2511Riprap

2511.1DESCRIPTION

This Work consists of providing and placing stone riprap, with or without grouting, as a protective covering on earth slopes, piers, abutments, walls, or other Structures, where the soil is susceptible to erosion. The Department classifies riprap by type as random riprap or hand placed riprap, depending on the method of placement and the stone size specified.

2511.2MATERIALS

B Filter Materials

2511.3CONSTRUCTION REQUIREMENTS

A General Provide and place stone riprap as shown on the Plans or as directed by the Engineer. Excavate and shape the foundation for the riprap, with or without filter Material , to the cross- sections as shown on the Plans. Compact loose foundation Material before placing the riprap or filter Material. Place a Layer of riprap on a filter Material, at the thickness required by the Contract. Grout riprap as required by the Contract. Fully grouted riprap is not allowed in public waters. B Filter Material Place filter Material under the riprap unless otherwise required by the Contract. The Contractor may choose the type of filter Material, except as required by the Contract.

B.1 Granular Filter Spread granular filter Material to a minimum thickness of 6 inches over the prepared foundation, or as required by the Contract. Deposit granular Material, placed under water, directly on the foundation using a bucket or similar container. Do not discharge the granular Material above the water surface. B.2 Geotextiles When placing geotextile filter Material ensure that the foundation surface is relatively smooth and free of stones, sticks, and other debris or irregularities that might puncture the fabric. Place the filter Material and conduct construction operations without tearing, puncturing, or shifting the fabric. Place the fabric with the longest dimension parallel to the direction of water flow . If using fabric that is not seamed, overlap splices and joints at least 18 inches, for installations above water. When fabric is installed underwater overlap splices and joints at least 36 inches. Provide shingled joint laps in the flow direction and from top to bottom of a slope to direct water flow over the joint without undermining the geotextile filter. The Contractor may sew multiple fabric pieces together, as specified in 3733, “Geosynthetic Materials,” in lieu of joint overlapping. Bury the upgrade edges of the fabric a minimum of 6 inches to direct water flow over the fabric and prevent undermining. If not seamed, place washered steel pins, edge stakes, stones, or other Material at locations and in quantities as approved by the Engineer, to prevent movement of the geotextile filter during placement of the riprap. Do not dump stone at the top of the slope and roll stone down the slope . If placing stones directly on the geotextile filter, do not operate Equipment on top of the stones after placement. Do not operate construction Equipment directly on top of the geotextile. Do not use geotextile filter Material under hand placed or grouted riprap, unless otherwise required by the Contract. The Contractor may place geotextile filter on slopes no steeper than 1:3 . For slopes steeper than 1:3, retrench the geotextile at least every 15 feet or as required by the Contract. Do not use geotextile filter on slopes steeper than 1:2. C Riprap Stone Do not drop stones on the fabric from a height greater than 1 foot unless the fabric is covered with a 6 inch thick granular cushion course. If covered, the Contractor may drop riprap stones from a height no greater than 3 feet. When placing riprap, start at the lowest elevations and work upwards. Before placement of riprap stone on geotextile, the Engineer may require the Contractor to demonstrate that the placement methods will not damage the fabric . The Engineer may order the removal of at least 4 square yard of riprap to inspect for fabric damage in accordance with 1511, “Inspection of Work.” C.1 Random Riprap Position random riprap to provide a uniform distribution of the various sizes of stone and produce a dense, well-keyed Layer of stones with the least practical voids volume. Level the surface flush with the surrounding ground to produce a reasonably uniform appearance and the thickness required by the Contract. Wash riprap clean before placing underwater.

C.2 Hand-Placed Riprap Embed the stones for hand-placed riprap in the foundation Material, with the axis of the stone that most nearly approximates the Contract-required thickness of riprap laid perpendicular to the foundation slope. Lay stones with the least practicable space between them. Position the stones to stagger the joints up the slope. Place each stone to allow the foundation Material and adjacent stones to carry its mass. Use selected stones set to line and grade to define the ends and edges of each riprap area. After laying the larger stones, fill the spaces between the stones with firmly seated, smaller stones to produce a uniform surface. Wash riprap clean before placing underwater. D Grouting For fully grouted riprap, ensure that grout fills the spaces between stones throughout the entire thickness of the riprap. Immediately before placing the grout for grouted riprap, thoroughly wet the stones with water . Do not pour grout over stones that have become surface dry. Sweep the surface of the grouted riprap with a stiff broom to finish. E Thickness Requirements Ensure the riprap placed on each separate area has a minimum thickness of at least 80 percent of the thickness required by the Contract and an average thickness of at least 95 percent of the thickness required by the Contract when measured at right angles to the face. F Quality Control (QC) Refer to the requirements in the Schedule of Materials Control for Project specific requirements. F.1 Gradation and Certification Requirements For riprap meeting 3601.2A, “Random Riprap,” test one gradation per year for each product using either:

