# 7.5: First-Flush

36. Describe the purpose of the first-flush.

37. Use the exponential decay method to determine the optimal first-flush volume for a roof with a footprint of 1100 $$ft^2$$ in Columbia, Missouri and a λ of 0.8.

38. Use the area-based rule of thumb to determine the optimal first-flush volume for a roof with a footprint of 1100 $$ft^2$$ in Columbia, Missouri.

39. Describe an existing method, or create and describe your own method, to capture and evacuate the first-flush water. Draw and label your design.