Constructed Wetland

Those wetlands intentionally constructed on sites that did not possess a wetland. This is used for the primary purpose of stormwater treatment. Constructed wetlands are normally considered as part of the stormwater collection and treatment system.

Conveyance System

The drainage facilities, both natural and man-made, which collect, contain, and provide for the flow of surface and stormwater from the highest points on an area of land to a receiving water. These may include swales and small drainage courses, basins, streams, rivers, lakes, and wetlands. The human-made elements of the conveyance system include gutters, ditches, pipes, channels, and most retention/detention facilities.

Clean Water Act (CWA)

The federal environmental law that includes the management of stormwater.

Detention Pond

A type of stormwater detention facility.

Drain Cleaning

Storm drains, catch basins, or street drains are common names for in-ground structures that capture surface water runoff. The captured runoff is then conveyed through pipes towards treatment, infiltration, or discharge areas.

Drainage Facility

A constructed or engineered feature that collects, conveys, stores or treats surface and stormwater runoff. Drainage facilities include but not be limited to all constructed or engineered streams, pipelines, channels, ditches, gutters, lakes, wetlands, closed depressions, flow control or water quality treatment facilities, erosion and sedimentation control facilities, and other drainage structures and appurtenances that provide for drainage.

Drywell Cleaning

Drywells are in-ground concrete structures similar in size and shape to storm manholes, but with a porous or perforated wall. Drywells are designed to infiltrate stormwater into the ground. If a drywell fills up or the walls become plugged, maintenance is needed. We recommend drywells be inspected at least once every two years to ensure they are working properly. Learn more about drywells or contact us to schedule an inspection.

Engineered Soil—Landscape System

This is a self-sustaining soil and plant system that simultaneously supports plant growth, soil microbes, water infiltration, nutrient and pollutant adsorption, sediment and pollutant biofiltration, water interflow, and pollution decomposition. This system must be protected from compaction and erosion to function properly. The system shall be planted and/or mulched as part of the installation. The engineered soil/plant system shall have the following characteristics:

  1. Be protected from compaction and erosion.
  2. Have a plant system to support a sustained soil quality.
  3. Possess permeability characteristics of not less than 6.0, 2.0, and 0.6 inches/hour for hydrologic soil groups A, B, and C, respectively (per ASTM D 3385). D is less than 0.6 inches/hour.
  4. Possess minimum percent organic matter of 12, 14, 16, and 18 percent (dry-weight basis) for hydrologic soil groups A, B, C, and D, respectively (per ASTM D 2974).”

Filter Maintenance

Filters are media filled cartridges that absorb and retain pollutants from stormwater runoff. Filters are rechargeable or replaceable depending on their manufacturer and condition. Common stormwater runoff structures that contain filters are vaults, catch basins and manholes.


Additional empty holding space available as emergency fillable area that is over the designed holding capacity

Heavy Metals

Metals of high specific gravity, present in municipal and industrial wastes, that pose long-term environmental hazards and are regulated, especially in stormwater run off at industrial permitted facilities. Such metals include:

  • Cadmium
  • Chromium
  • Cobalt
  • Copper
  • Lead
  • Mercury
  • Nickel
  • Zinc

Hydrologic Soil Groups

A soil characteristic classification system defined by the U.S. Soil Conservation Service in which a soil may be categorized into one of four soil groups (A, B, C, or D) based upon infiltration rate and other properties.

Type A: Low runoff potential. Soils having high infiltration rates, even when thoroughly wetted, and consisting chiefly of deep, well drained to excessively drained sands or gravels. These soils have a high rate of water transmission.

Type B: Moderately low runoff potential. Soils having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission.

Type C: Moderately high runoff potential. Soils having slow infiltration rates when thoroughly wetted, and consisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine textures. These soils have a slow rate of water transmission.

Type D: High runoff potential. Soils having very slow infiltration rates when thoroughly wetted, and consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a hardpan, till, or clay layer at or near the surface, soils with a compacted subgrade at or near the surface, and shallow soils or nearly impervious material. These soils have a very slow rate of water transmission.

Impervious Surface

A hard surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development; and/or a hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development.

Such as: roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and other surfaces which impede the natural infiltration of surface and stormwater runoff.

Low Impact Development (LID)

The use of site design and on-site Best Management Practices (BMPs) for the purpose of limiting surface water runoff and pollutant generation from a development site in order to more closely mimic the flow regime and water quality parameters found on an undisturbed site.


