Section 40.0520 - Basis for Tier Classification(1)Disposal Site Information. (a) Any person performing Tier Classification for a disposal site shall evaluate such disposal site using the Tier Classification Criteria described in 310 CMR 40.0520(2) based upon: 1. for an initial Tier Classification, data, facts and other information obtained during a Phase I - Initial Site Investigation and documented in the Phase I Report pursuant to 310 CMR 40.0480, and any other relevant data, facts or information known by such person at the time of the initial Tier Classification; and2. for reclassification, any data, facts and other information obtained subsequent to the initial Tier Classification that are relevant to determining whether the disposal site conditions meet the Tier I Criteria at 310 CMR 40.0520(2).(b) For an initial Tier Classification or reclassification, all relevant data, facts and other information considered during Tier Classification shall be documented in the applicable Phase Report(s) and the LSP Tier Classification Opinion. LSPs shall use the Response Action Performance Standard in 310 CMR 40.0191 to develop an LSP Tier Classification Opinion.(c) Any person performing an initial Tier Classification or reclassification may account for risk reduction measures, if any, conducted at the disposal site pursuant to 310 CMR 40.0400 prior to performing such Tier Classification or reclassification, including Immediate Response Actions, Release Abatement Measures and Utility-related Abatement Measures.(2)Tier I Criteria. Any disposal site which meets the following criteria at the time of Tier Classification shall be classified as Tier I: (a) there is evidence of groundwater contamination with oil and/or hazardous material at concentrations equal to or exceeding the applicable RCGW-1 Reportable Concentration set forth in 310 CMR 40.0360, and such groundwater is located within an Interim Wellhead Protection Area, Zone II or within 500 feet of a Private Water Supply Well;(b) an Imminent Hazard is present;(c) one or more remedial actions are required as part of an Immediate Response Action pursuant to 310 CMR 40.0414(2); or(d) one or more response actions are required as part of an Immediate Response Action to eliminate or mitigate a Critical Exposure Pathway pursuant to 310 CMR 40.0414(3).(3) Any disposal site that meets one or more of the Tier I Criteria set forth in 310 CMR 40.0520(2) and is classified as Tier I may be reclassified as Tier II pursuant to 310 CMR 40.0530 once the Tier I Criteria no longer apply at the disposal site, and, with regard to the Tier I Criteria at 310 CMR 40.0520(2)(b), (c) and (d), an Immediate Response Action Completion Statement is submitted or has been submitted documenting the completion of the Immediate Response Actions.(4)Tier II Classification. Any disposal site that is not Tier ID pursuant to 310 CMR 40.0502 or 310 CMR 40.0520(5) and does not meet the Tier I Criteria described at 310 CMR 40.0520(2) shall be classified as Tier II.Amended by Mass Register Issue 1503, eff. 3/1/2024.Amended by Mass Register Issue S1516, eff. 3/1/2024.