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600 LORING AVENUE - PIN PHASE 1 ISI & TIER 1 CLASSIFICATION RECEIVEDENVIRONMENTAL CO N E C O • OLOGICAL AUG 4� 2025 SURVEY Engineers & Scientists CIVIL July 26,2025 CITY OF SALEM Coneco Project No. 12519.002 BOARD OF HEALTH Dr. Sara Moore,Chairperson City of Salem Board of Health 98 Washington Street 3'Floor Salem,Massachusetts 01970 RE: Public Involvement Notification Phase I Initial Site Investigation and Tier I Classification Report Non-PCB Mineral Oil Dielectric Fluid Release Pad-Mounted Electrical Transformer 600 Loring Avenue Salem,Massachusetts Release Tracking Number 3-50554 Dear Chairperson Moore: Pursuant to 310 CMR 40.1403 of the Massachusetts Contingency Plan(MCP),the following serves as written notification of the submittal of a Phase I Initial Site Investigation and Tier I Classification Report. This submittal is regarding a release of non-polychlorinated biphenyl(non-PCB)mineral oil dielectric fluid(MODF)that occurred from a pad-mounted electrical transformer formerly located at the above-referenced location. A copy of the above-referenced report will be available for viewing on or about July 26,2025,at the Department of Environmental Protection Northeast Regional Office (MassDEP-NERO)in Woburn,Massachusetts. A copy of this report may also be obtained by contacting the undersigned in writing. A copy of the Phase I Initial Site Investigation summary of findings and conclusions is appended to this notice. A legal notice regarding this release will be published in The Salem News on or about July 26,2025. A copy of this notice is included with this letter. A copy of the Disposal Site Plan is also attached for reference. Additional Public Involvement Activities may be requested pursuant to 310 CMR 40.1403(9). This submittal is being made on behalf of Massachusetts Electric Company(MECO),the party conducting response actions relating to this release. If you have any questions,please contact the undersigned. Respectfully Submitted, Coneco Engineers& Scientists, Incorporated uYUUvE� VI��� Nicholas R.Holtgrefe Brain F. Klingler, PG,LSP Project Manager Principal Geologist MMP:NRH:BFK;jw U:\\12519.002_Municipal_Notice_PhaseI_TierI Enclosures: Copy of Phase I Initial Site Investigation Summary of Findings and Conclusions Copy of Notice of Initial Site Investigation and Tier I Classification Disposal Site Plan cc: MECO MassDEP-HERO 4 First Street,Bridgewater,MA 02324 (508)697-3191 (800)548-3355 Coneco.com Summary of Findings and Conclusions of Phase I Initial Site Investigation Non-PCB Mineral Oil Dielectric Fluid Release Pad-Mounted Electrical Transformer 600 Loring Avenue Salem,Massachusetts Release Tracking Number 3-50554 Conditions of the area impacted by a historical release of non-PCB MODF from a 150 kVA pad- mounted electrical transformer formerly in use at the commercial property identified as 600 Loring Avenue in Salem,Massachusetts,were evaluated in a manner consistent with applicable guidelines for a Phase I-ISI as presented in 310 CMR 40.0480 of the MCP. Response actions performed in association with RTN 3-50554 included a review of pertinent Disposal Site history,the removal of approximately 5 cubic yards of remediation and investigation-derived waste,the advancement of three soil borings, four bedrock borings,the installation of five groundwater monitoring wells, and the collection and laboratory analysis of soil and groundwater samples. Based on the information and observations described herein, the following is a summary of the investigation findings: • On August 7,2023,MECO identified staining indicative of a historical release of non-PCB MODF from a 150 kVA pad-mounted electrical transformer. Coneco observed approximately 10 square-feet of surficial staining on the concrete transformer pad and underlying soil. No indication of a sudden release of MODF greater than the applicable RQ was observed by MECO or Coneco. • The MODF associated with the leaking transformer was confirmed to be"non-PCB" in accordance with 40 CFR 761.3 and 310 CMR 40.0000. • Based on the initial capacity of the transformer, and the volume of remaining non-PCB MODF recovered from the leaking transformer, Coneco estimated that approximately 140 gallons of non-PCB MODF had been released at the Disposal Site • In order to