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Line 12:
Line 12: − + − + − * Length between culverts should be 5 meters or greater. + − * Designed with a bottom width between 0.6-2.4 m (allows shallow flows and adequate water treatment). + − + − + − * Steeper side slopes may be susceptible to erosion from incoming lateral flows. A maximum slope of 2.5:1 is recommended (Tool default). − − * For infrequently mown swales, STEP recommends maximum flows of 33% of vegetation height. − * Convey locally required design storm (~10 mm year storm) at non-erosive velocities. +
→Design Assumptions
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
* Native soil infiltration rate for Full Infiltration Design scenario was assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.
* Native soil infiltration rate for Full Infiltration Design scenario was assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.
* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from pretreatment structures annually, and removal of weeds twice a year. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing (where applicable)
* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from outlet catch basin annually, and removal of weeds twice a year. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing.
* Designed with a trapezoidal or triangular cross section.
* Designed with a trapezoidal cross section with a top width of 4.75 m, bottom width of 0.75 m, and 2.5:1 side slopes (tool default values).
*
* Longitudinal slope of 3%.
* Longitudinal slope should be between 0.5 and 4%. Check dams should be incorporated on slopes greater than 3%.
* Includes concrete curb check dams (0.3 m in height) for every 10 m of swale length (4 in total).
* Side slopes should be flat to aid in providing pre-treatment for lateral incoming flows and maximize swale filtering surface.
* Includes a 8.4 m wide driveway and 300 mm diameter culvert.
* Maximum flow depth should be 50% of grass height for regularly mown swales, to maximum of 75 mm.
* Designed for a maximum velocity of 0.3 m/s.
* Designed for a maximum velocity of 0.3 m/s.
===Notes===
===Notes===