| This paper takes a petrochemical engineering project in Changxing Island(Dalian) as an example.An investigationof the hydrogeological conditions and environmental geological problems was implemented. By collecting data and experimental methods, a serial of hydrogeological parameters and geotechnical parameters were applied to establish a hydraulic model in study area. Meanwhile, evaluation of groundwater quality status and solute transport modeling were accomplished. According to the results, pollution prevention and treatment measures were discussed. Through a series of studies, the main conclusions are as follows:1.As seawater is the major constituent of groundwater in reclamation area, the total hardness(TH) and total dissolved solids(TDS) of some water samples exceeded limited values. NH3-N was detected in all monitoring holes and some had exceeded limited values. The largest overdose multiple of TH is 11.13 times. The largest overdose multiple of TDS is 122 times.The largest overdose multiple of NH3-N is 16.65 times.The largest overdose multiple of nitrate nitrogen is 0.613 times. The largest overdose multiple of nitrate is 9.5 times.The largest overdose multiple of iron is 11.2 times.The largest overdose multiple of manganese is 9.4 times. The lithology of hilly zone and sea-filled rubble is sandstone or shale. In some regions, the contents of iron and manganese are relatively high resulting in concentration exceeds.2.By the comparison of different scenarios of groundwater pollution prediction results, it could be found that with a given source intensity, the difference of groundwater migration in different sites is significant. For different leakage scenarios in general situation of the accident, by the end of the simulation(30 years), the maximum migration distance varied but eventually polluted to the seawater. Therefore, in views of impermeable measures, the features of pollution source and hydrogeological conditions should be taken into account both.3.The unconfined aquifer in study area is in the reclamation area. The lithology is plain fill. The specific yield of aquifer and coefficient of permeability were relatively large, so the contaminant transport rate in the porous mediawas relatively greatwhich was easier for causing the marine pollution.4.Under the Risk situation, the diesel oil tank explosion and crude oil tank explosion have done severe harm. Groundwater pollution prediction results showed that,the pollution halo was expanding with time. Pollution halo center migrated to the downstream with the flow of the water, until it reached the sea, it would cause a certain degree of pollution to the ocean. Therefore, if an explosion accident happened, we should immediately take effective emergency measures, in order to protect the groundwater environment, to avoid the plight of groundwater pollution which meant difficult to repair for a long time.5. The corresponding measures should be taken for sewage storage, treatment process, piping, equipment and structures to prevent and reduce pollutants running, dripping, leaking, reducing the environmental risk accidents of leakage pollution to a minimum extent. Pipeline installation USES the principle of "visualization", laying pipeline on the ground as far as possible, making early detection and early treatment to the pollutants, reducing groundwater pollution which was caused by the buried pipeline leakage. The project area was divided into the pollution control section, general pollution control area and key pollution control area. The impermeable layer of general pollution prevention area should be not less than 1.5 m thick which permeability coefficient was 1.0×10-7 cm/s. The impermeable layer of key pollution control area should be no less than 6.0 m thick which permeability coefficient was 1.0×10-7 cm/s.The useful life of seepage control facilities was designed no lower than the useful life of corresponding equipment, underground pipes, or the design of the building and structures. |
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