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Criterion Details

PD-18 Site Vegetation, Maintenance and Irrigation

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Project Development Scorecard

  • Rural Basic
  • Urban Basic
  • Rural Extended
  • Urban Extended


Promote sustainable site vegetation within the project footprint by selecting plants and maintenance methods that benefit the ecosystem.

Sustainability Linkage

Triple Bottom Line

Using sustainable site vegetation supports the environmental and economic sustainability principles by enhancing and protecting the ecosystem by choosing native and non-invasive species, and by reducing maintenance costs.

Background & Scoring Requirements


For the purpose of this criterion, the key terms are defined as follows:

  • “Native plant species” – Plants native to the EPA Level III ecoregion per the EPA’s Level III and IV Ecoregions of the Continental United States website1 that contains the roadway project site or known to naturally occur within 200 miles of the roadway construction site (also see Sustainable Sites Initiative’s Guidelines and Performance Benchmarks2).
  • “Non-invasive plant species” – The following items should be performed to ensure that a plant species is considered “non‐invasive”: 1) Consult existing local (e.g. city, county, and State natural resources agencies) vegetation policy and procedure that is applicable to the roadway project and ensure vegetation selected and seed mixes used are specifically formulated to prevent the use of invasive plant species and noxious weeds. The National Invasive Species Information Center’s website3 provides information on how to identify invasive species, 2) Use local and/or regional lists to identify invasive plant species; and 3) Comply with noxious weed laws. The Natural Resources Conservation Service provides Federal- and State-listed noxious species lists by state at USDA’s Introduced, Invasive, and Noxious Plants website4
  • “Noxious weeds” – Plants introduced into an ecosystem, which are often invasive, that once established are highly destructive, competitive and difficult to control. They have economic and ecological impacts and are very difficult to control once established. Some noxious weeds are a public health threat to humans and animals, while others destroy native and beneficial plant communities, increase erosion concerns, and clog waterways.
  • “Site vegetation” – All vegetation associated with a particular roadway project and shall include all vegetation within the roadway’s right-of-way or disturbed area associated with the roadway project (whichever is greater). This can include, but is not limited to, roadside vegetation, decorative planting (e.g., planter boxes or potted plants in urban areas), and vegetation contained in stormwater facilities (e.g., bioswales and rain gardens). Vegetation includes plants and plant propagules such as seeds.

Highway corridors provide opportunities for the movement of invasive species through the landscape. Invasive plant or animal species can move on vehicles and in the loads they carry. Invasive plants can be moved from site to site during spraying and mowing operations. Weed seed can be inadvertently introduced into the corridor during construction on equipment and through the use of mulch, imported soil or gravel, and sod. Some invasive plant species might be deliberately planted in erosion control, landscape, or wildflower projects. Millions of miles of highway rights-of-ways traverse public and private lands. Many of these adjacent lands have weed problems and the highway rights-of-way provide corridors for further spread. (Federal Highway Administration Guidance on Invasive Species5).

As explained by the United States National Arboretum (USNA) on their Invasive Plants website6, invasive species are particularly problematic in construction areas and road cuts as they thrive where the continuity of a natural ecosystem is breached. Ultimately, invasive plants alter habitats and reduce biodiversity. Rich, diverse plant communities can become barren, inhospitable expanses of invasive plants with little value to wildlife. Invasive plants may even deplete groundwater resources. Plants introduced to North America from other parts of the world have come to dominate millions of acres of forest, desert, prairie, and wetlands by out-competing native species.

Native plant species are beneficial and sustainable for roadway projects as they are well adapted to their native climate and soil types. Once established, native plants require little to no maintenance. Properly selected native plant species do not need insecticides or routine irrigation to thrive (sometimes, spot irrigation is needed to control invasive species). Native plants provide habitat for native animals and insects; native wildlife prefers native plants.

While not as beneficial to a native ecosystem, non-invasive plant species that are adapted to site conditions and climate can be considered if there are no native species available that would meet design intent. The following attributes should be considered in determining whether plants are appropriate for the site: cold hardiness, heat tolerance, salt tolerance, soil moisture range, plant water use requirements, soil volume requirements, soil pH requirements, sun/shade requirements, pest susceptibility, and maintenance requirements.” (Sustainable Sites Initiative’s Guidelines and Performance Benchmarks2) Both native and non-native plants selected should embody these attributes.

