“Green Parking” in Action

As Tropical Storm Andrea rushed up the coast Friday and dumped almost 3 inches of rain on Philadelphia within 24 hours, I was able to observe a new green parking lot in action. It is encouraging to see Philadelphia’s stormwater management guidelines being implemented. This parking lot is associated with a new neighborhood hardware store that must have triggered the City’s stormwater management requirements because the development resulted in an area of land disturbance of 15,000 square feet or more. The regulations govern both erosion and sedimentation control during construction and the level of post-construction stormwater management that is required.

There is an entire section within the Philadelphia Water Department that reviews development plans to ensure compliance with the different stormwater management guidelines. All new development (or redevelopment) that meet certain thresholds, must use stormwater best management practices (BMPs) to infiltrate the first 1″ of rainfall over the entire DCIA (directly connected impervious area) on the site. In order to maintain/restore the natural water balance and promote groundwater recharge, the stormwater must be infiltrated on-site unless there are other limiting factors such as in-sufficient infiltration rates or soil contamination.

Green Parking Lot Island

Without a curb between the planted median and the sidewalk, some runoff is able to drain into the vegetation. I couldn’t tell walking by, but it is possible that more runoff is captured and piped into the vegetated median by the linear drain across the sidewalk.

Green Parking Lot Swale

Some of the runoff from the parking lot is able to drain into this (not-quite-yet-fully-vegetated) swale through several curb cuts. The rip-rap at the curb cut entrances and around the overflow drain helps reduce erosion.

Just down the street, this giant asphalt parking lot had a couple of tree pits that were completely flooded (probably due to severely compacted soils) and runoff was flowing out into the street.

Just down the street, this giant asphalt parking lot had a couple of tree pits that were completely flooded (probably due to severely compacted soils) and runoff was flowing directly out into the street.

Advertisements