Where is a curtain drain most effective?

A curtain drain is most effective when placed entirely around leaching trenches because its primary function is to intercept groundwater and redirect it away from sensitive areas such as septic systems or leaching fields. By placing a curtain drain around the perimeter of the leaching trenches, it prevents excess water from affecting the trenches, ensuring proper absorption and reducing the risk of saturation or failure of the leaching system.

This placement helps to keep the area around the trenches drier, allowing for better drainage and effectively prolonging the lifespan of the leaching system. Proper drainage is essential since high groundwater levels can lead to the leaching system becoming overwhelmed, which can cause untreated effluent to surface or migrate to potable water sources, presenting a public health concern.

The other choices do not offer the same level of effectiveness. For instance, placing a curtain drain in the center of a trench would not adequately manage water flow from the surrounding area, while positioning it at the base of a slope might only address some surface water issues without managing subsurface flow effectively. Similarly, having a curtain drain alongside a water body might help in some scenarios but does not provide the same protective advantage for leaching trenches as a complete perimeter installation.