Problem 1 A hotel project is to be developed in an open space of 1.477 acres in San Jose. After development, the project site will consist of building structure, driveway, parking area, walkway, landscape area, and open area. They are denoted by "DMA" and are described in the following table. The post-construction stormwater will be controlled by an infiltration basin located in the open area. Please determine the depth and surface area of the infiltration basin based on (1) the Urban Runoff Quality Management approach and (2) California Stormwater BMP approach. Please note: The required drawdown time for the infiltration basin is 48 hours. The in-situ infiltration rate is 2.1 in/hr for the project site. The mean annual precipitation at the project site is 14.4 inches. Required capture of stormwater runoff is 80%. Runoff coefficient is 0.90 for building structure, driveway, parking area, and walkway; and is 0.20 for landscape area and open space. Time to fill the infiltration basin is 2 hours. Post-development Characteristics of DMAS Sub-area Description Area (sq-ft) Impervious (%) DMA-1 Building Structure 12,494 100 DMA-2 Driveway 18,354 100 DMA-3 Parking Area 14,556 100 DMA-4 Walkway 3,047 100 DMA-5 Landscape Area 11,433 0 DMA-6 Open Space 4,454 0 Problem 1 A hotel project is to be developed in an open space of 1.477 acres in San Jose. After development, the project site will consist of building structure, driveway, parking area, walkway, landscape area, and open area. They are denoted by "DMA" and are described in the following table. The post-construction stormwater will be controlled by an infiltration basin located in the open area. Please determine the depth and surface area of the infiltration basin based on (1) the Urban Runoff Quality Management approach and (2) California Stormwater BMP approach. Please note: The required drawdown time for the infiltration basin is 48 hours. The in-situ infiltration rate is 2.1 in/hr for the project site. The mean annual precipitation at the project site is 14.4 inches. Required capture of stormwater runoff is 80%. Runoff coefficient is 0.90 for building structure, driveway, parking area, and walkway; and is 0.20 for landscape area and open space. Time to fill the infiltration basin is 2 hours. Post-development Characteristics of DMAS Sub-area Description Area (sq-ft) Impervious (%) DMA-1 Building Structure 12,494 100 DMA-2 Driveway 18,354 100 DMA-3 Parking Area 14,556 100 DMA-4 Walkway 3,047 100 DMA-5 Landscape Area 11,433 0 DMA-6 Open Space 4,454 0
