When must high soil compaction of 85% or greater be maintained?

Maintaining a high soil compaction of 85% or greater is essential to ensure the stability and protection of underground utilities, particularly when physical constraints prevent achieving the desired minimum cover depth. In the context of the question, the requirement for high compaction at a minimum cover of 30 inches highlights the importance of safeguarding infrastructure that may be susceptible to external loads or environmental factors.

When the minimum cover is lower than ideal, such as in situations where installation depth is limited, maintaining high soil compaction helps to mitigate risks like soil erosion or mechanical damage. Achieving a compaction level of 85% or greater in these scenarios ensures that the surrounding soil can adequately support the weight of overlying materials or loads and reduces the potential for settling or shifting that could compromise the integrity of the installed structures, such as conduits or buried cables.

This emphasis on compaction becomes increasingly crucial as the depth of cover decreases further, directly impacting the design and performance of outside plant systems. In contrast, there are higher cover depths beyond this threshold—like 36 inches—where the soil may not necessarily require as stringent compaction standards, allowing for more natural soil behaviors without significant risk to the installed systems.