SECTION 228 - EROSION CONTROL BLANKET
228.01 Description. This work consists of furnishing, placing, and maintaining an
Erosion Control Blanket (ECB) of the type speci fied on seeded or ot her designated areas in accordance with the plans and specifications.
228.02 Materials. The erosion control blankets shall be a temporary, organic and/or
inorganic re-vegetative blanket with non-organic, photodegradable or biodegradable netting. The netting shall be bonded sufficie ntly to the parent material to prevent separation of the net from the parent material for the life of the product. For those blankets that have netting attached, the netting and stitching shall be photodegradable and/or biodegradable. The photodegradable s titching shall be of the same material with similar properties as the netting such that the expected degradation periods are the same. The weight of the netting shall not exceed 15% of the total blanket weight. The Contractor will be permitted to furnish and install a multi-width blanket with seams securely bonded by stapling, staking, stitching, or other methods meeting the approval of the Engineer. The erosion control blanket must be one from the Department's current APL for the type indicated.
228.02.1 Blanket Types. The following are the types of erosion control blankets.
Type I blankets shall be a processed degradable natural and/or polymer fibers mechanically bound together by a single rapidly degrading, synthetic or natural fiber netting or an open weave textile of processed rapidly degrading natural or polymer yarns or twines woven into a continuous matrix. Type II blankets shall be a processed degradable natural and/or polymer fibers mechanically bound together between two rapidly degrading, synthetic or natural fiber nettings. Type III blankets shall be an erosion control blanket composed of processed slow degrading natural or polymer fibers mechanically bound together between two slow degrading synthetic or natural fiber nettings to form a continuous matrix or an open weave textile composed of processed slow degrading natural or polymer yarns or twines woven into a continuous matrix. Type IV blankets shall be an erosion control blanket composed of processed slow degrading natural or polymer fibers mechanically bound together between two slow degrading synthetic or natural fiber nettings to form a continuous matrix or an open weave textile composed of processed slow degrading natural or polymer yarns or twines woven into a continuous matrix. In addition to being on the Department's current APL, the blankets must meet the following general requirements. TYPES OF BLANKETS Type Maximum Gradient C Factor *, ** Minimum Tensile Strength *** I <3:l (H:V) <0.15 50 lbs/ft II <2:1 (H:V) <0.20 75 lbs/ft III <1.5:1 (H:V) <0.25 100 lbs/ft IV <1:1 (H:V) <0.25 125 lbs/ft * "C" Factor calculated as the ratio of soil loss from the ECB protected slope (tested at specified or greater gradient, h:v) to the ratio of soil loss from unprotected (control) plot in large-scale testing. ** Acceptable large-scale test methods may include ASTM D 6459, or other independent testing deemed acceptable by the Engineer. *** Minimum Average Roll Values using ASTM D 6818.
228.02.2 Stakes. Unless otherwise specified by the manufacturer of the erosion control
blanket, stakes used to secure the blanket shall be one of the following:
1.a double prong "U" shaped wire staple made from 11-gauge or heavier steel wire with an approximate length of eight inches (8”) after bending,
2.a biodegradable anchoring device meeting the requirements of ASTM D 5338, or
3.an equal approved by the Engineer.
228.02.3 Acceptance Procedure. Prior to use, the Contractor must furnish the Engineer
three copies of the manufacturer's certifica tion for each shipment of erosion control blanket material stating the number of rolls furnished and that the material in the shipment conforms to the same composition as that listed on the Department's current APL. When wire staples are used, also furnish the Engineer three copies of a certification from the manufacturer or distributor stating the wire size for staples for each shipment. The certifications by the manufacturer or di stributor will be prima facie evidence of the materials meeting the requirements of the specifications.
228.03 Construction Requirements. The Contractor shall furnish and install protective
covering blankets for erosion control on prepared areas of slopes at locations shown on the plans or designated by the Engineer. Erosion control blankets shall be installe d according to manufacturer recommendation or install according to the detail plan sheet. The deta il plan sheet is to be used as a guide in lieu of the manufacture recommendations.
228.03.1 Site Preparation. The area to receive the erosion control blanket should be
fine graded to a smooth profile and relativel y free from all weeds, cl ods, stones, roots, sticks, or other foreign material that may prevent the blanket from bearing completely on the surface. Any voids on the slope shall be filled and properly compacted. Any seeded areas damaged or destroyed duri ng placement of the erosion blanket shall be reseeded as specified for the original seeding at no additional costs to the State.
228.03.2 Trench Preparation. An anchor trench shall be prepared at the top of the
slope by excavating a trench six inches deep by six inches wide. The erosion control blanket shall be anchored into the trench by staking on 1-foot centers. The stakes shall be driven at least flush with the soil surface. The anchor tr ench shall be backfilled and compacted with soil. A minimum of three feet shall be allowed from the anchor trench to the crest of the slope. A similar anchor trench shall be installed at the bottom of the slope to terminate the installation. The trench shall be installed similar to the above except the erosion control blanket shall be rolled 24 inches past the toe of the slope. The terminal end of the erosion control blanket shall be staked on 1-foot centers.
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Source: Standard Specifications for Road and Bridge Construction, 2017 Edition. Pages 178–180 of 1,113. View official source ↗