Definition
An alternate bid is a price quoted separately from the base bid for a clearly defined unit of scope — either work added on top of the base (an add-alternate) or work removed from it (a deduct-alternate). The bidding documents name each alternate and describe exactly what it covers, and every bidder prices it on the same line, so the option can be accepted or rejected at award without re-bidding the job. The purpose is flexibility: the base bid covers the must-have scope, and the alternates let the owner trim or extend the work to fit the money actually available.
For a heavy-civil GC reading the sub bids it receives, an alternate is not a discount or a negotiation. It is a discrete, pre-priced scope decision that travels with the bid. The effective contract value depends on which alternates you choose to accept, so the same set of sub bids can produce several different award totals.
A worked example
You receive bids on a paving package. A sub's base bid is $1,200,000 for the required structural section and a single binder lift. Listed below it is an add-alternate of $140,000 for a second asphalt wearing lift across the same area — an upgrade the owner wants but has not funded. If the budget closes with room to spare, you accept the alternate and the award is $1,340,000; if money is tight, you award the base bid at $1,200,000 and the second lift drops out. The alternate gives the owner that lever without forcing a re-bid, and it tells you up front what the upgrade actually costs from this sub rather than as a later change order.
Why it matters when you evaluate sub bids
Alternates are where naive comparison breaks. If one sub folds the second lift into its base bid and another carries it as a $140k add-alternate, the cover-sheet totals are not measuring the same scope — the apparent low bid may simply have excluded the alternate work. To compare the field apples-to-apples, you have to level base against base and alternate against alternate, then re-rank under each award scenario you might actually choose. A sub that is low on the base can lose once the alternate you intend to accept is priced in, so the alternate prices belong in the ranking, not in a footnote.
How Bid Reasoner handles it
Bid Reasoner reads each sub bid and, for bids submitted through the bidder portal, records the base bid and the sub's stated alternates in separate fields, so an add- or deduct-alternate is harder to bury in a base total. Its two-way scope-coverage gap analysis catches the case where one sub priced the second lift as an alternate and another excluded it entirely, listing the missing item by pay-item code when your scope of work carries the second lift as a coded item. You can then re-run the analysis under any of the 7 decision modes — including Budget-Constrained — across all 6 dimensions, so price, scope, and schedule are weighed the way this award needs. The deterministic pricing rules still run on an alternate priced as a line item: a unit price at or under $1.00 is flagged, and so is one at 2x or more, or 0.5x or less, of the median for that pay item when three or more bids price it.