1. Retaining walls are not considered when the groundwater level is low, the soil quality is good or the septic tank volume is small. There is no retaining wall on your construction drawing, which may be the reason mentioned above.

By the way, if the septic tank adopts the standard drawing, it may be that the designer did not consider the need to make a retaining wall. Because water supply and drainage majors sometimes pay little attention to geological data.

2. It depends on whether the construction scheme or construction organization design has engineering contents, and whether the construction scheme or construction organization design is approved by the construction unit. If the foregoing contents of this article are not available, the retaining wall shall not be considered. If the retaining wall is considered in the construction plan and approved by the construction unit, it can be considered, but there must be specific measures in the plan, otherwise the engineering quantity cannot be calculated.

3. Without accurate geological data, the designers of construction drawings and construction schemes did not consider this aspect.

Specific to your question, if there is no such content in the drawings or construction plan, at least in the construction budget stage, retaining walls do not need to be considered. Even if it meets the conditions mentioned in Article 3, it is also a visa claim after construction.