HYDROLOGY
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SPADRA LAND DEVELOPMENT PROJECT
STORM DRAIN DESIGN
Our team established a new storm drain network within the proposed site. This network incorporates approximately 4500 L.F. of new storm drain main, 28 catch basins, and a system of curb & gutter including cross gutters that all drain into the San Jose Creek Channel.
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Per LA County standards and best practices, a 50-year storm and 24-hr design frequency was used to obtain an existing peak flow value of 56 cfs. After taking into consideration the proposed land use, the peak flow for our site increased to an estimated 141 cfs. This resulted in the use of a 24-inch main and laterals which were sized at 18 inches.
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Lastly, City of Pomona standards were used when placing the pipe. Our team incorporated a minimum 3-foot cover and 0.5% grade.
LOW IMPACT DEVELOPMENT (LID)
Due to the size and land use designation of the site, our team implemented Low Impact Development standards in order to adhere to Los Angeles County standards and promote a more sustainable design.
Under the advice of our industry advisor and Water Resources Professor Dr. Fairbank, the team utilized LA County HydroCalc to determine values for peak discharge and volume as previously mentioned.
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In order to produce a more accurate analysis, our water team divided the site into seven subwatersheds based off of land use and natural contours.
Using equations outlined within LA County LID Standards and the 85th percentile depth, our team identified the minimum volume of water required to treat for a project of our size and land use. This value being about 48,000 cubic feet.
ADS STORMTECH CHAMBERS
After identifying the volume of water necessary to treat, our team conducted research to identify a possible solution and select a system suitable for our water quality needs.
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We first assessed the feasibility of commonly used systems such as an infiltration trench and detention basin. However, considering the limitations of space on our site and after consulting with local jurisdictions, our team chose to incorporate ADS StormTech Chambers.
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These chambers essentially act as a retention system that filters water and initiates infiltration back into the ground.
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This system used the least amount of space in comparison to other alternatives and exceeded the required amount of water to be treated per LA County LID, at a capacity of over 50,000 cubic feet.