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Schedule Forensics Field guide

TDOT scheduling requirements: Standard Specifications 108.03 and the 100SS

The Tennessee Department of Transportation states its scheduling requirement at 108.03, "Prosecution of Construction", of the Standard Specifications for Road and Bridge Construction, 1 January 2021, in four lettered parts, A through D. Part D, "Schedule Revisions", applies across all of them.

The base book is not the current text. The Supplemental Specifications — 100SS, carrying revisions dated through 26 December 2024, amends 108.03 in four separate entries and adds two payment subsections that did not exist in the 2021 book. Two of those amendments change things a reader would otherwise get wrong: the duration bands that decide which tier applies, and how often the CPM schedule is updated. Where the two disagree, this page states both and marks which is the later instrument.

Three tiers, set by project duration

Tier Base book, 1 January 2021 100SS, revision 7 September 2021 What is required
Plan of operations Durations less than 90 days Durations less than 9 months A plan of operations showing sequence, location and the period for each item or group of like items, with manpower and equipment. The Engineer uses a straight-line plot to determine progress (108.03.A)
Baseline bar chart 90 days to 24 months 9 months to 24 months A baseline bar chart at the preconstruction meeting, hard copy and native electronic file, with a narrative (108.03.B)
CPM Greater than 24 months, or when required by contract Unchanged A full CPM execution schedule in Primavera P6 (108.03.C)

The heading change is the whole of the amendment for A and B: the 100SS entry dated 9 September 2021 revises those two headings and nothing else about them. A project of, say, six months falls in the bar-chart tier under the base book and in the plan-of-operations tier under the 100SS.

What 108.03 requires

Requirement What the text states Clause
Scheduling software Primavera Project Management (P6), named and mandatory, for the CPM tier. The bar-chart tier names no product but asks for the native file of whatever generated the chart, and for related reports — predecessor and successor, a sort by total float, a sort by early start — if scheduling software was used 108.03.C; 108.03.B.3
Submission format CPM: one hard copy and one electronic copy with every submission, including an .xer schedule file; Gantt charts as PDF fitted to 11x17, showing Activity ID, description, original duration, remaining duration, total float and calendar ID, in three cuts — the critical path sorted by early start, every activity still incomplete at the data date, sorted first by area then by early start, and a 60-day look-ahead sorted by early start 108.03.C.1
First submission An Initial Project Schedule within 30 calendar days after award, detailed as a baseline for all work contemplated in the first 120 calendar days after the Work Order, beginning at the award date and carrying enough of the rest to identify the critical path and all contractual milestones. It is reviewed at the preconstruction conference and must be accepted before work begins 108.03.C.2
Baseline deadline A draft baseline CPM schedule within 90 calendar days after the Effective Date, with a review meeting. Adjustments or additional information follow within 14 calendar days. Payments may be withheld, or limited to the value of materials under 109.08, until the Engineer accepts it 108.03.C.3
Update frequency Bar-chart tier: monthly, within 10 calendar days after the progress estimate pay period cut-off, with a cover letter, and submitted to the Engineer within 48 hours after the job site meeting. CPM tier: monthly in the base book; the 100SS entry of 1 June 2023 changes this to quarterly, and the entry of 26 December 2024 adds that if construction falls more than 3 months behind, updates go monthly at no additional cost until the project completes or the schedule is no longer 3 months behind 108.03.B; 108.03.C.4; 100SS
Narrative Required in both tiers. Bar-chart: quantities and estimated daily production rates for controlling activities, the calendar, planned crews, expected equipment and subcontractors, and anticipated adverse weather days per month. CPM: the sequencing approach with its assumptions and restrictions, a description of the critical path, a description of the near-critical paths, potential conflicts and mitigation, submittal approvals needed, the calendars, weather accommodation, and the execution plan including oversize and overweight transport permits 108.03.B; 108.03.C.1.c
Near critical, defined Activities not on the critical path with less than 20 days of total float 108.03.C.1.c.iii
Update narrative Adds sources of delay with a detailed history, corrective action and the adjustments made; work planned for the next period; pending change orders; and every change to the schedule, itemised — activities added, deleted or revised by change order, duration changes, relationship changes, and changes to the planned sequence or the method and manner of performance 108.03.C.4.d
Revised schedule trigger Where actual construction runs behind the plan of operations or the schedule by whichever is the smaller of 15% and 60 calendar days, a revised schedule showing timely completion goes in for approval. The Engineer may also request one; named circumstances include a delay of 15% or more to a milestone or completion date, a difference of 60 calendar days between actual sequence or duration and the schedule (the 100SS quantified this; the base book said only "a difference"), and a change order altering the planned sequence or method. Revised schedule due within 10 calendar days of the request 108.03.D; 100SS 1 June 2023
Time impact analysis Not named as a procedure in 108.03. No fragnet, windows or time impact analysis method appears in the subsection 108.03
Float ownership Float is held in common by the two parties, and each may draw on the whole of it until nothing is left. Float suppression techniques are then banned by name — see below 108.03.C.3
Activity durations No more than 20 workdays in either tier unless the Engineer allows otherwise 108.03.B.2; 108.03.C.3.c
Relationship logic Finish-to-start only, without leads or lags, unless otherwise approved. Out-of-sequence progress — activities posting progress without their predecessors complete — is not allowed without the Engineer's written approval 108.03.C.3.d; 108.03.C.4.b
Constraints The interim, milestone and project completion dates specified in the contract are the only contractual constraints permitted in the schedule logic 108.03.C.3.e
The schedule as a pay item The 100SS adds Item 108-03, CPM Project Schedule to the subletting item list (19 December 2022) and creates 108.11 and 108.12 to measure and pay it as a percentage of a lump sum bid, released against a table of milestones and completion percentages 100SS; 108.11, 108.12
Withholding Bar-chart tier: failure to update by the due date lets the Engineer withhold up to 10% of the monthly progress estimate. CPM tier under the 100SS: payment for the schedule item is withheld, plus up to an additional 10% of that month's estimate for a missing Initial Project Schedule or baseline, and up to an additional 5% for a missing quarterly update 108.03.B; 100SS 108.12

