Definition - What does Grade Tolerance mean?
Grade tolerance can be defined as the maximum deviation or limits of variation that a drill or borehole can deviate without affecting the usefulness of the pipeline. Trenchless technology utilizes subsurface tunneling methods such as microtunneling, horizontal directional drilling (HDD) and pipe jacking. Some methods such as HDD are used to install pressure pipelines and do not require stringent grade tolerances though there is a limit to which the borehole can deviate.
Trenchlesspedia explains Grade Tolerance
Grade tolerance plays a very important role in gravity fed systems such as water and sewer pipelines. Deviation from line and grade can cause major problems in drainage leading to blockages and backflows. Microtunneling and pipe jacking have a good track record of staying within line and grade and are preferred methods where line and grade are of prime importance.
Keeping within line is also very important especially when pipelines have to pass through congested areas where there is a maze of pipelines and conduits.