A. Glossary

Applicant: A property owner, developer, or other person or entity who has filed an application to the Philadelphia Water Department (PWD) for approval to engage in or be exempt from any Regulated Activity at a Development Site in the City of Philadelphia.

Combined Sewer Overflows (CSO): A combined sewer overflow is an intermittent overflow or other untreated discharge from a municipal combined sewer system to the water of the Commonwealth occurring before the sewage treatment plant.

Conceptual Stormwater Management Plan: A preliminary stormwater management plan used by PWD Stormwater Plan Review to understand what is proposed at the project site, to confirm the proposed project limits of disturbance (LOD), and to assess the proposed stormwater management strategy. Conceptual Stormwater Management Plan requirements are described in Chapter 2 of this Manual.

Demolition: The razing or destruction, whether entirely or in significant part, of a building, structure, site, or object; including the removal of a building, structure, site, or object from its site or the removal or destruction of the façade or surface.

Design Storm: The magnitude and temporal distribution of precipitation from a storm event defined by probability of occurrence (e.g., five-year storm) and duration (e.g., 24 hours), used in the design and evaluation of stormwater management systems.

Developer: Any landowner, agent of such landowner, or tenant with the permission of such landowner, who makes or causes to be made a subdivision of land or land Development project prior to issuance of the Certificate of Occupancy.

Development:  Any human-induced change to improved or unimproved real estate, whether public or private. Development encompasses, but is not limited to, New Development, Redevelopment, Demolition, and Stormwater Retrofit. It includes the entire Development Site, even when the project is performed in phases.

Development Site: The land area where any Development activities are planned, conducted, or maintained, regardless of individual parcel ownership.  It includes contiguous areas of disturbance across Streets and other rights of way, or private streets and alleys, during any stage of or on any portion of a larger common plan of development or sale.

Diffused Drainage Discharge: Drainage discharge not confined to a single point location or channel, such as sheet flow or shallow concentrated flow.

Directly Connected Impervious Area (DCIA):  An Impervious Surface that is directly connected to the drainage system. DCIA generates surface runoff with a direct hydraulic connection to on-site drainage systems (e.g., inlets, curbs and gutters, pipes, etc.), PWD’s drainage systems, or stormwater management practices (SMPs) without flowing over pervious areas.

Disconnected Impervious Cover (DIC): Impervious cover from which runoff is directed toward pervious areas for management within the landscape.

Earth Disturbance: Any construction or other activity that disturbs the surface of land, including but not limited to, excavations, embankments, land development, subdivision development, and the moving, depositing, or storing of soil, rock, or earth. Other examples of earth disturbance in the context of PWD Stormwater Regulations are listed in Section 1.1.3.

Erosion and Sediment (E&S) Control Plan: A site-specific plan consisting of both drawings and a narrative that identifies measures to minimize accelerated erosion and sedimentation before, during, and after Earth Disturbance. E&S Plan requirements are described in Chapter 2 of this Manual.

Evaporation and Transpiration (Evapotranspiration): Evaporation is the process by which water changes from a liquid to gas. Transpiration is the process by which water moves through a plant and evaporates into the atmosphere from its leaves and exterior surfaces. The sum of evaporation and transpiration are commonly referred to as evapotranspiration.

Existing Conditions: Physical conditions on the site including land use, impervious surface, topography, vegetation, soils, and hydrology that exist on the site on the date the owner starts the development process.

Groundwater Recharge: The replenishment of existing natural underground water supplies from precipitation or overland flow without degrading groundwater quality.

Hotspots: Areas where land use or activities have contaminated the soil underlying the site such that infiltration of stormwater would likely cause groundwater contamination through leaching of the soil.

Impervious Liner: A physical barrier to prevent water from crossing a system boundary such as infiltrating through the subgrade beneath a stormwater management practice. Liners may include, but are not limited to, compacted till liners, clay liners, geomembrane liners, and concrete liners.

Impervious Surface: Any building, pavement, or other material that substantially bars the natural infiltration of surface water into the soil.

Infiltration: The process by which water enters the soil from the ground surface and can be measured as a rate.

