It is often the case where we prepare or analyse a schedule without documenting the
basis for it. The Basis of Schedule (BOS) is an important document that is needed
as a reference to support the schedule, both during the actual presentation of the
schedule and for future reviews (especially helpful when the people originally involved
are no longer available or past history becomes hazy and the "amnesia syndrome" starts
to set in).
While a lot of the information making up the schedule itself is self evident with
no further need for clarification (for example the data showing relationships and
constraints) other information including critical information - which might be of
great significance, and may also change over time - may not. Adding notes to the
schedule, whether done via the scheduling software itself or spreadsheet, while helpful,
still cannot substitute the need to have a formal Basis of Schedule document.
So what exactly do we want to document in the Basis of Schedule? While the contents
should be tailored to the needs of the interested parties a basic Basis of Schedule
could cover the following:
- Schedule purpose. For whom is the schedule prepared for and end usage, who is the
client and listing of point of contacts for future reference.
- Project scope. Details of what the project entails, including project metrics where
relevant (such as size, volume, capacity, weight), purpose/ application of project,
location of project, etc. Also worthwhile mentioning the type of contract, weather
firm fixed price/ lump sum, fixed price/ unit price, cost reimbursable, or target.
- Period of Performance. What is the expected award date, project construction start,
- Critical Path. Narrative describing the schedule's critical path(s). In case of
a change order, for there to be an extension of time granted, it must be shown that
the change in scope of work impacts the critical path.
- Key Dates and Constraints. What are the key milestone dates and particular constraints,
for example we could have a large piece of equipment that must be ready for lift
in 48 weeks, and the super-sized crane availability window is from week 48 for 3
weeks, after which it will be demobilized to another project.
- Execution plan and resource usage. Brief summary of how the project is planned
to be executed with particular focus on factors affecting the schedule including
specifying workweek, resources and equipment availability and composition, use of
overtime or double shifts, etc.
- Schedule duration basis. How were activity durations estimated. What was the data
source (e.g. published productivity norms, proprietary normalized or historical project
- Risks and project unique factors. Summary of risks (schedule threats) with emphasis
on items affecting the schedule, as well as listing project unique factors such as
project location specific market and geographic conditions including site access,
labour availability, weather, time of year, previous experience with similar projects,
complexity of project.
-Contributors. Who was involved in the schedule development/ review and what roles
did they play and what data and assumptions did they contribute.