448 SECTION 856 EROSION CONTROL BLANKET AND TURF REINFORCEMENT MAT
856.01 Erosion Control Blanket (Ecb)
A.General. Provide erosion control blanket (ECB) of organic biodegradable mulch material such as straw, curled wood excelsior, coconut fiber, or any combination of these materials. Provide ECB that has a consistent thickness of mulch material evenly distributed over the entire area. Secure the ECB materials on at least one side with netting. Use netting of photodegradable polypropylene or other plastic material fused to the strand intersections. Provide ECB that has a minimum width of 48 inches and is weed and pest free. Provide ECB that meets the requirements of Tables 856-01 and 856-02 for the type specified in the contract. The requirements in Tables 856-01 and 856-02 are derived from information obtained from the Erosion Control Technology Council. All values must be within 10 percent of the values shown on the table. Table 856 -01 ECB Type 1 and 2 TYPE ECB 1 ECB 2 Straw Wood Straw Wood Material 100% Straw 100% Excelsior Fibers 100% Straw 100% Excelsior Fibers Fiber Length 80% Must Be Greater Than 3 inches 80% > 6 inches 3 inches 6 inches Min Thickness ASTM D 6525 0.25 inch 0.25 inch 0.25 inch 0.25 inch Net Opening Minimum (inch) 0.5 × 0.5 0.75 × 0.75 0.5 × 0.5 0.75 × 0.75 Max Shear Stress @ 0.50 inches soil loss ASTM D 6460 N/A 1.50 lbs/sf 1.50 lbs/sf 1.75 lbs/sf Slope Gradient Application ≤ 3H:1V < 3H:1V - 2H:1V ≤ 2H:1V < 2H:1 - 1.5H:1V Net Backing Type Rapid Photodegradable Polypropylene Polypropylene Functional Longevity ≤ 3 months ≤ 12 months Min Machine Direction Tensile Strength ASTM D 6818 50 lbs/ft 75 lbs/ft Table 856 -02 ECB Type 3 and 4 TYPE ECB 3 ECB 4 Straw/Coconut Wood Coconut Wood Material 70% Straw and 30% Coconut Fibers 100% Excelsior Fibers 100% Coconut Fibers 100% Excelsior Fibers Fiber Length 80% Must Be Greater Than 3 inches 80% > 6 inches 3 inches 80% > 6 inches Min Thickness ASTM D 6525 0.25 inch 0.25 inch 0.25 inch 0.50 inch Max Shear Stress @ 0.50 inches soil loss ASTM D 6460 1.75 lbs/sf 2.00 lbs/sf 2.25 lbs/sf 2.25 lbs/sf Slope Gradient Application ≤ 1.5H:1V ≤ 1.5H:1V ≤ 1H:1V ≤ 1H:1V Net Backing Type Polypropylene Black UV Stabilized Polypropylene Functional Longevity 12 to 24 months > 24 months Minimum Tensile Strength ASTM D 6818 100 lbs/ft 125 lbs/ft
B.Wood Excelsior Blanket. Provide wood excelsior blanket that consists of a machine-produced blanket of curled wood excelsior in which 80 percent of the fibers are 6 inches or longer. Provide a wood excelsior blanket that is smolder -resistant without the use of additives.
C.Straw Blanket. Provide straw blanket that consists of agricultural straw in which 80 percent of the fibers are at least 3 inches in length. The straw shall be certified by an accredited agency to be 100 percent weed free.
D.Straw and Coconut Blanket. Provide a machine-produced straw and coconut blanket that consists of 70 percent straw and 30 percent coconut fibers by weight in which 80 percent of the fibers are 3 inches or longer.
856.02 Turf Reinforcement Mat (Trm)
Provide turf reinforcement mat (TRM) that is a three dimensional structure of entangled filaments. Use filaments that are either bonded by heat fusion at the intersections or stitched with polypropylene, nylon or polyester threads between two UV -Stabilized nettings. Provide TRM that is resistant to biological, chemical, environmental, and ultra- violet degradation. Provide a TRM that promotes and maintains the integrity of the grass root system. Provide TRM that meets the requirements of Table 856-03 for the type specified in the contract. 450 Table 856-03 TRM TYPE TRM 1 TRM 2 Matrix Fill Material Wood Excelsior, Coconut or Polymer Fibers 100% Stabilized Polypropylene Fibers Min Mass Unit Area ASTM D 6475 (natural fibers) 6566 (synthetics) 0.625 lbs/sy 0.625 lbs/sy Minimum Thickness ASTM D 6525 0.25 inch 0.5 inch Minimum Roll Width 6.5 ft 6.5 ft Size of Net Opening 0.5 × 0.5 inch 0.5 × 0.5 inch Max Shear Stress @ 0.50 inches soil loss ASTM D 6460, under vegetated conditions 6.0 lbs/sf 8.0 lbs/sf ASTM D 6818 125 lbs/ft 150 lbs/ft
856.03 Staples
Use staples for ECM and TRM that are constructed of 11 gauge or heavier steel wire and that are either U -shaped measuring at least 1 inch across the top and at least 8 inches along each leg, or that are T-shaped measuring at least 4 inches a cross the top and at least 8 inches in length. In Depth Review 2022 Section 858 451 SECTION 858 GEOSYNTHETICS
858.01 Geosynthetic Material
Provide fabric consisting of polymeric filament or yarns such as polypropylene, polyethylene, polyester, polyamide, or polyvinylidene chloride. Woven slit film geotextile material is not allowed. Use fabric composed of filaments or yarns that are formed into a stable network that retain their relative position to each other. Use material that is inert to commonly encounter ed chemicals and meets requirements of Table 858 -01 or Table 858-02. Values in Table 858-01 and 858-02 represent average roll values. Use geosynthetics for materials included on Table 858-01 from manufacturers or suppliers that maintain compliance with the NTPEP audit program for geosynthetics. Include the NTPEP number identifying the material test results on the Certificate of Compliance. Submit the CoC a minimum of 21 days before material is incorporated into the work. Table 858 -01 Geosynthetics for Separation, Riprap, and Reinforcement Geosynthetic Material Property Test Method Separation2 Riprap RR Reinforcement R1 S1 S2 Ultimate Grab Strength1, lbs., min. ASTM D 4632 180 180 200 350 Wide Width Tensile Strength1, lbs / inch., min. ASTM D 4595 N/A N/A N/A 270 Ultimate Grab Elongation1, % ASTM D 4632 N/A N/A 15 (min) 25 (max) Trapezoid Tearing Strength, lbs., min. (any direction) ASTM D 4533 50 50 50 100 Static Puncture Strength lbs., min. ASTM D 6241 405 405 435 1000 AOS less than mm, (greater than US STD. Sieve) ASTM D 4751 0.212 (70) 0.15 (100) 0.3 (50) 0.6 (30) Permittivity, sec.-1, min. ASTM D 4491 0.5 0.05 0.5 0.5 UV Resistance (After 500 hrs.) % min Strength Retained ASTM D 4355 70 70 70 70 Sewn -Seam Strength, lbs ASTM D 4632 160 160 180 310 1 Weakest principal direction. 2 Separation fabrics shall be nonwoven fabrics.
Source: North Dakota Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 483–485 of 550.