Yes, a project team may earn the credit even when remediation is not complete provided there is an approved ongoing remediation plan in place and the applicable regulatory authority has approved the site for its intended use.
Brownfield requirements are determined at the federal, state, or local level and vary from one jurisdiction to another. For LEED, there are no minimum thresholds (volume or area) required to meet this credit as long as the site—or a portion of it—is classified as a brownfield.
No. If the remediation occurred prior to when the property was purchased, you are no longer developing a contaminated site. SSc3 addresses sites that are subject to corrective action; it doesn't address the past history of the site.
Yes, an environmental professional will need to verify that contamination is located on the site using the specified standards for testing and verification. This helps identify the scope of contamination and thus the scope of remediation that will be required.
Given the effort, expense, and risk involved in many brownfield projects, one LEED point is probably not a worthy reward. It would probably be more useful to think of this credit as a token, and to acknowledge that developers aren't likely to choose a brownfield site to earn this point. There is a silver lining, however, in that urban infill sites, which are often brownfields, are typically well-rewarded in LEED's density-related credits.
USGBC has not identified specific standards for judging this, or defined certain codes as compliant with the credit, or not. The stringency of other codes relative to EPA's Construction General Permit is judged on a case-by-case basis.
As long as the project has been actively implementing an ESC plan during the current development of the project site, you should be okay. If that's not the case, then the outcome will depend on project specifics, and you will likely need official guidance from GBCI.
Ideally, use your cameras to imprint a visible date on a corner of the image. Most cameras offer this option. Digital files also typically encode a date when the file was created, or encode that date in the file name, and while these methods aren't ideal, some project teams have reported success submitting this type of documentation.
This prerequisite offers several options for documentation, including date-stamped photographs, a narrative describing the ESC plan implementation, or a builder declaration of periodic inspection and documentation of ESC implementation. You can rely on project specifics to choose the best option for you—LEED has no preference.
LEED does not offer specific requirements on ESC control measures, beyond the standards that it references, and the documentation requirements. LEEDuser recommends working with a civil engineer who understands the LEED and EPA requirements, and relying on the professional judgment of the engineer for specific technical questions. LEEDuser has not heard that LEED reviewers are deeply scrutinizing ESC plans and coming back with highly technical questions.