USACE Chicago District is conducting market research for a large-scale civil works construction contract for the Thomas J. O’Brien Lock and Dam Major Rehabilitation in Chicago, Cook County, Illinois. The anticipated contract is firm-fixed-price under FAR Part 15, may be set aside for small businesses or procured through full and open competition, and has an estimated performance duration of three years (1,095 calendar days). The work includes guide and chamber wall grout repair, repair of a barge-impacted upper guide wall, replacement of sector gate operating machinery, culvert valve gates and actuators, controlling-works gates and actuators, jib cranes, and electrical/control, emergency lighting, backup generator/UPS, and roof drain outfall upgrades. Firms must demonstrate bonding and working-capital capacity sufficient for a single contract significantly exceeding the NAICS 237990 size standard, experience with heavy marine/civil projects over $75M involving active navigation locks and underwater mass tremie grouting or cofferdam dewatering, and ability to execute high-density mechanical/electrical replacements within a rigid 120-day lock outage. The market survey also requests input on small business subcontracting, Project Labor Agreement impacts, availability of EPA CPG/BioPreferred materials, and long-lead equipment items exceeding 12 months fabrication.