Manual. Record and submit results using Form G&B-108a, Riprap Gradation D85 and FHWA Hydraulic Toolbox, found on the MnDOT Grading and Base website

Record and submit results using and submit Form G&B-108a, Riprap Gradation D85 and FHWA Hydraulic Toolbox, found on the MnDOT Grading and Base website

Manual. Record and submit results using Form G&B-108b, Riprap Gradation Wolman Method, found on the MnDOT Grading and Base website For riprap meeting 3601.2B, “Hand placed Riprap,” provide certification that the stone meets Contract-required thickness of riprap, following guidance in 2511.3C.2, “Hand-Placed Riprap,” and individual stones have a weight of at least 50 pounds. F.2 Carbonate Quarried Riprap For riprap meeting 3601.2A, “Random Riprap,” or 3601.2B, “Hand-placed Riprap,” the supplier is required to have an approved QC Plan, prior to delivery of stone, when either of the following apply:

The Carbonate riprap QC Plan requirements are found on the MnDOT Geology Web page. Contact the MnDOT Geology Unit a minimum of 60-Calendar Days prior to supplying riprap. Provide certification, for each product, using Form G&B-104b, “Riprap Quality Control Plan,” and attach required test(s). F.3 Riprap meeting 3601.2C, “Gabions and Revet Mattresses,” 3601.2D, “Granular Filter under Class I Random Riprap,” and 3601.2E, “Granular Filter Under Riprap, Gabion, and Revet Mattress” Provide certification using Form G&B-104, “Certification of Aggregates and Granular Materials,” found on the MnDOT Grading and Base website. G Quality Assurance (QA) The Department will inspect the Material for compliance to the requirements of 3601, “Riprap Material.” Obtain the Engineer’s approval of the quality of the stone before delivering the stone to the Project. The Engineer will inspect the stone for compliance to the gradation requirements after delivery of the stone to the Project. G.1 Riprap meeting 3601.2A, “Random Riprap,” 3601.2B, “Hand-placed Riprap” For gradation compliance of riprap meeting 3601.2A, “Random Riprap,” the Engineer will visually inspect the riprap and perform the D85 test, test method 5-692.210, listed in the Grading and Base Manual and complete Form G&B-108a, Riprap Gradation D85 and FHWA Hydraulic Toolbox, found on the MnDOT Grading and Base website. If the material fails to meet requirements based on the visual check or the D85 results, the Engineer will test the gradation using one of the following methods:

Base Manual and Form G&B-108a, Riprap Gradation D85 and FHWA Hydraulic Toolbox

Form G&B-108a, Riprap Gradation D85 and FHWA Hydraulic Toolbox

and Form G&B-108b, “Riprap Gradation Wolman Method” For riprap meeting 3601.2B, “Hand-placed Riprap,” the Engineer will visually inspect the riprap to ensure it meets the requirements of 2511.3C.2, “Hand-Placed Riprap.” G.2 Granular Filter meeting 3601.2D, “Granular Filter Under Class I Riprap,” or 3601.2E, “Granular Filter Under Other Riprap, Gabion, and Revet Mattress” For gradation compliance, the Engineer may use either visual inspection or perform gradation per Laboratory Manual. G.3 Carbonate Quarry Riprap The Department will sample for insoluble residue and test per the Laboratory Manual .

2511.4METHOD OF MEASUREMENT

A Riprap If measuring riprap of each type and class by volume, the Engineer will calculate the volume based on the actual surface dimensions as staked and the thickness shown on the P lans or specified in the Special Provisions.

If measuring riprap of each type and class by mass, the Engineer will calculate the mass based on Scale tickets of Materials delivered and placed within the staked areas. B Filter Materials If measuring filter Materials by weight, the Engineer will calculate the weight based on S cale tickets of Material delivered and placed within the staked areas. If measuring filter Materials by volume, the Engineer will calculate the volume based on the actual surface dimensions as staked and the thickness as shown on the P lans. The Engineer will measure geotextile filter Material by area based on the actual surface dimensions as staked, with no allowance for overlaps or seams.

2511.5BASIS OF PAYMENT

The Contract Unit Price for riprap of each type and class includes the cost of providing the Materials, excavating and preparing the foundations, and placing the riprap stone, grouting, and filter Materials as required by the Contract. The Department will pay for filter Materials of the type specified, if included in the Contract. The Department will pay for riprap and filter Material on the basis of the following schedule: Item No. Item Unit

2511.504 Geotextile Filter Type * square yard

7 Random Riprap Class ___ǁ cubic yard

7 Hand-placed Riprap cubic yard

7 Grouted Riprap cubic yard

7 Granular Filter cubic yard

9 Random Riprap Class ___ǁ ton

9 Granular Filter ton

* Specify Type – 3, 4, or 7. See 3733, “Geosynthetic Materials” ǁ Specify Class – See 3601.2A.1, “Sizing Requirements”