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Green Infrastructure

Green Infrastructure Design and Implementation

Properly designed, constructed, and maintained green infrastructure practices provide the greatest benefit to water resources and the community. Access guidance on this page about construction, operation and maintenance, and common design challenges.

On this page:

Design Manuals

States, counties, municipalities, and nonprofits across the United States and Canada have developed stormwater design manuals that emphasize green infrastructure approaches (also called “low impact development” or “environmental site design”). Each manual includes:

  • detailed design guidelines tailored to the local physical and regulatory landscape; and
  • planning and design approaches as well as structural stormwater controls.

Access these examples of design manuals by clicking their links:

Arizona: Green Infrastructure for Southwestern Neighborhoods(50 pp, 3.64 MB, About PDFExitCommunity leaders and professionals interested in applying green infrastructure in southwestern neighborhoods can use this guide for retrofitting existing neighborhood streets, rights-of-way, and parking lots with green infrastructure practices.

Florida: Low Impact Development Manual for Sarasota County(85 pp, 5.1 MB, About PDF) ExitProfessionals in planning, design, construction, operations, and maintenance of building and development projects can use this manual for technical guidance and design specifications for the green infrastructure practices deemed most appropriate for the county.

Georgia: Coastal Stormwater Supplement to the Georgia Stormwater Management Model(542 pp, 13 MB, About PDF)Exit

This supplement provides:

  • comprehensive guidance on an integrated, green infrastructure-based approach to natural resource protection, stormwater management, and site design; and
  • details on site planning and design approaches, and green infrastructure practices (e.g., applicability, design, installation, and maintenance).

Maryland: Maryland Stormwater Design Manual Exit

These two volumes provide:

  • an overview of how to size, design, select, and locate best management practices (BMPs) at a new development site to comply with state stormwater performance standards; and
  • details on landscaping, BMP construction specifications, step-by-step BMP design examples, and design tools.

Minnesota: State of Minnesota Stormwater Manual Exit

These two volumes present:

  • stormwater management in the physical and regulatory context of Minnesota; and
  • technical and engineering guidance for stormwater professionals and regulators.

New York: New York State Stormwater Management Design Manual(642 pp, 13.4 MB, About PDF)

This manual provides:

  • an overview of how to select, locate, size, and design BMPs at a development site to comply with state stormwater performance standards; and
  • definitions, design specifications, and computational methods for specific green infrastructure practices.

Texas: San Antonio River Basin Low Impact Development Technical Guidance Manual(415 pp, 18.6 MB, About PDFExit

This manual provides:

  • guidance to communities on the selection, design, inspection, and maintenance of green infrastructure practices; and
  • clear design guidance that is customized to the unique land formations and soil conditions in the region.

Toronto: Credit Valley Conservation Low Impact Development Stormwater Management Planning and Design Guide Exit

This guide provides developers, consultants, municipalities, and landowners with:

  • planning and design approaches as well as information on green infrastructure stormwater controls; and
  • an overview, a design template, and a summary of maintenance and construction costs for each structural control discussed.

The Credit Valley Conservation Landscape Design Guide for Low Impact Development Exit

This appendix for landscape architects and engineers:

  • complements the Stormwater Management, Planning and Design Guide; and
  • provides information on plant selection, planting, and landscape maintenance.

Washington: Low Impact Development Technical Guidance Manual for Puget Sound(256 pp, 7.7 MB, About PDFExit 

This manual provides stormwater managers and site designers with:

  • detailed design guidelines for particular practices; and
  • summaries of pollutant removal efficiencies, maintenance requirements, and costs.

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Design Tools

CalculatorUse one of the many modeling tools available to assist you in complying with local stormwater regulations and/or meeting voluntary performance standards. See Modeling Tools for details about a variety of modeling resources.

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Design Challenges

DesertSite characteristics can limit the application of green infrastructure practices and require slight design modifications. Read about some of the most common design challenges cited by stormwater professionals. See: How Can I Overcome Barriers to Green Infrastructure?

Clay or Glacial Till

Clay and glacial till often have low infiltration rates. For sites dominated by these soils, you might assume that infiltration-based stormwater controls are not feasible. Design of green infrastructure practices for those sites can require greater care, but you can take these steps in your design to meet water quality goals:

1. Measure soil infiltration rates: Determine the infiltration rate of site soils before starting to design stormwater controls. A generally accepted guideline for the infiltration rate of native soils beneath infiltration practices is greater than 0.25–0.5 inches/hour. Not incorporating measured infiltration rates into rain garden design can have negative results, as was Seattle Public Utilities' experience with the Ballard Roadside Raingardens pilot project.

