听力原文：The company, which was not the sole source of the pollution but is the only business working on the cleanup, has already spent several million dollars installing ventilation systems and creating a network of wells, pumps and filters to extract chemical contaminants from groundwater. The vapor problem came to light in 2003 as a result of air-quality tests sought by residents. The vapor problem was mainly caused by the chemical containments from the ground water out of the company.