Reducing excessive storm water flows
in an urban community
by Vicki Putala, P.E. and Elizabeth Clay
In 1835 Livonia Township, a predominately agricultural community comprised of dairy farms and fruit orchards, was established. The area grew slowly until after World War II when growth became rapid. In 1950 the community voted to become a city and today is a major urbanized area with population just over 100,000 people, making it the second largest city in Wayne County and the eighth largest in Michigan. 
Located in Southeast Michigan approximately 14 miles west of downtown Detroit, Livonia is a well-planned mix of residential, industrial, commercial and civic development.
Learning over time to protect the environment
The city developed its first storm water management plan in 1957. The city was growing, and emphasis was directed at preventing flooding and allowing for urban development. To accomplish this, an extensive storm sewer network was constructed to efficiently and effectively remove storm water from streets and neighborhoods and discharge it into the receiving open drainage courses. This was the common and accepted method for storm water management at that time.
In the 46 years since the city’s first storm water management plan, our society has become aware of the impact that storm water is having on our rivers, lakes, steams, plants and wildlife. We now realize that the previous mindset for storm water management, of quickly removing storm water from streets and neighborhoods, is causing excessive flows in streams and causing severe stream bank erosion in addition to increased sediment and pollutant loads.
Livonia has begun to work with other Rouge River Watershed communities as part of their NPDES Voluntary General Storm Water Permit, which was developed in response to concerns about non-point source pollution. During these meetings, the city and other participating communities began to understand the negative impact of excessive storm flows on the Rouge River and its tributaries. 
It is important that communities within the watershed work together because one community cannot on its own significantly reduce peak storm flows since much of the storm flows are a cumulative effect from upstream neighbors. However, these storm water management issues can be mitigated by a team approach. If each community does a small part, the overall benefit will be substantial and the water quality of the Rouge River will be greatly improved. 
To address stream bank erosion and other concerns, the city updated its Storm Water Management Plan (SMP) in 2002. This SMP focused on identifying the condition of the open drainage system with an emphasis on finding areas suitable for regional storm water detention. The SMP included an evaluation of stream bank erosion, which was found to be a significant problem throughout much of the city’s open drainage system. 
Caused by excessive flows, channel erosion can threaten homes and property, topple trees resulting in logjams, destroy fish and wildlife habitat and impair water quality. To prevent worsening of the current stream bank erosion, peak storm flows need to be reduced. It was determined that storm water storage would help alleviate this problem.
Addressing future  and current needs
In an effort to prevent additional runoff, Livonia has incorporated the Wayne County storm water ordinance for all new site developments. This ordinance requires storm water from all new developments to be restricted by the use of detention or retention basins to a maximum rate of 0.15 cfs/acre. The ordinance also requires a three-foot permanent pool of water in the basin for the removal of sediment and pollutants through settling and bacterial activity. In addition, a forebay is required as a method of pretreatment for sediment and pollutant removal and can enhance the effectiveness of the storage basin and reduce basin maintenance.
Because Livonia is already a developed city, using the Wayne County storm water ordinance for new developments helps prevent additional problems from excessive flows, but does not address the problems that exist from current runoff. The city must also create regional storm water storage to alleviate current flows. Regional storage basins are needed not only to reduce the excessive flows that cause erosion, but to provide much needed storm water treatment, which has great positive impacts further downstream. 
In Livonia’s SMP, 24 locations were investigated for the suitability of constructing a regional storm water storage basin. Of those locations, 14 appeared feasible. These sites were rated and prioritized based on a variety of factors including cost, potential for flow reduction, potential to minimize downstream erosion and site limitations.
Finding a cooperative solution
Recently, while reviewing site plans for a new residential development, Livonia recognized that the area of development bordered one of the locations identified in the SMP as being a feasible site to construct a regional storm water storage basin. The city took this opportunity to work cooperatively with the developer to create regional storage. 
Because the development has to incorporate the Wayne County storm water standards, storm water runoff from the site must be detained, and because a basin will already be built for the development, the city worked with the developer to expand this basin for the creation of regional storage. The project is significant in that it is the first time the city has had an opportunity to work cooperatively with a developer in creating a solution to a public storm water problem.
In assessing the possible storage the city could obtain by expanding the developer’s basin, it was found that large storms could not be retained at the site; however, smaller more frequent storms could be stored. These more frequent storms are often responsible for much of the stream bank erosion. Therefore, it is anticipated that constructing regional storage at this site will have beneficial impacts downstream.
The city will continue to use Wayne County detention standards for new developments and, when given the opportunity, Livonia will create regional storage using its SMP as a tool. Storm water management is most effective with a regional approach. If each community does a small part, the overall benefit will be substantial and the water quality of the Rouge River will greatly increase. Livonia’s efforts are one step towards success. 
Vicki Putala, P.E., and Elizabeth Clay are members of Orchard, Hiltz & McCliment’s Environmental and Water Resources Group. OHM is an Affiliate in the Michigan Municipal League’s Business Partnership Program. Vicki and Elizabeth can be contacted at 734-522-6711 or putala@ohm-eng.com and clay@ohm-eng.com respectively.
Captions
Example of stream bank erosion in the City of Livonia
Proposed site for regional storm water storage