Description
This action was awarded as an 8(a) Sole Source Set-Aside under the authority of section 8(a) of the Small Business Act. In accordance with these specifications the Contractor shall supply all plant, labor, materials, appurtenances, equipment, shop facilities, supervision, tools, staging, scaffolding and any other items necessary to complete the herein detailed improvements to the shotcrete and adjacent areas at Abiquiu Dam. Soil Anchors Soil anchors shall be at least 5/8-inch diameter, epoxy coated steel bars. Submit written certification for coating material and coated bars with the delivery of the bars. ASTM A722/A722M, Type [I] [or] [II], conforming to the coating requirements of ASTM A775/A775M, 8 mils minimum thickness. Coating at the anchorage end may be omitted over the length provided for threading the nut against the bearing plate. Anchor head shall consist of steel bearing plate with wedge plate or steel bearing plate with nut for bar anchors. Threaded anchorage items for epoxy coated bars shall be designed to fit over the epoxy coating. Contractor shall ensure that shotcrete reinforcement rebar will reside behind bearing plate. Centralizers shall be fabricated from plastic, steel or other approved material which is non-detrimental to the pre-stressing steel. Wood shall not be used. The centralizer shall be able to support the tendon in the drill hole and position the tendon so a minimum of 1/2 inch of grout cover is provided. Centralizers and spacers shall permit grout to freely flow up the drill hole. Provide drilling equipment suitable for advancing the drill tools to the depths and at the alignment specified. Cement grout mixture proportions are the responsibility of the Contractor. Submit the mixture proportions that will produce grout of the quality required, thirty days prior to installation of anchors. Provide applicable test reports to verify that the grout mixture proportions selected will produce grout of the quality specified. Grout for grouting anchors shall consist of a homogenous, pumpable, stable mixture of Portland cement and water. Submit the proposed mix design to the Government Representative for approval. The water content shall be the minimum necessary for proper placement but the water-cement ratio shall not exceed 45 percent by weight. Final proportions of materials shall be based on results of tests made on sample mixtures of grout. The minimum compressive strength of two-inch cubes, molded, cured, and tested in accordance with ASTM C109/C109M, shall be 3,500 psi at the time of stressing. Repair Existing Shotcrete and Place New Shotcrete. Contractor shall complete the repairs and new shotcrete placement shown in Attachment 1. Volume of shotcrete to be placed is approximately 3 cubic yards. Shotcrete used shall meet the following criteria: Cement shall comply with ASTM C150 Type 1. Proportion shotcrete mixture by mass complying with ASTM C94.C94M. Cement shall contain a minimum 13 percent silica fume as supplementary cementing material. Silica fume shall comply with ASTM C1240. Contain 5 pounds per cubic yard of polypropylene fibers whose lengths range from 3/4" to 1-1/2”. Fiber reinforcement shall conform to ASTM C11116/C1116M. Aggregate gradation shall fall within the following ranges: Aggregate size % Passing 3/4” 100 1/2" 80-95 3/8” 70-90 0.19 (No 4) 50-70 0.093 (No 8) 35-55 0.046 (No 16) 20-40 0.024 (No 30) 10-30 0.012 (No 50) 5-17 Use ONLY potable water. Air entrainment shall be between 8 and 12 percent prior to pumping. Per ACI 506.2, 28-day compressive strength shall not be less than 4,000 psi. Compressive strength shall be assessed in accordance with ACI 301. Any forms used to line or grade shall have adequate support to remain rigid during shooting. The placement of and clearance around reinforcement shall permit complete encasement of reinforcement with shotcrete. All surfaces shall be dampened immediately prior to shooting. No standing water shall be visible. Use temporary coverings to protect adjacent surfaces from the deposit of overspray or impact from the nozzle stream. Provide a working surface that permits nozzlemen unobstructed access to the receiving surface. Place shotcrete first in corners, recesses, and other areas where rebound or overspray cannot easily escape. The supply of shotcrete material and air pressure at the nozzle shall be uniform, providing a steady, continuous flow of shotcrete with non-detrimental surging or pulsing. Maintain the velocity and consistency of shotcrete exiting the nozzle at a uniform rate appropriate for the given job conditions so that satisfactory material consolidation and minimum rebound is achieved. Apply shotcrete using a circular or elliptical motion of the nozzle while building the required thickness. Use sufficient material velocity, material consistency, and distance from the end of the nozzle to the receiving surface to produce maximum consolidation of the shotcrete and full encapsulation of the reinforcing steel. Do not reuse rebound or overspray in the Work. Contractor shall remove hardened overspray and rebound from adjacent surfaces. Place shotcrete to encase reinforcement and other embedments, and provide a minimum cover of 2-1/2 inches. Do not place shotcrete when temperature is above 95 degrees, or below 50 degrees Fahrenheit. All shotcrete shall be gun finish. Curing period shall be for a minimum duration of 7 days. Contractor shall ensure ponding or continuous sprinkling during curing. If ambient temperatures fall below 50 degrees Fahrenheit, Contractor shall provide cold weather protection. All steel reinforcement shall be No 4 rebar. Concrete Slab, Drain Pipe, Headwall, and Riprap Contractor shall complete the concrete placement, pipe installation, headwall construction, and riprap placement shown in Attachment 1. Concrete shall have a 28-day minimum compressive strength of 3,000 psi. Pipe installation will require approximately 40 feet of pipe and various elbows to match existing surface contours. Pipe and fittings shall be a polyvinylchloride (PVC) type, and at least schedule 40. Pipe shall be installed to permit complete shotcrete encasement. Minimum shotcrete cover in all directions shall be 2-1/2”. Riprap stone shall be durable, non-friable, and of suitable quality to ensure performance in the structure and climate in which it is to be used. The stone shall be angular in shape and the length to thickness ratio shall not exceed 3:1. It shall be free of cracks, seams, and other defects that would tend to increase unduly its deterioration from natural causes. The inclusion of objectionable quantities of rock spalls, dirt, sand, clay, and rock fines will not be permitted. Riprap stone shall be comprised of rock ranging in size from 4 to 10 inches (2 to 4 inches for void fill area shown in Attachment 1). Site Grading and V-ditches. Complete grading and create v-ditches detailed in Attachment 1. A winrow shall be create along the entire length of disturbed vehicle access road. V-ditch shall extend the entire length specified on Attachment 1 and tie into existing grades at each end. The intent of this contract is to repair compromised components and provide reliable infrastructure that ensures mission capability at Abiquiu Dam. All work is to be done according to industry standard practice, within all Federal and State regulations pertaining to the provision and distribution of safe drinking water and using materials appropriate to the type of work.