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Case Studies

Transportation agencies across the United States are using INVEST to evaluate and improve sustainability within their agency and on their projects.

Case studies focus on the general use of INVEST and its implementation and/or scoring practices. Some focus more on process/application, some focus on a few select criteria, some focus on the overall experience of using INVEST. Case Studies are developed by the agency which submits them, with review and input by FHWA.

Use the map and filters below to find case studies relevant to your projects and/or agency.

Arizona DOT - State Route 30 Sustainable Project Development


Lead Agency: Arizona Department of Transportation (ADOT)

INVEST Modules: Project Development


 Download the Arizona DOT Round 3 Final Report (3,338 kb) and Appendices (18,448 kb)

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.

Using INVEST for the SR 30 project will add to the ADOT’s body of knowledge of projects analyzed and scored with the PD module. As noted above, the ADOT has scored over 50 projects in the agency’s 5-year construction program using the PD module—initially with a specific focus on statewide roundabout projects. The ADOT then expanded the scoring to projects ranging from pavement preservation, to bridge deck rehabilitation, to the addition of new lane miles. The ADOT was particularly interested in how INVEST could supplement the agency goals of furthering efforts surrounding sustainable infrastructure.


Since 2005, the Arizona Department of Transportation (ADOT) has been studying State Route 30, a proposed new freeway corridor that would serve as an alternate route to Interstate 10. The study areavextends from Sarival Avenue on the west to 59th Avenue on the east, and Lower Buckeye Road on the north to the Gila and Salt rivers on the south. The project spans about 13-miles and passes through the cities of Goodyear, Avondale, Phoenix and portions of unincorporated Maricopa County.

In early 2015, after several years of study, the ADOT presented the public with four build alternatives (North, Center, Hybrid, and South). All four (4) alternatives were evaluated with a comprehensive screening process using twenty-four (24) technical (environmental and engineering) criteria, eight (8) cost and right-of-way criteria, and seven (7) agency and public support criteria. Also considered was a No-Build Alternative, which explored the impacts of not building a transportation corridor in the study area.

In November 2017, ADOT held a public meeting that provided information on the four build alternatives and the No-Build Alternative, concluding with an announcement that only the No-Build Alternative and the Hybrid Alternative were being carried forward for detailed analysis and additional public input. The Hybrid Alternative would now be referred to as the Recommended Build Alternative (or RBA).

In early 2019, after carefully considering the findings from the multi-year screening process that evaluated twenty-four (24) environmental and engineering criteria, eight (8) cost and right of way criteria, and the public and agency feedback received during the Spring 2019 Public Hearing, the ADOT is recommending the RBA as the Recommended Alternative. A finding of no significant impact (FONSI) is anticipated upon air quality conformity in 2019.

Map of Recommended Build Alternative

Connecting sustainability and NEPA

In addition to the extensive INVEST scoring effort and sustainability review, ADOT initiated an effort early in the Design Concept Report (DCR) and Environmental Assessment (EA) contract negotiations to have hours included for this effort but also to explore how sustainability and NEPA integrate. As such, step one was to designate this 13-mile regional transportation corridor project as ADOT’s first ever sustainable transportation corridor of interest. Step two was to incorporate sustainable transportation language into the October 2017 public meeting.

Public Information Meeting information on SR30

Step 3 was to utilize the 100 INVEST hours incorporated into the DCR/EA scope of work to conduct the independent scoring and case study development. Step 4 was to conclude the scoring and create a baseline for considering sustainability in design. This baseline was especially important to establish a starting point once final design was started in this $1.7b freeway.

State Route 30, Sarival to Loop 202

SR 30 INVEST PD Module Criteria Scoring Results

The first step in the ADOT SR 30 PD process was to determine the type of project, based on the scorecards described above. The SR 30 study area is located in a rapidly growing and urbanizing area in the western part of Phoenix and the adjacent towns of Avondale and Goodyear. Agricultural land currently exists within the SR 30 study area, but it is rapidly transitioning to residential subdivision and commercial land uses. By the proposed SR 30 design year in 2040, the general plans for Phoenix, Avondale, and Goodyear anticipate that much of the existing agricultural land will have been developed into urban land uses.

The scorecard that best meets the needs of the SR 30 project is Urban Extended. The Urban Extended scorecard requires that all thirty-three (33) criteria of the PD module be evaluated and scored. The evaluation and scoring of the PD module for the SR 30 project was conducted by a consultant design engineering firm retained by the ADOT to conduct preliminary design, engineering, National Environmental Policy Act compliance, and public involvement for the project. The personnel involved with the design, engineering, and environmental assessment of SR 30 conducted the evaluation and scoring to ensure all aspects of the project’s sustainability were considered for each PD module criterion.

The PD module scorecard for the SR 30 project—which includes how each criterion was scored, scoring notes, and next actions—can be reviewed in the appendix. The score for the SR 30 project was 57 points, which was Silver on the INVEST Achievement Level. 

Key findings of the independent PD module evaluation and scoring for the SR 30 project, regarding ADOT’s sustainability practice areas of strength, are discussed below. For the full SR 30 scorecard, see Appendix B of ADOT's Round 3 Final Report.

PD‐03 Context Sensitive Project Development (Points available: 10, Points awarded: 7) – Contextsensitive solution principles were incorporated into the SR 30 design to address identified constraints to the extent possible. The ADOT typically adds landscaping and artistic treatments to structures on every freeway project, so credit is taken for that normal course of project development.

