Stellantis Mack Assembly Plant

Detroit, Michigan

In February of 2019, Stellantis (Formerly FCA) announced a $1.6 billion investment to convert the two plants that comprised the Mack Avenue Engine Complex into a future assembly site. The new assembly complex was part of their $4.5 billion investment that impacted five existing facilities in Michigan and aimed at creating 6,500 new jobs for the area. This investment would create 3,850 new jobs to support production. In the second quarter of 2019, Stellantis began construction on the future site of the next-generation Jeep Grand Cherokee, making it the newest assembly plant in Detroit in nearly 30 years.

PEA Group led the site design and engineering efforts for the renovation and expansion of the Stellantis facility on Detroit’s east side. The project is the largest and most complex project PEA Group has been involved with to date. The project involved over 80 PEA Group team members, including civil engineers, landscape architects, geotechnical engineers, professional surveyors, and support staff. The project planning started in early 2018 and construction began in the second quarter of 2019.

The project included the renovation of two existing automotive plants totaling over 1,900,000 square feet of building floor area on nearly 178-acres in Detroit. The construction will include a new 358,000 square foot paint shop building with utility trestle connections to the existing plants. Other building additions and modifications were a new enclosed test track building, new and renovated guardhouses, upgrades to the on-site wastewater treatment plant, fire tank, and pump house.

The site improvements included modifications and expansion of existing parking lots, truck docks, railyard areas, truck, and employee gate entrances, storage tanks, pump and water reuse systems, fire protection systems, sewer systems, security fencing, turnstiles, and gates, as well as stormwater management and landscaping improvements throughout the site. Additional off-site trailer marshaling lots and other finish vehicle parking lots are included in the design scope for a total area of approximately 180-acres.

PEA Group performed multiple geotechnical investigations totaling 1,900 linear feet of drilling and 20 pavement cores. Our team provided recommendations and analyses related to shallow and deep foundations, foundation settlement, earth retention walls, pavement design, and subgrade evaluations. PEA Group also provided construction materials testing services for the FCA Mack S8 parking lot, including subgrade evaluations, base aggregate density testing, and casting over 1,200 concrete cylinders.

To accommodate the stormwater volumes, PEA Group designed a stormwater basin in the adjacent neighborhood. The basin was purposefully designed as a stormwater management tool and a natural feature for the surrounding community. The new “stormwater park” is landscaped using native trees, shrubs, and perennials. The pond collects and treats an average of approximately 31 million gallons of rainfall per year and has a capacity of approximately 3 million gallons for any single rain event, storing the equivalent of a 100-year storm. The 34.15-acres are tributary to the pond, with 29.5-acres of pavement area used for finished vehicle parking and trailer marshaling. Other stormwater detentions and pre-treatment facilities are in place throughout the site to collect and treat the entire 116-acre Stellantis Mack site, which sees an average of 105 million gallons of stormwater per year.

Our team also assisted Stellantis and the City of Detroit in the development of a series of neighborhood vignettes that studied the visual impacts of the proposed facility on the existing neighborhood and made design recommendations to mitigate these impacts through landscape planting, art installation, and green stormwater features as public amenities.

Now operational, this plant breathes new life into the once fading Motor City. The focus of this new plant is not just to produce vehicles but to produce new opportunities in Detroit for years to come.

Project Type
  • 2021 CREW Impact Award: Renovation/Adaptive Reuse Category
  • 2021 Michigan Concrete Association’s Award of Excellence: Special Innovative Category
Rendering of Fiat Chrysler Automotive Mack Site