SECTION 920 — RIPRAP 900-55 — RIPRAP
920.01 Description.
This work includes providing riprap on prepared surfaces of the sizes and layer thicknesses at the required locations. The work also includes placing stone bedding and filter fabric.
920.02 Materials.
Use materials that conform to Subsections M10.03, M10.03.1 and M10.03.2. Use gravel borrow that conforms to Subsection M01.02. Use geosynthetic fabric material that is suitable for erosion control applications and that complies with SECTION M20 and/or is included on the Department’s Approved Materials List. Use stone bedding that conforms to Subsection M10.03.1.
920.03 Construction Methods.
General. Ensure that slopes to be protected by riprap are free of brush, trees, stumps, and other unsuitable material and are graded to a smooth surface. Remove all unsuitable material to the required depth and replace with gravel borrow. Compact f ill as specified in Subsection 202.03.3(a) and (b). If a toe trench is shown on the Plans, excavate the trench and maintain until the riprap is placed. Provide protection for structure foundations as early as the foundation construction permits. Clean the area to be protected of waste materials and prepare the surfaces as required. Place riprap in conjunction with the construction of the embankment , avoiding the mixing of embankment and riprap materials. Maintain the riprap protection until accepted, and replace any material displaced to the required lines and grades at no additional cost to the Department. Geosynthetic Fabric. Ensure that the installation of geosynthetic fabric conforms to the manufacturer’s guidelines, with the minimums below.
a.Finished Ground. Ensure that t he finished ground is smooth and well compacted. Remove all rock, dirt clods, grass clumps, trash, and other obstructions that will prevent the mat from lying in direct contact with the soil surface and cause the fabric to puncture or tear.
b.O verlap . Provide a minimum overlap width of 2 ft.
c.Anchor Pins. Install anchor pins immediately after placement of each section to protect from wind uplift.
Part 900 — Incidental Construction and Services August 2025
900-56 SECTION 920 — RIPRAP
d.Placement. Ensure that the fabric is toed-in at the top and toed-in or toe-wrapped at the bottom. Bedding For Riprap. Place the bedding material on the prepared slope or area to the specified thickness of each layer. Proceed with the placement of stone bedding from the bottom up to the top of the slope. Do not dump the stone bedding onto the fabric from the top of the slope and then allow the stone to roll down the surface of the fabric. Place bedding in one operation, using methods that will preclude the segregation of particle sizes within the layer. Ensure that the surface of the finished layer is even and free from mounds or windows. Use additional layers of bedding material, when required, that preclude the mixing of materials in different layers. Placed Riprap. Place stone on the prepared slope or area to produce an evenly graded mass of stone with the minimum practical percentage of voids. Place the entire mass of stone to conform to the required lines, grades, and thicknesses. Place riprap to its full course thickness in one operation and avoid displacing the underlying material. Do not place riprap in layers, or dump into chutes, or use other methods likely to cause segregation. Ensure that the larger stones are well distributed and that the entire mass of stone conform s to the specified gradation in Subsection M10.03.2. Place and distribute all materials comprising riprap protection to preclude large accumulations of either the larger or smaller sizes of stone. Place stones for riprap on a prepared slope in a pattern that contains minimum voids. Ensure that the top surface of the riprap conforms to a true and even plane with a tolerance of ±4 in. Break joints as practical, and avoid joint openings to underlying soil by arranging stone sizes and chock the openings with smaller stones. Place larger stones near the base of the slope. Lay the stones to rest on the bank and not on adjacent stones by laying stones from the top of the bank downward to ensure independent support for each such stone. Produce a compact riprap protection in which all sizes of material are placed in their proper proportions. Hand placing or rearranging of individual stones by mechanical equipment may be required as necessary to secure the results specified. When riprap and bedding material are dumped under water, increase the thickness of the layers as shown on the Plans. Use placement methods that will minimize segregation.
920.04 Method of Measurement.
Riprap is measured by the number of square yards as computed from surface area.
Part 900 — Incidental Construction and Services August 2025
SECTION 920 — RIPRAP 900-57
920.05 Basis of Payment.
The Department will pay for the completed and accepted quantities as follows: Pay Item Pay Unit Riprap SY The price constitutes full for all labor, materials, and equipment, including excavation for riprap or bedding, preparation of subgrade, filter fabric, bedding material, trimming and fine grading, hauling and placing the material, and all incidentals required to finish the work, complete and accepted. Riprap placed outside the specified limits will not be paid for, and the Contractor will be required to remove and dispose of the excess riprap at no additional cost to the Department.
Referenced in this section
Riprap in other states
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Source: Standard Specifications for Road and Bridge Construction (Blue Book), 2022 (Aug 2025 compilation) Edition. Pages 662–664 of 951. View official source ↗