In view of the great impact of the NPS (Non Point Source) pollutant on water quality BMPs (Best Management Practices) used to control NPS pollutant become a significant strategy. The major pollutants in runoff of the impervious area are heavy metal and solid substance most of which involve the toxicity. This kind of area, mainly including parking lots, gas station, vehicle service facilities and equipment storage and maintenance area is named Hot Spots. Because the area accumulates a mass of heavy metal in its storm runoff, it becomes a seriously polluted runoff with high heavy metal and the runoff tends to be discharged into the water body without treatment. Although the area of watershed is small, during the storm event, the non-processed thick runoff aggregate and are likely to affect water quality and ecosystem. According to the present project, MCTT (Multi-Chambered Treatment Train) was set up at the parking lot of Ping-Lin Expressway Management Station. The whole process had gone through different steps, from operating the machine to evaluating water quality and completed in May 2007; the system increasingly becomes stable. When it comes to evaluating the system in its design, construction, and water quality, the results meet the goal. This system has run for three months and has collected the data of six storm events; researchers calculate mass flux via MCTT and then estimate reduction efficiency of MCTT for pollutants. MCTT provided reductions of SS for 89％, COD for 44％, E. Coli for 66%, NH3-N for 61%, TP for 52％, Pb for 64％, Cu for 65%, Zn for 85％, and Oil for 44%. Moreover, the outcome showed that MCTT is an effective measure to control runoff pollutant of hot spots. Because MCTT can be designed as an underground facility, it can be applied to the crowded area where the landuse tends to be more expensive.

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