## 5 Conclusions  
An in-situ approach and hybrid MLGI, i.e., NN-PSO+EBK, was applied to assess and evaluate the GW quality in Calapan City, Oriental Mindoro, Philippines. Physicochemical characteristics and metals concentrations were detected onsite at various sampling locations. Generally, the physicochemical analysis of GW samples met the WHO and PNSDW guidelines. The average values for temperature, pH, EC, and TDS were within the permissible limits though few sampling locations exceeded the permissible limits of WHO and PNSDW. The pH of all samples was within the limits set by the PNSDW. Barangays Buhuan, Camansihan, Gutad, Ibaba East (Site 2), Ibaba West, Ilaya, Lazareto, Maidlang, Masipit, Nag-iba II, Pachoca, Parang, San Vicente East, Sta. Cruz, and Sto. Nino recorded elevated EC values. This was attributed to the addition of leachable salts. Also, the recorded TDS values suggested probable impaired palatability by having values significantly below the recommended range of 600\(-\)1000 ppm. Heavy metals analysis showed that only Fe detected in multiple GW samples had concentration above the WHO and PNSDW maximum permitted levels. This condition presents health concerns to the consumers. The record on Fe concentration in Brgy. Gutad GW samples were above WHO and PNSDW limit. Other GW samples recorded target metals concentration within the WHO and PNSDW permissible limits. The spot sampling analysis results showed that the generated maps by hybrid technique such as NN-PSO+EBK were reliable in describing the heavy metal concentration in the city of Calapan based on its MSE, R and AIC values.  
This study is useful as a reference to providing techniques on gathering data for GW quality monitoring to help attain SDGs 6. It is suggested to conduct a study targeting other metals and regular monitoring of its concentration using this hybrid MLGI technique. Additionally, the regular monitoring is necessary to better understanding of the possible health consequences. Furthermore, a health risk assessment based on GW quality should be conducted. Another, preliminary interventions on GW quality control is necessary.  
**Author Contributions:** Conceptualization, D.B.S.; methodology, K.L.M.d.J. and D.B.S.; software, K.L.M.d.J. and D.B.S.; validation, D.B.S., L.C.M., K.S.E. and E.M.D.A.; formal analysis, K.L.M.d.J. and D.B.S.; investigation, L.C.M., E.M.D.A., K.S.E. and D.B.S.; resources, D.B.S.; data curation, D.B.S., L.C.M., E.M.D.A., K.S.E. and E.B.C.; writing--original draft preparation, K.L.M.d.J., L.C.M. and E.M.D.A.; writing--review and editing, E.B.C., D.B.S. and K.L.M.d.J.; visualization, K.L.M.d.J.; supervision, D.B.S.; project administration, D.B.S.; funding acquisition, D.B.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Philippine Council for Health Research and Development of the Department of Science and Technology, Philippines.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** All data are contained in the manuscript.  
**Acknowledgments:** This is to recognize the 'in-kind' support of Mapua University, Manila, Philippines, and the Calapan City local government units. In addition, the Philippines Mines and Geosciences Bureau by providing the hazard maps for MIMAROPA region.  
**Conflicts of Interest:** The authors declare no conflict of interest.  
**Appendix A**