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Reporting groundwater quality anomalies caused by grouting of wells

관정 그라우팅 시공에 의한 지하수 이상 수질 현상 보고

  • Koh, Chang-Seong (Jeju Groundwater Research Center, Jeju Research Institute) ;
  • Hyun, Beom-Seok (Jeju Groundwater Research Center, Jeju Research Institute) ;
  • Koh, Eun-Hee (School of Ocean and Earth Sciences, Jeju National University)
  • 고창성 (제주연구원 제주지하수연구센터) ;
  • 현범석 (제주연구원 제주지하수연구센터) ;
  • 고은희 (제주대학교 지구해양과학부)
  • Received : 2024.07.30
  • Accepted : 2024.10.08
  • Published : 2024.10.31

Abstract

In the Hankyung-Daejeong watersheds of western Jeju Island, several groundwater wells showed abnormal measurements of high electrical conductivity (EC) and pH. To identify the causes of this abnormal water quality, we conducted borehole imaging, vertical EC logging, groundwater quality analysis, and SEM-EDS analysis of white suspended matter in the well. Most of the wells showing abnormal water quality had well-grouting below the water table, with borehole EC values ranging from 300 to 10,000 μS/cm. The wells exhibited higher ion concentrations compared to nearby wells and had a high pH range of 8.2 to 12.7, indicating a slightly to strong alkalinity. The primary components of the white-colored suspended matter were identified as oxygen and magnesium. These findings suggest that the abnormal water quality of the study wells is caused by the cement mortar used for grouting during well construction rather than by nitrate contamination or seawater intrusion. To prevent the influence of well-grouting on water quality during groundwater well development, an establishment of standards for groundwater development and utilization facilities is needed.

본 연구에서는 제주도 서부 한경-대정수역에서 높은 전기전도도(EC)와 pH가 관측된 10개의 지하수 관정을 대상으로 이상 수질 발생 원인을 파악하기 위해서 관정 시공 상태 확인, 공내 영상 및 EC 수직 검층, 음·양이온 이온 분석, 지하수 내 백색 부유물에 대한 SEM-EDS 분석을 수행하였다. 이상 수질을 보인 대부분의 관정은 지하수면 하부 구간까지 오염방지 그라우팅이 이루어졌고, 공내 EC는 300~10,000 μS/cm 범위의 값을 나타냈다. 또한, 인근 지하수 관정보다 높은 음·양이온 농도를 갖는 점, pH가 8.2~12.7로 약염기~강염기성을 띄는 점, 백색 부유물의 주요 구성 성분이 산소와 마그네슘인 점을 근거로 연구대상 관정의 이상 수질 현상은 질소 오염원이나 해수의 영향에 의해 유발된 것이 아니라, 관정 시공 시 채움 그라우팅에 사용된 시멘트 몰탈로부터 비롯되었음을 국내 최초로 보고한다. 지하수 관정 개발 과정에서 이루어지는 오염방지 그라우팅이 수질에 영향을 미치지 않도록 하기 위해서는 향후 지하수 개발·이용시설기준 제정이 필요하다.

Keywords

Acknowledgement

지하수 수질 분석 및 SEM-EDS 분석을 수행한 제주특별자치도 보건환경연구원과 제주특별자치도개발공사 먹는물연구소 연구원님들께 감사를 표합니다.

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