LID BMPs include, but are not limited to:

  • Bioretention
  • Rain gardens
  • Permeable pavements
  • Roof downspout controls
  • Dispersion
  • Soil quality and depth
  • Minimal excavation foundations
  • Vegetated roofs
  • Water re-use.

Manhole Cleaning

Storm manholes are in-ground structures designed to provide maintenance access and serve as a gathering point from multiple upstream structures. Manholes help convey stormwater to the treatment, infiltration, or discharge areas.

Nonpoint Source (NPS) Pollution

NPS pollution occurs when rainfall, snowmelt, or irrigation runs over land or through the ground, picks up pollutants, and deposits them into water courses or groundwater.


National Pollutant Discharge Elimination System. The part of the Clean Water Act which requires point source discharges to obtain permits. These permits, referred to as NPDES permits. Sometimes referred to as Industrial Permits as one class of NPDES permit. Another class is MS4 Permits that require municipalities to also regulate private property industrial and commercial stormwater runoff within municipal boundaries.


A point where collected and concentrated surface and storm water runoff is discharged from a pipe system, culvert, or end of channel.

Pre-developed Condition

The assumed site predevelopment land cover stormwater flow conditions.

Rain Garden

A small basin with compost-amended native soils and adapted regional native plants. The depression is designed to pond and temporarily store stormwater runoff from adjacent areas and allow stormwater to pass through the amended soil profile into the ground. Rain gardens generally, do not have an outfall other than the ground.


The process of collecting and holding stormwater runoff for long periods of time, such as in a pond, lake, or wetland.

Sand Filter

A man-made depression or basin with a layer of sand that treats stormwater as it percolates through the sand and is discharged through central collector pipes


Stormwater Facility

Designed infrastructure that control the discharge of stormwater.

Stormwater facilities included storage facilities (ponds, vaults, underground tanks, and infiltration systems); water quality facilities (wet ponds, biofiltration swales, constructed wetlands, sand filters, and oil/water separators); and conveyance systems (ditches, pipes, and catch basins), and more.

Stormwater facilities require on-going maintenance to ensure they continue to perform as intended. Maintenance of storage facilities typically includes the removal of accumulated sediment and debris, routine mowing, and minor repairs to mechanical appurtenances. Management of water quality facilities is more complex, requiring intensive vegetation management, inspection and maintenance of flow control features, and restoration or replacement of filter media.

Stormwater Facility- Commercial

Commercial developments (which include business properties) are subject to stormwater management regulations and remain the property and responsibility of the commercial landowner or facility manager.

Municipal NPDES permits require annual Post Construction inspections of commercial facilities to confirm commercial owners are performing inspections and maintenance. Un-maintained BMPs can lead to a lawsuit when localized flooding occurs.

Stormwater Facility- Residential

Residential stormwater facilities typically serve all or part of a single development and are built on a tract dedicated to this purpose. While the design and construction of these facilities is the responsibility of the developer, generally the HOA or property owner will assume responsibility for their long-term operation and maintenance.

Stormwater Management

The application of site design principles and construction techniques to control precipitation runoff, prevent sediments and other pollutants from entering surface waters and use source controls, and treatment of this runoff.

Structural BMP

Constructed facilities or measures to help protect receiving water quality and control stormwater quantity. Examples include storage, vegetation, infiltration, and filtration.


These systems are planted depressions that allow stormwater runoff the opportunity to be absorbed by plants and soils or be conveyed to other downstream discharge systems. Swales not only convey stormwater but also help to treat runoff to reduce pollutants.


A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. Water quality standards identify the uses for select regional waterbodies as chosen by the EPA. The Clean Water Act, section 303, establishes the water quality standards and TMDL programs

Treatment BMP or Facility

A BMP that is intended to remove pollutants from stormwater. A few examples of treatment BMPs are Wet ponds, oil/water separators, biofiltration swales, or constructed wetlands.


Plastic pipes with holes drilled through the top, installed on the bottom of an infiltration BMP, which are used to collect and remove excess runoff and prevent unnecessary ponding.

Underground Stormwater Detention

Underground stormwater detention systems are plastic, metal, or concrete chambers designed to store stormwater runoff. This system may infiltrate stores water back into the ground or have a restricted or metered release downstream. Annual inspections may be required. Contact us to ensure your system works properly and is functioning within compliance standards.