Stormwater Quality Design Manual (May 2007) - City of Sacramento ...

Chapter 3As the name implies (and as described in Chapter 2), runoff reduction measures areintended to reduce the amount of runoff traveling off the site. This is achieved byminimizing impervious surfaces, disconnecting impervious surfaces from the stormdrain system, and promoting infiltration where possible. Even sites with clay soilscan benefit from application of runoff reduction control measures. Several differenttypes of runoff reduction measures are described in Chapter 5:• Porous pavement• Disconnected pavement• Alternative driveways• Disconnected roof drains• Interceptor trees• Green roofUse of runoff reduction controlscan decrease the size of requireddownstream water quality controlsRefer to Table 3-2 to identify which types of measures are acceptable for your projectand then use the worksheets in Appendix D to calculate the runoff reduction creditsyou can achieve by incorporating one or more of these measures into your project.Then use the worksheets to calculate any remaining water quality volume or flow thatneeds to be treated and proceed to Step 6 to select the treatment control facilities. Ifthe entire water quality volume (WQV) can be retained on-site using runoff reductionmeasures, treatment control measures will not be required and you can advance toStep 7.Step 6: Select Treatment Control MeasuresTreatment control measures are intended to filter and settle pollutants out of runoffbefore it travels off the site. If treatment controls are required per Table 3-2 (and stillneeded after the calculation of runoff reduction credits in Step 5), select theappropriate treatment control measures. To do so, use your analysis in step 3, thedetails in Table 3-2 regarding whether a given control measure is acceptable for theproject category, and the information in Chapter 6. Chapter 6 includes fact sheets fora variety of treatment control measures:• Constructed wetland basin• Water quality detention basin (three types: wet, dry,combination)• Infiltration basin• Infiltration trench• Sand filter• Stormwater planter (two types: flow-through andinfiltration)• Vegetated filter strip• Vegetated swaleTreatment controlmeasures areintended to filterand settlepollutants out ofrunoff before ittravels off the siteStormwater Quality Design Manual for the Sacramento and South Placer Regions3-6 May 2007