2013 Issue

75 • Are bioretention cells able to reduce nutrient transport and stormwater runoff to traditional infrastructure in semiarid climates? • What are the infiltration rates through the bioretention cell and into the natural sub-soils? • What is the impact of the infiltration on potential groundwater recharge? • What is the impact of vegetation configuration on biodiversity, or the richness of the macro invertebrate environment? Two retention facilities at the low side of the park have been constructed with two feet of permeable material overlain by top soil and plants that are native to the Wasatch Front (Figure 2). The material shown in this diagram is Utelite, but the actual applica- tion used regular angular gravel as commonly found at a gravel pit along the Wasatch Front. It was important to test conditions that are easy and economical to replicate on other projects so that the methods and practices are sustainable. The retention facilities are shown as Cell #1 and Cell #2 in Figure 1. An array of shallow monitoringwells is equippedwith soil moisture sensors tomeasure the infiltration rates and perform water quality testing. Bioretention facilities provide the benefit of decentralizing the management of stormwater but have the added risk of variable infiltration rates. How sustainable are infiltration rates over time, especially as oils, grease and sediment build up? Can the plants absorb and treat these pollutants? It is anticipated that we might know the answer to some of these questions sometime in 2013. The results of the study will be released to Cottonwood Heights and will also be featured in a series of courses at the University of Utah. The project will be presented as an example in the State of UtahNonpoint Source Stormwater Management Plan, and courses in conjunction with the American Water Resources Association (AWRA) and the Utah Rivers Council will address design, plant selection and the environmental benefits of bioretention in Utah. It’s ironic that as park patrons enjoy Cottonwood Heights’ first large park since the city incorporated seven years ago, few people stop and consider the fact that the macro invertebrate ecology of the Jordan River may be benefiting from all the excitement. The results of this study by the Urban Water Research Group may pave the way to widespread implementation of bioretention facilities throughout the state. As a city engineer, the greatest concern is impact to the groundwater. If the native plants and shallow soils can treat the pollutants before the water has a chance to percolate, we will have a very effective tool to manage stormwater and reduce downstream impact, both quantitatively and qualitatively. It carries the potential to change the approach and look of landuse planning by departing from the traditional project based approach to an on-site program based approach, where maintenance of the retention areas is key to the long term benefit of our water quality. We have come a long way with pol- lution prevention in our Country. In time, it is likely that this will just become part of what we will do, like our attitudes toward litter control from the last half century. So the next time you enjoy a sunny day observing the children’s art at Mountview Park or take shade under a well-engineered pavilion as children run through the splash pad, remember that the water quality of theGreat Salt Lakemay benefit from the retention facility at this park every time it rains. It is our hope that through this park project we can better understand how to engineer economical ways to reduce pollution so that someday we can recreate freely in the pristine waters of the Jordan River! References 1. Houdeshel, C.D., Pomeroy, C.A., Hair, L., Moeller, J. (2011). Cost Estimating Tools for Low-Impact Development Best Management Practices: Challenges, Limitations and Implications. Journal of Irrigation and Drainage. 2. Low Impact Development Center (2009). RainGarden Design Templates. RetrievedOcto- ber, 2011 from: http://www.lowimpactdevelopment.org/raingarden_design/index.htm. 3. National Research Council (NRC) Committee on Reducing Stormwater Discharge Con- tributions to Water Pollution. (2008). Reducing Urban Stormwater Management in the United States. The National Academies Press. Washington, DC. 4. Prince George’s County, Maryland PGCo. 2001. The Bioretention Manual, Dept. of Environmental Resources, Prince George’s County, Md. 5. U.S. EPA (2006). Bioretention (Rain Gardens) Information Sheet. Accessed October 2011 from: http://www.epa.gov/npdes/pubs/gi_action_strategy.pdf 6. U.S. EPA (2009). Federal Stormwater Management Requirements. Accessed June 2011 from: http://www.epa.gov/greeningepa/stormwater/requirements.htm 7. U.S. EPA (2010). Green Infrastructure in Arid and Semiarid Climates. Accessed September, 2011 from: http://www.epa.gov/npdes/pubs/arid_climates_casestudy.pdf. Tile Art Depicting a Water Theme by 4th Grade Students in Cottonwood Heights