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• __ OSTP Pressure Distribution <br /> UNIVERSITY <br /> Minnesota Pollution Design Worksheet OF MINNESOTA r ,,�' <br /> Control Agency <br /> 1. Select Number of Perforated Laterals in system/zone: 3 o weotexu� r ( g� <br /> � onsvp paa-w't►�,C Minimum'iy � ► ;,d <br /> (2 feet is minimum and 3 feet is maximum spacing) ar1� perforations spaced 3�apatt �! 2"of rock r o <br /> I. <br /> 2. Select Perforation Spacing: 3.0 ft <br /> _f:;2:a t2 <br /> '►, • ► '►} ► 9 of rock YD�•/ , ,►,$,a �I <br /> 3. Select Perforation Diameter Size 1/4 inch ' 'Az'' '' . T <br /> Perforation sizing:'."to V." <br /> Perforation spacing:2'to 3' <br /> 4. Length of Laterals =Media Bed Length-2 Feet. Perforation can not be closer then 1 foot from edge. v 11.05.31 <br /> 38 - 2ft = 36 ft <br /> 5. Determine the Number of Perforation Spaces. Divide the Length of Laterals (Line 4)by the Perforation Spacing (Line 2)and <br /> round down to the nearest whole number. <br /> Number of Perforation Spaces = 36 ft 3 ft = 12 Spaces <br /> 6. Number of Perforations per Lateral is equal to 1.0 plus the Number of Perforation Spaces (Line 5). <br /> Perforations Per Lateral = 12 Spaces + 1 = 13 Perfs. Per Lateral <br /> Check table below to verify the number of perforations per lateral guarantees less than a 10%discharge variation. The value is <br /> double if the a center manifold is used. <br /> Maximum Number of Perforations Per Lateral to Guarantee<10%Discharge Variation <br /> %4 Inch Perforations 7/32 Inch Perforations <br /> Pipe Diameter(Inches) Perforation Spacing Pipe Diameter(Inches) <br /> Perforation Spacing(Feet) I <br /> 1 114 11 2 3 (Feet) 1 114 11t 2 3 i <br /> 2 10 13 18 30 60 2 11 16 21 34 68 <br /> 21. 8 12 16 28 54 21h 10 14 20 32 64 <br /> 3 8 12 16 25 52 3 9 14 19 30 60 i <br /> 3/16 Inch Perforations / <br /> 1.8 Inch Perforations <br /> Pipe Diameter(Inches) Perforation Spac (Inches)ing Pipe Diameter(Ih <br /> Perforation Spacing(Feet) <br /> 1 114 11.1 2 3 (Feet) t 114 11 2 3 <br /> 2 12 18 26 46 87 2 21 33 44 74 149 <br /> 21.: 12 17 24 40 80 2/ 20 30 41 69 135 <br /> 3 12 16 22 37 75 3 20 29 38 64 128 <br /> 7. Total Number of Perforations equals the Number of Perforations per Lateral (Line 6)multiplied by the Number of <br /> Perforated Laterals (Line 1). <br /> 13 Perf. Per Lateral X 3 Number of Perf. Laterals = 39 Total Number of Perf. <br /> 8. Calculate the Square Feet per Perforation. Recommended value is 4-10 ft 2 per perforation. Perforation wzehar5e(GPM) <br /> Perforation Diameter <br /> Does not apply to At-Grades Head(It) <br /> Bed Area = Bed Width (ft)X Bed Length(ft) ,.o• o.,s 0.41 0.56 0.74 <br /> 1.5 0.22 0.51 0.69 0.9 <br /> 10 ft X 38 ft = 380 ft2 2.0° 0.26 0.59 0.80 1'04 <br /> 2.5 0.29 0.65 0.89 1.17 <br /> 3.0 0.320.72 0.98 1.28 <br /> Square Foot per Perforation =Bed Area divided by the Total Number of Perforations (Line 7). 4.0 0.37 . 0.83 1.13 1.47 <br /> 5.0` 0.41 0.93 t.26 1.65 <br /> Dwellings with 3/16 inch to 1/4 inch <br /> 380 ft2 = 39 perforations = 9.7 ft2/perforations 1 foot <br /> perforations <br /> Dwellings with 1/8 inch perforations <br /> 2 feet Other establishments and PASTS with 3/16 <br /> 9. Select Minimum Average Head: 1.0 ft inch to 1/4 inch perforation <br /> 5 feet Ocher establishments end MSTS with 1/8 inch <br /> perforation <br /> 10. Select Perforation Discharge (GPM)based on Table III: 0.74 GPM per Perforation <br /> 11. Determine required Flow Rate by multiplying the Total Number of Perforations (Line 7)by the Perforation Discharge (Line 10). <br /> 39 Perforations X 0.74 GPM per Perforation = 29 GPM <br />