Inver Grove Heights Becomes Model City for Stormwater Management
For 4 days in the summer of 2014, nearly 10” of rain fell in the Twin Cities metro area. Flooding was extensive and damage reached several hundred million dollars. This was not the case in the hydologically landlocked northwest area of Inver Grove Heights, MN. Not only did property flooding not occur there, but no stormwater runoff left the area. How is this possible in a
developing area? The answer lies in the city’s innovative, breakthrough approach to stormwater management.
During the intense building boom of the early 2000’s, development in the entire northwest area (3,000 acres) of Inver Grove Heights was hindered by the high costs of managing stormwater in a hydrologically landlocked area. Traditional planning called for 13 pump stations, a new 4-mile outlet to the Mississippi River, plus 24 miles of piping for a total capital cost of $26 million. Local firm, Emmons & Olivier Resources, Inc. (EOR) stepped in to help. EOR’s zero-discharge, Low Impact Development (LID) approach to this challenge involved no pumps, no river outlet, and only 3 miles of piping for a capital cost of $8 million, resulting in a savings of $18 million. Brett Emmons, principal at EOR and lead designer, explains, “Advantages to this approach included delaying build-out costs, more desirable neighborhoods, and better environmental outcomes. It was a truly win-win solution.”
EOR’s Enhanced LID approach is a paradigm shift away from traditional “pipe-and-pump” stormwater systems. The plan took advantage of the city’s existing features to mimick natural hydrology and maximize infiltration. The precedent-setting Argenta Hills commercial development provides evidence of the benefits of this new approach. This system features numerous innovative practices: raingardens, porous asphalt parking, pervious paver intersections, infiltration basins, and reuse. After several years in service, these stormwater
features are functioning very effectively and accomplishing the project’s zero runoff goals. Not only did the new approach reduce cost, it also helped to retain the site’s unique natural characteristics, and added amenities such as “green streets” and unique urban open space.
In the past many engineers argued that LID approaches were not effective on a large scale or for flood control, but this project, with the high bar of meeting zero runoff, solidly proves otherwise. In 2015 the American Council of Engineering Companies (ACEC) took notice and awarded this project their National Grand Award. This prestigious honor calls attention to the stormwater management ingenuity and creative engineering that went into this project and shows that Inver Grove Heights will serve as a model for expanding this approach to other cities across the United States in the years to come. EOR’s CEO Brett Emmons presented the award to the Inver Grove Heights City Council on June 22, 2015 at their 7:00 pm meeting at the Inver Grove Heights City Hall.