Federal agencies have the following responsibilities concerning the abatement of radon in space when radon levels exceed current EPA standards:

(a) Retest abated areas and make lessors retest, as required, abated areas to adhere to EPA standards.

(b) Test non-public water sources (in remote areas for projects such as border stations) for radon according to EPA guidance. Radon levels that exceed current applicable EPA standards must be mitigated. Federal agencies must retest, as required, to adhere to EPA standards.