Which of the following bid documents contains additional or supplemental information to the design documents?

The bid document that contains additional or supplemental information to the design documents is indeed the addendum. An addendum is used to modify and clarify the original bid documents that have already been issued. It may include changes in the specifications, adjustments to project schedules, or further instructions that provide essential information to potential bidders.

This supplemental information ensures that all bidders have the same understanding of the project requirements, avoids misunderstandings, and prevents misinterpretation which could lead to discrepancies in bids. Addenda are issued before the bid opening date and are typically numbered for easy reference, allowing for organized updates and changes to the bid documents.

In contrast, the other choices serve different purposes. Instructions to bidders provide guidance on how to prepare and submit a bid, but do not supplement design documents directly. Alternates are options included in a bid to allow for variations in scope or price but do not qualify as supplemental information to existing documents. General conditions lay out the contractual obligations and responsibilities of all parties involved, which are vital but not considered additional information related specifically to the design documents.