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Corrective Action Plan Page 6 <br /> Hydraulic Properties of Soils <br /> To evaluate the hydraulic properties of the soils beneath the site, a series of groundwater <br /> pumping tests have been conducted using well NAV 6 as the pumped well and well NAV <br /> 3 as an observation well (Ref 11 ) These tests indicated that the sands that occur under <br /> the site at depths between approximately 14 and 25 ft behave as a leaky, confined aquifer <br /> but there is a significant degree of hydraulic communication between the sand aquifer and <br /> the overlying silty clays The bottom of the sand aquifer is defined by a second stratum of <br /> arealy-extensive silty clays <br /> When considered as a single equivalent hydrostratigraphic unit, the strata from the water <br /> table to a depth of 25 ft beneath the ground surface has the following hydraulic <br /> properties <br /> Transmissivity = 4,300 gpd/ft <br /> Specific Yield = 0 01 <br /> When considered separately, the following hydraulic conductivities have been estimated <br /> for the sands and silty clays found in the subsurface beneath the site <br /> Silty Clays <br /> Horizontal Hydraulic Conductivity = 40 gpd/ftz (2 0 x 10-3 cm/sec } <br /> Sands <br /> Horizontal Hydraulic Conductivity = 400 gpolftz (2 0 x 10-2 cm/sec ) <br /> Strata Affected by Hydrocarbons <br /> Figures 7 and 8 also present an interpretation of the extent to which the soils beneath the <br /> surface of the 152 East 11th Street property have been affected by components of <br /> gasoline The vertical distribution of contamination at Sections A'-A" and B'-B' on Figure <br /> 6 was estimated from the results of analyses of soil and groundwater samples recovered <br /> from the nearby wells and borings, olfactory indicators of contarrunation reported in the <br /> boring logs and consideration of the hydrostratigraphy of the site The interpretations <br /> shown are believed to be conservative but, given the hydrostratigraphic complexity of the <br /> site, they should not be taken to be definitive <br /> Subsurface soil has been contaminated in a zone that extends downward from lust above <br /> the water table (i a approximately 7 5 ft below the ground surface) to varying depths up <br /> to a maximum of about 18 ft on the north side of the 152 East 11 th Street property (in <br /> the vicinity of well ULT 9) This zone includes the silty and sandy clays in the strata that <br />