Which type of sewage tank can be buried at the shallowest depth?

The correct choice is plastic, as it is generally more lightweight than other materials such as concrete, fiberglass, or steel. This reduced weight allows for a safer installation process, particularly in shallow depths where stability and support are critical. Plastic tanks are typically resistant to corrosion and do not require as much structural support compared to concrete, which can be heavy and potentially shift if not properly installed or supported. Additionally, due to their design and material properties, plastic tanks can accommodate the necessary drainage and functionality while being installed at shallower depths without compromising their integrity. This makes plastic an ideal choice where a sewer tank needs to be buried at minimal depths.