Tvq
Tm
Tr
Qoa
Tsa
Sespe and Alegria
Formation
Rincon Shale
Monterey Shale
2000 Feet
0
500
1000
1500
0
100
200
300
400
500
600
700
-100
-200
Interceptor Trench
Projected Locations
Quarternary alluvial deposits (Qoa) –
Unconsolidated loamy clay, silt, sand, and gravel.
Monterey Formation (Tm) –
Upper Miocene, consisting of buff-white, thickly bedded,
highly fractured, siliceous marine shale ( claystone and
silistone, with some minor carbonate and tuff interbeds).
The claystone is slightly to moderately fractured, and deeply
weathered to a depth of approximately 28 feet below ground surface (bgs).
Aquifer.
Rincon Formation (Tr) – A lower Miocene marine deposit
comprised of grayish-brown, thin to poorly bedded marine
siltstone and claystone. They weather to an expansive clay soil.
The weathered zone reaches thicknesses of 15-20 ft in some
locations. The unweathered Rincon is mainly massive, but
zones of intensely fractured rock have been observed.
The stratigraphic thickness of the Rincon is approximately 1,470
feet at the site. The Rincon Formation is considered relatively
impermeable although locally it provides small quantities of water
due to the secondary (fracture) porosity.
Vaqueros Formation (Tvq) –
. Lower Miocene, consisting of
medium to coarse-grained, friable to hard, cross-bedded, massive sandstone.
Soil weathered from the Vaqueros Formation is described as well-graded
silty sand. The stratigraphic thickness of the Vaqueros Formation is
approximately 670 feet at the site.The Vaquieros is the principal water-
bearing formation in the region. It yields small to moderate quantities of
water to wells.
Aquifer
Sespe and Alegria Formations (Tsa) –
The stratigraphic
thickness of this unit is 1,665 feet at the site. The Sespe Formation is
comprised of massive medium-grained sandstones interbedded with
siltstones. The Alegria Formation consists of massive sandstones, The
Sandstones are moderately to well-cemented and locally form prominent
ridges. The Sespe and Alegria Formations are aquifers in the region
that also yield small to moderate quantities of water.
Aquifer.
Cross Section A-A’
