Based on the Geological Map of the Philippines
Groundwater Availability Map of the Philippines,
Apatut’s Geology is:
Upper Miocene sediments, and volcanic; largely
marine clastics, reef limestone and andesitic-basaltic
pyroclastics and lavas (N2)
Late Oligocene to Middle Miocene sediments and
volcanics; mainly marine sandstone, shale and reef
limestone; some conglomerate, coal measures and
marine andesitic-basaltic pyroclastics and lavas (N1)
Based on the Groundwater Availability Map of the
Philippines, Apatut’s aquifers are made up of rocks in
which flow is dominantly intergranular. These are
mostly local and less productive aquifers with well
yields mostly about 2L/s but as high as 20 L/s in some
sites, with very low to moderate permeability. These
may be of three kinds:
There are Quaternary coastal aquifers whose yields
are restricted by sea water intrusion and inland
aquifers that are restricted by low storage due to
limited aquifer are and/or thickness, ,or to recharge
potential due to thick clay cover.
There are also Pliocene to Pleistocene semiconsolidated to unconsolidated sediments, both
marine and terrestrial; includes water-laid
pyroclastics and localized terrace deposits. Well
yields mostly within 0.3 to 7 L/s. Aquifers usually
have limited thickness.
Lastly, there are Upper Miocene to Pliocene
sediments and volcanic, mainly sandstone, shale,
some conglomerate, coal measures and marine
andesitic and basaltic pyroclastics. Known well yields
mostly 2L/s for the younger rocks and less than 0.01
to 0.5 L/s for the older rocks with a few productions
well yields of less than 10 to 30 L/s pumped from the
Bagiuo City Aquifer.