2. Amend soils beneath infiltration practices: Amend clay soils with compost or other organic matter to increase soil infiltration rates, while improving soil fertility and the ability of the soil to remove pollutants. The Low Impact Development Center has developed a design specification for soil amended with compost:

The Low Impact Development Center Soil Amendment Compost Specification Exit

3. Plant deep-rooted vegetation: Enhance soil infiltration rates by planting deep-rooted vegetation and creating small conduits for water to infiltrate and increase biological activity in the soil. The U.S. Geologic Survey found that the median infiltration rate of a clay soil plantedwith prairie species (0.88 inches/hour) was more than three times the rate of a clay soil planted in turf (0.28 inches/hour). See 2010 report: Evaluation of Turf-Grass and Prairie-Vegetated Rain Gardens in a Clay and Sand Soil in Madison, Wisconsin(82 pp, 5.3 MB, About PDF)

4. Expand the storage layer and include an underdrain: Including a larger storage layer with an underdrain can significantly slow peak flows and increase infiltration, protecting stream banks and potentially reducing combined sewer overflows.

5. Use practices that do not require infiltration: Integrate practices into your treatment drains to mitigate stormwater impacts, including:

  • rainwater harvesting,
  • green roofs,
  • vegetated swales, and
  • other practices designed for decreasing peak flow that do not require soils with high infiltration rates.

Poor Urban Soils

Many cities want to revitalize their urban areas by transforming vacant lots and other neglected spaces into green infrastructure assets. But the soils on the lots often:

  • are severely compacted;
  • lack sufficient organic matter; and
  • contain construction debris.

Evaluate and recondition urban soils: You can use various methods to recondition poor quality soils depending the intended use of the site. A site intended for urban agriculture might require extensive reconditioning, whereas a site intended for recreation might require only moderate improvement.

In 2011, EPA completed Evaluation of Urban Soils: Suitability for Green Infrastructure or Urban Agriculture, a report that provides a concise, practical, and scientifically based overview of the typical conditions of urban soils. It recommends ways in which you can rehabilitate or recondition soils to support either use.

Brownfield Sites

Cities also are looking at redeveloping brownfield sites—properties where the presence (or likely presence) of contaminants could complicate redevelopment or reuse. Integrating green infrastructure into these sites can benefit the environment and the community. But implementing infiltration-based stormwater management practices must be done carefully, so contaminants in the soil are not mobilized, increasing the risk of groundwater contamination.

Perform site analysis and planning: In 2013, EPA released Implementing Stormwater Infiltration Practices at Vacant Parcels and Brownfield Sites. This document guides decision-makers through a series of questions to determine whether infiltration or other stormwater management approaches are appropriate for a specific brownfield property.

Sediment-Laden Stormwater

In arid regions, bare soils are common and rates of erosion and sedimentation are relatively high. Fine sediments delivered by stormwater flows can clog infiltration practices and degrade their performance. Stormwater professionals use these and other strategies in their design and maintenance of effective green infrastructure practices in areas with high sediment loads.

  • Include a mulch layer: Mulch acts as a filter for sediments carried in stormwater. Add a mulch layer above infiltration practices and replace the layer when it is filled to protect the soil and gravel layers below from sedimentation.
  • Include a sediment trap: A “sediment trap” is a small depression bordered by a small berm that captures and collects sediment at the entrance to a bioretention area. Use traps at the inflow of green infrastructure features to facilitate the removal of accumulated sediment and prevent the feature from becoming clogged.
  • Perform periodic maintenance: If you include a mulch layer or sediment trap in your stormwater management practice, regularly remove the accumulated sediment to maintain the practice’s function.

Cold Weather

Stormwater professionals frequently raise questions about the performance of green infrastructure practices in cold weather. Research by the University of New Hampshire indicates that green infrastructure practices in their climate demonstrate excellent water quality treatment and peak flow reduction year-round. See: University of New Hampshire Stormwater Center Research Exit

Semi-arid/Arid Regions

Significant research and practices have been implemented in drier regions such as the Southwestern United States, but more research is needed as outlined in this 2016 report, Arid Green Infrastructure for Water Control and Conservation State of the Science and Research Needs for Arid/Semi-Arid Regions.

