haven National Laboratory in Suffolk County where the yield from the Lloyd was relatively 

 small despite the considerable amount of development to which the test wells were subjected. 



The Lloyd sand seems to consist of two or three water-bearing- zones separated by layers 

 of clay or less permeable zones which are commonly very thin but which may be as much as 

 40 feet in thickness. The layers of clay in the Lloyd cover large areas but do not appear to be of 

 Island-wide extent. A pumping test by Jacob (49) at well Q 1030 at Rockaway Park in Queens 

 County shows that the entire thickness of the Lloyd sand at that locality acted as a hydrologic 

 unit despite the presence of intraformational layers of clay. This hydrologic property appears 

 to be characteristic of the Lloyd in many other parts of Long Island. 



The Lloyd sand is everywhere overlain by the clay member of the Raritan formation except 

 possibly at the western end of the Island, and on some of the necks in the northern part of 

 Nassau County. The clay provides an impermeable cover for the Lloyd sand member and thus 

 the Lloyd is a true artesian aquifer. Recharge may occur by means of valleys cut through the 

 Raritan clay, valleys which are now filled with more permeable material of late Cretaceous or 

 Pleistocene age; or by slow seepage of water through the clay into the Lloyd sand. In the 

 western end of the Island, particularly in Kings County, Pleistocene deposits are in direct 

 contact with the Lloyd. As the water level in Lloyd observation wells in Kings County and 

 western Queens County stands higher above sea level than in Pleistocene wells in Kings County, 

 it is believed that the Lloyd is continually discharging water into these Pleistocene beds. 



Lloyd sand — Kings County: The limiting line of the deposits roughly bisects the 

 County along a northeast-southwest line. According to present correlations, the Lloyd sand 

 member is missing in the area north and west of the limiting line shown on the accompanying 

 contour map of the Lloyd. This absence may be due either to non-deposition or erosion of the 

 Lloyd, and subsequent deposition of younger Cretaceous or Pleistocene deposits directly upon 

 bedrock. The elevation of the upper surface of the Lloyd ranges from about 250 to 680 feet 

 below sea level. Its thickness ranges from about 100 feet to about 250 feet, increasing toward 

 the southeast. The Lloyd sand may be in contact with the Jameco gravel in parts of Kings 

 County where it forms part of the walls of buried valleys filled with the Jameco gravel. Records 

 for six Lloyd wells are shown in the accompanying correlation table for Kings County. Only 

 2 of these wells, industrial wells in southeastern Kings County, are in use at present. 



Lloyd sand member — Queens County: The Lloyd sand member underlies all of Queens 

 Countj^ except a small area in the northwestern part of the County where bedrock rises close 

 to the land surface. It appears to be missing also in the vicinity of La Guardia air field and 

 in a small area near Whitestone in the northeastern part of the County. The absence of the 

 aquifer, as in Kings County, may be the result of either erosion or non-deposition. The aquifer 

 thins out rapidly in the northwestern part of the county, suggesting that this area may repre- 

 sent the original limit of deposition of the Lloyd. The elevation of the top of the Lloyd ranges 

 from about 100 to 900 feet below sea level. Its thickness ranges from about 2 feet in northern 

 Queens to over 300 feet in southeastern Queens. The Lloyd sand takes on increasing impor- 

 tance as an aquifer in Queens County where it is tapped by a number of industrial and public 

 supply wells. 



Lloyd sand member — Nassau County: Except for a small area near the northern tip of 

 Manhasset Neck, the Lloyd sand member appears to underlie all of Nassau County. The top of the 

 Lloyd ranges from about 100 to 1,400 feet below sea level, and its thickness ranges from about 

 60 to 300 feet. More Lloyd wells have been drilled in Nassau County than in any of the other 

 three Long Island Counties. Most of the Lloyd wells in Nassau County are situated along the 

 north and south shores and many of them yield large quantities of water by natural flow. In 

 many places along the shore lines, particularly on the south shore, the Lloyd sand is the only 

 aquifer from which moderate to large supplies of fresh water can be pumped. Most of the 



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