I-696 Slope Restoration Project (Erosion Control)

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What we are doing:

In the metropolitan Detroit Region, erosion on steep slopes adjacent to the interstate is a serious maintenance, safety and aesthetic issue. Currently, the standard treatment for covering slopes is seeding. While seeding can be a solution to some erosion problems, it is presenting many challenges as well. The goal of this project is to demonstrate an alternative to turf as a solution for slope stabilization. The American Recovery and Reinvestment Act (ARRA) gives us the opportunity to demonstrate and introduce these alternatives.

Project goals:

On I-696 between the interchanges of I-75 and I-94, the Michigan Department of Transportation (MDOT) is investing $9 million dollars in this slope restoration project in an effort to fulfill these main objectives:
  • Alleviate and reduce the safety and financial concerns associated with mowing steep slopes.
  • Decrease or eliminate environmental damage to Michigan waterways by covering the eroded slopes with vegetation that catches run-off and slows down water velocity.
  • Showcase alternative slope treatments that can be used in similar slope situations around the metro area.
  • Reduce maintenance costs associated with mowing, and redirect savings to address other important maintenance operations such as litter collection, weeding, and watering.
  • Find attractive alternative plants that will flourish in harsh urban conditions and will create interest and beauty for the traveler as well as the adjacent residents and businesses.

Environmental Benefits and Fun Facts:

  • 55,000 plants will be installed on this project. Laid end on end they would stretch 21 miles.
  • Largest plant installation MDOT has ever contracted.
  • Project is funded by the American Recovery and Reinvestment Act to bring economic relief the area.
  • When planted all the plants will remove 33 million pounds of carbon dioxide from the air over a 40 year period.
  • Through the use of shredded bark, this job recycled nearly 182,000 trees.

Frequently Asked Questions:


Why are we spending nine million dollars on landscaping?

At first glance, the project appears to be simple landscaping, but it is a horticultural solution to the complex legal and environmental problem of erosion on steep slopes throughout the metro Detroit area. The Michigan Department of Transportation is required to follow the laws set forth under Part 91, Soil Erosion and Sedimentation Control of the Natural Resources and Environmental Protection Act Public Acts 1994 PA 451, which protects soil and sediments from entering Michigan's waterways. If the MDOT doesn't comply with this law, stiff fines can be incurred on a daily basis until the sedimentation is contained. This project will correct current erosion problems with the following outcomes. 1) Avoid costly fines from the Michigan Department of Environmental Quality 2) Decrease mowing operations in order to improve safety for motorists and workers while eliminating damage caused by mowing. 3) Improve the appearance of the interstate for the traveling public through this important corridor. 4) Improve the air quality and protect the local waterways from sediment pollution.

Why are you using so many plants, wouldn't it be cheaper to plant turf grass seed or sod?

Turf grass has many drawbacks in stabilizing steep slopes. The root system of turf only extends 6 inches into the ground, when mowers drive over these shallow rooted plants, ruts are left in the soil, then rainwater washes the ruts out further and finally the washed out ruts spill gravel, dirt and debris down slope and into the storm drain, which ends up in our great lakes waterways.

Why is mowing dangerous on steep slopes?

In order to mow such extensive areas of turf, larger equipment is used. This large, cumbersome equipment is not agile and in some cases can flip and throw the operator down the slope and into oncoming traffic, seriously injuring or killing the operator and/or motorist.

How is the project going to eliminate erosion and preserve costly storm sewer infrastructure?

Compost is an organic soil that absorbs many times its weight in water, which is beneficial to catching fast moving rain droplets and drawing them deep into the soil. Plant foliage serves to catch and slow water droplets, minimizing the impact of water damage on exposed soil, which mediates slope damage in the form of rills, gulleys or ruts. Less water discharge means reduced storm sewer capacity, minimizing construction and maintenance of costly storm sewer infrastructure, and less sediment pollution ending up in our beautiful great lakes.

Why are we installing a barrier wall at the edge of the road shoulder?

The barrier wall offers protection to motorists and allows the slopes to be somewhat flattened, which helps to reduce the speed at which water flows down slope. At the top of the wall there will be a swale (depression to hold water) that will catch rain fall before it can spill over the wall, reducing the spread of gravel, dirt, and debris on the interstate and eventually into Lake St. Clair.

Will we be able to access the interstate and adjacent residential streets during construction?

Yes. On the interstate only one lane will be closed, in both directions, at any one particular time. A single lane will be open on the service drive at all times.

Will there be dirt during construction season?

When pneumatic compost is applied it is blown from a machine called an express blower, this can sometimes produce clouds of dust that travel, especially in dry, windy weather. Soil drifting should only be temporary and occur in less than ideal weather conditions.

What specific types of plants will be planted and why were they chosen?

Plants were chosen after careful research determined their hardiness to the Michigan climate and their ability to withstand drought, heat, and other adverse roadside conditions. See a complete list of plant names by genus and species.

What kind of economic benefit will this project provide to the community?

It is expected that this project will generate revenue in multiple industries, such as local and statewide plant nurseries, construction and engineering firms, and suppliers of concrete and associated building materials. It will also provide related construction jobs and an influx of business to local restaurants and shops along the corridor.

When will the project start and end?

The project is scheduled to start on April 1, 2010 continuing in phases until late Fall of 2012.

What areas of I-696 will be affected?

The project runs from I-75 to the I-94 interchange, approximately 9.18 miles east bound and west bound for a total cumulative length of 18.36 miles.

How many plants are you planning to install?

55,000 total trees, shrubs, perennials and vines.

How do shrubs, vines and deciduous and evergreen trees better stabilize the slope?

All of these types of plants have deep fibrous and woody root systems. A combination of plants with different types of root structures will securely hold the soil in place because the roots knit together to hold the subsoil. While you can't see this network of roots, it is of critical importance in stabilizing the soil and keeping it in place.

How long will it take for the plants to cover the slopes?

The design calls for plants to be placed at distances closer than what is typically used in a standard planting design. This closer spacing will help the plants establish faster by cooling the soil and the surrounding micro-climate. When combined with the fertile compost, it is expected that some of the smaller shrubs at the top of the wall will fill in relatively quickly and should be double their size in three to five seasons.

Will all those plants block my view of adjacent business signs?

No. The plants selected will only be within the MDOT's right-of-way (property) and because they are being planted on a steep slope the height of each plant is minimized from the service drive.

Will we have problems with rodents or other pests making their home on the slopes?

Rodents are attracted to food scraps and other organic matter. Since there will be a significant cost savings from reduced mowing, the department plans to redirect funds to trash removal on this section of freeway. That should reduce the food source and the likelihood of creating inviting habitat for nuisance animals. At this time the department is not anticipating using any type of poison to control animal populations.

Has this treatment been used or studied in any other regions of the country?

Yes. Many nationwide transportation departments use compost as an erosion control method and other states have installed vegetative cover. For example the Texas Department of Transportation and the Montana Department of Transportation studied the use of compost in wind-blow eroded slopes with great success. The Cornell University Horticulture department has studied different species of shrubs for the sole purposes of slope stabilization.

Who do I contact to report a problem on the construction site or for more information?

The Michigan Department of Transportation
Oakland Transportation Service Center,
800 Vanguard Drive, Pontiac, MI  48341
Phone: 248-451-0001.