Scoring Requirements

In order to achieve points for this criterion, the following prerequisite must be met:

Prerequisite PD-18.1P 

0 points. All site vegetation shall use, or consist of, native and/or non-invasive species and non-noxious species only.  The project shall minimize disturbance of native species.

Requirement PD-18.1

1 – 3 points. Vegetation Planning and Selection

Implement one or more of the features in Table PD-18.1.A. Points for features are cumulative if the project has more than one feature; however, Requirement PD-18.1 shall not exceed a total of three points. 





Minimum Requirements



Long-term vegetation planning

Have an integrated vegetation management plan to maintain the project and/or corridor, including management of site vegetation and management of invasive species (or continued efforts to eradicate them). This could include a plan and/or financing to support site vegetation.



Vegetation to replace or enhance structures

Use non-invasive species for snow fences, sight screens, or other otherwise constructed items (vegetation for more than 50% of the project need for snow fences, sight screens to meet this requirement) and/or use non-invasive species to enhance the aesthetics of structural features, such as retaining walls and noise walls.



Invasive species prevention during construction

Bring only equipment free of dirt, mud, and organics into sensitive sites, such as wetlands, prairies, and water bodies. Have a written plan for the inspection and cleaning of vehicles to prevent the unintentional spread of invasive species during construction.



Native species


  • Plants or seed with a variety of native plant species only. (Non-invasive and non-noxious plants transplanted from impact areas within the project limits may be used.)
  • Use five or more native species in plantings to increase biodiversity and native habitat for wildlife. Selection of native species shall be appropriate for the context of the project.
  • Salvage rare plants and retain existing vegetation where possible.
  • Reuse native plants salvaged from other projects.
  • Eradicate all existing invasive and noxious plant species or, in cases where eradication is impossible, implement an invasive species management plan.

Requirement PD-18.2

1 – 3 points. Maintenance and Irrigation

Implement one or more of the features in Table PD-18.2.A. Points for features are cumulative if project has more than one feature; however, Requirement PD-18.2 shall not exceed a total of three points. 





Minimum Requirements



Non-mechanical maintenance

No mowing or other mechanical means of maintenance is planned or required for long-term vegetation maintenance.



No long-term irrigation

No irrigation is planned or needed after the plant establishment period.



Non-potable water for irrigation

Use captured rainwater, gray water, captured stormwater, non-potable water conveyed by a public agency, and /or other context-appropriate non-potable water (both in the plant establishment period and beyond) for irrigation needs.



Reduction in use of fertilizers, insecticides, and herbicides

Appropriately use only fertilizers and pesticides (herbicides, insecticides, fungicides) acceptable in USDA Organic farming. No use of synthetic fertilizers or synthetic pesticides during the construction and plant establishment period.



Above-Referenced Resources

The following resources are referenced in this criterion and consolidated here:

  1. EPA, Level III and IV Ecoregions of the Continental United States website,
  2. The Sustainable Sites Initiative, Guidelines and Performance Benchmarks (2009),
  3. USDA, National Invasive Species Information Center’s website,
  4. USDA, Introduced, Invasive, and Noxious Plants website,
  5. FHWA, Federal Highway Administration Guidance on Invasive Species (August 10, 1999),
  6. USNA, Invasive Plants (2008),

Additional Resources

The following resources provide information on this criterion topic in addition to the sources directly referenced:

  1. USDA, Introduced, Invasive, and Noxious Plants,
  2. FHWA, Roadside Use of Native Plants,

Case Studies & Criterion Examples

Western Federal Lands - Going-to-the-Sun-Road Rehabilitation Project: The Going-to-the-Sun Road (Sun Road) is the first American roadway designated both a National Historic Landmark and a National Civil Engineering Landmark. Going-to-the-Sun Road is the only road through the heart of Glacier National Park in Montana. It was completed in 1932, and it is the only road that crosses the park, going over the Continental Divide at Logan Pass. Sun Road has more than 475,000 vehicles traveling it during peak visitor season from June to October, or about 3,500 vehicles per day. The Western Federal Lands Highway Division (WFL) within the Federal Highway Administration used the INVEST Project Development (PD) module to evaluate the Sun Road Rehabilitation Project. Stand out criteria included PD-03: Context Sensitive Project Development, PD-07: Habitat Restoration, PD-18: Site Vegetation, PD-19: Reduce and Reuse Materials, and PD-28: Construction Quality Control Plan.