eliminate the source of the release and stabilize environmental conditions at the Site, MECO de-energized and removed the leaking transformer(i.e., eliminated release source)on August 7,2023. • On August 7 and 8,2023,approximately 3 cubic yards of impacted media were removed as part of initial LRA activities. Due to safety concerns associated with the customer electricity demands, structural concerns associated with excavation adjacent to the Site building, and an impending storm event forecasted for the early morning of August 8,2023,remedial excavation activities were suspended on August 8, 2023. • Laboratory analytical results identified EPH concentrations in excess of the applicable Method 1 Risk Characterization Standards in soil samples collected at the termination of LRA excavation activities. • On February 8, 2024,three soil borings were advanced at the Site of which were completed as groundwater monitoring wells CMW-01 through CMW-03. Laboratory analytical results for selected soil samples collected from the borings indicated that no concentrations of EPH were detected in excess of the applicable Method 1 Risk Characterization Standards. • On July 19 and 22, 2024,bedrock groundwater monitoring wells CMW-02R and CMW-03R were installed in the locations of CMW-02 and CMW-03,respectively and two additional groundwater monitoring wells, CMW-101 and CAW-102,were installed to further delineate the potential extent of non-PCB MODF impacts to groundwater. • On July 23, 2024, Coneco gauged the newly installed monitoring wells. Based on the observation of LNAPL having a thickness of approximately 10.2 inches within monitoring well CMW-02R, conditions represented a 72-hour Reportable Condition as described in 310 CMR 40.0313(1). MassDEP notification was completed within 72 hours of the identification of a reportable condition in accordance with the specifications of 310 CMR 40.0332. At the time, MassDEP provided verbal approval to conduct IRA activities and RTN 3-50554 was assigned to the release by MassDEP. • IRA activities performed at the Disposal Site associated with RTN 3-50554 since July 2024,have included monthly monitoring well gauging, LNAPL removal from monitoring well CMW-02R, proper off-Site disposal of recovered LNAPL,and quarterly groundwater sampling of Disposal Site monitoring wells. • IRA activities,consisting of the further assessment of the nature and extent of remaining non- PCB MODF impacts and potential remediation of impacted soil and/or groundwater, will continue at the Disposal Site in accordance with the IRA Plan submitted to MassDEP dated September 24,2024. • The release occurred from a point source at a commercial property. The potential routes for human exposure include particulate inhalation, ingestion, and/or dermal contact with soil during utility maintenance or construction conducted within the limits of the Disposal Site. • No indoor air, surface water, drainage structures, or other potentially sensitive potentially sensitive environmental receptors are known to have been impacted by the subject release. Based on the evaluation of current Disposal Site conditions in relation to the Tier I Inclusionary Criteria,performed in accordance with 310 CMR 40.0520(4),the Disposal Site meets the criteria for Tier I Classification. NOTICE OF PHASE I INITIAL SITE INVESTIGATION AND TIER I CLASSIFICATION Non-PCB Mineral Oil Dielectric Fluid Release Pad-Mounted Electrical Transformer, 600 Loring Avenue Salem, Massachusetts Release Tracking Number 3-50554 A release of oil and/or hazardous material has occurred at this location, which is a Disposal Site as defined by M.G.L. c. 21 E, § 2 and the Massachusetts Contingency Plan, 310 CMR 40.0000. To evaluate the release, a Phase I Initial Site Investigation was performed pursuant to 310 CMR 40.0480. As a result of this investigation, the site has been classified as Tier I pursuant to 310 CMR 40.0500. On July 26, 2025, the Massachusetts Electric Company filed a Tier I Classification Submittal with the Department of Environmental Protection (MassDEP). To obtain more information on this disposal site, please contact Brian F. Klingler, PG, LSP, Coneco Engineers & Scientists, Incorporated, 4 First Street, Bridgewater, Massachusetts 02324, (508) 697-3191. 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