Which type of septic tank arrangement is permitted under the guidelines?

The choice of a single properly sized compartment aligns with the guidelines for septic tank arrangements, as it emphasizes the importance of design efficiency and proper waste management. A single compartment tank, when appropriately sized according to the expected load, can effectively treat and store wastewater, ensuring that the effluent is adequately processed before being released into the drain field.

This arrangement typically simplifies maintenance and management, as it provides a straightforward method for waste processing. Proper sizing is crucial to prevent overflows and promote effective decomposition of organic matter by anaerobic bacteria, which is essential for reducing environmental impacts and maintaining system functionality.

Other options present arrangements or conditions that either do not meet standard requirements or may introduce complications. For instance, two single-compartment tanks can lead to redundancy but may not optimize the treatment process as effectively as a properly sized single compartment. Tanks situated above ground do not inherently constitute acceptable design criteria and may pose risks if not designed to specific engineering and regulatory standards. Similarly, restricting tanks to only specific materials could limit options without enhancing the system's performance or safety.