TxDOT - Embedding INVEST in Contracting for the Corpus Christi Harbor Bridge: The Texas Department of Transportation (TxDOT) used INVEST during the procurement process for the Harbor Bridge Project in Corpus Christi. TxDOT’s request for proposals (RFP) required that bidders describe how their proposal would meet a “Platinum” rating on the INVEST PD module and a “Silver” rating on the INVEST OM module. The sustainability score, along with price and other factors, was part of the total score for selecting among the four bidders. This provided a strong incentive for bidders to achieve high sustainability at low cost. The winning bidder committed to a range of sustainability practices that will bring tangible benefits to the community.

Arizona DOT - Using INVEST to Integrate Sustainability: The Arizona Department of Transportation (ADOT) decided to use all three modules of INVEST – System Planning, Project Development, and Operations and Maintenance – to help the agency meet its sustainability goals across the transportation life cycle.  ADOT used INVEST to integrate and advance existing sustainability efforts and to push forward new efforts.  INVEST’s comprehensive sustainability framework and criteria helped ADOT institutionalize sustainability across the agency and with local partners through inclusion in manuals, trainings, and awards.  This case study focuses on ADOT’s use of the Project Development module.

Arizona DOT - State Route 30 Sustainable Project Development: This case study describes the use of the INVEST PD module to analyze and score the ADOT State Route (SR) 30 project—an approximately 13-mile section of new freeway in the Phoenix metropolitan area. The new freeway would be built five (5) miles south of Interstate 10 and would run from Sarival Road in Goodyear east to Loop 202 (South Mountain Freeway) in the western section of Phoenix in Maricopa County, Arizona. SR 30 is a proposed new freeway managed by the ADOT that would eventually link with the proposed ADOT Interstate 11 project in western Maricopa County near Tonopah at its western terminus and with the existing Interstate 17 at the Durango Curve in Phoenix at its eastern terminus. The section of SR 30 analyzed and scored using INVEST is currently in the preliminary design and environmental assessment evaluation phase pursuant to the National Environmental Policy Act.

Arizona DOT - Sonoran Corridor Study: In February 2017, the Federal Highway Administration (FHWA) and Arizona Department of Transportation (ADOT) initiated an environmental review process for the Sonoran Corridor, which would connect Interstate 19 and Interstate 10 south of the Tucson International Airport. A Corridor Selection Report (CSR) and Tier 1 Environmental Impact Statement (EIS) were prepared as part of this process in accordance with the National Environmental Policy Act (NEPA) and other regulatory requirements. The project objective is to identify an appropriate and approximate 2000-foot corridor for a future roadway that would be subject to a detailed design and a Tier 2 environmental review to identify a final roadway alignment and necessary project mitigation treatments. At the direction of ADOT, this case study evaluates processes and methodologies used for development of the Sonoran Corridor Tier 1 EIS compared to INVEST guiding principles.

Scoring Sources

The project is considered to have met this criterion if the requirements above can be reasonably substantiated through the existence of one or more of the following documentation sources (or equal where not available):

  1. A vegetation or landscape plan showing type, size, and location of all plant species. This can often be found in the standard project plans.
  2. The specification sections relating to site vegetation. These are typically found in the technical specifications.
  3. A copy of, or reference to (e.g., web address), the policy or procedure used to select plant species.
  4. A design study report approved by the appropriate agency or authority that includes analysis of existing site vegetation, impacts, reuse of vegetation, references to evaluate the invasive species and noxious plants, and planned vegetation species.
  5. An integrated vegetation management plan covering the long-term maintenance of vegetation (including irrigation, fertilizer and pesticide use, mechanical maintenance, and control of invasive species.)