Lewisville Dam Safety Modification (LDSM) Spillway   5

The scope of the project includes all work required for construction to make necessary repairs to Lewisville Dam, Lewisville, Texas. The measures to address the structural stability concerns associated with PFM 6 consist of posttensioned anchors installed through the ogee weir, and an upstream geomembrane blanket. An anchor field testing program to gather foundation information to verify the anchoring capacity assumptions of the Eagle Ford shale foundation is complete with the relevant data and reports included in the Design Documentation Report and Geotechnical Data Report. A work platform will be required to install the anchors along the downstream slope of the monoliths.

Install 73 post-tensioned strand anchors on the spillway. The anchors will be founded approximately 130 feet below the spillway weir foundation. All anchors will be installed and tensioned before performing any demolition on apron slabs. Install permanent load cells on one anchor per monolith. Install cable through trench cut into weir to right abutment, up the abutment to a terminal box at the top of the abutment for monitoring. Test anchors as specified and per the PTI.

The upstream geomembrane blanket will be installed in the approach channel of the spillway below the current grade and attached to the ogee monoliths. A cofferdam will be required across the approach channel for the installation of the membrane. The approach channel has a relatively flat slope in the area and a water depth of 2 to 3 feet at conservation pool elevation.

The apron slab overlay will cover the existing apron slabs to address uplift and sliding concerns associated with PFM 7. The overlay slab joints will be positioned so they will be offset from the existing slab joints. The joints between the overlay slabs will be doweled and include a water stop. Each overlay slab will have anchors installed; the number of anchors varies depending on the distance from the ogee weir. The apron slabs will be thickened in the area around the anchors to prevent pullout. A drainage layer will be included between the two slabs. Maintaining a consistent moisture content is necessary to reduce the shrinking and swelling of the foundation which led to the heave in the existing apron slabs. Some existing heaved apron slabs will be removed and replaced prior to placing the drainage system and overlay.

The existing apron slab extension will be demolished and replaced with a system of two drilled pier walls reinforced with heavy structural steel sections and connected across the top with cap beams. The downstream wall will be buried deep to prevent headcutting scour from undermining the apron slab. The upstream wall will be used as an anchor to brace the downstream wall from downstream deflections. The walls are tied with a new apron slab reinforced for tension.

Training walls were evaluated for stability and potential for overtopping during extreme flood events. Construct concrete extensions on top of the existing training walls. Reinforcement will be epoxy anchored into the top of the walls. Remove backfill from behind the walls and install new drainage piping. Place vertical butyl rubber joint seals extending from top of footing to 1' above backfill on the soil side of the walls. Install new drainage and backfill. Contractor must keep enough stockpile on site to backfill the walls should a flow event exceeding 5' of flow in the apron occur. Offsets in the training wall joints on the spillway sides will be ground smooth to minimize potential for cavitation and stagnation pressures. One monolith stem wall will be removed and replaced.

Non-Overflow monoliths left and right of the spillway will have backfill stabilized with lime to reduce likelihood of slides. Instrumentation to monitor structural behavior will include load cells in the post-tensioned anchors and uplift cells in the apron slab drainage fill.

Set-Aside: Unrestricted

Place of Performance: Lewisville, TX

Construction of Magnitude: Between $25M - $100M

Period of Performance: 1,258 Calendar Days

All offerors are advised that this project may be delayed, cancelled, or revised at any time during the solicitation, selection, evaluation, and/or final award process.

Downloading the Solicitation: The solicitation will be available on or about 15 days after the posting of this pre-solicitation notice. Plans and Specification will not be provided in hard paper copy. The solicitation and all amendments for this Request for Proposal will be posted on SAM.gov accessed through https://www.sam.gov under the solicitation number W9126G21R0004.

It is the offeror's responsibility to check SAM.gov frequently for any amendments or changes to the solicitation.

The Government is not responsible for any loss of internet connectivity or for an offeror's inability to access the documents posted at the referenced website.

If you would like to list your firm so that others can see you are an interested vendor, you must click the "Add Me to interested Vendors" button in the listing for this solicitation on SAM.gov accessed through https://www.sam.gov.

The site visit for this project should occur approximately 2 weeks after the posting of the solicitation.