Sounds like they'll be dozing down some hills/mountains or going under existing infrastructure in order to build the proposed alignments. Utility relocation, specifically gravity sewer, could also call for some very deep excavations.
It would seem that such a definition would not be rational, considering the many permutations of projects and conditions. Given that, I would consider, on any site, that if an excavation goes beyond the depth of adjacent foundations, and covers an area exceeding normal footing excavation, that the term could be applied.
Don't forget to consider that such excavations must include provisions for protection of adjacent structures.
mass excavation typically includes rough grading of the site. Often done with scrapers, graders, bulldozers - large equipment. structure or footing excavations, typically done with a bucket might not be included. for large buildings with basements, the basement excavation might be considered mass excavation. It would seem that there wouldn't be much need for mass excavation in a fully developed urban setting.
From a grading contractor's perspective there are two types of excavation: 'open' also called 'mass' excavation and 'trench' or 'pit' excavation. Trench excavation is typically defined as 10' wide or narrower. If it isn't trench excavation it's mass excavation.
But don't forget you might have "rock" excavation. As well, the "mass excavation" might contain boulders, or, if old fill, large concrete fragments - which might require other BOQ items. (Typically boulders/conc frags over 1m3 have a pay item).
