CSI’s project delivery and ethical guidance (as reflected in CDT materials and standard practice) emphasize:

Known information that may affect cost, risk, or safety must be disclosed consistently and fairly to all bidders.

The design professional must act in a manner that is honest, transparent, and protective of public safety, even when data is incomplete.

The bid documents should not conceal information that could materially affect the work, even if its full extent is uncertain.

Applying those principles:

The design team has evidence (one contaminated boring) that contamination may exist onsite. Even if the extent is unknown, that fact is potentially material to bidders (cost of remediation, handling of contaminated soils, schedule impacts).

The best course is to disclose what is known and ensure all bidders have access to the same geotechnical information. This is exactly what Option B proposes:

Place a clear note or disclaimer in the contract documents stating that contaminants were encountered in at least one boring and may be present elsewhere.

Recommend that the owner make the geotechnical report available to all bidders, so every bidder can evaluate the risk and price accordingly.

Why the other options are inconsistent with CSI-aligned practice:

A. Withhold the information… – Concealing known contamination is unethical and undermines fair bidding. Even with unit prices for remediation, bidders would be pricing blindly without knowing that contamination has already been detected.

C. Insist the owner undertake additional investigation… – While the design team should recommend further investigation, it cannot “insist” beyond professional advice, especially where the owner has clearly stated financial constraints. Regardless, disclosure of existing data is still required.

D. Proceed with design as is… – Ignoring known contamination and calling it “statistically insignificant” is not defensible; even one contaminated boring is important information that must be shared.

So, the most appropriate and CSI-consistent choice is Option B: disclose the potential and share the geotechnical report so all bidders are equally informed.

CSI references (by name only, no links):

CSI Project Delivery Practice Guide – sections on procurement, fair competition, and disclosure of information

CDT ethics and professional conduct principles regarding risk disclosure to bidders