What should the installer do if a boulder is encountered at the elevation where the tank will be placed?

• A. Remove the boulder
• B. Ignore and proceed
• C. Increase tank size
• D. Place the tank elsewhere

Answer: (A)

When placing a septic tank, it must sit on a flat, solid, well-prepared base. A boulder at the planned elevation would prevent full contact with the soil and keeping the base level, which can cause uneven support, gaps, and settlement. That kind of instability can stress the tank, crack joints, or lead to leaks once backfilled. The proper action is to remove the boulder so the tank can rest on a smooth, level surface and be correctly bedded and backfilled. If moving the rock isn’t possible, you’d have to reconsider the site or installation plan, but removing the obstruction is the standard approach.