What term describes the rate of fall or rise of a pipeline or ground surface in reference to the horizontal plane?

The term that describes the rate of fall or rise of a pipeline or ground surface in reference to the horizontal plane is known as slope or grade. This concept is critical in various construction and engineering applications, including the installation of septic systems. A properly calculated slope ensures adequate drainage and prevents issues like flooding or stagnation of wastewater, which could lead to system failure and environmental hazards.

Understanding the slope is essential for determining how waste will move through pipes and how water will flow across ground surfaces. If the slope is too steep, it can cause excessive velocity leading to erosion. Conversely, if the slope is too gentle, it can lead to blockages and insufficient drainage. Therefore, maintaining the correct slope is vital to the functionality and longevity of a septic system.

The other terms presented, such as soil map, soil evaluation, and soil absorption rate, relate to aspects of soil understanding and analysis but do not specifically define the gradient or angle of a surface in a drainage context. Soil maps represent the types of soil in an area, soil evaluation assesses soil quality and suitability, while the soil absorption rate indicates how quickly water is absorbed. These elements are important in the overall assessment and design of a septic system but do not pertain directly to the concept of slope