Two new stormwater retention tanks recently built at BP Oil's refinery in Toledo, Ohio, feature the tallest reinforced-concrete radius walls in the country. The below-grade twin tanks, each 52.5 feet tall and 200 feet in diameter, were built for the refining company at a cost of $18 million to comply with new Resource Conservation and Recovery Act stormwater and wastewater regulations. Construction of the massive tanks began in October 1992 and was completed in March 1994. To achieve this 18-month completion time, contractor Rudolph/Libbe Inc., Walbridge, Ohio, used a special space-saving retaining wall system to contain earth on the confined 10-acre jobsite and cast 80-foot wall sections in four-day cycles.