Management District: Sub-area delineations that determine peak rate attenuation requirements. A Development Site located in more than one Management District shall conform to the requirements of the district into which the site discharges

Manual: The most recent version of the Philadelphia Stormwater Management Guidance Manual.

New Development: Development project on an unimproved tract of land where structures or impervious surfaces were removed before January 1, 1970.

Non-Structural Design: Stormwater management practices that incorporate, preserve, and protect existing natural features while promoting treatment, infiltration, evaporation, and transpiration of precipitation close to where it falls.

Operation & Maintenance (O&M) Agreement: An agreement or declaration which outlines the maintenance requirements associated with the Post-Construction Stormwater Management Plan.

Pavement Disconnection: A type of DIC and a reduction in DCIA when pavement runoff is directed to a vegetated area that allows for infiltration, filtration, and an increased time of concentration.

Post-Construction Stormwater Management Plan (PCSMP): A complete stormwater management plan set as described in the PWD Stormwater Regulations and in this Manual. PCSMP requirements are described in Chapter 2 of this Manual.

Predevelopment Condition: For New Development and Redevelopment, the dominant land use for the previous ten years preceding the planned project.

Record Drawings: Construction drawings revised to represent the as-built conditions.

Redevelopment: Development on an improved tract of land that includes, but is not limited to, the demolition or removal of existing structures or impervious surfaces and replacement with new impervious surfaces. This includes replacement of impervious surfaces that have been removed on or after January 1, 1970.

Registered Professional: A licensed Professional Engineer, Registered Architect, Landscape Architect, Professional Land Surveyor, Professional Geologist, or Licensed Contractor registered in the Commonwealth of Pennsylvania.

Regulated Activity: Development on a Development Site in the City of Philadelphia that results in an area of Earth Disturbance greater than or equal to 15,000 square feet, greater than or equal to 5,000 square feet in the Darby and Cobbs Creeks Watershed, or as otherwise required by local, State, or Federal requirements. The area of Earth Disturbance during the construction phase determines requirements for the erosion and sediment controls and post-construction stormwater management.

Review Path: A linear series of submission, review, and approval/exemption procedures the applicant will navigate to demonstrate a project’s compliance with, or exemption from, the PWD Stormwater Regulations.

Review Phase: A step in a Review Path.  Each Review Path has one or more Phases.  Each Phase corresponds to one or more submittals of information for PWD's review.

Roof Runoff Isolation: The routing of runoff from non-vehicular roof area that is not commingled with untreated runoff.

Rooftop Disconnection: A type of DIC and a reduction in DCIA when a roof downspout is directed to a vegetated area which allows for infiltration, filtration, and increased time of concentration.

Sewershed: An area of land, or catchment, which drains via storm drain infrastructure to a common outlet point.

Site Assessment: An investigation of the administrative and physical factors that shape the development and stormwater management plan for a proposed site.  The assessment consists of three components – collection of background site factors, site factors inventory, and site factors analysis.

Storage Volume: The volume of stormwater runoff that can be held within the above-ground surface area and the pore spaces of any subsurface media or structure of a stormwater management practice.

Stormwater Management Practice (SMP): Any man-made or natural structure, system, landscape feature, channel, or improvement designed, constructed, installed, and/or used to detain, infiltrate, or otherwise control stormwater runoff quality, rate, or quantity.

Stormwater Pretreatment: Techniques employed to remove pollutants before they enter the SMP, including, but not limited to, the techniques listed as pretreatment in this Manual.

Stormwater Retrofit: The voluntary rehabilitation and/or installation of SMPs on a property to better manage stormwater runoff.

Street: Tract of land or part thereof with public access used for vehicular and/or pedestrian traffic, which is maintained by a City Agency, City Related Agency, other Government Agency, or a Non-Profit Organization Created by the City, as determined by the Department.

Street Maintenance Activities: Earth Disturbance activities within an existing Street as determined by the Department and described in the Manual Section 1.1.3.

Tree Disconnection Credit: A type of DIC and a reduction in DCIA when existing or newly proposed tree canopy from an approved species list extends over, or is in close proximity to, impervious area.

Watershed: An area of land that contains a common set of drainage pathways, streams, and rivers that all discharge to a single large body of water, such as a large river, lake, or ocean.