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BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

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On the map use an arrow to delineate flows. Indicate steep, moderate, andgradual slopes, and identify crowns and low spots in pavement. Drainagepatterns include surface drainage features and existing drainage infrastructure.Surface drainage features include streams, ponds, wetlands, lakes, manmadechannels, and stormwater runoff from impervious surfaces. Existing drainageinfrastructure includes sediment traps, infiltration systems (e.g. linear gravelinfiltration, infiltration basins, rain gardens), and conveyance systems (e.g.swales or slotted channel drains). Determine if any existing drainageinfrastructure on-site may be used as is or if it can be retrofitted easily toaccommodate the design storm. To determine this you will need to know theamount of volume generated from impervious surfaces from the 20-yr/1-hrstorm and the capacity of any existing systems.DISCHARGE LOCATIONSIdentify where stormwater drains. Does it drain to existing infrastructure, apervious and vegetated dispersion area, pond up on impervious surfaces, ordischarge off-site? If water discharges off-site to the county/city right of way acollection and conveyance system shall be installed to direct water to atreatment/infiltration area, unless the site has a constraint that makesinfiltration on-site impractical. For example, if water is flowing from adriveway to the street a swale or slotted channel drain shall be installed at theproperty line to convey water to an area where it can infiltrate on-site.Collection and conveyance systems convey water to an appropriate infiltrationsystem without causing erosion. If there are existing drain inlets (DI) on thesite identify them as well as where they outfall. Does the DI discharge to anarea on-site where infiltration exists or is feasible? If so the existinginfrastructure may be used to retrofit the site with <strong>BMP</strong>s. Note theconnectedness between DI’s and outfalls.Running a hose on a property can help identify flow patterns and discharge locations.CHAPTER 2: Site AnalysisTRPA <strong>BMP</strong> HandbookPage 2-12 2012

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