NASCLA Accredited Commercial General ContractorSite WorkMedium
A site superintendent is overseeing the final grading of a commercial parking lot. The design calls for a 2% slope for drainage. If the parking lot is 100 feet long in the direction of the slope, what is the total elevation change from one end to the other?
- A2 feet
- B2.5 feet
- C4 feet
- D1 foot
Show answer & explanationAnswer & explanation
Correct answer: A. 2 feet
A 2% slope means a 2-foot change in elevation for every 100 feet of horizontal distance. Therefore, for a 100-foot long parking lot with a 2% slope, the total elevation change is 2 feet. Calculation: (2/100) * 100 feet = 2 feet.
Why the other options are wrong
- B. 2.5 feet would be a 2.5% slope over 100 feet.
- C. 4 feet would be a 4% slope over 100 feet.
- D. 1 foot would be a 1% slope over 100 feet.
Slope Calculation (Percentage)
Slope percentage is calculated as (vertical rise / horizontal run) * 100%. To find elevation change, rearrange to: vertical rise = (slope % / 100) * horizontal run.
- Slope % = (Rise / Run) * 100%.
- Used for grading and drainage.
- Ensures proper water runoff.
Memory trick: Slope percent is rise over run, times one hundred, when the grading is done.