216Soil Retention Covering

Soil Retention Covering

Description

216.01This work consists of furnishing, preparing, applying, placing, and securing soil retention

blankets and turf reinforcement mats (TRM) for erosion control on roadway slopes or channels as designated in the Contract.

Materials

216.02Soil retention covering shall be either a soil retention blanket or a TRM as specified in

the Contract. It shall be one of the products listed on CDOT’s Approved Products List and shall conform to the following:

fibers mechanically bound together between two slowly degrading synthetic or natural fiber nettings to form a continuous matrix and shall conform to the requirements of Tables 216-1 and 216-2. The blanket shall be of consistent thickness with the fiber evenly distributed over the entire area of the mat.

When specified, lightweight polypropylene netting shall be 1.5 pounds per 1,000 square feet; heavyweight netting shall be 2.9 pounds per 1,000 square feet.

When biodegradable blanket is specified, the thread shall be 100 percent biodegradable; polypropylene thread is not allowed.

When photodegradable netting is specified, the thread shall be polyester, biodegradable or photodegradable.

Blankets and nettings shall be non-toxic to vegetation and shall not inhibit germination of native seed mix as specified in the Contract. The materials shall not be toxic or injurious to humans. Class 1 blanket shall be an extended term blanket with a typical 24-month functional longevity. Class 2 blanket shall be a long-term blanket with a typical 36-month functional longevity. The class of blanket is defined by the physical and performance characteristics.

machine-produced mat consisting of 70 percent certified weed free agricultural straw or Colorado native grass straw and 30 percent coconut fiber. The blanket shall be either biodegradable or photodegradable. Blankets shall be sewn together on a maximum 2-inch centers. Netting shall be as follows:

When biodegradable netting is specified, the top and bottom netting shall be 100 percent biodegradable organic jute fiber. Netting shall be constructed using a weave unattached at intersections, which allows the strands of the net to move independently of each other.

When photodegradable netting is specified, the bottom side shall be lightweight polypropylene. The top side shall be heavyweight or lightweight polypropylene.

216.02

machine-produced mat of 100 percent curled wood excelsior, 80 percent of which shall be 6 inches or longer in fiber length. It shall be either biodegradable or photodegradable. Blankets shall be sewn together at a maximum of 4-inch centers. Netting shall be as follows:

When biodegradable netting is specified, the top and bottom netting shall be 100 percent biodegradable organic jute fiber. Netting shall be constructed using a weave unattached at intersections, which allows the strands of the net to move independently of each other.

When photodegradable netting is specified, the bottom side shall be lightweight polypropylene. The top side shall be heavyweight or lightweight polypropylene.

produced mat consisting of 100 percent coconut fiber. It shall be either biodegradable or photodegradable. Netting shall be as follows: When biodegradable netting is specified, the top and bottom netting shall be 100 percent biodegradable organic jute fiber. Netting shall be constructed using a weave that is unattached at the intersections, and which allows the strands of the net to move independently of each other.

When photodegradable netting is specified, the bottom and top side shall be heavyweight polypropylene. Table 216-1 Physical Requirements for Soil Retention Blanket – Photodegradable or Biodegradable Blankets Min. Mass per Minimum Unit Photo/Bio Minimum Thickness Acceptable Area Size of Net Size of Net Degradable Roll ASTM Matrix Fill ASTM Opening Opening Bio- Class Width D6525 Material 6475 Photodegradable degradable Min. 0.50"x0.50" Straw/ Min. 0.50"x0.50" Max 1 6.5 ft 250 mils Coconut 8 oz/sy Max 0.75"x0.75" 0.50"x1.0" Min. 0.50"x0.50" NONE 1 6.5 ft 250 mils Excelsior 8 oz/sy Max 1.0"x2.0" Min. 0.50"x0.50" Min. 0.50"x0.50" Max 2 6.5 ft 200 mils Coconut 8 oz/sy Max 0.75"x0.75" 0.50"x1.0"

216.02

Table 216-2 Performance Requirements for Soil Retention Blanket – Photodegradable or Biodegradable Blankets Photo/Bio Slope Minimum Tensile Degradable Application Strength MD2 Class “C” Factor1 ASTM D6818 ASTM D6459 1 < 0.10 at 3:1 8.33 lbs./in 2 < 0.10 at 3:1 10.42 lbs./in Table 216-2 Notes: “C” Factor is calculated as ratio of soil loss from soil retention blanket protected slope (tested at specified or greater gradient, 3H:1V) to ratio of soil loss from unprotected (control) plot in large- scale testing. MD is for machine direction testing (along the length of the roll).

