MBTA details RAM plan for Alewife-area Red Line access tunnel; finds asbestos in shallow fill and proposes conservative air monitoring

The Massachusetts Bay Transportation Authority on a virtual public meeting presented a draft Release Abatement Measure (RAM) plan for a proposed high‑rail access tunnel west of the Charles River near Alewife, and its licensed site professional summarized recent soil testing, proposed excavation methods, air‑monitoring plans and a preliminary schedule.

MBTA deputy director for community engagement Ashley Armand opened the meeting, and Brian Miller, the project's licensed site professional with CDW Consultants, outlined the RAM plan. MBTA said the project aims to add a high‑rail access point to improve Red Line reliability, shorten shutdowns and reduce the scale and frequency of customer impacts during maintenance. The agency targets a construction notice to proceed in March 2026, mobilization in June 2026 and construction through roughly March 2028.

Why it matters: MBTA reported a focused soil sampling program (148 asbestos analyses) that detected asbestos fibers in 56 of 148 samples, concentrated in the upper 6 feet of fill material. Of those, 49 detections were below 1% and one sample showed the highest detection at about 1.92%. MBTA said deeper natural soils did not contain asbestos and therefore the team will assume the 0–6‑foot fill interval may contain asbestos where fill is present.

What the RAM plan proposes: CDW and MBTA described a combined approach using an approved RAM plan and, where required, a MassDEP nontraditional work plan for the top 6 feet of soil. The excavation cross section presented shows discrete hazardous‑waste zones, asbestos‑bearing fill and clean natural soils beneath. MBTA estimated approximately 9,400 cubic yards of soil will be excavated for the tunnel project, of which about 3,400 cubic yards are asbestos‑containing material to be handled as asbestos waste (and some soils designated as listed hazardous waste due to naphthalene detections).

Air and community monitoring: The team proposed 8 perimeter air monitors and 4 community monitoring locations, plus four desk monitors that can be moved daily with prevailing winds. All airborne fiber results would be reported within two hours of sample collection; any exceedance would prompt an immediate temporary work stoppage and corrective actions (for example additional soil wetting, suspension in heavy winds or modified excavation methods). MBTA said trucks hauling asbestos soils will be lined, sealed and decontaminated prior to leaving the site, and that no stockpiling of asbestos soils will occur on site.

Conservative exposure threshold: MBTA noted Mass guidance often uses a 0.01 fibers per cubic centimeter threshold and said the project will use a conservative action limit of 0.007 fibers/cc, a risk‑based threshold used on other nearby disposal work. MBTA emphasized daily reporting to MassDEP and described additional controls (continuous wetting, perimeter fencing, adaptive monitor placement).

Hazardous‑waste screening and volumes: A subset of samples for naphthalene and formaldehyde found naphthalene in 12 of 31 samples with one concentration above MassDEP reportable limits; formaldehyde was not detected in the five samples analyzed. MBTA stated soils with listed hazardous‑waste concentrations will be managed accordingly and that acceptable final capping will match previously approved MassDEP plans for the remainder of the property (noting a capping configuration described in project documents).

Project constraints and excavation method: MBTA explained the excavation will use sheet piling (a wide, watertight 'box' or cofferdam), with asbestos removal prioritized early in construction to limit time under any nontraditional work plan. MBTA described the construction type as cut‑and‑cover with sheet piles and heavy shoring to about 30 feet depth in places, and said the sheet piles also provide flood containment for the excavation footprint.

Next steps: The RAM plan was submitted to MassDEP in August 2024 and a hard copy is available at the Cambridge Public Health Department; public comment on the RAM plan was announced to close October 30 (MBTA said they were open to written requests for extensions). MBTA said follow‑up public meetings would cover design, construction impacts and mitigation detail and that the project is in MBTA’s capital plan with funds committed.

Sources and attribution: Technical findings and quotes come from CDW’s Brian Miller (licensed site professional) and MBTA staff during the public meeting. Specific numbers and procedures above were described in the presentation materials and on the record during the Q&A session.

What remains unresolved: MBTA presented mitigation measures and a monitoring program but acknowledged some practical constraints (wide excavation, need for heavy struts and welding) that complicate full negative‑pressure tenting. MBTA committed to continue coordination with the developer’s LSP and Cambridge departments and to incorporate additional means and methods where feasible.