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

Runoff Reduction Fact SheetDisconnected PavementExamples:Divided Sidewalks and parking lot medians – Consider the use of porous pavement in vegetatedsidewalk strips and parking lot medians to provide paths for pedestrians to walk across the area withoutdamaging vegetation. See photo.Hybrid Parking Lot - Traffic loading requirements typically differ between parking lot drive aisles andstalls in parking lots. More durable conventional pavement surfaces will typically be required for the maindrive aisles and areas used by garbage, delivery and fire trucks, while porous pavement may beappropriate for the stalls (or a portion of the stalls) used by cars. The permeable stalls may be used tocarry flow from the main drive aisles to the storm drain system, allowing for infiltration anddisconnecting the main aisle pavement from the system. A water barrier may be required between regularload-bearing pavement/streets and porous pavement materials to keep water from undermining the regularpavement subbase; verify this with the local permitting agency.This hybrid parking lot concept has been applied successfully in many areas of the country, including theSan Francisco Bay Area. Generally, pervious pavement or cobblestone block set in sand will be preferredby the permitting agency, however, depending on frequency and type of use, modular block pavement,reinforced grass, or gravel may be appropriate. For example, these techniques could work well in aseasonal overflow parking lot, a public park or a trailhead.Pavers in parking lot. Photo: City of Emeryville..Design CriteriaDesign criteria for disconnected pavement are listed in Table DP-1.Construction ConsiderationsIn hybrid parking lots, stall markings can beindicated with one of several techniques, dependingon the type of permeable surface: wood headerslaid in a field of pervious pavement, a change incobblestone block color, concrete bands, orrounded raised pavement markers similar to thoseused on highways (“Botts’ Dots”). (Start at theSource, 1999)Bike and Pedestrian Trails – Consider the use ofgravel or other porous material alongside bike andpedestrian trails to infiltrate and filter some of therunoff. For example, the City of Folsom requires agravel shoulder for its Class I bike trails.• Ensure that flow entering a porous area from an impervious surface is spread evenly and the areaaccepting the flow is lower than the impervious surface.• If using porous pavement, follow the construction guidelines given in the Porous Pavement FactSheet located elsewhere in this chapter.• Once construction is complete, stabilize the entire tributary area and the vegetation within thefeature itself, before allowing runoff to enter the feature.Long-term Maintenance RecommendationsRefer to the inspection and maintenance recommendations in the Porous Pavement fact sheet.Stormwater Quality Design Manual for the Sacramento and South Placer RegionsDP-4 May 2007