Wetherby-based Augean will pay an initial consideration of £9.2m, net of £4.5m of cash acquired, and will pay an additional sum of up to £4.75m, subject to Colt winning certain contracts.
Hull-based Colt reported revenue of £7m last year and earnings of £1.4m.
Augean said Colt will boost its industry and infrastructure division and the deal is expected to be immediately earnings enhancing. All 75 Colt employees will be transferred to Augean, including key executives, who will remain with the business.
Augean said Colt provides a broad range of industrial services, which complement its existing offering, to a range of customers including major industrial companies, oil refineries, rail and utilities.
Colt's services include specialist tank cleaning and high pressure jetting, hydro abrasive cutting, asbestos removal, waste management and tanker haulage.
Augean's CEO Dr Stewart Davies said: “We are delighted to announce the acquisition of Colt as we continue to strengthen Augean’s position in the UK hazardous waste management market.
"The acquisition is immediately earnings enhancing and creates synergies with our existing service offering, enabling the group to address a wider breadth and depth of client needs and adding new top-tier clients.
"It also accelerates our strategy to grow shareholder value by developing sustainable market positions and providing customers with innovative solutions.”
Colt will give the group UK-wide coverage of specialist industrial services that will expand its existing service, treatment and disposal infrastructure.
It will also bring lucrative customer relationships with top-tier companies that need hazardous waste disposal, providing opportunities for cross-selling, and a fleet of specialist vehicles and equipment.
Analyst Jo Reedman at N+1 Singer said: "The acquisition is expected to provide good opportunities for cross-selling, as Colt has framework agreements with tier 1 customers providing on-site industrial services and waste management services which are complementary to those offered by Augean.
"The business is well-invested and well-run, with management and all 75 employees joining Augean."