; (B) in such protocol— (i) prohibit the use of techniques that minimize the detection of lead or copper in drinking water; (ii) require sampling under this section to occur not less than once per year; (iii) include criteria for site selection that prioritize testing at high-risk buildings (as defined in subsection (g)); (iv) require sampling in all schools and child care centers served by the public water system at all designated drinking water taps, to be designated by the respective schools and child care centers; and (v) require the sampling methodology to be scientifically based; and (C) develop instructions for compliance with such protocol for dissemination to public water systems and customers thereof. (c) Action level exceeded (1) Investigations The Administrator (or the State exercising primary enforcement responsibility) shall require on-site investigations to identify the source of lead in all residential or nonresidential facilities with individual samples with a lead or copper concentration above the action level, which investigations shall— (A) subject to paragraph (3), be completed by the public water system or local health department within 10 business days of the sample result; and (B) include additional samples at additional locations outside of the facility sampled to identify the potential scope of elevated lead or copper levels. (2) Notification Whenever a public water system detects a lead or copper concentration level above the action level, the system shall, within 2 calendar days of detecting such an exceedance that is specific to one or more facilities, notify the persons at such facilities. (3) No response from owner of facility The requirement of paragraph (1)(A) to complete an investigation concerning a facility is deemed to be satisfied if— (A) within the period of 10 business days described in such paragraph, the public water system or local health department makes at least 3 attempts to contact the owners of the facility, including— (i) at least once in person