b.
Liquefaction hazard screening
(1) Susceptibility. Based upon review of the
available geologic information, the site is underlain by
Pleistocene-age deposits with soil-like characteristics,
rather than rock-like characteristics. Although the
liquefaction susceptibility of the deposits is probably
not greater than low according to Table F-1, the deposits
cannot be categorically rated as having a very low
susceptibility; therefore, liquefaction hazard cannot be
screened out on the basis of the susceptibility criterion.
(2) Groundwater. The groundwater table at the
site was encountered at depths between about 30 and 45
feet (9.1 and 13.7 m). These depths are less than 50 feet
(15 m) below the ground surface; therefore, liquefaction
hazard cannot be screened out on the basis of the
groundwater depth.
(3) Soil conditions. The available logs of borings
drilled at the site indicate that predominantly fine sand,
silty fine sand, and fine sandy silt (cohesionless)
deposits underlie the site and the reported penetration
resistance (blowcount) data suggest that these deposits
vary in compactness from loose to very dense. The
loose to medium dense [i.e., (N1)60 < 30] deposits were
encountered at shallow depths within the profile, well
above the groundwater table; whereas, the cohesionless
deposits situated below the groundwater table are dense
to very dense [i.e., (N1)60 > 30]. Additionally, the silty
clay and clayey silt strata interbedded with the deeper
cohesionless deposits are described as very stiff to hard.
On the basis of these soil conditions, the screening
criteria indicate that the liquefaction hazard at the site is
not significant and that the site may be eliminated from
further liquefaction evaluation.
G-5
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