Angostura Dam Spillway Concrete Repair

454-600-60005 The point of contact is Contracting Officer Linda Melnick. All questions and correspondence concerning this solicitation should be submitted via email to lmelnick@usbr.gov. The scope of the project includes the following: Saw-cutting and removing damaged concrete on the spillway chute and replacing with new concrete. Background: The Bureau of Reclamation constructed Angostura Dam between 1946 - 1949. Angostura Dam is located on the Cheyenne River approximately 10 miles southeast of Hot Springs, South Dakota and approximately 60 miles south of Rapid City, South Dakota. The dam consists of a 967-foot-long concrete gravity structure and a 1,063-foot-long zoned earth embankment with a hydraulic height of 136 feet and a reservoir storage capacity of 123,048 acre-feet. The 274-foot-wide-by-117-foot-tall spillway is a mass-concrete ogee-crested overflow structure within the concrete portion of the dam, with a total discharge capacity of 247,000 cubic feet per second. Releases are controlled through five (5) 50-foot-wide-by-30-foot-tall radial gates, which are kept submerged throughout the year to accommodate reservoir operations. The spillway chute increases in slope from 0 to 55 degrees over a length of approximately 110 feet, and at its base is a 180-foot-long-by 10-foot-deep stilling basin that also remains full year-round. The downstream face of the spillway exhibits significant degradation due to freeze-thaw cycling, particularly along the lift lines and contraction joints where slow but constant seepage through the dam contributes to ice accumulation throughout the winter. Also prevalent across the downstream face are large pop-outs caused by the saturation, expansion, and dislodgement of the 6-inch-minus aggregate used in the original concrete. Current repair plans involve: o Removing approximately 4,500 total square feet of concrete (in multiple repair locations) to a depth of six-inches: o Installing lateral reinforcement bars at each of the repair locations: o Preparing the exposed surfaces for concrete placement; and o Placing new cast-in-place concrete or shotcrete to the original grade. o Trowel-finishing the surface to a tolerance of 1/8-inch (abrupt) or 1/32-inch (gradual). Construction constraints include the following: o Vehicular and equipment access to the spillway is very limited. The concrete portion of the dam crest is only 9 feet wide, and no vehicular access is permitted across the metalgrated bridge deck above the radial gates. Side access is limited to 50 feet away on one side only. An old service road leads to an abandoned powerplant near the river channel downstream, but it is currently inadequate for heavy traffic and does not provide access to the riverbed or stilling basin. o The anticipated construction window is between August 15 and November 30 to avoid potential flood releases through the spillway. o The reservoir cannot be lowered during construction, so water will remain on the radial gates. o The stilling basin cannot be dewatered either, and allowing material to fall into it should be avoided. We will meet at Maverick Junction prior to driving to the dam. From Rapid City Regional Airport, you follow Terminal Rd and Airport RD to SD-44W. Stay on SD-44W for 5.4 miles. Turn left onto US16 Bypass/Elk Vale RD for 2.3 miles. Using the Left lane take the on ramp onto SD-79 S/Heartland Expressway, follow this for 47.6 miles. We will meet at the Coffee Cup Travel Plaza TA Express (address: 27638 US-385, Hot Springs, SD 57747) on the east side of the highway Junction SD-79, US 385, and US 18. We will meet at the Coffee Cup Travel Plaza at 1230. Drive time is 55 minutes from Rapid City Regional Airport to Coffee Cup. The magnitude of this project is between $1,000,000 and $5,000,000. PSC: Z2KA- Repair or Alteration of Dams Services. The Small Business Size Standard is $45 Million. This project is issued for a Total Small Business Set Aside.

Division 02 -	Existing Conditions, Subsurface Investigation.
Division 31 -	Earthwork, Site Clearing, Grading, Excavation and Fill, Subgrade Preparation, Excavation, Shoring, Tunneling and Mining, Tunnel Excavation.
Division 35 -	Waterway and Marine Construction, Dam Construction and Equipment.