Table 1.

Table 1. Major hydrogeologic units of the Long Island groundwater reservoir.

Hydrogeologic Unit	Approximate Maximum Thickness	Water-Bearing Character
Upper glacial aquifer	400’	Mainly sand and gravel of moderate to high permeability; also includes clayey deposits of low permeability.
Gardiners Clay	150’	Clay, silty clay, and a little fine sand of low to very low permeability.
Jameco aquifer	200’	Mainly medium to coarse sand of moderate to high permeability.
Magothy aquifer	1000’	Coarse to fine sand of moderate permeability; locally contains highly permeable gravel, and abundant silt and clay of low to very low permeability.
Raritan Clay	300’	Clay of very low permeability; some silt and fine sand of low permeability.
Lloyd aquifer	300’	Sand and gravel of moderate permeability; some clayey material of low permeability.