Department of Public Works and Highways(DPWH)

Good day! I'm doing research on the right-of-way agreement/arrangement of the operator of NAIAX in Pasay. My questions are: 1) What is the legal basis of building an elevated road along and above an existing body of water such as Estero de Tripa de Gallina? 2) Is the NAIAx operator making payments to the government for the use of the space above the body of water? 3) Likewise, for the columns (supporting the elevated expressway) that were erected on public roads (median and sidewalks), is the NAIAx operator give payments to the government for the use of these public facilities? Thank you