Not Your Typical SWPPP Story

CityPlace site following a major rain event

Implementing an effective Stormwater Pollution Prevention Plan, or SWPPP, is an important part of construction-site planning. Woodbury’s 100-acre mixed-use CityPlace development offers a distinctive example of how a project team managed stormwater, erosion control and significant rain events.

What Is a SWPPP?

A SWPPP is designed to prevent construction-site stormwater runoff from entering local lakes, ponds and wetlands. Runoff can carry sediment and pollutants from a site into clean water, potentially harming surrounding areas.

The Minnesota Pollution Control Agency oversees construction stormwater permitting in Minnesota. Owners and builders must inspect sites throughout a project and after major rain events. The plan also identifies how the project team will prevent polluted stormwater runoff from reaching nearby waters.

CityPlace’s Challenges

To better understand the CityPlace SWPPP, the team spoke with Kraus-Anderson Project Manager Bob Janssen, who had extensive experience working with the Minnesota Pollution Control Agency and on SWPPP projects.

Some of the project’s largest challenges included:

  • Grading.
  • The site’s topography, including hills, fills and cuts of up to 30 feet.
  • Managing a large volume of water.
  • Responding to significant rainfall.

Hydromulch used for erosion control at CityPlace

The first challenge was the scale of the site. Planning, grading and managing 100 acres was a complex undertaking. To improve cost management and constructability, the full site was graded at one time.

During rain events, all water had to remain on-site, creating a considerable volume to manage.

“When assembling the SWPPP, you need to plan and prepare for these kinds of challenges and make sure drainage is always going toward the interior of the site and to the site’s pond system,” Janssen said.

The site experienced significant rain in 2015 and 2016, including two 50-year rain events in 2015.* SWPPPs typically prepare for smaller, more frequent rain events, so these storms required quick thinking and proactive planning from the team on several occasions.

Janssen said the best response to a large rain event was to “have a plan before contacting the MPCA.” This approach allowed the team to communicate its response plan and explain how it would address the situation.

Why Was CityPlace Successful?

The project introduced several innovative approaches. By applying different best management practices, or BMPs, the SWPPP team tested methods and management practices suited to the site’s conditions.

  • Hydromulch.
  • Erosion-control blanket.
  • Biologs.
  • Collaboration.
  • Ongoing documentation and communication.

Silt fence retaining stormwater on-site at CityPlace

One of the most important BMPs was collaboration. The project was among the first to develop its own inspection checklist through iAuditor, an inspection-management tool.

Janssen’s team found that building trust and communicating with project partners, including the City of Woodbury, Kraus-Anderson Development, Elion Partners, Westwood and Frattalone, supported stronger project outcomes.

“Many people are scared of the MPCA,” Janssen said. “The way that we see it is that sending reports to them gives them a sense of our transparency. This lets them know that we’re not hiding anything and confirms that we are doing what is needed.”

Janssen’s team documented conditions weekly and sent reports to the city and the Minnesota Pollution Control Agency.

The CityPlace team demonstrated practices that could support higher-quality, more cost-effective SWPPPs. Janssen emphasized that SWPPPs are living documents, intended to change and adapt as site conditions require.

Learn more about Kraus-Anderson’s sustainability services and broader commercial construction experience.

Here is a short video showing the CityPlace site and how the team kept a large volume of water contained on-site.

*A 50-year rain event is a storm of a magnitude statistically expected to occur, on average, once every 50 years.

CATEGORY: Construction