to Ground Water along Coasts. 28$ 



are furnished by the plant of the American Steel & Wire 

 Co. and the connected plant of the Penn. Seaboard Steel 

 Corporation at New Haven. When these plants were 

 engaged on war work during 1918, and the demand for 

 water was excessive, the Penn. Seaboard Steel Corpora- 

 tion drew from its wells about 330,000 gallons a day or 

 10 million gallons per month. The water, which at first 

 was sweet and drinkable, became very salty, evidently 

 from salt water drawn in from the harbor. On the small 

 plain upon which these plants are located not more than 

 a quarter of a square mile serves as a catchment area 

 for ground water. It appears, therefore, that the rate 

 of pumping greatly exceeded the ability of the catchment 

 area to supply water. The rate of 330,000 gallons a day 

 for a quarter of a square mile is somewhat more than 

 a million gallons a day to the square mile, a figure which 

 is considerably above the safe draft upon a drainage basin 

 near the sea under conditions such as prevail in Connecti- 

 cut. One million gallons a day to the square mile is 

 20.8 inches a year, or about 45 per cent of the total annual 

 rainfall in the New Haven region. 



The effects of pumping on a large scale near the sea 

 have been carefully studied by the Board of Water 

 Supply for the City of New York. 16 For an intake area 

 of 157 square miles on Long Island, where the climate is 

 about the same as in Connecticut and where the surface 

 formation is glacial drift, Spear estimates the safe yield 

 at 77 million gallons a day, or very nearly half a million 

 gallons a day to the square mile. This figure is a much 

 closer approximation to the safe capacity of ground water 

 reservoirs under such conditions. 



The limit to which wells can safely be pumped or the 

 depth to which the water table can safely be lowered can 

 never be exactly determined, except by actual tests. The 

 statement made by many writers, that if the water table 

 is lowered below mean sea level salt water is induced to 

 flow inland, is only partly true. An appreciable gradient, 

 several feet to the mile, is necessary to permit ground 

 water to flow through the rocks. Therefore, where salt 

 water extends only a short distance beneath the coast, a 



16 Spear, W. E. : An additional supply of water for the city of New York 

 from Long Island sources, New York Board of Water Supply, vol. 1, pp. 

 144-159. 1912. 



