In order to prevent soil and groundwater pollution, ensure the sustainablity of soil and groundwater use, 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 completion of 331 gas stations investigation. Sinotech Engineering Consultants, Ltd. (Sinotech) carried out Plan A, covering Central and Northern Taiwan, while MWH Taiwan carried out Plan B, covering Central and Southern Taiwan.
Plan B was aimed to investigate the level of soil and groundwater pollution at 164 gas stations in Central and Northern Taiwan. The findings from the investigation will be used as references for the subsequent pollution control. The investigation was implemented in the following three stages:
1. Stage 1: Detected and measured the fuel vapor of soil gas monitoring well.
2. Stage 2: Based on the results of Stage 1, sampled and analyzed soil and groundwater collected from simple wells at the gas stations with high pollution potential.
3. Stage 3: Installed standard monitoring wells at the gas stations with high pollution potential, to sample and analyze groundwater in which the pollutants are beyond the control standard from Stage 2 investigation.
For Stage 1, 164 gas stations were investigated, covering basic functional tests of 2,805 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 21 samples by using PID and FID, and Gas Chromatography (GC) analysis of 164 soil vapors. Through the evaluation of the fuel gas concentration detected by soil gas monitoring wells, the results indicated that there were 0 gas station with the highest pollution potential (Class A) and 2 gas stations with the second highest pollution potential (Class B).
For Stage 2, 33 gas stations in total were investigated, including:
- 29 stations in total which were classified as Class A to Class E due to their high fuel gas concentration, and were classified as Level 1 and Level 2 on GC analysis;
- 4 high –pollution-potential gas stations under the project of the EPA, 2010, “Inspection of facilities for preventing the pollution of groundwater bodies and monitoring equipment at gas stations and providing the owners advice on reporting monitoring results through internet”;
The investigation tasks of 33 gas stations in Stage 2 consisted of detection and analysis of 117 soil and 91 groundwater samples from simple wells. The findings showed that among those 33 stations, there were 9 stations with soil pollutant concentration exceeding standard, and another 11 stations with groundwater pollutant concentration over the control standard as well.
For Stage 3, we further analyzed the 12 gas stationsin, in which 6 out of 12 consists groundwater pollutant concentration over the control standard.
It was concluded that there are 11 gas stations which are either with over-standard soil pollutant concentration, or with over-standard groundwater pollutant concentration:
- 5 stations with over-standard soil pollutant concentration
- 2 stations with over-standard groundwater pollutant concentration
- 4 stations with over-standard soil and groundwater pollutant concentration
In sum, all of these 11 polluted stations should be remedied in accordance with the Soil and Groundwater Pollution Remediation Act. In addition, to serve as references for the environmental protection agencies in the follow-up administrative control measures, the correlation analyses of the basic information of the investigated-gas stations, groundwater pollution control facilities, periodic declaration reports, and pollution potential were also conducted.