PD‐07 Habitat Restoration (Points available: 7, Points awarded: 5) – The Salt, Gila, and Agua Fria Rivers are within the SR 30 study area but have only intermittent annual flow. Much of the natural riparian habitat has been disturbed by other uses, such as quarry operations. The Tres Rios Flow Regulated Wetlands Complex is a High Quality Aquatic Resource located between 99th and 91st Avenues and adjacent to the City of Phoenix 91st Avenue Wastewater Treatment Plant. The SR 30 Recommended Alternative was aligned to avoid impacts on this complex and is located within 100 feet of its boundary,  which is worth 4 points. Additionally, the Recommended Alternative includes a drainage facility to drain stormwater away from the complex on its western boundary, thus preventing potential freeway runoff from affecting the complex.

PD-08 Stormwater Quality and Flow Control (Points available: 6, Points awarded: 3) – Given the location of SR 30 in relation to the Salt, Gila, and Agua Fria Rivers and other resources that include the Tres Rios wetlands and levee in the SR 30 study area, drainage was an important consideration in the development of the stormwater management system. The flow control was developed using a peak flow basis, using a worst-case scenario of a 100-year flood, although the ADOT standard is a 50-year flood. For water quality, the on-site stormwater collection system was developed based on ADOT Best Management Practices. Runoff collected in the catch basins would be conveyed in storm drains. First flush volumes would be treated for both sedimentation and petroleum products within the basins, but the volume of water treated would not exceed 80 percent of the total runoff volume, so no credit is applicable. With regard to managing the runoff volume, this project is managing 100 percent of the flows from the project site and, in addition, is collecting and managing the off-site flows that cross the corridor. This provides flood control protection for all property from the project corridor south to the Salt and Gila Rivers. This constitutes a far greater managed flow protection than 124 percent, thus the 3-point score.

PD‐09 Ecological Connectivity (Points available: 4, Points awarded: 2) – The Recommended Alternative was selected over the Southern Alternative, which would have been located in close proximity to the Salt River. Also, ADOT is in the process of preparing a Biological Evaluation to both minimize and avoid biological impacts from the SR 30 project. Wildlife connectivity was evaluated in the Biological Evaluation and Draft Environmental Assessment. The U.S. Fish and Wildlife Service and Arizona Department of Environmental Quality have been and will continue to be involved throughout the SR 30 planning, design, engineering, and environmental process.

PD‐12 Transit and HOV Facilities (Points available: 2, Points awarded: 2) – The third phase of the SR 30 project implementation, which is not yet programmed, would widen the 3+0 section (three general purpose lanes in each direction) constructed in the second phase to a 4+1 section (four general purpose lanes and one HOV lane in each direction) in the median of SR 30 when travel demand warrants it, and when funding is available. The fourth and final phase would involve a high-capacity transit corridor, the space for which is being preserved inside the SR 30 right-of-way footprint for some future date and future mode.

PD‐13 Freight Mobility (Points available: 7, Points awarded: 3) – SR 30 satisfies PD-13.1g – Increase transportation efficiencies for moving freight, because this is a new limited-access freeway with gradeseparated crossings and interchanges with arterial streets and a crossing of the Agua Fria River. This new facility would reduce truck traffic on the local arterial street system and would provide an alternative route to Interstate 10, which currently accommodates a high percentage of trucks with a poor level of service during peak travel times.

PD‐14 ITS for System Operations (Points available: 5, Points awarded: 3) – This score is based on the ITS applications typically used on the Phoenix freeway system that are constructed, operated, and maintained by ADOT. Specifically, items PD-14.1d – Information Dissemination, g – Ramp Control, and i – Surveillance.

PD‐18 Site Vegetation, Maintenance and Irrigation (Points available: 6, Points awarded: 6) – ADOT has a native plant-only seeding policy within right-of-way areas. ADOT requires contract specifications for the control of noxious and invasive plant species. The specification requires the contractor to identify and remove any designated invasive or noxious plant species prior to any earthwork activities. Additionally, these requirements have been diversified from just grass seeding for erosion control to now include annual and perennial wildflowers, forbs, and shrubs to more closely resemble Arizona’s diversified native roadside vegetation.

PD‐22 Long Life Pavement (Points available: 12, Points awarded: 7) – The Design Elements section of the SR 30 Design Concept Report states that the entire ultimate SR 30 roadway typical section would be paved with long-lasting Portland cement concrete pavement (PCCP) and overlaid with a rubber asphalt friction course. The friction course may have to be replaced every 10 to 15 years, but the PCCP materials traditionally last at least 40 years in the Phoenix area. ADOT standard specifications include a pay incentive for pavement smoothness for both the PCCP and the asphalt friction course.

PD‐28 Construction Quality Control Plan (Points available: 5, Points awarded: 5) – ADOT construction contracts pay for a contractor quality control item to ensure quality compliance beyond field inspection. ADOT will also pay premiums for material quality that far exceeds the minimum.

SR 30 is currently in the preliminary design and environmental assessment phase of the project. ADOT will have the ability to review and reassess the sustainability aspects of SR 30 through the use of the INVEST PD Scoring Module as it progresses through the various stages of design and public involvement through final design and construction. It is possible that the SR 30 project may achieve a higher sustainability score through the use of current INVEST PD best practices that ADOT may choose to adopt or new ones that may be added to the PD Scoring Module in newer INVEST versions that FHWA develops in the future.

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