Blankets shall be tested for physical properties and have published data from an independent testing facility. Large scale testing of Slope Erosion Protection (“C” factor) shall be performed by an independent testing facility.

UV stabilized, corrosion resistant, non-degradable synthetic fibers, filaments, or nets processed into a permanent three-dimensional matrix of the thickness specified in Tables 216-3 and 216-4. TRMs shall provide sufficient thickness, strength, and void space to permit soil filling and retention, and the development of vegetation within the matrix. The class of TRM is defined by the physical and performance characteristics as specified in the following tables.

216.02

Table 216-3 Physical Requirements for Turf Reinforcement Mat

Minimum Minimum Acceptable Product Thickness Size of Net Roll Matrix Fill Class ASTM Opening2 Width Material2 D6525 Excelsior, Minimum: Straw/Coconut, 0.50"x0.50" 1 6.5 ft 250 mils Coconut, or Maximum: Polymer fibers 0.75"x0.75" 100% UV Stabilized Maximum 2 6.5 ft 250 mils Synthetic or 0.50"x 0.50" Coconut Fibers 100% UV Stabilized Maximum 3 6.5 ft 250 mils Synthetic 0.50"x 0.50" Fibers

Table 216-3 Notes: For TRMs containing degradable components, all property values shall be obtained on the non-degradable portion of the matting alone. For TRMs with nets and fill material. Netted TRMs shall be sewn together on a maximum 2-inch centers.

Table 216-4 Performance Requirements for Turf Reinforcement Mat Minimum UV Minimum Tensile Stability at Permissible Shear Product Strength 500 Stress* Class MD Hours ASTM (Unvegetated) ASTM D6818 D4355 ASTM D6460 1 125 lb/ft 80% 1.8 lb/sf 2 150 lb/ft 80% 2.5 lb/sf 3 175 lb/ft 80% 3.1 lb/sf Table 216-4 Notes: *Permissible shear stress is the minimum shear stress that a product must be able to sustain when placed on a channel un-vegetated without physical damage or excess soil loss. Failure is defined as 1/2 inch of soil loss during a 30-minute flow event in large scale testing.

216.03

TRMs shall be tested for physical properties and have published data from an independent testing facility.

Large scale testing of Permissible Shear Stress shall be performed by an independent testing facility.

and have a 1-inch crown. “T” shaped staples will not be permitted. A sample of the staples and a Certificate of Compliance (COC) including the manufacturer's product data showing that the product meets the Contract requirements shall be submitted for approval at the Environmental Pre-construction Conference. Installation of the blanket will not begin until approval has been received from the Engineer in writing.

plate, a tendon rod or wire rope, and a locking head or percussion anchor. Each element of the anchor shall be composed of corrosion resistant materials. The anchor and wire rope shall have a breaking strength of 9,500 pounds utilizing standard tensile testing and ASTM A1007-07. The anchor shall have a minimum 1,000 pounds’ ultimate holding strength in normal soil and a manufacturer’s recommended 216.03 minimum driven depth of 3.5 feet. A sample of the anchors and a Certificate of Compliance (COC) including the manufacturer's product data showing that the product meets the Contract requirements shall be submitted for approval at the Environmental Pre-construction Conference. Installation of the blanket will not begin until approval has been received from the Engineer in writing.

Construction Requirements

216.03The Contractor shall install soil retention coverings per Standard Plan M-216-1 and the

following procedure:

the installation area.

staples will be allowed. Install anchor trenches, seams, and terminal ends as shown on the plans. The Contractor shall install TRMs using the following procedure:

product thickness.

216.04

the soil.

seeded area and TRM. When applicable, the covering shall be unrolled with the heavyweight polypropylene netting on top and the lightweight polypropylene netting in contact with the soil.

