Addressing Environmental Issues Is A Large Part
Of The I-494 Project

Granite McCrossan, Mn/DOT's contractor for the I-494 design build project, has given a great deal of consideration to environmental issues during both the design and construction phases. There are a number of environmental protection activities and requirements on a design-build project such as this that Granite McCrossan must follow. Project operations have to comply with local, state, and federal environmental statutes, which in addition to generating lots of paperwork, typically include:

• The Clean Water Act, which requires a Storm Water Pollution Prevention Plan (SWPPP), and a Spill Prevention Control and Countermeasures (SPCC) Plan.
• The Clean Air Act, which requires the control of dust and permitting of facilities likely to cause dust, such as crushers, hot asphalt plants, or concrete batch plants.
• Local noise ordinances, which control the time, duration, and level of noise-generating activities.
• State, federal, and local waste disposal ordinances, which control the removal and disposal of asphaltic materials, concrete rubble, and/or hazardous and non-hazardous wastes.
• A General Permit to Discharge Storm Water Associated with Construction Activity under the NPDES/SDS permit program. This would include a SWPPP and provisions to control sediment-laden runoff.

Granite McCrossan’s construction site pollution control efforts will primarily be aimed at controlling dust, runoff, minimizing erosion and managing sediments. Sedimentation has the greatest potential for harming water quality so controlling and preventing it will be a top priority. Conducting construction operations with this approach and concern for the impact on the environment will help avoid problems before they occur.

Chopped straw helps prevent runoff near Excelsior Boulevard

A large amount of earthwork is required on any major construction project like this, and that means lots of ground cover, including grass, plants and bushes, must be removed. On the more level areas of the project, loose exposed soil is covered with a layer of chopped straw, which reduces dust and erosion caused by rain and wind.

Perhaps the most noticeable sign of our efforts to control runoff and erosion is in the green tint you can see on excavated slopes along the side of the freeway and in the median. It’s a material known as hydromulch. A mixture of grass seed, fertilizer, and wood fiber mulch (shredded wood fibers dyed green), it’s combined with water to form a slurry, which is then sprayed on the excavated areas, holding the loose dirt in place. The green tint is a biodegradable dye that helps keep track of where the hydromulch has been sprayed. Once the grass seed begins to sprout it naturally helps to prevent erosion by sending out roots and stabilizing the soil.

Hydromulch sprayed on hillsides holds loose soil in place