Hydrogeochemistry of tunnel seepage water along the contact of zone of metasedimentary and granitic rock within the Pahang–Selangor Raw Water Transfer Tunnel Project, Malaysia

Sharifah Farah Fariza Syed Zainal, Mohd Ashraf Mohamad Ismail, Roslanzairi Mostafa, Nobuya Narita, Norzani Mahmood, Soon Min Ng

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Groundwater obtained from water inflows during the excavation of the Pahang-Selangor RawWater Transfer Tunnel (P-SRWTT) was analyzed to determine the characteristics of groundwater that flows along the main range granite and the metasedimentary geological boundary. A total of 61 tunnel seepage water (TSW) samples were immediately obtained after tunnel excavation. Hydrogeochemical analyses, including physicochemical and major ion analyses, were performed on TSW samples. Results show that the TSW sample in the P-SRWTT is meteoric water, which infiltrates at different elevations and flow paths. The prolonged interactions of groundwater in the metasedimentary rock and contact zones produced Ca2+- HCO3 -SO4 2−, Ca2+-HCO3 , and Ca2+-Na+-HCO3 in the water. Electrical conductivity (EC) values reach as high as 345.80 and 313.22 μs/cm in the metasedimentary rock and contact zones, respectively. Most water in these two zones present temperatures lower than 30 °C, which is comparable with the expected geothermal gradient of 35 °C/km. Ca2+-Na+- HCO3 is the dominant water type in the granite zone with an average EC of 288.37 μs/cm. Na+-HCO3 waters are generated through the interaction between Ca2+-HCO3 and Na+ in granitic rocks. The zone of warm Na+-HCO3 waters, presenting an average temperature of 35 °C at an overburden of more than 400 m, shows some anomalies from the expected geothermal gradient of 35°/km. The hydrogeochemistry analyses provide a good understanding of the complex hydrogeological system at the two major geological formations along the tunnel.

Original languageEnglish
Article number265
JournalArabian Journal of Geosciences
Volume9
Issue number4
Early online date28 Mar 2016
DOIs
Publication statusPublished - Apr 2016

Keywords

  • Granite
  • Hydrogeochemistry
  • Metasedimentary
  • Tunnel seepage water

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)

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