EPA's Region 8 Green Infrastructure website provides many examples of practices as well as tools and guidance tailored to the arid west.

Limited Water Supply for Irrigation

Limited water resources can be a barrier to green infrastructure in arid and semiarid regions. Follow the principles of xeriscaping to conserve water resources:

  • Create a plan: Create a plan that balances water supply and demand.
    • An annual water budget for a landscape of native plants at native densities.
    • A monthly water budget for a landscape of exotic plants at higher plant densities.
  • Use low water use plants: You can drastically reduce, if not eliminate the irrigation requirements of green infrastructure practices by using native and drought-tolerant plants.
  • Use efficient irrigation systems: Make your irrigation systems most efficient by:
    • grouping plants according to their water needs; and
    • adjusting the frequency and depth of irrigation according to plant type, plant maturity, and season.
  • Consider soil amendments: Healthy soils are essential to retaining soil moisture, sustaining vegetation, and treating stormwater runoff. If your site’s soils are poor, amend them with organic material.
  • Use mulches: Organic mulch can increase water retention and pollutant removal while building soil structure and suppressing weeds. Note, however, that many desert trees and shrubs react poorly when their trunks come in contact with mulch.
  • Maintain your xeriscape: All landscapes require maintenance, and xeriscaping is no exception.

Space Constraints

Many green infrastructure features require land area to allow stormwater to infiltrate into the soil. This can pose a challenge when space is limited (e.g., in a retrofit project or right-of-way). Designers have developed many strategies, however, for overcoming this challenge:

  • Use features that serve multiple purposes: Integrate swales and bioretention areas into landscaped areas, medians, or parking strips. Use permeable pavements to provide volume reduction and water quality treatment without requiring additional space.
  • Use features that fit into small spaces: Design planter boxes, tree pits, and other green infrastructure features that will fit into small spaces.
  • Use subsurface storage or infiltration: You can use subsurface storage or infiltration tanks as an alternative when space is too limited for any surface practices.

Coastal Erosion and Resiliency

Coastal areas are particularly vulnerable to the effects of climate change. Designing green infrastructure for protecting these areas must consider the natural resources as well as the potential for population displacement. NOAA's Office of Coastal Management offers programs and tools for designing and implementing solutions that support coastal resiliency. 

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Implementation

Parking LotErrors made in the implementation phase can severely compromise the performance and public acceptance of well-designed stormwater management practices. Access these resources about lessons learned from construction mistakes and ensuring that practices are built as designed.

Low Impact Development Construction Guide(95 pp, 10 MB, About PDFExit

This guide includes:

  • an overview of common LID construction errors;
  • a discussion of how construction procedures and sequencing for LID sites differ from conventional sites; and
  • recommendations for improving contracts, plans, and communication to avoid construction errors.

New York City High Performance Landscape Guidelines(273 pp, 7.6 MB, About PDFExit These guidelines include a discussion on how to anticipate potential construction problems and make construction practices more sustainable. Written for design and construction of public parks, but can be applied more broadly.

Ballard Roadside Raingardens, Phase I — Lessons Learned PDF

Prepared by Seattle Public Utilities to document lessons learned in design and construction of the Ballard Roadside Rain Gardens pilot project, including the importance of:

  • reviewing project goals and objectives with construction management staff;
  • consulting with the geotechnical engineers throughout the design and construction process; and
  • thorough and timely community outreach.

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Homeowner Resources

State and local governments in different parts of the country have produced guides for homeowners on installing rain barrels and rain gardens. Access these examples by clicking their links:

New York: Guidance Manual for Homeowners: Managing Stormwater Runoff Using Green Infrastructure(8 pp, 4 MB, About PDFExit A brief how-to manual developed by the Stormwater Coalition of Albany County to guide homeowners through siting, designing, and installing a rain garden or rain barrel on their property.

Oregon: Stormwater Management Facilities: Operation and Maintenance for Private Property Owners(22 pp, 295 K, About PDFGeneral guidelines for homeowners and homeowners associations on how to inspect and maintain stormwater management facilities, including sediment removal, vegetation management, and erosion.

Wisconsin: Rain Gardens: A How-To Manual for Homeowners(32 pp, 5 MB, About PDF) Information for homeowners and landscape professionals on how to design and build rain gardens on residential lots.

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