Fairchild Challenge 2 Math 2018-2019

Math required to calculate amount of precipitation.

  1. The surface areas of different sections of the school were calculated by breaking the school up into simple shapes. Using elementary geometry, we found the surface area of:
  • The school’s grass surface area = 18,225 ft.^2
  • The school’s main lot surface area = 9,000 ft.^2
  • The school’s moat surface area = 3,825 ft.^2
  • The school’s student lot surface area = 11,250 ft.^2
  • The school’s roof surface area = 36,225 ft.^2

2. Using the surface area and the annual precipitation of our area this year so far (4.4 ft.), we multiplied the two values together to find the amount of rain that falls onto our school.

  • The school’s amount of rainfall in the grass area= 80,190 ft.^3 (This value is not counted in our runoff calculations due to the initial grass area’s 100 % permeability)
  • The school’s amount of rainfall in the main lot = 39,600 ft.^3
  • The school’s amount of rainfall in the moat = 16,830 ft.^3
  • The school’s amount of rainfall on the student lot = 49,500 ft.^3
  • The school’s amount of rainfall on the roof = 159,390 ft.^3

3. All of these calculations are before our team devised a runoff reduction plan. The only rainfall that was being absorbed into the ground was the rain that fell onto the grass area. Westinghouse Arts Academy’s majority ground makeup is concrete, so the main lot, moat, student lot, and roof are all impervious. The cubic feet of water that currently run off into the Turtle Creek Watershed, not calculating the grass area due to it’s 100% starting permeability, would be 265,320 ft.^3 * 7.48 gallons per cubic foot of water = 1.984 million gallons of stormwater runoff currently being released directly into the Turtle Creek Watershed.

4. Understanding our current problem, our team decided to implement green stormwater solutions:

  • The student lot and moat will be rebuilt using permeable pavers. This material is excellent for reducing runoff because it is 100% permeable, like grass.
  • The team decided to create a living roof for our large flat roof using the extensive technique comprised of 3 to 4 inches of sedum. The plants and soil added to the roof would decrease the roof’s annual surface runoff by 55% without the weight load created by an intensive rooftop garden.
  • The majority of the additional runoff would be collected in 100 gallon rain barrels connected to the downspouts in the front and back of the school. We would empty these rain barrels every two weeks.
  • The school’s main lot will not be transformed into permeable pavement because it was recently finished. Instead, our team would like to include a rain garden in the grass area to account for the extra runoff from the main parking lot. This rain garden would include a Beehive Rim with a drain rock. This rain garden would absorb 100% of the main lot’s surface runoff.

5. Next, we had to calculate the amount of rainfall that was absorbed after our stormwater solutions were implemented.

  • The school’s amount of rainfall in the main lot = 39,600 ft.^3 * 1.00 = 39,600 ft.^3 of rainwater would be collected because the rain garden would account for 100% of the main lot’s runoff.
  • The school’s amount of rainfall in the moat = 16,830 ft.^3 * 1.00 = 16,830ft.^3 of rainwater would be collected by the moats permeable pavement.
  • The school’s amount of rainfall on the student lot = 49,500 ft.^3 of rainwater would be collected by the student lot’s permeable pavement.
  • The school’s amount of rainfall on the roof = 159,390 ft.^3 * .55 = 87,665ft.^3 of rainwater would be collected by the living roof.
  • 2,085 ft^3 of rainwater would be collected by rain barrels located by the roof because the roof would have additional runoff of 159,390ft.^3 – 87,995ft.^3= 71,395ft.^3 of rain not collected by the roof. After the rain barrels, 69,310ft.^3 of rainwater would run off into the Turtle Creek Watershed. 69,310ft.^3 * 7.48 gallons per cubic foot of water = 518,438 gallons of water that runoff into the Turtle Creek watershed.

6. Lastly, we had to calculate the percentage of water that was not running in the Turtle Creek after our stormwater solutions.

  • The amount of water running into Turtle Creek Watershed before our stormwater solutions = 1.984 million gallons of water.
  • The amount of water running into Turtle Creek Watershed after our stormwater solutions = 518,438 gallons of water.