216.04Slope Application. Soil retention coverings shall be installed on slopes as follows:

The upslope end shall be buried in a trench 3 feet beyond the crest of the slope if possible. Trench depth shall be a minimum of 6 inches unless required by the manufacture to be deeper. Before backfilling begins, staples shall be placed across the width of the trench. The trench shall then be backfilled to grade with soil amended with soil conditioning or topsoil, compacted by foot tamping, and seeded. Fabric shall be brought back over trench and secured with staples or earth anchors at 1 foot on center. There shall be an overlap wherever one roll of fabric ends and another begins, with the uphill covering placed on top of the downhill covering. Staples shall be installed in the overlap. There shall be an overlap wherever two widths of covering are applied side by side. Staples shall be installed in the overlap. Staple checks shall be installed on the slope length at a maximum of every 35 feet. Each staple check shall consist of two rows of staggered staples. The down slope end shall be buried in a trench 3 feet beyond the toe of slope. Before backfilling begins, staples shall be placed across the width of the trench. The trench shall then be backfilled to grade with soil amended with soil conditioning or topsoil, compacted by foot tamping, and seeded. Fabric shall be brought back over the trench and secured with staples or earth anchors. If a slope runs into state waters or cannot be extended 3 feet beyond the toe of slope, the end of covering shall be secured using a staple check as described above. Coverings shall be securely fastened to the soil by installing staples or earth anchors at the minimum rate shown on the Standard Plan M-216-1. Staple or earth anchor spacing shall be reduced where required due to soil type or steepness of slope.

216.05Channel Application. Soil retention coverings shall be installed as follows on a

channel application: Coverings shall be anchored at the beginning and end of the channel across its entire width by burying the end in a trench. Trench depth shall be a minimum of 6 inches, unless a larger depth is specified by the manufacturer’s recommendations. Before backfilling begins, staples shall be placed across the width of the trench. The trench shall then be backfilled to grade with soil amended with soil conditioning or topsoil and compacted by foot tamping and seeded. Fabric shall be brought back over the trench and stapled. Covering shall be unrolled in the direction of flow and placed in the bottom of the channel first. Seams shall not be placed down the center of the channel bottom or in areas of concentrated flows when placing rolls side by side.

There shall be an overlap wherever one roll of covering ends and another begins with the upstream covering placed on top of the downstream covering. Two rows of staggered staples shall be placed.

216.06

There shall be an overlap wherever two widths of covering are applied side by side. Staples shall be placed in the overlap. The covering shall have a channel check slot every 30 feet along the gradient of the flowline. Check slots shall extend the entire width of the channel. The covering shall be buried in a trench. Before backfilling begins, staples shall be placed across the width of the trench. The trench shall then be backfilled to grade with soil amended with soil conditioning or topsoil, compacted by foot tamping, and seeded. Fabric shall be brought back over the trench and continued down the channel. Coverings shall be securely fastened to the soil by installing staples at the minimum rate shown on the plans. Staple spacing shall be reduced where needed due to soil type or high flows.

216.06Maintenance. The Contractor shall maintain the soil retention coverings until all work

on the Contract has been completed and accepted. Maintenance shall consist of the repair of areas where damage is due to the Contractor’s operations. Maintenance shall be performed at the Contractor’s expense. Repair of those areas damaged by causes not attributable to the Contractor’s operations shall be repaired by the Contractor and will be paid for at the contract unit price. Areas shall be repaired to reestablish the condition and grade of the soil and seeding before application of the covering. Method of Measurement

216.07Soil retention coverings, including staples, complete in place and accepted, will be

measured by the square yard of finished surface, excluding overlap, which is installed and accepted. Earth anchors will be measured by the actual number of earth anchors complete in place and accepted. Basis of Payment

216.08The accepted quantities of soil retention coverings will be paid for at the contract unit

price per square yard. The accepted quantities of earth anchors will be paid for at the contract unit price for each installed.

Payment will be made under: Pay Item Pay Unit Soil Retention Blanket (_) (Photodegradable Class _) Square Yard Soil Retention Blanket (_ ) (Biodegradable Class _) Square Yard Turf Reinforcement Mat (Class _) Square Yard Earth Anchors Each

Preparation of seedbed, fertilizing, and seeding will be measured and paid for per Section 212. Placing and preparation of seedbed, fertilizing, and seeding of soil under the TRM layer will be measured and paid for per Section 212.

Topsoil or amended soil and seed placed on the TRM will be measured and paid for per Sections 207 and 212.

Staples will not be measured and paid for separately but shall be included in the work.

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