During site evaluation, you must determine whether the high groundwater table is within what distance from the bottom of the proposed trenches?

During site evaluation, you must determine whether the high groundwater table is within what distance from the bottom of the proposed trenches?

• A. Sixty centimeters
• B. Ninety centimeters
• C. One hundred twenty centimeters
• D. Fifty centimeters

Answer: (B)

A safe vertical separation between the bottom of the trenches and the high groundwater is needed so wastewater has a chance to be treated by the soil before it could reach groundwater. The standard distance used in site evaluations is ninety centimeters. You determine this by checking whether the highest groundwater level is within that distance of the trench bottom. If the groundwater is within 0.9 meters, the usual trench design isn’t viable and you’d need to adjust the system or pursue an alternative over time and soil conditions. If the groundwater is deeper than that, the separation is considered adequate. The other distances aren’t the threshold you’re using here; being closer than ninety centimeters is not acceptable under typical guidance, while being farther than that meets the minimum requirement.

A safe vertical separation between the bottom of the trenches and the high groundwater is needed so wastewater has a chance to be treated by the soil before it could reach groundwater. The standard distance used in site evaluations is ninety centimeters. You determine this by checking whether the highest groundwater level is within that distance of the trench bottom. If the groundwater is within 0.9 meters, the usual trench design isn’t viable and you’d need to adjust the system or pursue an alternative over time and soil conditions. If the groundwater is deeper than that, the separation is considered adequate.

The other distances aren’t the threshold you’re using here; being closer than ninety centimeters is not acceptable under typical guidance, while being farther than that meets the minimum requirement.