Non weight restricted /on structure planting soils

PWD Stormwater Soil was originally developed by the Philadelphia Water Department as part of a large green infrastructure policy.  The PWD Stormwater Soil was designed to mitigate stormwater runoff when used in applications such as rain gardens, bioretention basins and bioswales.  The soil is designed to absorb, infiltrate, and filter stormwater runoff into the ground where it can safely recharge groundwater systems and reduce surface flooding. PWD requires blenders to certify their compliance of this mix twice a year. Laurel Valley Soils has been involved with the PWD Green Infrastructure program from inception and has been an approved supplier every year. Many other cities and municipalities have since adopted this well preforming specification. The goal of a bioretention basin is to capture and divert stormwater runoff displaced from impervious surfaces. Well-designed basins also filter out untreated pollutants that otherwise might flow directly into waterways. Many bioretention basins are large in scale and while they can have attractive plantings, these utilitarian designed basins are generally located out of sight, at the low end of a parking lot or downslope from a building or road.

A stormwater management plan is now a requirement with all new construction that creates impervious surfaces. Water must be contained on site or at least slowed down to prevent flooding and pollutant movement. Bioretention basins are part of the building and zoning code and are required for most building projects including renovations and expansions. The understanding and design of these soils is evolving rapidly.