Materials

(а) Riser pipe. The riser pipe and the 2-foot blank pipe on the bottom of the screen shall be 4-inch diameter, flush-joint Schedule 80, type 2110 PVC pipe.

(б) Screen. The screen shall be 4-inch, Schedule 80, type 2110 PVC screen. The screen shall be slotted with.025-inch slots in sufficient numbers to give a minimum area of opening of 5 percent. The screen sec­tion of the well shall extend from the top of any semi-

Подпись: Rainfall Intensity, inch/hour Amount, inches 4.5 2.25 3.0 3.00 2.0 4.00

pervious strata as shown by the boring logs, or as en­countered, to the depth specified.

(c) Filter sand. Filter sand around the well screen shall be washed (clean) uniform sand or crushed stone composed of hard, tough, and durable particles free from any adherent coating. The filter sand shall contain no detrimental quantities of vegetable matter, nor soft, friable, thin, or elongated particles, and shall meet the following gradation requirements:

Filter Sand B

U. S. Standard

Percent by weight

Sieve No.

passing

8

95-100

10

92-100

14

75-100

16

65-95

20

30-77

30

10-30

40

1-13

50

0-5

(5) Jet-eductor pumps and header pipe. The jet- eductor pumps shall have the specified pumping ca­pacities, The pressure pumps for operating the jet – eductor pumps shall have a diesel engine with a horse­power of at least 110 and a capacity of 1800 gallons per minute at a total dynamic head of at least 150 feet on a continuous basis. The standby pumps shall have the same horsepower and capacity. The pressure header pipe shall be Schedule 40; the return header pipe shall have a minimum wall thickness of 0.20 inch. The sump pumps for the jet-eductor systems shall be an electric, automatic priming type, with a capacity of pumping 600 gallons per minute at TDH = 50 feet.