters) of sewn seam and are at least 5 feet (1.5 meters) wide. If production seams are sewn in both the machine and cross-machine directions, provide sewn seam samples that are oriented in both the machine and cross-machine directions.

Replace or repair geosynthetic that is torn or punctured. Remove the damaged area and place a patch of the same type of geosynthetic overlapping 36 inches (900 millimeters) beyond the damaged area or sew a seam around the damaged area.

207.04 Geotextile and Geogrid Separation and Stabilization Applications.

(a) Surface preparation. Before placing the geotextile, geogrid, or both, prepare the surface as follows:

(1) Existing ground. Cut trees and shrubs flush with the ground surface. Do not remove the topsoil and vegetation mat. Clear the area of vegetation and obstructions according to Sections 201 and 203. Remove sharp objects and large rocks. Fill depressions or holes with suitable material to provide a smooth surface.

(2) Subgrade. Prepare the subgrade according to Subsections 204.13(c) and (d).

(3) Subexcavation. Perform subexcavation according to Subsection 204.07.

(b) Geotextile or geogrid placement. Place geogrid on top of geotextile when both are shown at the same elevation in the plans. Place the geosynthetic smooth, taut, and wrinkle free on the underlying surface. Conform to curves. Overlap in the direction of construction. Overlap at least 24 inches (600 millimeters) at the ends and sides of adjoining sheets or sew the joints according to the manufacturer’s recommendations. Do not place longitudinal overlaps below anticipated wheel loads. Hold the geosynthetic in place with pins, staples, or piles of cover material.

(c) Backfilling.

(1) First layer placement and compaction. End dump the backfill material onto the geotextile or geogrid from the edge of the geosynthetic or from previously placed cover material. Do not operate equipment directly on the geosynthetic. Spread the end-dumped pile of cover material maintaining a 12 inch (300 millimeters) lift over the geosynthetic. Avoid sudden stops, starts, or turns of the construction equipment. Fill ruts from construction equipment with additional cover material. Do not blade material down to remove ruts. If rutting exceeds 3 inches (75 millimeters) during placement, decrease the construction equipment size, decrease the equipment weight, or increase the first lift thickness as directed by the CO.

Compact according to Subsection 204.11. Do not use sheepsfoot or studded compaction equipment.

Compact the cover material with pneumatic-tire or nonvibratory smooth drum rollers.

(2) Subsequent layer placement and compaction. Place subsequent layers according to Subsection 204.10.

Compact according to Subsection 204.11. Vibratory rollers may be used unless pumping or foundation failures occur. Repair damaged areas and then use only nonvibratory rollers.

207.05 Reinforcement Geotextile and Geogrid. See Section 263 for reinforcement geotextile and geogrid placement.

207.06 Geotextile Filter Applications.

(a) Geotextile placement. For slope or wave protection, place the long dimension of the geotextile down the slope. For stream bank protection, place the long dimension of the geotextile parallel to the centerline of the channel.

Overlap or sow seams at the ends and sides of adjoining sheets.

(1) Overlapping. Overlap the uphill or upstream sheet over the downhill or downstream sheet. For above water applications, overlap the geotextile at least 12 inches (300 millimeters). For underwater applications, overlap the geotextile at least 36 inches (900 millimeters).

(2) Sewing. Sew the geotextile seam according to the manufacturer’s recommendations.

Offset end joints of adjacent sheets at least 5 feet (1.5 meters). Use key trenches or aprons at the crest and toe of slopes to hold the geotextile in place. As an alternative use anchor pins, at least 18 inches (450 millimeters) long and spaced at 36 inch (900 millimeters) centers to hold the geotextile sheets in place.

(b) Backfilling. Place aggregate, slope protection, or riprap on the geotextile starting at the toe of the slope and proceeding upward. Place riprap onto the geotextile from a height of less than 12 inches (300 millimeters). Place slope protection rock or aggregate backfill onto the geotextile from a height less than 36 inch (900 millimeters). Do not allow stones weighing more than 100 pounds (45 kilograms) to roll down the slope. In underwater applications, place the geotextile and cover material in the same day.

207.07 Geomembrane Applications. Submit a geomembrane installation plan at least 10 days before installing the geomembrane. Include a drawing of the panel layout identifying the location of seams. Include a seam detail and a written description of the seaming procedure.

(a) Surface preparation. Provide a smooth, flat, firm, unyielding foundation for the geomembrane with no sudden, sharp, or abrupt changes or break in grade. Remove rocks, stones, sticks, sharp objects, and debris of any kind protruding more than ½ inch (13 millimeters) above the prepared surface.

(b) Geomembrane placement. Orient seams parallel to the line of maximum slope. Use sandbags or piles of cover material to hold the geomembrane in place. Do not drive equipment directly on the geomembrane.

(c) Backfilling. Place backfill material within the same work shift that the geomembrane is installed. End dump backfill material onto the edge of previously placed cover material and roll it into place. Do not push material along the geomembrane which can result in damage or wrinkling.

207.08 Acceptance. Geosynthetics will be evaluated under Subsection 106.03. Submit a production certification for geosynthetics.

Geosynthetic installation will be evaluated under Subsections 106.02 and 106.04.

Sewn joints will be evaluated under Subsection 106.02.

Measurement

207.09 Measure the Section 207 pay items listed in the bid schedule according to Subsection 109.02.

When measuring geosynthetics by the square yard (square meter), measure on the plane parallel to the slope face.

Do not measure overlapping material.

Payment

207.10 The accepted quantities will be paid at the contract price per unit of measurement for the Section 207 pay item listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05.