Cost analysis resources

Misunderstandings about how operation and maintenance costs for LID practices compare to those of conventional stormwater facilities like detention ponds, oil and grit separators and swales has been one of the significant barriers to their acceptance in the United States and arguably worldwide. In comparison to conventional stormwater facilities, LID practices have lower life cycle costs, perform better and provide additional benefits, such as improved aesthetics, urban heat island mitigation, and air quality improvement (US EPA, 2013). For example, in a controlled field study at the University of New Hampshire Stormwater Center (Houle et al., 2013), maintenance demands and costs were compared over the first 4 years of operation for seven different types of stormwater control measures (SCM), including conventional practices (vegetated swale, wet and dry ponds) and LID practices (gravel wetland, bioretention, porous asphalt, sand filter). Through estimates of annualized maintenance costs per unit drainage area treated and per unit mass of pollutant removed, they found that LID systems have lower marginal maintenance burdens and higher water quality treatment capabilities than conventional practices like detention ponds and swales. Activities associated with maintaining LID practices were found to be less expensive and more predictable than those for conventional systems. For a recent review of international research on life cycle cost and benefit analyses of LID stormwater practices see Xu et al. (2019)

The following collection of tools includes our own and external resources.

STEP LID Life Cycle Costing Tool (Ontario)

STEP LID Life Cycle Costing Tool includes Bioretention, Enhanced grass swales, Green roofs, Infiltration chambers, Infiltration trenches, Permeable pavements, and Rainwater harvesting cisterns

The Sustainable Technologies Evaluation Program has produced a life cycle costing tool specific to Ontario. STEP built the tool after evaluating LID practices and design scenarios for input costs, maintenance requirements, rehabilitation costs and practice designs relevant to Canadian climates. The tool is in a simple to use Excel format and is free to download. STEP LID Life Cycle Costing Tool

See the LID Life Cycle Costing Tool page for more about the tool along with cost estimates for common design scenarios, and cost comparisons by LID practice type and design configuration.

Green Infrastructure Optimization Tool (Great Lakes)

The Greater Lakes Green Infrastructure Optimization Tool gives a preliminary assessment of green infrastructure options. Land-cover types (and technologies) include: Existing and proposed buildings, existing and proposed paved parking areas, walkways and roadways, open space, pasture, meadow, brush, woodland/grassland, woods and bare soil.

GI tool from the Great Lakes Commission

Green Values Stormwater Toolbox (Great lakes, USA)

A free tool for evaluating the costs and benefits of green infrastructure. It is based on the hydrology of the Great Lakes region, and produced by the Center for Neighborhood Technologies, a non-profit organisation in the USA.

CNT's Toolbox webpage

CNT's Green Values calculator tool

United States Environmental Protection Agency (US EPA)

The US EPA's National Stormwater Calculator provides a regionalized, planning-level cost estimation tool for LID stormwater practices in the United States that has been recently updated. For an article describing the updated tool see Bernagros et al. (2021) .

US EPA National Stormwater Calculator tool

A collection of other cost-benefit analysis resources from the Green Infrastructure team at the US EPA can be found at the following link.

Cost benefit resources from US EPA

CIRIA's BeST tool (UK)

A tool which monetizes Ecosystem Services (ESS) and Triple Bottom Line (TBL) criteria to assess LID options (described as Sustainable Drainage Systems, SuDS). The tool guides the user to consider some or all of the co-benefits listed below . Whilst the relative values may be useful for assessing options, the currency of this model is in GBP (£).

BeST

• Air Quality
• Amenity
• Biodiversity and Ecology
• Building temperature
• Carbon sequestration
• Crime
• Economic growth
• Education
• Enabling development
• Flexible infrastructure
• Flood risk
• Groundwater recharge
• Human health
• Pumping wastewater
• Rainwater harvesting
• Recreation
• Treating wastewater
• Tourism
• Traffic calming
• Water quality of receiving water

Proprietary

• Autocase

See also

• Trees for costing tools particularly focused on street trees and urban canopy.
• Rainwater harvesting for advice specific to RWH systems.
• Funding
• Managing Costs and Containing Risks using the One Water Approach

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

The temporary storage of stormwater to control discharge rates, and allow for sedimentation.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

A vegetated area such as a bog, fen, marsh, or swamp, where the soil or root zone is saturated for part of the year.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.

Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm.

The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.

Sustainable Technologies Evaluation Program

Natural vegetation and vegetative technologies in urban settings such as: urban forests; green roofs; green walls; green spaces; rain gardens; bioswales; community gardens; natural and engineered wetlands and stormwater management ponds; and porous pavement systems. These systems are designed to provide multiple benefits, such as moderate temperatures, clean air and water, and improve aesthetics.

A biological community, including humans and their natural environment.

The addition of water to ground water by natural or artificial processes.

The infiltration and movement of surface water into the soil, past the vegetation root zone, to the zone of saturation or water table.

Rainwater harvesting.

Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.