A logic ruleset stated as prohibitions

Three CPM requirements, read together, describe a narrow schedule. Relationships are finish-to-start, without leads or lags, unless the Engineer approves otherwise. The only contractual constraints allowed are the interim, milestone and completion dates the contract itself specifies. Out-of-sequence progress is not allowed without written approval — which is a different instrument from the usual one. Most specifications that address out-of-sequence work pick a calculation mode for it, retained logic or progress override, and let the software absorb it. Tennessee instead makes performing the work that way the thing requiring permission.

The float clause then carries its own list. After stating that float is shared and either party may use it until depleted, 108.03.C.3 names the techniques that may not be used to suppress it: preferential sequencing, which the text glosses as steering the critical path onto work more exposed to delay the Department would cause; lead and lag restraints used for that purpose; float constraints pinned at zero, whether total or free; activity times stretched beyond what the work needs; calendars manipulated; and constraint dates the contract does not call for.

Several of those are properties of an exported file and several are not. Whether a schedule carries zero-float constraints, lags, or relationship types other than finish-to-start is readable from the export. Why an activity was given the duration it has is not, and preferential sequencing is a claim about intent that no file records.

The schedule as a paid deliverable

The base book made the cost of preparing and updating the schedule incidental to all contract items in both tiers. The 100SS keeps that for the bar-chart tier and reverses it for CPM: Item 108-03 is a lump sum bid item, measured as a percentage of that lump sum and paid against a table.

The release table itself changed once. The version added 7 September 2021 keys releases to estimate numbers and to the percentage of the total contract amount on the previous estimate; the version substituted 1 June 2023 keys the first two releases to deliverables instead — 10% on the Initial Project Schedule and 40% on the baseline CPM schedule — then continues against contract percentage. So on a CPM-tier project the schedule has a line on the bid form and a payment curve of its own, and the withholding provisions bite there before they reach the monthly estimate.

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