In order to prevent soil and groundwater pollution, ensure the sustainable use of soil and groundwater, and fulfill the regulations of Soil and Groundwater Pollution Remediation Act, the Environmental Protection Administration (the EPA) initiated the Project of Investigating Soil and Groundwater Pollution at Gas Stations(the Seventh Phase)- Plans A and B in 2011, including 331 gas stations. Sinotech Engineering Consultants, Ltd.(Sinotech) was entrusted to carry out Plan A, covering Central and Northern Taiwan, while MWH Taiwan was assigned to carry out Plan B, covering Central and Southern Taiwan.
Plan A performed by Sinotech was aimed to investigate soil and groundwater pollution at 167 gas stations in Central and Northern Taiwan. The findings from the investigation will be used as references for the follow-up pollution control activities. The investigation was implemented in the following three stages:
1. Stage 1: was to detect and measure the fuel vapor of soil gas monitoring well.
2. Stage 2: based on the results of Stage 1, was to conduct soil and groundwater sampling and analysis from simple wells at the gas stations with high pollution potential.
3. Stage 3: was to install standard monitoring wells and conduct groundwater sampling and analysis at the gas stations investigated in Stage 2 found to have groundwater pollutants beyond the control standard.
For Stage 1, 167 gas stations were investigated, covering basic functional tests of 2,849 soil gas monitoring wells, measurement of fuel vapor concentration by using Lower Explosive Limit(LEL), Photo Ionization Detector(PID), and Flame Ionization Detector (FID), and measurement of soil vapor of 17 samples by using PID and FID, and gas chromatography(GC) analysis of 154 soil vapors. The results indicated that through the evaluation of the fuel gas concentration detected by soil gas monitoring wells, there were 6 gas stations with the highest pollution potential (Class A) and 5 gas stations with the second highest pollution potential (Class B). In addition, the result of soil vapor GC analysis indicated that 13 gas stations with the highest pollution potential (1st Class) and 21 gas stations with the second highest pollution potential (2nd Class)
For Stage 2, 38 gas stations were investigated, consisting of the detection and analysis of 133 soil and 108 groundwater samples from simple wells. The findings showed that the soil pollutant concentration of 5 gas stations and groundwater pollutant concentration from the simple wells at 8 gas stations were over the control standard. For Stage 3, 4 out of the 8 gas stations investigated had the groundwater pollutant concentration over the control criteria.
It was concluded that the soil pollutant concentration of 5 gas stations and groundwater pollutant concentration of 3 gas stations were above the respective control standards. Moreover, 1 gas stations had soil and groundwater pollutant concentration above the control standard. All of these polluted stations should be remedied in accordance with the Soil and Groundwater Pollution Remediation Act. In addition, the correlation analyses of the basic data of the gas stations investigated in the project, groundwater pollution control facilities, periodic declaration reports, and pollution potential at the gas stations were also conducted. The outcomes will serve as references for the environmental protection agencies in the follow-up administrative control measures.