CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A C-27 contractor is supervising the final grading of a residential backyard. The design calls for a minimum 2% slope away from the building foundation for the first 10 feet. If the finished grade at the foundation is 100.00 feet, what should be the minimum elevation of the finished grade at 10 feet away from the foundation?
- A100.20 feet
- B102.00 feet
- C99.80 feet
- D100.10 feet
Show answer & explanationAnswer & explanation
Correct answer: A. 100.20 feet
A 2% slope means a 2-foot change in elevation for every 100 feet of horizontal distance. For 10 feet of horizontal distance, the change in elevation (rise) is (2/100) * 10 feet = 0.20 feet. Since the slope is away from the foundation, the elevation should increase. Therefore, 100.00 feet + 0.20 feet = 100.20 feet.
Why the other options are wrong
- B. This would be a 20% slope (2 feet over 10 feet), which is much steeper than the required 2%.
- C. This would be a 2% slope *towards* the foundation, which is incorrect for drainage.
- D. This represents a 1% slope (0.10 feet over 10 feet), which does not meet the minimum 2% requirement.
Slope Calculation (Percent)
Calculating elevation change based on percentage slope and horizontal distance. Percent slope = (Rise / Run) * 100.
- Percent slope is rise over run times 100.
- A 2% slope means 2 units of rise for 100 units of run.
- Slope away from foundation means elevation increases.
Memory trick: RISE over RUN, then times a HUNDRED for percent.