Depth, 75% 90% 100% 75% 90% 100% inches 3-5 90 138 210 450 690 1230 6-7 72 108 180 360 540 900 8 66 90 150 330 450 750 Table 5. Surface Area of Rain Gardens Assuming Sandy Soils. Rain Surface Area of Rain Garden with Surface Area of Rain Garden with Garden Impervious Drainage Area of 600 sq. ft. Impervious Drainage Area of 3000 sq. ft. Depth, 75% 90% 100% 75% 90% 100% inches 3-5 25 42 102 120 210 510 6-7 18 36 72 90 180 360 8 18 30 66 90 150 330 Table 5. Surface Area of Rain Gardens Assuming 1000 sq. ft. of Drainage Area. Rain Surface Area of Rain Garden with Clay Surface Area of Rain Garden with Sandy Garden Loam Soils Soils Depth, 75% 90% 100% 75% 90% 100% inches 3-5 150 230 410 40 70 170 6-7 120 180 300 30 60 120 8 110 150 250 30 50 110 Suggestion: Should we set a minimum and maximum rain garden size? A minimum of 100 sq. ft. and a maximum of 600 square feet. Anything over 600 sq. ft. must be into smaller cells. Drawn Down Time Most literature describing criteria for infiltration devices suggest the drawn down time for the surface pool of water be less than 24 hours. The concern is the plants might not survive being submerged for more than a day. The following tables show the drawn down times for clay loam and silt loam soils for different depths of rain gardens. Table 6. Draw Down Times for 8 inch Deep Rain Gardens with Clay Loam and Silt Loam Soils. Rain Drawn Down Times for Clay Loam Draw Down Times for Silt Loam Soils, Garden Soils, Hours Hours Depth, 75% 90% 100% 75% 90% 100% inches
Depth, inches 75% 90% 100% 75% 90% 100% 3-5 90 138 210 450 690 1230 6-7 72 108 180 360 540 900 8 66 90 150 330 450 750 Table 5. Surface Area of Rain Gardens Assuming Sandy Soils. Rain Garden Depth, inches Surface Area of Rain Garden with Impervious Drainage Area of 600 sq. ft. Surface Area of Rain Garden with Impervious Drainage Area of 3000 sq. ft. 75% 90% 100% 75% 90% 100% 3-5 25 42 102 120 210 510 6-7 18 36 72 90 180 360 8 18 30 66 90 150 330 Table 5. Surface Area of Rain Gardens Assuming 1000 sq. ft. of Drainage Area. Rain Garden Depth, inches Surface Area of Rain Garden with Clay Loam Soils Surface Area of Rain Garden with Sandy Soils 75% 90% 100% 75% 90% 100% 3-5 150 230 410 40 70 170 6-7 120 180 300 30 60 120 8 110 150 250 30 50 110 Suggestion: Should we set a minimum and maximum rain garden size? A minimum of 100 sq. ft. and a maximum of 600 square feet. Anything over 600 sq. ft. must be into smaller cells. Drawn Down Time Most literature describing criteria for infiltration devices suggest the drawn down time for the surface pool of water be less than 24 hours. The concern is the plants might not survive being submerged for more than a day. The following tables show the drawn down times for clay loam and silt loam soils for different depths of rain gardens. Table 6. Draw Down Times for 8 inch Deep Rain Gardens with Clay Loam and Silt Loam Soils. Rain Garden Depth, inches Drawn Down Times for Clay Loam Soils, Hours Draw Down Times for Silt Loam Soils, Hours 75% 90% 100% 75% 90% 100%
Sizing-Factors-for-Std.-03282017.docx