Storm Water Quality Innovations
Annie Johnston, Julia Ashton, Nicole Carter
The Clean Water Act and regulations promulgated there under require Total Maximum Daily Loads (TMDLs) be developed for impaired water bodies on state’s 303(d) list. Lake Thunderbird is on the list of Oklahoma’s 2008 303(d) list of impaired beneficial uses of water supply for public and private use. The Department of Environmental Quality (DEQ) manages the TMDL program for the State of Oklahoma. Lake Thunderbird has load allocations to reduce turbidity and chlorophyll-a levels while maintaining sufficient oxygen levels in the lake to attain water quality targets to restore impaired beneficial uses and protect public health. DEQ is looking to reduce turbidity, nutrients, and bacteria in storm water discharge by installing an easy to maintain system in storm drain inlets in order to maintain these load allocations. As a group we will design this inlet system for residential areas throughout the watershed. Refer to Figure 1 below for the DEQ-TMDLs for Lake Thunderbird.
The DEQ has assigned us with the task of filtering storm water in order to meet the TMDLs allocated for Lake Thunderbird. Right now the nutrients, bacteria and turbidity levels are too high. The target nutrients is nitrogen and phosphorus, and the target bacteria are E-coli and chlorophyll-a. In order to reduce these levels, Storm Water Quality Innovations, is focusing on the curbside inlet to filter and settle out these pollutants. DEQ has some additional requirements for this project. The final product should be cost effective, meaning that it needs to compete with other products that are on the market. The design should limit the chance of flooding if the design fails. The design should also be able to be cleaned by a street sweeper during their regular street cleanings. Our design includes pervious pavement leading up to the curb inlet and a flow through chamber sack with filtration media and gravel placed inside. Tests are to be done to maximize the efficiency of the final product. At the end of the Fall and Spring semester, this design will be presented along with other alternatives.
Scope of Work
The focused design consist of: 1. A strip of pervious pavement on either side of the grate leading up to a flow through chamber sack placed inside the curb inlet that holds filtration media and gravel. 2. A similar design with rumble strips, similar to what is on the shoulder of highways, on either side of the grates leading up to the flow through chamber as stated above. 3. A flow through chamber as described above. Pervious pavement has pores that will capture the sediment in the storm water as the water goes to the curb inlet. In order to make the design meet specifications and to maximize the efficiency, many tests will be performed. Once the filtration media is chosen and the flow through chamber is constructed, they will be tested along with the pavements. The water will run over the pavement into the chamber and collected as it flows through the media. In the sack inlet the size of the gravel is going to be varied from pea gravel to river rock to determine the best combination with the various filtration media. Once all tests are complete we will determine the best combination of gravel with media, the best mixture of pervious pavement, and the sediment, nutrient, and bacteria removal rates from our design.