Pre-bid/proposal meetings are held to interpret the technical and procurement aspects of the solicitation documents. This gives potential offerors a chance to voice their concerns. During a pre-bid/proposal meeting, these concerns are taken in consideration to help improve the solicitation documents. Pre-bid/proposal meetings are held with the hope to give offerors all the proper information needed to assist them with submitting a bid or proposal that responds to the requirements.
In construction there is a provision and a clause that would appear in the solicitation relative to the reviewing the site and hold an organized visit.
•52.236-3 -- Site Investigation and Conditions Affecting the Work
•52.236-27 -- Site Visit (Construction)
Neither of these two provides an option in the provision or clause’s wording to make it mandatory.
Additionally on can refer to GAO Decision B-220386, Jan 8, 1986, which states in part that “A firm's failure to attend a site visit is not a valid basis to reject an otherwise acceptable offer.”
The following text is extracted from the GAO Decision
“WE SEE NO REASONABLE BASIS ON WHICH THE NAVY COULD LIMIT THE PROCUREMENT TO THOSE FIRMS WHICH HAD ATTENDED THE INITIAL SITE VISIT, AS THE PROTESTER'S INTERPRETATION WOULD REQUIRE. IN ANY EVENT, A BIDDER'S FAILURE TO MAKE A SITE VISIT, EVEN WHERE THE SOLICITATION SO REQUIRES, IS NOT A VALID BASIS ON WHICH TO REJECT AN OTHERWISE RESPONSIVE BID. EDWARD KOCHARIAN & CO., INC., 58 COMP.GEN. 214 (1979), 79-1 CPD PARA. 20. ACCORDINGLY, EVEN ASSUMING THAT THE SOLICITATION CONTAINED A MANDATORY SITE INSPECTION PROVISION, A FIRM'S FAILURE TO ATTEND THE SITE VISIT WOULD NOT PROVIDE A BASIS ON WHICH TO REJECT ITS OFFER.”
While this case is older, it has been cited in many current cases and appears to be the standard. Based on these two findings, it would not be advisable to make a pre-proposal conference or site visit mandatory or make it a criteria for the basis of selection (RFP) or responsiveness (IFB).