312Riprap Slope and Channel Protection

312.01 Description

Protect slopes and channels with a covering of geotextile and riprap or an aggregate filter blanket.

312.02 Materials

Aggregate Filter Blanket 901.01, CR-6 Riprap 901.02 Geotextile Section 919, Class as specified

312.03 Construction

312.03.01 Excavation. Excavate for riprap and cutoff walls to the specified lines and grades.

Ensure that the subgrade is smooth and firm, free from protruding objects that would damage the geotextile, and constructed in an acceptable manner. For excavated material, refer to 402.03.01.

312.03.02 Geotextile. Place geotextile on the prepared subgrade with the adjacent edges

overlapping at least 2 ft. Replace or repair damaged geotextile as directed.

312.03.03 Aggregate Filter Blanket. When an aggregate filter blanket is specified, construct it

to the specified lines and grades and compact it in an acceptable manner.

312.03.04 Riprap Placement. Ensure that the underlying surface is free of brush, trees, and

stumps, and is acceptable to the Engineer. Place the first section of riprap consisting of at least 5 tons, which will be inspected by the Engineer for conformance to gradation and placement requirements. If approved, this section will be used to evaluate quality control for the remainder of the project. If the material is rejected, remove it from the project and place additional sections, each at least 5 tons. Begin the placement of the riprap with the bottom cutoff walls or toe sections. Place the larger stones in the cutoff walls and along the outside edges of the limits of slope and channel protection. Place the riprap with equipment that produces a uniformly graded mass of stones. Ensure that the surface elevation of completed riprap installations is flush with adjacent channel bed or bank slope elevations and does not create an obstacle to the flow. Ensure that the outer 312 — RIPRAP SLOPE AND CHANNEL PROTECTION 2026 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS riprap surfaces are even and present a generally neat appearance. The plus or minus tolerance of the surface of the finished riprap installation is 3 in. for Class I Riprap and 6 in. for Class II and III Riprap from the lines and grades shown on the Contract Documents when measured perpendicular to the exterior surface of the stonework. Place and distribute the stone so the resulting layer will contain a minimum of voids and there will be no pockets of same size material. Place the stone to its full course thickness in one operation in a manner that the underlying material is not be displaced or worked into the course of riprap being placed. When an aggregate filter blanket is used, proceed with the placement of the riprap in a controlled manner to avoid disruption or damage to the layer of bedding material.

312.03.05 Backfill. Backfill any excavation voids existing along the edges of the completed slope

and channel protection, and compact it in an acceptable manner.

312.04 Measurement and Payment

The payment will be full compensation for all excavation, geotextile, riprap, backfill, compaction, disposal of excess material, prewashing when required, preparation of quality control section, and for all material, labor, equipment, tools and incidentals necessary to complete the work.

312.04.01 Riprap Slope and Channel Protection will be measured and paid for at the Contract unit

price per square yard. Area measurements will be actual surface measurements.

312.04.02 Cutoff Walls will be measured and paid for at the Contract unit price per linear foot.

312.04.03 Riprap for Scour Protection will be measured and paid for at the Contract unit price per

ton for the item Class II Riprap For Scour Protection.

312.04.04 Aggregate Filter Blanket will be measured and paid for at the Contract unit price per

square yard for the depth specified.